WorldWideScience

Sample records for uppermost unconfined aquifer

  1. An evaluation of aquifer intercommunication between the unconfined and Rattlesnake Ridge aquifers on the Hanford Site

    International Nuclear Information System (INIS)

    Jensen, E.J.

    1987-10-01

    During 1986, Pacific Northwest Laboratory conducted a study of a portion of the Rattlesnake Ridge aquifer (confined aquifer) that lies beneath the B Pond - Gable Mountain Pond area of the Hanford Site. The purpose was to determine the extent of intercommunication between the unconfined aquifer and the uppermost regionally extensive confined aquifer, referred to as the Rattlesnake Ridge aquifer. Hydraulic head data and chemical data were collected from the ground water in the study area during December 1986. The hydraulic head data were used to determine the effects caused by water discharged to the ground from B Pond on both the water table of the unconfined aquifer and the potentiometric surface of the confined aquifer. The chemical data were collected to determine the extent of chemical constituents migrating from the unconfined aquifer to the confined aquifer. Analysis of chemical constituents in the Rattlesnake Ridge aquifer demonstrated that communication between the unconfined and confined aquifers had occurred. However, the levels of contaminants found in the Rattlesnake Ridge aquifer during this study were below the DOE Derived Concentration Guides

  2. Nitrate reduction in an unconfined sandy aquifer

    DEFF Research Database (Denmark)

    Postma, Diederik Jan; Boesen, Carsten; Kristiansen, Henning

    1991-01-01

    of total dissolved ions in the NO3- free anoxic zone indicates the downward migration of contaminants and that active nitrate reduction is taking place. Nitrate is apparently reduced to N2 because both nitrite and ammonia are absent or found at very low concentrations. Possible electron donors......Nitrate distribution and reduction processes were investigated in an unconfined sandy aquifer of Quaternary age. Groundwater chemistry was studied in a series of eight multilevel samplers along a flow line, deriving water from both arable and forested land. Results show that plumes of nitrate...... processes of O2 and NO3- occur at rates that are fast compared to the rate of downward water transport. Nitrate-contaminated groundwater contains total contents of dissolved ions that are two to four times higher than in groundwater derived from the forested area. The persistence of the high content...

  3. Radial flow towards well in leaky unconfined aquifer

    Science.gov (United States)

    Mishra, P. K.; Kuhlman, K. L.

    2012-12-01

    An analytical solution is developed for three-dimensional flow towards a partially penetrating large- diameter well in an unconfined aquifer bounded below by a leaky aquitard of finite or semi-infinite extent. The analytical solution is derived using Laplace and Hankel transforms, then inverted numerically. Existing solutions for flow in leaky unconfined aquifers neglect the unsaturated zone following an assumption of instantaneous drainage due to Neuman. We extend the theory of leakage in unconfined aquifers by (1) including water flow and storage in the unsaturated zone above the water table, and (2) allowing the finite-diameter pumping well to partially penetrate the aquifer. The investigation of model-predicted results shows that aquitard leakage leads to significant departure from the unconfined solution without leakage. The investigation of dimensionless time-drawdown relationships shows that the aquitard drawdown also depends on unsaturated zone properties and the pumping-well wellbore storage effects.

  4. Unconfined aquifer response to infiltration basins and shallow pump tests

    Science.gov (United States)

    Ostendorf, David W.; DeGroot, Don J.; Hinlein, Erich S.

    2007-05-01

    SummaryWe measure and model the unsteady, axisymmetric response of an unconfined aquifer to delayed, arbitrary recharge. Water table drainage follows the initial elastic aquifer response, as modeled for uniform, instantaneous recharge by Zlotnik and Ledder [Zlotnik, V., Ledder, G., 1992. Groundwater flow in a compressible unconfined aquifer with uniform circular recharge. Water Resources Research 28(6), 1619-1630] and delayed drainage by Moench [Moench, A.F., 1995. Combining the Neuman and Boulton models for flow to a well in an unconfined aquifer. Ground Water 33(3), 378-384]. We extend their analyses with a convolution integral that models the delayed response of an aquifer to infiltration from a circular infiltration basin. The basin routes the hydrograph to the water table with a decay constant dependent on a Brooks and Corey [Brooks, R.H., Corey, A.T., 1966. Properties of porous media affecting fluid flow. Journal of the Irrigation and Drainage Division ASCE 92(2), 61-88] unsaturated permeability exponent. The resulting closed form model approaches Neuman's [Neuman, S.P., 1972. Theory of flow in unconfined aquifers considering delayed response of the water table. Water Resources Research 8(4), 1031-1045] partially penetrating pump test equation for a small source radius, instantaneous, uniform drainage and a shallow screen section. Irrigation pump data at a well characterized part of the Plymouth-Carver Aquifer in southeastern Massachusetts calibrate the small source model, while infiltration data from the closed drainage system of State Route 25 calibrate the infiltration basin model. The calibrated permeability, elasticity, specific yield, and permeability exponent are plausible and consistent for the pump and infiltration data sets.

  5. Using Genetic Algorithm to Estimate Hydraulic Parameters of Unconfined Aquifers

    Directory of Open Access Journals (Sweden)

    Asghar Asghari Moghaddam

    2009-03-01

    Full Text Available Nowadays, optimization techniques such as Genetic Algorithms (GA have attracted wide attention among scientists for solving complicated engineering problems. In this article, pumping test data are used to assess the efficiency of GA in estimating unconfined aquifer parameters and a sensitivity analysis is carried out to propose an optimal arrangement of GA. For this purpose, hydraulic parameters of three sets of pumping test data are calculated by GA and they are compared with the results of graphical methods. The results indicate that the GA technique is an efficient, reliable, and powerful method for estimating the hydraulic parameters of unconfined aquifer and, further, that in cases of deficiency in pumping test data, it has a better performance than graphical methods.

  6. WTAQ - A computer program for aquifer-test analysis of confined and unconfined aquifers

    Science.gov (United States)

    Barlow, P.M.; Moench, A.F.

    2004-01-01

    Computer program WTAQ was developed to implement a Laplace-transform analytical solution for axial-symmetric flow to a partially penetrating, finite-diameter well in a homogeneous and anisotropic unconfined (water-table) aquifer. The solution accounts for wellbore storage and skin effects at the pumped well, delayed response at an observation well, and delayed or instantaneous drainage from the unsaturated zone. For the particular case of zero drainage from the unsaturated zone, the solution simplifies to that of axial-symmetric flow in a confined aquifer. WTAQ calculates theoretical time-drawdown curves for the pumped well and observation wells and piezometers. The theoretical curves are used with measured time-drawdown data to estimate hydraulic parameters of confined or unconfined aquifers by graphical type-curve methods or by automatic parameter-estimation methods. Parameters that can be estimated are horizontal and vertical hydraulic conductivity, specific storage, and specific yield. A sample application illustrates use of WTAQ for estimating hydraulic parameters of a hypothetical, unconfined aquifer by type-curve methods. Copyright ASCE 2004.

  7. Saturated-unsaturated flow in a compressible leaky-unconfined aquifer

    Science.gov (United States)

    Mishra, Phoolendra K.; Vesselinov, Velimir V.; Kuhlman, Kristopher L.

    2012-06-01

    An analytical solution is developed for three-dimensional flow towards a partially penetrating large-diameter well in an unconfined aquifer bounded below by a leaky aquitard of finite or semi-infinite extent. The analytical solution is derived using Laplace and Hankel transforms, then inverted numerically. Existing solutions for flow in leaky unconfined aquifers neglect the unsaturated zone following an assumption of instantaneous drainage due to Neuman. We extend the theory of leakage in unconfined aquifers by (1) including water flow and storage in the unsaturated zone above the water table, and (2) allowing the finite-diameter pumping well to partially penetrate the aquifer. The investigation of model-predicted results shows that aquitard leakage leads to significant departure from the unconfined solution without leakage. The investigation of dimensionless time-drawdown relationships shows that the aquitard drawdown also depends on unsaturated zone properties and the pumping-well wellbore storage effects.

  8. Semi-analytical solutions for flow to a well in an unconfined-fractured aquifer system

    Science.gov (United States)

    Sedghi, Mohammad M.; Samani, Nozar

    2015-09-01

    Semi-analytical solutions of flow to a well in an unconfined single porosity aquifer underlain by a fractured double porosity aquifer, both of infinite radial extent, are obtained. The upper aquifer is pumped at a constant rate from a pumping well of infinitesimal radius. The solutions are obtained via Laplace and Hankel transforms and are then numerically inverted to time domain solutions using the de Hoog et al. algorithm and Gaussian quadrature. The results are presented in the form of dimensionless type curves. The solution takes into account the effects of pumping well partial penetration, water table with instantaneous drainage, leakage with storage in the lower aquifer into the upper aquifer, and storativity and hydraulic conductivity of both fractures and matrix blocks. Both spheres and slab-shaped matrix blocks are considered. The effects of the underlying fractured aquifer hydraulic parameters on the dimensionless drawdown produced by the pumping well in the overlying unconfined aquifer are examined. The presented solution can be used to estimate hydraulic parameters of the unconfined and the underlying fractured aquifer by type curve matching techniques or with automated optimization algorithms. Errors arising from ignoring the underlying fractured aquifer in the drawdown distribution in the unconfined aquifer are also investigated.

  9. A semi-analytical solution for slug tests in an unconfined aquifer considering unsaturated flow

    Science.gov (United States)

    Sun, Hongbing

    2016-01-01

    A semi-analytical solution considering the vertical unsaturated flow is developed for groundwater flow in response to a slug test in an unconfined aquifer in Laplace space. The new solution incorporates the effects of partial penetrating, anisotropy, vertical unsaturated flow, and a moving water table boundary. Compared to the Kansas Geological Survey (KGS) model, the new solution can significantly improve the fittings of the modeled to the measured hydraulic heads at the late stage of slug tests in an unconfined aquifer, particularly when the slug well has a partially submerged screen and moisture drainage above the water table is significant. The radial hydraulic conductivities estimated with the new solution are comparable to those from the KGS, Bouwer and Rice, and Hvorslev methods. In addition, the new solution also can be used to examine the vertical conductivity, specific storage, specific yield, and the moisture retention parameters in an unconfined aquifer based on slug test data.

  10. Supplement to procedures, analysis, and comparison of groundwater velocity measurement methods for unconfined aquifers

    International Nuclear Information System (INIS)

    Zinkl, R.J.; Kearl, P.M.

    1988-09-01

    This report is a supplement to Procedures, Analysis, and Comparison of Groundwater Velocity Measurement Methods for Unconfined Aquifers and provides computer program descriptions, type curves, and calculations for the analysis of field data in determining groundwater velocity in unconfined aquifers. The computer programs analyze bail or slug tests, pumping tests, Geoflo Meter data, and borehole dilution data. Appendix A is a description of the code, instructions for using the code, an example data file, and the calculated results to allow checking the code after installation on the user's computer. Calculations, development of formulas, and correction factors for the various programs are presented in Appendices B through F. Appendix G provides a procedure for calculating transmissivity and specific yield for pumping tests performed in unconfined aquifers

  11. Development of a three-dimensional ground-water model of the Hanford Site unconfined aquifer system: FY 1995 status report

    International Nuclear Information System (INIS)

    Wurstner, S.K.; Thorne, P.D.; Chamness, M.A.; Freshley, M.D.; Williams, M.D.

    1995-12-01

    A three-dimensional numerical model of ground-water flow was developed for the uppermost unconfined aquifer at the Hanford Site in south-central Washington. Development of the model is supported by the Hanford Site Ground-Water Surveillance Project, managed by the Pacific Northwest National Laboratory, which is responsible for monitoring the sitewide movement of contaminants in ground water beneath the Hanford Site. Two objectives of the Ground-Water Surveillance Project are to (1) identify and quantify existing, emerging, or potential ground-water quality problems, and (2) assess the potential for contaminants to migrate from the Hanford Site through the ground-water pathway. Numerical models of the ground-water flow system are important tools for estimating future aquifer conditions and predicting the movement of contaminants through ground water. The Ground-Water Surveillance Project has supported development and maintenance of a two-dimensional model of the unconfined aquifer. This report describes upgrade of the two-dimensional model to a three-dimensional model. The numerical model is based on a three-dimensional conceptual model that will be continually refined and updated as additional information becomes available. This report presents a description of the three-dimensional conceptual model of ground-water flow in the unconfined aquifer system and then discusses the cur-rent state of the three-dimensional numerical model

  12. Groundwater flow to a horizontal or slanted well in an unconfined aquifer

    Science.gov (United States)

    Zhan, Hongbin; Zlotnik, Vitaly A.

    2002-07-01

    New semianalytical solutions for evaluation of the drawdown near horizontal and slanted wells with finite length screens in unconfined aquifers are presented. These fully three-dimensional solutions consider instantaneous drainage or delayed yield and aquifer anisotropy. As a basis, solution for the drawdown created by a point source in a uniform anisotropic unconfined aquifer is derived in Laplace domain. Using superposition, the point source solution is extended to the cases of the horizontal and slanted wells. The previous solutions for vertical wells can be described as a special case of the new solutions. Numerical Laplace inversion allows effective evaluation of the drawdown in real time. Examples illustrate the effects of well geometry and the aquifer parameters on drawdown. Results can be used to generate type curves from observations in piezometers and partially or fully penetrating observation wells. The proposed solutions and software are useful for the parameter identification, design of remediation systems, drainage, and mine dewatering.

  13. A correction for Dupuit-Forchheimer interface flow models of seawater intrusion in unconfined coastal aquifers

    Science.gov (United States)

    Koussis, Antonis D.; Mazi, Katerina; Riou, Fabien; Destouni, Georgia

    2015-06-01

    Interface flow models that use the Dupuit-Forchheimer (DF) approximation for assessing the freshwater lens and the seawater intrusion in coastal aquifers lack representation of the gap through which fresh groundwater discharges to the sea. In these models, the interface outcrops unrealistically at the same point as the free surface, is too shallow and intersects the aquifer base too far inland, thus overestimating an intruding seawater front. To correct this shortcoming of DF-type interface solutions for unconfined aquifers, we here adapt the outflow gap estimate of an analytical 2-D interface solution for infinitely thick aquifers to fit the 50%-salinity contour of variable-density solutions for finite-depth aquifers. We further improve the accuracy of the interface toe location predicted with depth-integrated DF interface solutions by ∼20% (relative to the 50%-salinity contour of variable-density solutions) by combining the outflow-gap adjusted aquifer depth at the sea with a transverse-dispersion adjusted density ratio (Pool and Carrera, 2011), appropriately modified for unconfined flow. The effectiveness of the combined correction is exemplified for two regional Mediterranean aquifers, the Israel Coastal and Nile Delta aquifers.

  14. Analytical solution of groundwater waves in unconfined aquifers with ...

    Indian Academy of Sciences (India)

    Selva Balaji Munusamy

    2017-07-29

    Jul 29, 2017 ... higher-order Boussinesq equation. The homotopy perturbation solution is derived using a virtual perturbation .... reality, seepage face formation is common for tide–aquifer interaction problems. To simplify the complexity of the.

  15. Summary and evaluation of available hydraulic property data for the Hanford Site unconfined aquifer system

    International Nuclear Information System (INIS)

    Thorne, P.D.; Newcomer, D.R.

    1992-11-01

    Improving the hydrologic characterization of the Hanford Site unconfined aquifer system is one of the objectives of the Hanford Site Ground-Water Surveillance Project. To help meet this objective, hydraulic property data available for the aquifer have been compiled, mainly from reports published over the past 40 years. Most of the available hydraulic property estimates are based on constant-rate pumping tests of wells. Slug tests have also been conducted at some wells and analyzed to determine hydraulic properties. Other methods that have been used to estimate hydraulic properties of the unconfined aquifer are observations of water-level changes in response to river stage, analysis of ground-water mound formation, tracer tests, and inverse groundwater flow models

  16. Approximate solutions for radial travel time and capture zone in unconfined aquifers.

    Science.gov (United States)

    Zhou, Yangxiao; Haitjema, Henk

    2012-01-01

    Radial time-of-travel (TOT) capture zones have been evaluated for unconfined aquifers with and without recharge. The solutions of travel time for unconfined aquifers are rather complex and have been replaced with much simpler approximate solutions without significant loss of accuracy in most practical cases. The current "volumetric method" for calculating the radius of a TOT capture zone assumes no recharge and a constant aquifer thickness. It was found that for unconfined aquifers without recharge, the volumetric method leads to a smaller and less protective wellhead protection zone when ignoring drawdowns. However, if the saturated thickness near the well is used in the volumetric method a larger more protective TOT capture zone is obtained. The same is true when the volumetric method is used in the presence of recharge. However, for that case it leads to unreasonableness over the prediction of a TOT capture zone of 5 years or more. © 2011, The Author(s). Ground Water © 2011, National Ground Water Association.

  17. Hydrology of the shallow aquifer and uppermost semiconfined aquifer near El Paso, Texas

    Science.gov (United States)

    White, D.E.; Baker, E.T.; Sperka, Roger

    1997-01-01

    The availability of fresh ground water in El Paso and adjacent areas that is needed to meet increased demand for water supply concerns local, State, and Federal agencies. The Hueco bolson is the principal aquifer in the El Paso area. Starting in the early 1900s and continuing to the 1950s, most of the municipal and industrial water supply in El Paso was pumped from the Hueco bolson aquifer from wells in and near the Rio Grande Valley and the international border. The Rio Grande is the principal surface-water feature in the El Paso area, and a major source of recharge to the shallow aquifer (Rio Grande alluvium) within the study area is leakage of flow from the Rio Grande.

  18. Analysis of flow near a dug well in an unconfined aquifer

    Science.gov (United States)

    Sridharan, K.; Sathyanarayana, D.; Reddy, A. Siva

    1990-11-01

    A numerical analysis of flow to a dug well in an unconfined aquifer is made, taking into account well storage, elastic storage release, gravity drainage, anisotropy, partial penetration, vertical flow and seepage surface at the well face, and treating the water table in the aquifer and water level in the well as unknown boundaries. The pumped discharge is maintained constant. The solution is obtained by a two-level iterative scheme. The effects of governing parameters on the drawdown, development of seepage surface and contribution from aquifer flow to the total discharge are discussed. The degree of anisotropy and partial penetration are found to be the parameters which affect the flow characteristics most significantly. The effect of anisotropy on the development of seepage surface is very pronounced.

  19. Semi-analytical solution of flow to a well in an unconfined-fractured aquifer system separated by an aquitard

    Science.gov (United States)

    Sedghi, Mohammad M.; Samani, Nozar; Barry, D. A.

    2018-04-01

    Semi-analytical solutions are presented for flow to a well in an extensive homogeneous and anisotropic unconfined-fractured aquifer system separated by an aquitard. The pumping well is of infinitesimal radius and screened in either the overlying unconfined aquifer or the underlying fractured aquifer. An existing linearization method was used to determine the watertable drainage. The solution was obtained via Laplace and Hankel transforms, with results calculated by numerical inversion. The main findings are presented in the form of non-dimensional drawdown-time curves, as well as scaled sensitivity-dimensionless time curves. The new solution permits determination of the influence of fractures, matrix blocks and watertable drainage parameters on the aquifer drawdown. The effect of the aquitard on the drawdown response of the overlying unconfined aquifer and the underlying fractured aquifer was also explored. The results permit estimation of the unconfined and fractured aquifer hydraulic parameters via type-curve matching or coupling of the solution with a parameter estimation code. The solution can also be used to determine aquifer hydraulic properties from an optimal pumping test set up and duration.

  20. General well function for pumping from a confined, leaky, or unconfined aquifer

    Science.gov (United States)

    Perina, Tomas; Lee, Tien-Chang

    2006-02-01

    A general well function for groundwater flow toward an extraction well with non-uniform radial flux along the screen and finite-thickness skin, partially penetrating an unconfined, leaky-boundary flux, or confined aquifer is derived via the Laplace and generalized finite Fourier transforms. The mixed boundary condition at the well face is solved as the discretized Fredholm integral equation. The general well function reduces to a uniform radial flux solution as a special case. In the Laplace domain, the relation between the drawdown in the extraction well and flowrate is linear and the formulations for specified flowrate or specified drawdown pumping are interchangeable. The deviation in drawdown of the uniform from non-uniform radial flux solutions depends on the relative positions of the extraction and observation well screens, aquifer properties, and time of observation. In an unconfined aquifer the maximum deviation occurs during the period of delayed drawdown when the effect of vertical flow is most apparent. The skin and wellbore storage in an observation well are included as model parameters. A separate solution is developed for a fully penetrating well with the radial flux being a continuous function of depth.

  1. Early-Time Solution of the Horizontal Unconfined Aquifer in the Buildup Phase

    Science.gov (United States)

    Gravanis, Elias; Akylas, Evangelos

    2017-10-01

    We derive the early-time solution of the Boussinesq equation for the horizontal unconfined aquifer in the buildup phase under constant recharge and zero inflow. The solution is expressed as a power series of a suitable similarity variable, which is constructed so that to satisfy the boundary conditions at both ends of the aquifer, that is, it is a polynomial approximation of the exact solution. The series turns out to be asymptotic and it is regularized by resummation techniques that are used to define divergent series. The outflow rate in this regime is linear in time, and the (dimensionless) coefficient is calculated to eight significant figures. The local error of the series is quantified by its deviation from satisfying the self-similar Boussinesq equation at every point. The local error turns out to be everywhere positive, hence, so is the integrated error, which in turn quantifies the degree of convergence of the series to the exact solution.

  2. Three-dimensional groundwater velocity field in an unconfined aquifer under irrigation

    International Nuclear Information System (INIS)

    Zlotnik, V.

    1990-01-01

    A method for three-dimensional flow velocity calculation has been developed to evaluate unconfined aquifer sensitivity to areal agricultural contamination of groundwater. The methodology of Polubarinova-Kochina is applied to an unconfined homogeneous compressible or incompressible anisotropic aquifer. It is based on a three-dimensional groundwater flow model with a boundary condition on the moving surface. Analytical solutions are obtained for a hydraulic head under the influence of areal sources of circular and rectangular shape using integral transforms. Two-dimensional Hantush formulas result from the vertical averaging of the three-dimensional solutions, and the asymptotic behavior of solutions is analyzed. Analytical expressions for flow velocity components are obtained from the gradient of the hydraulic head field. Areal and temporal variability of specific yield in groundwater recharge areas is also taken into account. As a consequence of linearization of the boundary condition, the operation of any irrigation system with respect to groundwater is represented by superposition of the operating wells and circular and rectangular source influences. Combining the obtained solutions with Dagan or Neuman well functions, one can develop computer codes for the analytical computation of the three-dimensional groundwater hydraulic head and velocity component distributions. Methods for practical implementation are discussed. (Author) (20 refs., 4 figs.)

  3. Geochemical Impacts of Leaking CO2 from Subsurface Storage Reservoirs to Unconfined and Confined Aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Qafoku, Nikolla; Brown, Christopher F.; Wang, Guohui; Sullivan, E. C.; Lawter, Amanda R.; Harvey, Omar R.; Bowden, Mark

    2013-04-15

    Experimental research work has been conducted and is undergoing at Pacific Northwest National Laboratory (PNNL) to address a variety of scientific issues related with the potential leaks of the carbon dioxide (CO2) gas from deep storage reservoirs. The main objectives of this work are as follows: • Develop a systematic understanding of how CO2 leakage is likely to influence pertinent geochemical processes (e.g., dissolution/precipitation, sorption/desorption and redox reactions) in the aquifer sediments. • Identify prevailing environmental conditions that would dictate one geochemical outcome over another. • Gather useful information to support site selection, risk assessment, policy-making, and public education efforts associated with geological carbon sequestration. In this report, we present results from experiments conducted at PNNL to address research issues related to the main objectives of this effort. A series of batch and column experiments and solid phase characterization studies (quantitative x-ray diffraction and wet chemical extractions with a concentrated acid) were conducted with representative rocks and sediments from an unconfined, oxidizing carbonate aquifer, i.e., Edwards aquifer in Texas, and a confined aquifer, i.e., the High Plains aquifer in Kansas. These materials were exposed to a CO2 gas stream simulating CO2 gas leaking scenarios, and changes in aqueous phase pH and chemical composition were measured in liquid and effluent samples collected at pre-determined experimental times. Additional research to be conducted during the current fiscal year will further validate these results and will address other important remaining issues. Results from these experimental efforts will provide valuable insights for the development of site-specific, generation III reduced order models. In addition, results will initially serve as input parameters during model calibration runs and, ultimately, will be used to test model predictive capability and

  4. Steady flow rate to a partially penetrating well with seepage face in an unconfined aquifer

    Science.gov (United States)

    Behrooz-Koohenjani, Siavash; Samani, Nozar; Kompani-Zare, Mazda

    2011-06-01

    The flow rate to fully screened, partially penetrating wells in an unconfined aquifer is numerically simulated using MODFLOW 2000, taking into account the flow from the seepage face and decrease in saturated thickness of the aquifer towards the well. A simple three-step method is developed to find the top of the seepage face and hence the seepage-face length. The method is verified by comparing it with the results of previous predictive methods. The results show that the component of flow through the seepage face can supply a major portion of the total pumping rate. Variations in flow rate as a function of the penetration degree, elevation of the water level in the well and the distance to the far constant head boundary are investigated and expressed in terms of dimensionless curves and equations. These curves and equations can be used to design the degree of penetration for which the allowable steady pumping rate is attained for a given elevation of water level in the well. The designed degree of penetration or flow rate will assure the sustainability of the aquifer storage, and can be used as a management criterion for issuing drilling well permits by groundwater protection authorities.

  5. S/O modeling technique for optimal containment of light hydrocarbons in contaminated unconfined aquifers

    International Nuclear Information System (INIS)

    Cooper, G.S. Jr.; Kaluarachchi, J.J.; Peralta, R.C.

    1993-01-01

    An innovative approach is presented to minimize pumping for immobilizing a floating plume of a light non-aqueous phase liquid (LNAPL). The best pumping strategy is determined to contain the free oil product and provide for gradient control of the water table. This approach combined detailed simulation, statistical analysis, and optimization. This modeling technique uses regression equations that describe system response to variable pumping stimuli. The regression equations were developed from analysis of systematically performed simulations of multiphase flow in an areal region of an unconfined aquifer. Simulations were performed using ARMOS, a finite element model. ARMOS can be used to simulate a spill, leakage from subsurface storage facilities and recovery of hydrocarbons from trenches or pumping wells to design remediation schemes

  6. Hydrogeologic framework of the uppermost principal aquifer systems in the Williston and Powder River structural basins, United States and Canada

    Science.gov (United States)

    Thamke, Joanna N.; LeCain, Gary D.; Ryter, Derek W.; Sando, Roy; Long, Andrew J.

    2014-01-01

    The glacial, lower Tertiary, and Upper Cretaceous aquifer systems in the Williston and Powder River structural basins within the United States and Canada are the uppermost principal aquifer systems and most accessible sources of groundwater for these energy-producing basins. The glacial aquifer system covers the northeastern part of the Williston structural basin. The lower Tertiary and Upper Cretaceous aquifer systems are present in about 91,300 square miles (mi2) of the Williston structural basin and about 25,500 mi2 of the Powder River structural basin. Directly under these aquifer systems are 800 to more than 3,000 feet (ft) of relatively impermeable marine shale that serves as a basal confining unit. The aquifer systems in the Williston structural basin have a shallow (less than 2,900 ft deep), wide, and generally symmetrical bowl shape. The aquifer systems in the Powder River structural basin have a very deep (as much as 8,500 ft deep), narrow, and asymmetrical shape.

  7. Three-dimensional semi-analytical solution to groundwater flow in confined and unconfined wedge-shaped aquifers

    Science.gov (United States)

    Sedghi, Mohammad Mahdi; Samani, Nozar; Sleep, Brent

    2009-06-01

    The Laplace domain solutions have been obtained for three-dimensional groundwater flow to a well in confined and unconfined wedge-shaped aquifers. The solutions take into account partial penetration effects, instantaneous drainage or delayed yield, vertical anisotropy and the water table boundary condition. As a basis, the Laplace domain solutions for drawdown created by a point source in uniform, anisotropic confined and unconfined wedge-shaped aquifers are first derived. Then, by the principle of superposition the point source solutions are extended to the cases of partially and fully penetrating wells. Unlike the previous solution for the confined aquifer that contains improper integrals arising from the Hankel transform [Yeh HD, Chang YC. New analytical solutions for groundwater flow in wedge-shaped aquifers with various topographic boundary conditions. Adv Water Resour 2006;26:471-80], numerical evaluation of our solution is relatively easy using well known numerical Laplace inversion methods. The effects of wedge angle, pumping well location and observation point location on drawdown and the effects of partial penetration, screen location and delay index on the wedge boundary hydraulic gradient in unconfined aquifers have also been investigated. The results are presented in the form of dimensionless drawdown-time and boundary gradient-time type curves. The curves are useful for parameter identification, calculation of stream depletion rates and the assessment of water budgets in river basins.

  8. Exposure Time Distributions reveal Denitrification Rates along Groundwater Flow Path of an Agricultural Unconfined Aquifer

    Science.gov (United States)

    Kolbe, T.; Abbott, B. W.; Thomas, Z.; Labasque, T.; Aquilina, L.; Laverman, A.; Babey, T.; Marçais, J.; Fleckenstein, J. H.; Peiffer, S.; De Dreuzy, J. R.; Pinay, G.

    2016-12-01

    Groundwater contamination by nitrate is nearly ubiquitous in agricultural regions. Nitrate is highly mobile in groundwater and though it can be denitrified in the aquifer (reduced to inert N2 gas), this process requires the simultaneous occurrence of anoxia, an electron donor (e.g. organic carbon, pyrite), nitrate, and microorganisms capable of denitrification. In addition to this the ratio of the time groundwater spent in a denitrifying environment (exposure time) to the characteristic denitrification reaction time plays an important role, because denitrification can only occur if the exposure time is longer than the characteristic reaction time. Despite a long history of field studies and numerical models, it remains exceedingly difficult to measure or model exposure times in the subsurface at the catchment scale. To approach this problem, we developed a unified modelling approach combining measured environmental proxies with an exposure time based reactive transport model. We measured groundwater age, nitrogen and sulfur isotopes, and water chemistry from agricultural wells in an unconfined aquifer in Brittany, France, to quantify changes in nitrate concentration due to dilution and denitrification. Field data showed large differences in nitrate concentrations among wells, associated with differences in the exposure time distributions. By constraining a catchment-scale characteristic reaction time for denitrification with water chemistry proxies and exposure times, we were able to assess rates of denitrification along groundwater flow paths. This unified modeling approach is transferable to other catchments and could be further used to investigate how catchment structure and flow dynamics interact with biogeochemical processes such as denitrification.

  9. Simulation of the transfer of hydrocarbons in unconfined aquifer in tropical zone: the case of benzene

    Science.gov (United States)

    Agnès Kouamé, Amenan; Jaboyedoff, Michel; Derron, Marc-Henri; Kouamé, Kan Jean

    2016-04-01

    Groundwater is the largest global reserves of continental freshwater (Bosca, 2002) and also an important source of drinking water in many parts of the world (Brassington. 2007). However, this resource is today threatened by pollution such as inadequate supply of drinking water services, inaccessibility and / or dilapidated sanitation facilities and excessive use fertilizers, and industrial wastewater and solid waste pesticides (Boubacar, 2010) and the rapid urbanization in great cities (Foster, 2001). Abidjan, the largest city in Côte d'Ivoire is also facing pollution problems such as illegal dumping of waste, waste oil spilled garages, land application of domestic and industrial wastewater, automotive workshops, overexploitation of sand in the Ebrié lagoon, open waste dump of Akouédo and the spill of about 400,000 liters of toxic waste from the ship "Probo Koala" in August 2006. The Abidjan aquifer or the Continental terminal aquifer is the main source of supply drinking water. It is mainly composed of sandy and it is an unconfined aquifer as a whole (Jourda, 1987). According to Gilli and al., (2012), the recharge of unconfined aquifers comes mostly from the infiltration of surface water including rainwater. These waters on their transport in the basement could carry certain pollutants into groundwater. Kouamé (2007) reports a potential groundwater pollution of the "Continental terminal" aquifer in Abidjan. In addition to the cases cited pollution, there has been a proliferation of service stations in the district of Abidjan and this can cause possible pollution. We deemed it necessary to conduct a study on the groundwater pollution of Abidjan by oil in general. We chose benzene to simulate organic pollution in case of accident. To observe the likely evolution of such contaminants in the subsurface, we developed hydrogeological models that couple groundwater flow and benzene transport with FEFLOW software in steady and transient states. The models are composed

  10. Flow to partially penetrating wells in unconfined heterogeneous aquifers: Mean head and interpretation of pumping tests

    Science.gov (United States)

    Dagan, G.; Lessoff, S. C.

    2011-06-01

    A partially penetrating well of length Lw and radius Rw starts to pump at constant discharge Qw at t = 0 from an unconfined aquifer of thickness D. The aquifer is of random and stationary conductivity characterized by KG (geometric mean), σY2 (log conductivity variance), and I and Iv (the horizontal and vertical integral scales). The flow problem is solved under a few simplifying assumptions commonly adopted in the literature for homogeneous media: Rw/Lw ≪ 1, linearization of the free surface condition, and constant drainable porosity n. Additionally, it is assumed that Rw/I well boundary conditions) and that a first-order approximation in σY2 (extended to finite σY2 on a conjectural basis) is adopted. The solution is obtained for the mean head field and the associated water table equation. The main result of the analysis is that the flow domain can be divided into three zones for : (1) the neighborhood of the well R ≪ I, where = (Qw/LwKA)h0(R, z, tKefuv/nD), with h0 being the zero-order solution pertaining to a homogeneous and isotropic aquifer, KA being the conductivity arithmetic mean, and Kefuv being the effective vertical conductivity in mean uniform flow, (2) an exterior zone R ⪆ I in which ?H? = (Qw/LwKefuh)h0(R?, z, tKefuv/nD), with Kefuh being the horizontal effective conductivity, and (3) an intermediate zone in which the solution requires a few numerical quadratures, not carried out here. The application to pumping tests reveals that identification of the aquifer parameters for homogeneous and anisotropic aquifers by commonly used methods can be applied for the drawdown measured in an observation well of length Low?Iv (to ensure exchange of space and ensemble head averages) in the second zone in order to identify Kefuh, Kefuv, and n. In contrast, the use of the drawdown in the well (first zone) leads to an overestimation of Kefuh by the factor KA/Kefuh.

  11. Semi-analytical solution for flow in a leaky unconfined aquifer toward a partially penetrating pumping well

    Science.gov (United States)

    Malama, Bwalya; Kuhlman, Kristopher L.; Barrash, Warren

    2008-07-01

    SummaryA semi-analytical solution is presented for the problem of flow in a system consisting of unconfined and confined aquifers, separated by an aquitard. The unconfined aquifer is pumped continuously at a constant rate from a well of infinitesimal radius that partially penetrates its saturated thickness. The solution is termed semi-analytical because the exact solution obtained in double Laplace-Hankel transform space is inverted numerically. The solution presented here is more general than similar solutions obtained for confined aquifer flow as we do not adopt the assumption of unidirectional flow in the confined aquifer (typically assumed to be horizontal) and the aquitard (typically assumed to be vertical). Model predicted results show significant departure from the solution that does not take into account the effect of leakage even for cases where aquitard hydraulic conductivities are two orders of magnitude smaller than those of the aquifers. The results show low sensitivity to changes in radial hydraulic conductivities for aquitards that are two or more orders of magnitude smaller than those of the aquifers, in conformity to findings of earlier workers that radial flow in aquitards may be neglected under such conditions. Hence, for cases were aquitard hydraulic conductivities are two or more orders of magnitude smaller than aquifer conductivities, the simpler models that restrict flow to the radial direction in aquifers and to the vertical direction in aquitards may be sufficient. However, the model developed here can be used to model flow in aquifer-aquitard systems where radial flow is significant in aquitards.

  12. Analysis of pumping tests of partially penetrating wells in an unconfined aquifer using inverse numerical optimization

    Science.gov (United States)

    Hvilshøj, S.; Jensen, K. H.; Barlebo, H. C.; Madsen, B.

    1999-08-01

    Inverse numerical modeling was applied to analyze pumping tests of partially penetrating wells carried out in three wells established in an unconfined aquifer in Vejen, Denmark, where extensive field investigations had previously been carried out, including tracer tests, mini-slug tests, and other hydraulic tests. Drawdown data from multiple piezometers located at various horizontal and vertical distances from the pumping well were included in the optimization. Horizontal and vertical hydraulic conductivities, specific storage, and specific yield were estimated, assuming that the aquifer was either a homogeneous system with vertical anisotropy or composed of two or three layers of different hydraulic properties. In two out of three cases, a more accurate interpretation was obtained for a multi-layer model defined on the basis of lithostratigraphic information obtained from geological descriptions of sediment samples, gammalogs, and flow-meter tests. Analysis of the pumping tests resulted in values for horizontal hydraulic conductivities that are in good accordance with those obtained from slug tests and mini-slug tests. Besides the horizontal hydraulic conductivity, it is possible to determine the vertical hydraulic conductivity, specific yield, and specific storage based on a pumping test of a partially penetrating well. The study demonstrates that pumping tests of partially penetrating wells can be analyzed using inverse numerical models. The model used in the study was a finite-element flow model combined with a non-linear regression model. Such a model can accommodate more geological information and complex boundary conditions, and the parameter-estimation procedure can be formalized to obtain optimum estimates of hydraulic parameters and their standard deviations.

  13. Estimation of hydraulic parameters from an unconfined aquifer test conducted in a glacial outwash deposit, Cape Cod, Massachusetts

    Science.gov (United States)

    Moench, Allen F.; Garabedian, Stephen P.; LeBlanc, Denis R.

    2001-01-01

    An aquifer test conducted in a sand and gravel, glacial outwash deposit on Cape Cod, Massachusetts was analyzed by means of a model for flow to a partially penetrating well in a homogeneous, anisotropic unconfined aquifer. The model is designed to account for all significant mechanisms expected to influence drawdown in observation piezometers and in the pumped well. In addition to the usual fluid-flow and storage processes, additional processes include effects of storage in the pumped well, storage in observation piezometers, effects of skin at the pumped-well screen, and effects of drainage from the zone above the water table.

  14. GEOCHEMICAL ASSESSMENT OF THE UNCONFINED AQUIFER IN A RECENTLY RECLAIMED WETLAND AREA: A CASE STUDY FROM THE PO RIVER DELTA

    Directory of Open Access Journals (Sweden)

    Dario Di Giuseppe

    2013-09-01

    Full Text Available This study focusses on the distribution of main anions and nitrogen species in the unconfined aquifer of a recently reclaimed land. In a 6 ha experimental field, 10 piezometers for water level measurement and groundwater sampling have been installed. After one year of monitoring, results show that the high chloride and ammonium concentrations are due to inherited from the previous brackish conditions and to organic matter mineralization, respectively. Seasonal variations and Cl/Br ratio show that the 1 m deep sub surface drainage system is the main factor conditioning the chemical characteristics and the piezometric depth of the aquifer

  15. A semianalytical model to predict recovery of light, nonaqueous phase liquids from unconfined aquifers

    International Nuclear Information System (INIS)

    Waddill, D.W.

    1997-01-01

    This paper describes the development and testing of a semianalytical model that may be used to design LNAPL containment and recovery systems at spill sites. The objective of this study was to derive an enhanced semianalytical algorithm for calculating recovery and trapping of free phase oil. The enhancements were derived and evaluated by comparison with an established numerical model that describes transient flow of oil and water. The semianalytical model employs an analytical solution for steady-state drawdown in an unconfined aquifer due to water pumping. When pumping rates are sufficient to contain the separate phase plume, the model calculates recoverable and residual oil volumes based on the initial free oil distribution. Refinements were implemented to calculate the water-table drawdown and the maximum unsaturated zone residual saturation (S og ) as functions of soil type. Also the influence of hysteresis on the oil-water capillary fringe was incorporated into the calculation of oil trapping below a rising oil-water interface. A method was derived to reduce saturated zone trapping to account for oil recovery that occurs while pumping proceeds. The above enhancements yielded close agreement between the semianalytical model and the transient model predictions of recoverable oil and residua oil in the unsaturated and saturated zones. The models were compared for hypothetical gasoline spills in a sandy and a silt loam soil, using a range of pumping rates and regional water-table fluctuations. Field data from a pipeline leak were evaluated by the semianalytical model for hypothetical scenarios involving oil recovery from three wells and a falling regional water table

  16. Saturated-unsaturated flow to a well with storage in a compressible unconfined aquifer

    Science.gov (United States)

    Mishra, Phoolendra Kumar; Neuman, Shlomo P.

    2011-05-01

    Mishra and Neuman (2010) developed an analytical solution for flow to a partially penetrating well of zero radius in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from responses recorded in the saturated and/or unsaturated zones. Their solution accounts for horizontal as well as vertical flows in each zone. It represents unsaturated zone constitutive properties in a manner that is at once mathematically tractable and sufficiently flexible to provide much improved fits to standard constitutive models. In this paper we extend the solution of [2010] to the case of a finite diameter pumping well with storage; investigate the effects of storage in the pumping well and delayed piezometer response on drawdowns in the saturated and unsaturated zones as functions of position and time; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the [1980]- [1976] model; use our solution to analyze 11 transducer-measured drawdown records from a seven-day pumping test conducted by University of Waterloo researchers at the Canadian Forces Base Borden in Ontario, Canada; validate our parameter estimates against manually-measured drawdown records in 14 other piezometers at Borden; and compare (a) our estimates of aquifer parameters with those obtained on the basis of all these records by [2008], (b) on the basis of 11 transducer-measured drawdown records by [2007], (c) our estimates of van Genuchten-Mualem parameters with those obtained on the basis of laboratory drainage data from the site by [1992], and (d) our corresponding prediction of how effective saturation varies with elevation above the initial water table under static conditions with a profile based on water contents measured in a neutron access tube at a radial distance of about 5 m from the center of the pumping well. We also use our solution to analyze 11 transducer-measured drawdown

  17. Determining flow, recharge, and vadose zone drainage in an unconfined aquifer from groundwater strontium isotope measurements, Pasco Basin, WA

    International Nuclear Information System (INIS)

    2004-01-01

    Strontium isotope compositions (87Sr/86Sr) measured in groundwater samples from 273 wells in the Pasco Basin unconfined aquifer below the Hanford Site show large and systematic variations that provide constraints on groundwater recharge, weathering rates of the aquifer host rocks, communication between unconfined and deeper confined aquifers, and vadose zone-groundwater interaction. The impact of millions of cubic meters of wastewater discharged to the vadose zone (103-105 times higher than ambient drainage) shows up strikingly on maps of groundwater 87Sr/86Sr. Extensive access through the many groundwater monitoring wells at the site allows for an unprecedented opportunity to evaluate the strontium geochemistry of a major aquifer, hosted primarily in unconsolidated sediments, and relate it to both long term properties and recent disturbances. Groundwater 87Sr/86Sr increases systematically from 0.707 to 0.712 from west to east across the Hanford Site, in the general direction of groundwater flow, as a result of addition of Sr from the weathering of aquifer sediments and from diffuse drainage through the vadose zone. The lower 87Sr/86Sr groundwater reflects recharge waters that have acquired Sr from Columbia River Basalts. Based on a steady-state model of Sr reactive transport and drainage, there is an average natural drainage flux of 0-1.4 mm/yr near the western margin of the Hanford Site, and ambient drainage may be up to 30 mm/yr in the center of the site assuming an average bulk rock weathering rate of 10-7.5 g/g/yr

  18. Position paper on the applicability of supplemental standards to the uppermost aquifer at the Uranium Mill Tailings Vitro Processing Site, Salt Lake City, Utah

    International Nuclear Information System (INIS)

    1996-03-01

    This report documents the results of the evaluation of the potential applicability of supplemental standards to the uppermost aquifer underlying the Uranium Mill Tailings Remedial Action (UMTRA) Project, Vitro Processing Site, Salt Lake City, Utah. There are two goals for this evaluation: provide the landowner with information to make an early qualitative decision on the possible use of the Vitro property, and evaluate the proposed application of supplemental standards as the ground water compliance strategy at the site. Justification of supplemental standards is based on the contention that the uppermost aquifer is of limited use due to wide-spread ambient contamination not related to the previous site processing activities. In support of the above, this report discusses the site conceptual model for the uppermost aquifer and related hydrogeological systems and establishes regional and local background water quality. This information is used to determine the extent of site-related and ambient contamination. A risk-based evaluation of the contaminants' effects on current and projected land uses is also provided. Reports of regional and local studies and U.S. Department of Energy (DOE) site investigations provided the basis for the conceptual model and established background ground water quality. In addition, a limited field effort (4 through 28 March 1996) was conducted to supplement existing data, particularly addressing the extent of contamination in the northwestern portion of the Vitro site and site background ground water quality. Results of the field investigation were particularly useful in refining the conceptual site model. This was important in light of the varied ground water quality within the uppermost aquifer. Finally, this report provides a critical evaluation, along with the related uncertainties, of the applicability of supplemental standards to the uppermost aquifer at the Salt Lake City Vitro processing site

  19. Determination of hydrogeological conditions in large unconfined aquifer: A case study in central Drava plain (NE Slovenia)

    Science.gov (United States)

    Keršmanc, Teja; Brenčič, Mihael

    2016-04-01

    In several countries, many unregulated landfills exits which releasing harmful contaminations to the underlying aquifer. The Kidričevo industrial complex is located in southeastern part of Drava plain in NW Slovenia. In the past during the production of alumina and aluminum approximately 11.2 million tons of wastes were deposit directly on the ground on two landfills covering an area of 61 hectares. Hydrogeological studies were intended to better characterized conditions bellow the landfill. Geological and hydrogeological conditions of Quaternary unconfined aquifer were analyzed with lithological characterization of well logs and cutting debris and XRF diffraction of silty sediments on 9 boreholes. Hydrogeological conditions: hydraulic permeability aquifer was determined with hydraulic tests and laboratory grain size analyses where empirical USBR and Hazen methods were applied. Dynamics of groundwater was determined by groundwater contour maps and groundwater level fluctuations. The impact of landfill was among chemical analyses of groundwater characterised by electrical conductivity measurements and XRF spectrometry of sand sediments. The heterogeneous Quaternary aquifer composed mainly of gravel and sand, is between 38 m and 47.5 m thick. Average hydraulic permeability of aquifer is within the decade 10-3 m/s. Average hydraulic permeability estimated on grain size curves is 6.29*10-3 m/s, and for the pumping tests is 4.0*10-3 m/s. General direction of groundwater flow is from west to east. During high water status the groundwater flow slightly changes flow direction to the southwest and when pumping station in Kidričevo (NW of landfill) is active groundwater flows to northeast. Landfills have significant impact on groundwater quality.

  20. Spatial variability of hydraulic conductivity of an unconfined sandy aquifer determined by a mini slug test

    DEFF Research Database (Denmark)

    Bjerg, Poul Løgstrup; Hinsby, Klaus; Christensen, Thomas Højlund

    1992-01-01

    The spatial variability of the hydraulic conductivity in a sandy aquifer has been determined by a mini slug test method. The hydraulic conductivity (K) of the aquifer has a geometric mean of 5.05 × 10−4 m s−1, and an overall variance of 1n K equal to 0.37 which corresponds quite well to the results...... obtained by two large scale tracer experiments performed in the aquifer. A geological model of the aquifer based on 31 sediment cores, proposed three hydrogeological layers in the aquifer concurrent with the vertical variations observed with respect to hydraulic conductivity. The horizontal correlation......, to be in the range of 0.3–0.5 m compared with a value of 0.42 m obtained in one of the tracer tests performed....

  1. Natural Recharge to the Unconfined Aquifer System on the Hanford Site from the Greater Cold Creek Watershed: Progress Report 2004

    Energy Technology Data Exchange (ETDEWEB)

    Waichler, Scott R.; Wigmosta, Mark S.; Coleman, Andre M.

    2004-09-14

    Movement of contaminants in groundwater at the Hanford Site is heavily dependent on recharge to the unconfined aquifer. As the effects of past artificial discharges dissipate, the water table is expected to return to more natural conditions, and natural recharge will become the driving force when evaluating future groundwater flow conditions and related contaminant transport. Previous work on the relationship of natural recharge to groundwater movement at the Hanford Site has focused on direct recharge from infiltrating rainfall and snowmelt within the area represented by the Sitewide Groundwater Model (SGM) domain. However, part of the groundwater recharge at Hanford is provided by flow from Greater Cold Creek watershed (GCC), a large drainage area on the western boundary of the Hanford Site that includes Cold Creek Valley, Dry Creek Valley, and the Hanford side of Rattlesnake Mountain. This study was undertaken to estimate the recharge from GCC, which is believed to enter the unconfined aquifer as both infiltrating streamflow and shallow subsurface flow. To estimate recharge, the Distributed Hydrology-Soil-Vegetation Model (DHSVM) was used to simulate a detailed water balance of GCC from 1956 to 2001 at a spatial resolution of 200~m and a temporal resolution of one hour. For estimating natural recharge to Hanford from watersheds along its western and southwestern boundaries, the most important aspects that need to be considered are 1)~distribution and relative magnitude of precipitation and evapotranspiration over the watershed, 2)~streamflow generation at upper elevations and infiltration at lower elevations during rare runoff events, and 3)~permeability of the basalt bedrock surface underlying the soil mantle.

  2. An analytical model for flow induced by a constant-head pumping in a leaky unconfined aquifer system with considering unsaturated flow

    Science.gov (United States)

    Lin, Ye-Chen; Li, Ming-Hsu; Yeh, Hund-Der

    2017-09-01

    A new mathematical model is developed to describe the flow in response to a constant-head pumping (or constant-head test, CHT) in a leaky unconfined aquifer system of infinite lateral extent with considering unsaturated flow. The model consists of an unsaturated zone on the top, an unconfined aquifer in the middle, and a second aquifer (aquitard) at the bottom. The unsaturated flow is described by Richard's equation, and the flows in unconfined aquifer and second layer are governed by the groundwater flow equation. The well partially penetrates the unconfined aquifer with a constant head in the well due to CHT. The governing equations of the model are linearized by the perturbation method and Gardner's exponential model is adopted to describe the soil retention curves. The solution of the model for drawdown distribution is obtained by applying the methods of Laplace transform and Weber transform. Then the solution for the wellbore flowrate is derived from the drawdown solution with Darcy's law. The issue of the equivalence of normalized drawdown predicted by the present solution for constant-head pumping and Tartakovsky and Neuman's (2007) solution for constant-rate pumping is discussed. On the basis of the wellbore flowrate solution, the results of the sensitivity analysis indicate that the wellbore flowrate is very sensitive to the changes in the radial hydraulic conductivity and the thickness of the saturated zone. Moreover, the results predicted from the present wellbore flowrate solution indicate that this new solution can reduce to Chang's et al. (2010a) solution for homogenous aquifers when the dimensionless unsaturated exponent approaches 100. The unsaturated zone can be considered as infinite extent in the vertical direction if the thickness ratio of the unsaturated zone to the unconfined aquifer is equal to or greater than one. As for the leakage effect, it can be ignored when the vertical hydraulic conductivity ratio (i.e., the vertical hydraulic

  3. Water-table altitude of the unconfined aquifer, Wood River Valley aquifer system, south-central Idaho, October 2012.

    Data.gov (United States)

    Department of the Interior — Water levels in 93 wells completed in the Wood River Valley aquifer system were measured during October 22–24, 2012; these wells are part of a network established...

  4. Transient Inverse Calibration of Site-Wide Groundwater Model to Hanford Operational Impacts from 1943 to 1996-Alternative Conceptual Model Considering Interaction with Uppermost Basalt Confined Aquifer; FINAL

    International Nuclear Information System (INIS)

    Vermeul, Vince R; Cole, Charles R; Bergeron, Marcel P; Thorne, Paul D; Wurstner, Signe K

    2001-01-01

    The baseline three-dimensional transient inverse model for the estimation of site-wide scale flow parameters, including their uncertainties, using data on the transient behavior of the unconfined aquifer system over the entire historical period of Hanford operations, has been modified to account for the effects of basalt intercommunication between the Hanford unconfined aquifer and the underlying upper basalt confined aquifer. Both the baseline and alternative conceptual models (ACM-1) considered only the groundwater flow component and corresponding observational data in the 3-Dl transient inverse calibration efforts. Subsequent efforts will examine both groundwater flow and transport. Comparisons of goodness of fit measures and parameter estimation results for the ACM-1 transient inverse calibrated model with those from previous site-wide groundwater modeling efforts illustrate that the new 3-D transient inverse model approach will strengthen the technical defensibility of the final model(s) and provide the ability to incorporate uncertainty in predictions related to both conceptual model and parameter uncertainty

  5. Use of static Quantitative Microbial Risk Assessment to determine pathogen risks in an unconfined carbonate aquifer used for Managed Aquifer Recharge.

    Science.gov (United States)

    Toze, Simon; Bekele, Elise; Page, Declan; Sidhu, Jatinder; Shackleton, Mark

    2010-02-01

    Managed Aquifer Recharge (MAR) is becoming a mechanism used for recycling treated wastewater and captured urban stormwater and is being used as a treatment barrier to remove contaminants such as pathogens from the recharged water. There is still a need, however, to demonstrate the effectiveness of MAR to reduce any residual risk of pathogens in the recovered water. A MAR research site recharging secondary treated wastewater in an unconfined carbonate aquifer was used in conjunction with a static Quantitative Microbial Risk Assessment (QMRA) to assess the microbial pathogen risk in the recovered water following infiltration and aquifer passage. The research involved undertaking a detailed hydrogeological assessment of the aquifer at the MAR site and determining the decay rates of reference pathogens from an in-situ decay study. These variables along with literature data were then used in the static QMRA which demonstrated that the recovered water at this site did not meet the Australian Guidelines for recycled water when used for differing private green space irrigation scenarios. The results also confirmed the importance of obtaining local hydrogeological data as local heterogeneity can influence of residence time in the aquifer which, in turn, influences the outcomes. The research demonstrated that a static QMRA can be used to determine the residual risk from pathogens in recovered water and showed that it can be a valuable tool in the preliminary design and operation of MAR systems and the incorporation of complementary engineered treatment processes to ensure that there is acceptable health risk from the recovered water. Crown Copyright 2009. Published by Elsevier Ltd. All rights reserved.

  6. Improved forward and inverse analyses of saturated-unsaturated flow toward a well in a compressible unconfined aquifer

    Science.gov (United States)

    Mishra, Phoolendra Kumar; Neuman, Shlomo P.

    2010-07-01

    We present an analytical solution for flow to a partially penetrating well in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from drawdowns recorded in the saturated and/or unsaturated zone. We improve upon a previous such solution due to Tartakovsky and Neuman (2007) by (1) adopting a more flexible representation of unsaturated zone constitutive properties and (2) allowing the unsaturated zone to have finite thickness. Both solutions account for horizontal as well as vertical flows throughout the system. We investigate the effects of unsaturated zone constitutive parameters and thickness on drawdowns in the saturated and unsaturated zones as functions of position and time; demonstrate the development of significant horizontal hydraulic gradients in the unsaturated zone in response to pumping; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten-Mualem constitutive model; use our solution to analyze drawdown data from a pumping test conducted by the U.S. Geological Survey at Cape Cod, Massachusetts; and compare our estimates of van Genuchten-Mualem parameters with laboratory values obtained for similar materials in the area.

  7. Fate and origin of 1,2-dichloropropane in an unconfined shallow aquifer.

    Science.gov (United States)

    Tesoriero, A J; Löffler, F E; Liebscher, H

    2001-02-01

    A shallow aquifer with different redox zones overlain by intensive agricultural activity was monitored for the occurrence of 1,2-dichloropropane (DCP) to assess the fate and origin of this pollutant. DCP was detected more frequently in groundwater samples collected in aerobic and nitrate-reducing zones than those collected from iron-reducing zones. Simulated DCP concentrations for groundwater entering an iron-reducing zone were calculated from a fate and transport model that included dispersion, sorption, and hydrolysis but not degradation. Simulated concentrations were well in excess of measured values, suggesting that microbial degradation occurred in the iron-reducing zone. Microcosm experiments were conducted using aquifer samples collected from iron-reducing and aerobic zones to evaluate the potential for microbial degradation of DCP and to explain field observations. Hydrogenolysis of DCP and production of monochlorinated propanes in microcosm experiments occurred only with aquifer materials collected from the iron-reducing zone, and no dechlorination was observed in microcosms established with aquifer materials collected from the aerobic zones. Careful analyses of the DCP/1,2,2-trichloropropane ratios in groundwater indicated that older fumigant formulations were responsible for the high levels of DCP present in this aquifer.

  8. Evaluation of unconfined-aquifer parameters from pumping test data by nonlinear least squares

    Science.gov (United States)

    Heidari, Manoutchehr; Wench, Allen

    1997-05-01

    Nonlinear least squares (NLS) with automatic differentiation was used to estimate aquifer parameters from drawdown data obtained from published pumping tests conducted in homogeneous, water-table aquifers. The method is based on a technique that seeks to minimize the squares of residuals between observed and calculated drawdown subject to bounds that are placed on the parameter of interest. The analytical model developed by Neuman for flow to a partially penetrating well of infinitesimal diameter situated in an infinite, homogeneous and anisotropic aquifer was used to obtain calculated drawdown. NLS was first applied to synthetic drawdown data from a hypothetical but realistic aquifer to demonstrate that the relevant hydraulic parameters (storativity, specific yield, and horizontal and vertical hydraulic conductivity) can be evaluated accurately. Next the method was used to estimate the parameters at three field sites with widely varying hydraulic properties. NLS produced unbiased estimates of the aquifer parameters that are close to the estimates obtained with the same data using a visual curve-matching approach. Small differences in the estimates are a consequence of subjective interpretation introduced in the visual approach.

  9. Cross-well slug testing in unconfined aquifers: A case study from the Sleepers River Watershed, Vermont

    Science.gov (United States)

    Belitz, K.; Dripps, W.

    1999-01-01

    Normally, slug test measurements are limited to the well in which the water level is perturbed. Consequently, it is often difficult to obtain reliable estimates of hydraulic properties, particularly if the aquifer is anisotropic or if there is a wellbore skin. In this investigation, we use partially penetrating stress and observation wells to evaluate specific storage, radial hydraulic conductivity and anisotropy of the aquifer, and the hydraulic conductivity of the borehole skin. The study site is located in the W9 subbasin of the Sleepers River Research Watershed, Vermont. At the site, ~3 m of saturated till are partially penetrated by a stress well located in the center of the unconfined aquifer and six observation wells located above, below, and at the depth of the stress well at radial distances of 1.2 and 2.4 m. The observation wells were shut in with inflatable packers. The semianalytical solution of Butler (1995) was used to conduct a sensitivity analysis and to interpret slug test results. The sensitivity analysis indicates that the response of the stress well is primarily sensitive to radial hydraulic conductivity, less sensitive to anisotropy and the conductivity of the borehole skin, and nearly insensitive to specific storage. In contrast, the responses of the observation wells are sensitive to all four parameters. Interpretation of the field data was facilitated by generating type curves in a manner analogous to the method of Cooper et al. (1967). Because the value of radial hydraulic conductivity is obtained from a match point, the number of unknowns is reduced to three. The estimated values of radial hydraulic conductivity and specific storage are comparable to those derived from the methods of Bouwer and Rice (1976) and Cooper et al. (1967). The values and skin conductivity, however, could not have been obtained without the use of observation wells.Normally, slug test measurements are limited to the well in which the water level is perturbed

  10. Karst connections between unconfined aquifers and the Upper Floridan aquifer in south Georgia: geophysical evidence and hydrogeological models

    Science.gov (United States)

    Thieme, D. M.; Denizman, C.

    2011-12-01

    Buried karst features in sedimentary rocks of the south Georgia Coastal Plain present a challenge for hydrogeological models of recharge and confined flow within the underlying Upper Floridan aquifer. The Withlacoochee River, the trunk stream for the area, frequently disappears into subsurface caverns as it makes its way south to join the Suwannee River in northern Florida. The Withlacoochee also receives inputs from small ponds and bays which in turn receive spring and seep groundwater inputs. We have mapped karst topography at the "top of rock" using ground-penetrating radar (GPR). Up to seven meters of relief is indicated for the paleotopography on Miocene to Pliocene rocks, contrasting with the more subdued relief of the modern landscape. Current stratigraphic and hydrogeological reconstructions do not incorporate this amount of relief or lateral variation in the confining beds. One "pipe" which is approximately four meters in diameter is being mapped in detail. We have field evidence at this location for rapid movement of surficial pond and river water with a meteoric signature through several separate strata of sedimentary rock into an aquifer in the Hawthorn formation. We use our geophysical and hydrological field evidence to constrain quantitative hydrogeological models for the flow rates into and out of both this upper aquifer and the underlying Upper Floridan aquifer, which is generally considered to be confined by the clays of the Hawthorn.

  11. Geochemical evidence for groundwater behavior in an unconfined aquifer, south Florida

    Science.gov (United States)

    Meyers, Jayson B.; Swart, Peter K.; Meyers', Janet L.

    1993-07-01

    Five well sites have been investigated along an east-west transect across the surfical aquifer system (SAS) of south Florida. Differences between rainfall during wet seasons (June-October) and evaporation during dry seasons (November-May) give surface waters of this region isotopically light ( δ 18O -22‰ and δ D -7.6‰ ) and heavy ( δ 18O +4.2‰ ) compositions, respectively. Surface waters and shallow groundwaters are enriched in 18O and D to the west, which is consistent with westward decrease in equal excess of rainfall. In the shallow portion of the SAS (less than 20 m, Biscayne sub-aquifer) heterogeneous stable isotopic compositions occur over short spans of time (less than 90 days), reflecting seasonal changes in the isotopic composition of recharge and rapid flushing. Homogeneous stable isotopic compositions occur below the Biscayne sub-aquifer, marking the zone of delayed circulation. Surface evaporation calculated from a stable isotope evaporation model agrees with previously published estimates of 75-95% by physical evaporation measurements and water budget calculations. This model contains many parameters that are assumed to be mean values, but short-term variability in some of these parameters may make this model unsuitable for the application of yearly mean values. For the Everglades, changes in the isotopic composition of atmospheric vapor during the dry season may cause the model to yield anomalous results when annual mean values are used. Chloride-enriched waters (more than 280 mg 1 -1) form a plume emanating from the bottom central portion of the transect. Elevated chloride concentration and light stable isotopic composition ( δ 18O ≈ -2‰ , δ D ≈ -8‰ ) suggest this plume is probably caused not by salinity of residual seawater in the aquifer, but by leakage from the minor artesian water-bearing zone of the Floridan aquifer system. Stable isotope values from Floridan aquifer groundwater plot close to the meteoric water line, in the

  12. Improved solution for saturated-unsaturated flow to a partially penetrating well in a compressible unconfined aquifer

    Science.gov (United States)

    Mishra, P. K.; Neuman, S. P.

    2009-12-01

    Tartakovsky and Neuman [2007] developed an analytical solution for flow to a partially penetrating well pumping at a constant rate from a compressible unconfined aquifer considering an unsaturated zone of infinite thickness. In their solution three-dimensional, axially symmetric unsaturated flow was described by a linearized version of Richards’ equation in which both relative hydraulic conductivity and water content vary exponentially with incremental capillary pressure head relative to its air entry value. Both exponential functions were characterized by a common exponent. We present an improved solution in which relative hydraulic conductivity and water content are characterized by separate parameters and the unsaturated zone has finite thickness. Our four-parameter representation of these functions is more flexible than the three-parameter version of Mathias and Butler [2006], who consider flow in the unsaturated zone to be strictly vertical and the pumping well to be fully penetrating. We investigate the effects of unsaturated zone thickness and constitutive parameters on drawdown in the unsaturated and saturated zones as functions of position and time. We then use our new solution to analyze data from synthetic and real pumping tests.

  13. On the coupled unsaturated–saturated flow process induced by vertical, horizontal, and slant wells in unconfined aquifers

    Directory of Open Access Journals (Sweden)

    X. Liang

    2017-03-01

    established with special consideration of the coupled unsaturated–saturated flow process and the well orientation. Groundwater flow in the saturated zone is described by a three-dimensional governing equation and a linearized three-dimensional Richards' equation in the unsaturated zone. A solution in the Laplace domain is derived by the Laplace–finite-Fourier-transform and the method of separation of variables, and the semi-analytical solutions are obtained using a numerical inverse Laplace method. The solution is verified by a finite-element numerical model. It is found that the effects of the unsaturated zone on the drawdown of a pumping test exist at any angle of inclination of the pumping well, and this impact is more significant in the case of a horizontal well. The effects of the unsaturated zone on the drawdown are independent of the length of the horizontal well screen. The vertical well leads to the largest water volume drained from the unsaturated zone (W during the early pumping time, and the effects of the well orientation on W values become insignificant at the later time. The screen length of the horizontal well does not affect W for the whole pumping period. The proposed solutions are useful for the parameter identification of pumping tests with a general well orientation (vertical, horizontal, and slant in unconfined aquifers affected from above by the unsaturated flow process.

  14. Evaluation of sampling equipment for RCRA [Resource Conservation and Recovery Act] monitoring in a deep unconfined aquifer

    International Nuclear Information System (INIS)

    Kasper, R.B.; Serkowski, J.A.

    1988-02-01

    Acceptable sampling devices identified include gas-operated bladder pumps and bailers constructed of nonreactive materials. In arid portions of the western United States, depths to ground water, which are often greater than 100 feet, make the use of bailers extremely time consuming. The efficiency of gas-operated bladder pumps decreases with depth, and special design and construction is often needed to accommodate higher gas pressures. Commercially available sampling pumps were evaluated for their suitability as sampling and purging equipment for installation in monitoring wells in a deep, unconfined aquifer. The test was conducted in a well where the depth to ground water was 340 feet. The objective was to identify equipment capable of discharge rates suitable for sampling (∼0.025 gpm) and, if possible, for purging (>1 gpm). The potential for physical or chemical alteration of the water sample was evaluated from literature sources and not specifically tested. Four positive-displacement pumps were tested, consisting of two bladder pumps, a gas-driven piston pump, and a mechanically-driven pump. All pumps could be installed in a 2-inch diameter well, although this was not important for the planned application. 4 refs., 1 tab

  15. Procedures, analysis, and comparison of groundwater velocity measurement methods for unconfined aquifers

    International Nuclear Information System (INIS)

    Kearl, P.M.; Dexter, J.J.; Price, J.E.

    1988-09-01

    Six methods for determining the average linear velocity of ground- water were tested at two separate field sites. The methods tested include bail tests, pumping tests, wave propagation, tracer tests, Geoflo Meter/reg sign/, and borehole dilution. This report presents procedures for performing field tests and compares the results of each method on the basis of application, cost, and accuracy. Comparisons of methods to determine the ground-water velocity at two field sites show certain methods yield similar results while other methods measure significantly different values. The literature clearly supports the reliability of pumping tests for determining hydraulic conductivity. Results of this investigation support this finding. Pumping tests, however, are limited because they measure an average hydraulic conductivity which is only representative of the aquifer within the radius of influence. Bail tests are easy and inexpensive to perform. If the tests are conducted on the majority of wells at a hazardous waste site, then the heterogeneity of the site aquifer can be assessed. However, comparisons of bail-test results with pumping-test and tracer-test results indicate that the accuracy of the method is questionable. Consequently, the principal recommendation of this investigation, based on cost and reliability of the ground-water velocity measurement methods, is that bail tests should be performed on all or a majority of monitoring wells at a site to determine the ''relative'' hydraulic conductivities

  16. Effects of a Changing Climate on Seasonal Variation in Natural Recharge of Unconfined Coastal Aquifers

    Science.gov (United States)

    Antonellini, Marco; Nella Mollema, Pauline

    2013-04-01

    Irregular rainfall patterns throughout the year result in the discontinuous natural recharge of coastal aquifers, which has an effect on the size of freshwater lenses present in sandy deposits. The thickness of the freshwater lenses is important in the context of farmland salinization and coastal ecosystems survival. This study presents numerical models that simulate continuous and discontinuous recharge in sandy coastal aquifers and the thickness of resulting fresh water lenses under current and future climate scenarios. Temperature data for the period 1960-1990 from LOCCLIM FAO and from the IPCC SRES A1b scenario for 2070-2100, have been used to calculate the potential evapotranspiration. Potential recharge was defined as the difference between the precipitation and potential evapotranspiration in twelve locations around the world: Ameland (The Netherlands), Auckland and Wellington (New Zealand), Hong Kong, Ravenna (Italy), Mekong (Vietnam), Mumbai (India), New Jersey (USA), Nile Delta (Egypt), Kobe and Tokyo (Japan), and Singapore. These locations have shallow coastal aquifers along low lying coasts and comparable aquifer structure, which is the result of similar sediment supply and deposition in the Holocene as well as by the sea level changes from the last ice age to the present time. Particular attention has been paid to temporal variations of natural recharge that can vary from continuous recharge throughout the year to discontinuous recharge. The most dramatic reduction in the magnitude of potential annual recharge by the end of this century will occur at lower latitudes (Mumbai, Singapore, Hong Kong and Mekong). The most pronounced change in length of the dry period occurs for Kobe (Japan) and Singapore even though the total annual amount of recharge remains practically the same. The Influence of variable recharge on the size of freshwater lenses surrounded by saline water is simulated with the SEAWAT model. Models where the recharge is applied

  17. Spatial and temporal dynamics of the microbial community in the Hanford unconfined aquifer

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Xueju; McKinley, James P.; Resch, Charles T.; Kaluzny, Rachael M.; Lauber, C.; Fredrickson, Jim K.; Knight, Robbie C.; Konopka, Allan

    2012-03-29

    Pyrosequencing analysis of 16S rRNA genes was used to study temporal dynamics of groundwater Bacteria and Archaea over 10 months within 3 well clusters separated by ~30 m and located 250 m from the Columbia River on the Hanford Site, WA. Each cluster contained 3 wells screened at different depths ranging from 10 to 17 m that differed in hydraulic conductivities. Representative samples were selected for analyses of prokaryotic 16S and eukaryotic 18S rRNA gene copy numbers. Temporal changes in community composition occurred in all 9 wells over the 10 month sampling period. However, there were particularly strong effects near the top of the water table when the seasonal rise in the Columbia River caused river water intrusion at the top of the aquifer. The occurrence and disappearance of some microbial assemblages (such as Actinobacteria ACK-M1) were correlated to river water intrusion. This seasonal impact on microbial community structure was greater in the shallow saturated zone than deeper in the aquifer. Spatial and temporal patterns for several 16S rRNA gene operational taxonomic units associated with particular physiological functions (e.g.methane oxidizers and metal reducers) suggests dynamic changes in fluxes of electron donors and acceptors over an annual cycle. In addition, temporal dynamics in eukaryotic 18S rRNA gene copies and the dominance of protozoa in 18S clone libraries suggest that bacterial community dynamics could be affected not only by the physical and chemical environment, but also by top-down biological control.

  18. Three-dimensional saturated-unsaturated flow with axial symmetry to a partially penetrating well in a compressible unconfined aquifer

    Science.gov (United States)

    Tartakovsky, Guzel D.; Neuman, Shlomo P.

    2007-01-01

    A new analytical solution is presented for the delayed response process characterizing flow to a partially penetrating well in an unconfined aquifer. The new solution generalizes that of Neuman (1972, 1974) by accounting for unsaturated flow above the water table. Three-dimensional, axially symmetric flow in the unsaturated zone is described by a linearized version of Richards' equation in which hydraulic conductivity and water content vary exponentially with incremental capillary pressure head relative to its air entry value (defining the interface between the saturated and unsaturated zones). Unsaturated soil properties are characterized by an exponent κ having the dimension of inverse length or, equivalently, a dimensionless exponent κD = κb, where b is initial saturated thickness. Our treatment of the unsaturated zone is similar to that of Kroszynski and Dagan (1975), who, however, have ignored internal (artesian) aquifer storage. According to Kroszynski and Dagan, aquifers that are not excessively shallow have values of κD (their parameter a) much greater than 10. We find that in such typical cases, unsaturated flow has little impact on early and late dimensionless time drawdown a short distance below the water table. Unsaturated flow causes drawdown to increase slightly at intermediate dimensionless time values that represent transition from an early artesian-dominated to a late water-table-dominated flow regime. Delayed drainage from the unsaturated zone becomes less and less important as κD increases; as κD → ∞, this effect dies out, and drawdown is controlled entirely by delayed decline in the water table as in the model of Neuman. The unsaturated zone has a major impact on drawdown at intermediate time and a significant impact at early and late times, in the atypical case of κD ≤ 1, becoming the dominant factor as κD approaches zero (the soil water retention capacity becomes very large and/or saturated thickness becomes insignificant). Our

  19. An Assessment of Factors Affecting Reactive Transport of Biodegradable BTEX in an Unconfined Aquifer System, Tehran Oil Refinery, Iran

    Directory of Open Access Journals (Sweden)

    A. Agah

    2012-12-01

    Full Text Available Risk-based assessment methods are commonly used at the contaminated sites by hydrocarbon pollutants. This paper presents the results of a two-dimensional finite volume model of reactive transport of biodegradable BTEX which have been developed for the saturated zone of an unconfined aquifer in the Pump station area of Tehran oil refinery, Iran. The model governing equations were numerically solved by modification of a general commercial software called PHOENICS. To reduce costs in general, many input parameters of a model are often approximated based on the used values in the contaminated sites with same conditions. It was not fully recognised the effect of errors in these inputs on modelling outputs. Thus, a sensitivity analysis was carried out to determine the influence of parameters variability on the results of model. For this analysis, the sensitivity of the model to changes in the dispersivity, distribution coefficient, parameters of Monod, Michaelis-Menten, first- and zero- order kinetics modes on the BTEX contaminant plume were examined by performing several simulations. It was found that the model is sensitive to changes in dispersivity and parameters of Michaelis-Menten, first- and zero- order kinetics model. On the other hand, the predictions for plumes assuming Monod kinetics are similar, even if different values for parameterization are chosen. The reason for this insensibility is that degradation is not limited by microbial kinetics in the simulation, but by dispersive mixing. Quantifying the effect of changes in model input parameters on the modelling results is essential when it is desired to recognise which model parameters are more vital on the fate and transport of reactive pollutants. Furthermore, this process can provide an insight into understanding pollutant transportation mechanisms.

  20. Uncertainty Quantification and Global Sensitivity Analysis of Subsurface Flow Parameters to Gravimetric Variations During Pumping Tests in Unconfined Aquifers

    Science.gov (United States)

    Maina, Fadji Zaouna; Guadagnini, Alberto

    2018-01-01

    We study the contribution of typically uncertain subsurface flow parameters to gravity changes that can be recorded during pumping tests in unconfined aquifers. We do so in the framework of a Global Sensitivity Analysis and quantify the effects of uncertainty of such parameters on the first four statistical moments of the probability distribution of gravimetric variations induced by the operation of the well. System parameters are grouped into two main categories, respectively, governing groundwater flow in the unsaturated and saturated portions of the domain. We ground our work on the three-dimensional analytical model proposed by Mishra and Neuman (2011), which fully takes into account the richness of the physical process taking place across the unsaturated and saturated zones and storage effects in a finite radius pumping well. The relative influence of model parameter uncertainties on drawdown, moisture content, and gravity changes are quantified through (a) the Sobol' indices, derived from a classical decomposition of variance and (b) recently developed indices quantifying the relative contribution of each uncertain model parameter to the (ensemble) mean, skewness, and kurtosis of the model output. Our results document (i) the importance of the effects of the parameters governing the unsaturated flow dynamics on the mean and variance of local drawdown and gravity changes; (ii) the marked sensitivity (as expressed in terms of the statistical moments analyzed) of gravity changes to the employed water retention curve model parameter, specific yield, and storage, and (iii) the influential role of hydraulic conductivity of the unsaturated and saturated zones to the skewness and kurtosis of gravimetric variation distributions. The observed temporal dynamics of the strength of the relative contribution of system parameters to gravimetric variations suggest that gravity data have a clear potential to provide useful information for estimating the key hydraulic

  1. Modeling slug tests in unconfined aquifers with both oscillatory and overdamped responses, and with low-K and high-K skin effects

    Science.gov (United States)

    Thoma, M. J.; Malama, B.; Barrash, W.; Bohling, G.; Butler, J. J.

    2009-12-01

    We extend the models for slug tests developed by Hyder et al. (1994) and Butler and Zhan (2004) to obtain a single general model for slug tests in unconfined aquifers in partially penetrating wells with a near-well disturbed zone (skin). The full range of responses, oscillatory to overdamped, is considered since both types of responses are common in wells in unconsolidated coarse fluvial aquifers, and others. The general semi-analytical solution allows for skin and formation storage as well as anisotropy in skin and formation hydraulic conductivity (K). The water table is treated as a fixed head boundary so the solution is applicable for wells screened below the water table. The model is validated by comparison with other models and by matching field data from unconfined fluvial aquifers at sites in Nebraska (MSEA) and Idaho (BHRS). We examine the effects of varying skin K and skin thickness to simulate the impact of a near-well disturbed zone that is lower (damage) or higher (filter pack) K than the formation. Results indicate that, for a given set of measured behavior at an example test zone, minor progressive decreases in estimated formation K occur with increases in assumed skin K, and moderate increases in estimated formation K occur with decreases in assumed skin K. Major increases (orders of magnitude) in estimated formation K occur with increased thickness of low-K skin. The importance of incorporating a finite-thickness representation of the skin, rather than the conventional infinitely thin representation, is also addressed.

  2. Construction and calibration of a groundwater-flow model to assess groundwater availability in the uppermost principal aquifer systems of the Williston Basin, United States and Canada

    Science.gov (United States)

    Davis, Kyle W.; Long, Andrew J.

    2018-05-31

    The U.S. Geological Survey developed a groundwater-flow model for the uppermost principal aquifer systems in the Williston Basin in parts of Montana, North Dakota, and South Dakota in the United States and parts of Manitoba and Saskatchewan in Canada as part of a detailed assessment of the groundwater availability in the area. The assessment was done because of the potential for increased demands and stresses on groundwater associated with large-scale energy development in the area. As part of this assessment, a three-dimensional groundwater-flow model was developed as a tool that can be used to simulate how the groundwater-flow system responds to changes in hydrologic stresses at a regional scale.The three-dimensional groundwater-flow model was developed using the U.S. Geological Survey’s numerical finite-difference groundwater model with the Newton-Rhapson solver, MODFLOW–NWT, to represent the glacial, lower Tertiary, and Upper Cretaceous aquifer systems for steady-state (mean) hydrological conditions for 1981‒2005 and for transient (temporally varying) conditions using a combination of a steady-state period for pre-1960 and transient periods for 1961‒2005. The numerical model framework was constructed based on existing and interpreted hydrogeologic and geospatial data and consisted of eight layers. Two layers were used to represent the glacial aquifer system in the model; layer 1 represented the upper one-half and layer 2 represented the lower one-half of the glacial aquifer system. Three layers were used to represent the lower Tertiary aquifer system in the model; layer 3 represented the upper Fort Union aquifer, layer 4 represented the middle Fort Union hydrogeologic unit, and layer 5 represented the lower Fort Union aquifer. Three layers were used to represent the Upper Cretaceous aquifer system in the model; layer 6 represented the upper Hell Creek hydrogeologic unit, layer 7 represented the lower Hell Creek aquifer, and layer 8 represented the Fox

  3. Changes in groundwater reserves and radiocarbon and chloride content due to a wet period intercalated in an arid climate sequence in a large unconfined aquifer

    Science.gov (United States)

    Custodio, E.; Jódar, J.; Herrera, C.; Custodio-Ayala, J.; Medina, A.

    2018-01-01

    The concentration of atmospheric tracers in groundwater samples collected from springs and deep wells is, in most cases, the result of a mixture of waters with a wide range of residence times in the ground. Such is the case of an unconfined aquifer recharged over all its surface area. Concentrations greatly differ from the homogeneous residence time case. Data interpretation relies on knowledge of the groundwater flow pattern. To study relatively large systems, the conservative ion chloride and the decaying radiocarbon (14C) are considered. Radiocarbon (14C) activity in groundwater, after correction to discount the non-biogenic contribution, is often taken as an indication of water age, while chloride can be used to quantify recharge. In both cases, the observed tracer content in groundwater is an average value over a wide range which is related to water renewal time in the ground. This is shown considering an unconfined aquifer recharged all over its area under arid conditions, in which a period of greater recharge happened some millennia ago. The mathematical solution is given. As the solution cannot be made general, to show and discuss the changes in water reserve and in chloride and radiocarbon concentration (apparent ages), two scenarios are worked out, which are loosely related to current conditions in Northern Chile. It is shown that tracer concentration and the estimated water age are not directly related to the time since recharge took place. The existence of a previous wetter-than-present period has an important and lasting effect on current aquifer water reserves and chloride concentration, although the effect on radiocarbon activity is less pronounced. Chloride concentrations are smaller than in current recharge and apparent 14C ages do not coincide with the timing, duration and characteristics of the wet period, except in the case in which recharge before and after the wet period is negligible and dead aquifer reserves are non-significant. The use of

  4. Joint Calibration of Submarine Groundwater Discharge (SGD) with Tidal Pumping: Modeling Variable-density Groundwater Flow in Unconfined Coastal Aquifer of Apalachee Bay, Gulf of Mexico

    Science.gov (United States)

    Li, X.; Hu, B.; Burnett, W.; Santos, I.

    2008-05-01

    Submarine Groundwater Discharge (SGD) as an unseen phenomenon is now recognized as an important pathway between land and sea. These discharges typically display significant spatial and temporal variability making quantification difficult. Groundwater seepage is patchy, diffuse, and temporally variable, and thus makes the estimation of its magnitude and components is a challenging enterprise. A two-dimensional hydrogeological model is developed to the near-shore environment of an unconfined aquifer at a Florida coastal area in the northeastern Gulf of Mexico. Intense geological survey and slug tests are set to investigate the heterogeneity of this layered aquifer. By applying SEAWAT2000, considering the uncertainties caused by changes of boundary conditions, a series of variable-density-flow models incorporates the tidal-influenced seawater recirculation and the freshwater-saltwater mixing zone under the dynamics of tidal pattern, tidal amplitude and variation of water table. These are thought as the contributing factors of tidal pumping and hydraulic gradient which are the driven forces of SGD. A tidal-influenced mixing zone in the near-shore aquifer shows the importance of tidal mechanism to flow and salt transport in the process of submarine pore water exchange. Freshwater ratio in SGD is also analyzed through the comparison of Submarine Groundwater Recharge and freshwater inflow. The joint calibration with other methods (natural tracer model and seepage meter) is also discussed.

  5. Three-dimensional analysis of future groundwater flow conditions and contaminant plume transport in the Hanford Site unconfined aquifer system: FY 1996 and 1997 status report

    Energy Technology Data Exchange (ETDEWEB)

    Cole, C.R.; Wurstner, S.K.; Williams, M.D.; Thorne, P.D.; Bergeron, M.P.

    1997-12-01

    A three-dimensional numerical model of groundwater flow and transport, based on the Coupled Fluid Energy, and Solute Transport (CFEST) code, was developed for the Hanford Site to support the Hanford Groundwater Project (HGWP), managed by Pacific Northwest National Laboratory. The model was developed to increase the understanding and better forecast the migration of several contaminant plumes being monitored by the HGWP, and to support the Hanford Site Composite Analysis for low-level waste disposal in the 200-Area Plateau. Recent modeling efforts have focused on continued refinement of an initial version of the three-dimensional model developed in 1995 and its application to simulate future transport of selected contaminant plumes in the aquifer system. This version of the model was updated using a more current version of the CFEST code called CFEST96. Prior to conducting simulations of contaminant transport with the three-dimensional model, a previous steady-state, two-dimensional model of the unconfined aquifer system was recalibrated to 1979 water-table conditions with a statistical inverse method implemented in the CFEST-INV computer code. The results of the recalibration were used to refine the three-dimensional conceptual model and to calibrate it with a conceptualization that preserves the two-dimensional hydraulic properties and knowledge of the aquifer`s three-dimensional properties for the same 1979 water-table conditions. The transient behavior of the three-dimensional flow model was also calibrated by adjusting model storage properties (specific yield) until transient water-table predictions approximated observed water-table elevations between 1979 and 1996.

  6. Monitoring the evolution and migration of a methane gas plume in an unconfined sandy aquifer using time-lapse GPR and ERT.

    Science.gov (United States)

    Steelman, Colby M; Klazinga, Dylan R; Cahill, Aaron G; Endres, Anthony L; Parker, Beth L

    2017-10-01

    Fugitive methane (CH 4 ) leakage associated with conventional and unconventional petroleum development (e.g., shale gas) may pose significant risks to shallow groundwater. While the potential threat of stray (CH 4 ) gas in aquifers has been acknowledged, few studies have examined the nature of its migration and fate in a shallow groundwater flow system. This study examines the geophysical responses observed from surface during a 72day field-scale simulated CH 4 leak in an unconfined sandy aquifer at Canadian Forces Base Borden, Canada, to better understand the transient behaviour of fugitive CH 4 gas in the subsurface. Time-lapse ground-penetrating radar (GPR) and electrical resistivity tomography (ERT) were used to monitor the distribution and migration of the gas-phase and assess any impacts to groundwater hydrochemistry. Geophysical measurements captured the transient formation of a CH 4 gas plume emanating from the injector, which was accompanied by an increase in total dissolved gas pressure (P TDG ). Subsequent reductions in P TDG were accompanied by reduced bulk resistivity around the injector along with an increase in the GPR reflectivity along horizontal bedding reflectors farther downgradient. Repeat temporal GPR reflection profiling identified three events with major peaks in reflectivity, interpreted to represent episodic lateral CH 4 gas release events into the aquifer. Here, a gradual increase in P TDG near the injector caused a sudden lateral breakthrough of gas in the direction of groundwater flow, causing free-phase CH 4 to migrate much farther than anticipated based on groundwater advection. CH 4 accumulated along subtle permeability boundaries demarcated by grain-scale bedding within the aquifer characteristic of numerous Borden-aquifer multi-phase flow experiments. Diminishing reflectivity over a period of days to weeks suggests buoyancy-driven migration to the vadose zone and/or CH 4 dissolution into groundwater. Lateral and vertical CH 4

  7. Three-dimensional analysis of future groundwater flow conditions and contaminant plume transport in the Hanford Site unconfined aquifer system: FY 1996 and 1997 status report

    International Nuclear Information System (INIS)

    Cole, C.R.; Wurstner, S.K.; Williams, M.D.; Thorne, P.D.; Bergeron, M.P.

    1997-12-01

    A three-dimensional numerical model of groundwater flow and transport, based on the Coupled Fluid Energy, and Solute Transport (CFEST) code, was developed for the Hanford Site to support the Hanford Groundwater Project (HGWP), managed by Pacific Northwest National Laboratory. The model was developed to increase the understanding and better forecast the migration of several contaminant plumes being monitored by the HGWP, and to support the Hanford Site Composite Analysis for low-level waste disposal in the 200-Area Plateau. Recent modeling efforts have focused on continued refinement of an initial version of the three-dimensional model developed in 1995 and its application to simulate future transport of selected contaminant plumes in the aquifer system. This version of the model was updated using a more current version of the CFEST code called CFEST96. Prior to conducting simulations of contaminant transport with the three-dimensional model, a previous steady-state, two-dimensional model of the unconfined aquifer system was recalibrated to 1979 water-table conditions with a statistical inverse method implemented in the CFEST-INV computer code. The results of the recalibration were used to refine the three-dimensional conceptual model and to calibrate it with a conceptualization that preserves the two-dimensional hydraulic properties and knowledge of the aquifer's three-dimensional properties for the same 1979 water-table conditions. The transient behavior of the three-dimensional flow model was also calibrated by adjusting model storage properties (specific yield) until transient water-table predictions approximated observed water-table elevations between 1979 and 1996

  8. Closed-form analytical solutions for assessing the consequences of sea-level rise on unconfined sloping island aquifers

    Science.gov (United States)

    Chesnaux, R.

    2016-04-01

    Closed-form analytical solutions for assessing the consequences of sea-level rise on fresh groundwater oceanic island lenses are provided for the cases of both strip and circular islands. Solutions are proposed for directly calculating the change in the thickness of the lens, the changes in volume and the changes in travel time of fresh groundwater within island aquifers. The solutions apply for homogenous aquifers recharged by surface infiltration and discharged by a down-gradient, fixed-head boundary. They also take into account the inland shift of the ocean due to land surface inundation, this shift being determined by the coastal slope of inland aquifers. The solutions are given for two simple island geometries: circular islands and strip islands. Base case examples are presented to illustrate, on one hand, the amplitude of the change of the fresh groundwater lens thickness and the volume depletion of the lens in oceanic island with sea-level rise, and on the other hand, the shortening of time required for groundwater to discharge into the ocean. These consequences can now be quantified and may help decision-makers to anticipate the effects of sea-level rise on fresh groundwater availability in oceanic island aquifers.

  9. Changes in the water-table altitude of the unconfined aquifer, Wood River Valley aquifer system, south-central Idaho, October 2006 to October 2012.

    Data.gov (United States)

    Department of the Interior — Water levels in 93 wells completed in the Wood River Valley aquifer system were measured during October 22–24, 2012; these wells are part of a network established...

  10. Wells measured for water-levels, unconfined and confined aquifers, Wood River Valley aquifer system, south-central Idaho, October 2006 and October 2012.

    Data.gov (United States)

    Department of the Interior — Water levels in 93 wells completed in the Wood River Valley aquifer system were measured during October 22–24, 2012; these wells are part of a network established...

  11. Coupling 3D groundwater modeling with CFC-based age dating to classify local groundwater circulation in an unconfined crystalline aquifer

    Science.gov (United States)

    Kolbe, Tamara; Marçais, Jean; Thomas, Zahra; Abbott, Benjamin W.; de Dreuzy, Jean-Raynald; Rousseau-Gueutin, Pauline; Aquilina, Luc; Labasque, Thierry; Pinay, Gilles

    2016-12-01

    Nitrogen pollution of freshwater and estuarine environments is one of the most urgent environmental crises. Shallow aquifers with predominantly local flow circulation are particularly vulnerable to agricultural contaminants. Water transit time and flow path are key controls on catchment nitrogen retention and removal capacity, but the relative importance of hydrogeological and topographical factors in determining these parameters is still uncertain. We used groundwater dating and numerical modeling techniques to assess transit time and flow path in an unconfined aquifer in Brittany, France. The 35.5 km2 study catchment has a crystalline basement underneath a ∼60 m thick weathered and fractured layer, and is separated into a distinct upland and lowland area by an 80 m-high butte. We used groundwater discharge and groundwater ages derived from chlorofluorocarbon (CFC) concentration to calibrate a free-surface flow model simulating groundwater flow circulation. We found that groundwater flow was highly local (mean travel distance = 350 m), substantially smaller than the typical distance between neighboring streams (∼1 km), while CFC-based ages were quite old (mean = 40 years). Sensitivity analysis revealed that groundwater travel distances were not sensitive to geological parameters (i.e. arrangement of geological layers and permeability profile) within the constraints of the CFC age data. However, circulation was sensitive to topography in the lowland area where the water table was near the land surface, and to recharge rate in the upland area where water input modulated the free surface of the aquifer. We quantified these differences with a local groundwater ratio (rGW-LOCAL), defined as the mean groundwater travel distance divided by the mean of the reference surface distances (the distance water would have to travel across the surface of the digital elevation model). Lowland, rGW-LOCAL was near 1, indicating primarily topographical controls. Upland, r

  12. Experimental and modeling results on geochemical impacts of leaking CO2 from subsurface storage reservoirs to an unconfined oxidizing carbonate aquifer

    Science.gov (United States)

    Qafoku, N. P.; Bacon, D. H.; Shao, H.; Lawter, A.; Wang, G.; Brown, C. F.

    2013-12-01

    Deep subsurface storage and sequestration of CO2 has been identified as a potential mitigation technique for rising atmospheric CO2 concentrations. Sequestered CO2 represents a potential risk to overlying aquifers if the CO2 leaks from the deep storage reservoir. Experimental and modeling work is required to evaluate risks to groundwater quality and develop a systematic understanding on how CO2 leakage may cause important changes in aquifer chemistry and mineralogy by promoting dissolution/precipitation, adsorption/desorption, and redox reactions. Solid materials (rocks and slightly weathered rocks) from an unconfined aquifer, i.e., the Edwards Aquifer in Texas, were used in this investigation. The experimental part consisted of: 1) wet chemical acid extractions (8M HNO3 solution at 90 0C); 2) batch experiments conducted at low solid to solution ratios to study time-dependent releases of major, minor and trace elements during periodic or continuous exposure to CO2 gas; 3) hydraulically saturated column experiments conducted under continuous and stop-flow conditions using a CO2 gas saturated synthetic groundwater; 4) pre- and post-treatment solid phase characterization studies. Major variables tested included reaction time (0-336 hours), CO2 flow rate (50 to 350 ml/min), brine concentration (0.1 and 1 M NaCl), rock type and particle size fraction. We are currently investigating the solution composition effects (i.e., presence of contaminants in the initial solution) on the fate and behavior of potential contaminants (As, Pb and Cd) in these systems. Results from the solid phase characterization studies showed that the mineralogy of the Edwards aquifer materials was dominated by calcite. Quartz and montmorillonite were also present in some samples. Acid extractions confirmed that the solid phase had appreciable amounts of potential contaminants (As, Cd, Cr, Cu, Pb and Zn). However, the results from the batch and column experiments demonstrated that these contaminants

  13. Soil-water content characterisation in a modified Jarvis-Stewart model: A case study of a conifer forest on a shallow unconfined aquifer

    Science.gov (United States)

    Guyot, Adrien; Fan, Junliang; Oestergaard, Kasper T.; Whitley, Rhys; Gibbes, Badin; Arsac, Margaux; Lockington, David A.

    2017-01-01

    Groundwater-vegetation-atmosphere fluxes were monitored for a subtropical coastal conifer forest in South-East Queensland, Australia. Observations were used to quantify seasonal changes in transpiration rates with respect to temporal fluctuations of the local water table depth. The applicability of a Modified Jarvis-Stewart transpiration model (MJS), which requires soil-water content data, was assessed for this system. The influence of single depth values compared to use of vertically averaged soil-water content data on MJS-modelled transpiration was assessed over both a wet and a dry season, where the water table depth varied from the surface to a depth of 1.4 m below the surface. Data for tree transpiration rates relative to water table depth showed that trees transpire when the water table was above a threshold depth of 0.8 m below the ground surface (water availability is non-limiting). When the water table reached the ground surface (i.e., surface flooding) transpiration was found to be limited. When the water table is below this threshold depth, a linear relationship between water table depth and the transpiration rate was observed. MJS modelling results show that the influence of different choices for soil-water content on transpiration predictions was insignificant in the wet season. However, during the dry season, inclusion of deeper soil-water content data improved the model performance (except for days after isolated rainfall events, here a shallower soil-water representation was better). This study demonstrated that, to improve MJS simulation results, appropriate selection of soil water measurement depths based on the dynamic behaviour of soil water profiles through the root zone was required in a shallow unconfined aquifer system.

  14. Hydrogeological and hydrochemical characterization of unconfined aquifer located in the alteration mantle of the Serra Geral Formation, in the Taquari-Antas river basin, northeast of Rio Grande do Sul State

    Directory of Open Access Journals (Sweden)

    Gisele Cemin

    2012-08-01

    Full Text Available This paper presents the hydrogeological and hydrochemical characterization of the unconfined aquifer located in the alteration mantle in the volcanic rocks from Serra Geral Formation, in the northeast region of Rio Grande do Sul State. This aquifer is conditioned by the soil, topography, lithology and climate, being characterized by a saturated layer thinner than 1,7 m, static levels between 0 and 1 m and low flow (<0,5 m3/h. These waters are of calcium or magnesium bicarbonate type, and low alkalinity and electrical conductivity, low calcium, magnesium, sodium, potassium and chloride concentrations, and high iron and manganese concentrations. Additionally, these waters have high concentration of nitrates (mean above 10 mg/L and the presence of total coliforms. These characteristics evidence a quick circulation between the recharging and discharge zones in the aquifer.

  15. Development of a hybrid 3-D hydrological model to simulate hillslopes and the regional unconfined aquifer system in Earth system models

    Science.gov (United States)

    Hazenberg, P.; Broxton, P. D.; Brunke, M.; Gochis, D.; Niu, G. Y.; Pelletier, J. D.; Troch, P. A. A.; Zeng, X.

    2015-12-01

    The terrestrial hydrological system, including surface and subsurface water, is an essential component of the Earth's climate system. Over the past few decades, land surface modelers have built one-dimensional (1D) models resolving the vertical flow of water through the soil column for use in Earth system models (ESMs). These models generally have a relatively coarse model grid size (~25-100 km) and only account for sub-grid lateral hydrological variations using simple parameterization schemes. At the same time, hydrologists have developed detailed high-resolution (~0.1-10 km grid size) three dimensional (3D) models and showed the importance of accounting for the vertical and lateral redistribution of surface and subsurface water on soil moisture, the surface energy balance and ecosystem dynamics on these smaller scales. However, computational constraints have limited the implementation of the high-resolution models for continental and global scale applications. The current work presents a hybrid-3D hydrological approach is presented, where the 1D vertical soil column model (available in many ESMs) is coupled with a high-resolution lateral flow model (h2D) to simulate subsurface flow and overland flow. H2D accounts for both local-scale hillslope and regional-scale unconfined aquifer responses (i.e. riparian zone and wetlands). This approach was shown to give comparable results as those obtained by an explicit 3D Richards model for the subsurface, but improves runtime efficiency considerably. The h3D approach is implemented for the Delaware river basin, where Noah-MP land surface model (LSM) is used to calculated vertical energy and water exchanges with the atmosphere using a 10km grid resolution. Noah-MP was coupled within the WRF-Hydro infrastructure with the lateral 1km grid resolution h2D model, for which the average depth-to-bedrock, hillslope width function and soil parameters were estimated from digital datasets. The ability of this h3D approach to simulate

  16. A 3-D numerical model of the influence of meanders on groundwater discharge to a gaining stream in an unconfined sandy aquifer

    DEFF Research Database (Denmark)

    Balbarini, Nicola; Boon, Wietse M.; Nicolajsen, Ellen

    2017-01-01

    Groundwater discharge to streams depends on stream morphology and groundwater flow direction, but are not always well understood. Here a 3-D groundwater flow model is employed to investigate the impact of meandering stream geometries on groundwater discharge to streams in an unconfined and homoge...

  17. Optimization of DRASTIC method by artificial neural network, nitrate vulnerability index, and composite DRASTIC models to assess groundwater vulnerability for unconfined aquifer of Shiraz Plain, Iran.

    Science.gov (United States)

    Baghapour, Mohammad Ali; Fadaei Nobandegani, Amir; Talebbeydokhti, Nasser; Bagherzadeh, Somayeh; Nadiri, Ata Allah; Gharekhani, Maryam; Chitsazan, Nima

    2016-01-01

    Extensive human activities and unplanned land uses have put groundwater resources of Shiraz plain at a high risk of nitrate pollution, causing several environmental and human health issues. To address these issues, water resources managers utilize groundwater vulnerability assessment and determination of protection. This study aimed to prepare the vulnerability maps of Shiraz aquifer by using Composite DRASTIC index, Nitrate Vulnerability index, and artificial neural network and also to compare their efficiency. The parameters of the indexes that were employed in this study are: depth to water table, net recharge, aquifer media, soil media, topography, impact of the vadose zone, hydraulic conductivity, and land use. These parameters were rated, weighted, and integrated using GIS, and then, used to develop the risk maps of Shiraz aquifer. The results indicated that the southeastern part of the aquifer was at the highest potential risk. Given the distribution of groundwater nitrate concentrations from the wells in the underlying aquifer, the artificial neural network model offered greater accuracy compared to the other two indexes. The study concluded that the artificial neural network model is an effective model to improve the DRASTIC index and provides a confident estimate of the pollution risk. As intensive agricultural activities are the dominant land use and water table is shallow in the vulnerable zones, optimized irrigation techniques and a lower rate of fertilizers are suggested. The findings of our study could be used as a scientific basis in future for sustainable groundwater management in Shiraz plain.

  18. Reduced-Order Model for the Geochemical Impacts of Carbon Dioxide, Brine and Trace Metal Leakage into an Unconfined, Oxidizing Carbonate Aquifer, Version 2.1

    Energy Technology Data Exchange (ETDEWEB)

    Bacon, Diana H.

    2013-03-31

    The National Risk Assessment Partnership (NRAP) consists of 5 U.S DOE national laboratories collaborating to develop a framework for predicting the risks associated with carbon sequestration. The approach taken by NRAP is to divide the system into components, including injection target reservoirs, wellbores, natural pathways including faults and fractures, groundwater and the atmosphere. Next, develop a detailed, physics and chemistry-based model of each component. Using the results of the detailed models, develop efficient, simplified models, termed reduced order models (ROM) for each component. Finally, integrate the component ROMs into a system model that calculates risk profiles for the site. This report details the development of the Groundwater Geochemistry ROM for the Edwards Aquifer at PNNL. The Groundwater Geochemistry ROM for the Edwards Aquifer uses a Wellbore Leakage ROM developed at LANL as input. The detailed model, using the STOMP simulator, covers a 5x8 km area of the Edwards Aquifer near San Antonio, Texas. The model includes heterogeneous hydraulic properties, and equilibrium, kinetic and sorption reactions between groundwater, leaked CO2 gas, brine, and the aquifer carbonate and clay minerals. Latin Hypercube sampling was used to generate 1024 samples of input parameters. For each of these input samples, the STOMP simulator was used to predict the flux of CO2 to the atmosphere, and the volume, length and width of the aquifer where pH was less than the MCL standard, and TDS, arsenic, cadmium and lead exceeded MCL standards. In order to decouple the Wellbore Leakage ROM from the Groundwater Geochemistry ROM, the response surface was transformed to replace Wellbore Leakage ROM input parameters with instantaneous and cumulative CO2 and brine leakage rates. The most sensitive parameters proved to be the CO2 and brine leakage rates from the well, with equilibrium coefficients for calcite and dolomite, as well as the number of illite and kaolinite

  19. Unconfined Groundwater Dispersion Model On Sand Layers In Coral Island

    OpenAIRE

    Sultan

    2016-01-01

    The research objective is to analyze the sand layer to determine the characteristics of the unconfined groundwater aquifer on coral island and found the dispersion model of unconfined groundwater in the sand layer in the coral island. The method used is direct research in the field, laboratory analysis and secondary data. Observations geological conditions, as well as the measurement and interpretation of geoelectrical potential groundwater models based on the value of the conductivity of gro...

  20. Unconfined versus confined speleogenetic settings: variations of solution porosity.

    Directory of Open Access Journals (Sweden)

    Klimchouk Alexander

    2006-01-01

    Full Text Available Speleogenesis in confined settings generates cave morphologies that differ much from those formed in unconfined settings. Cavesdeveloped in unconfined settings are characterised by broadly dendritic patterns of channels due to highly competing development.In contrast, caves originated under confined conditions tend to form two- or three-dimensional mazes with densely packed conduits.This paper illustrates variations of solution (channel porosity resulted from speleogenesis in unconfined and confined settings by theanalysis of morphometric parameters of typical cave patterns. Two samples of typical cave systems formed in the respective settingsare compared. The sample that represents unconfined speleogenesis consists of solely limestone caves, whereas gypsum cavesof this type tend to be less dendritic and more linear. The sample that represents confined speleogenesis consists of both limestoneand gypsum maze caves. The comparison shows considerable differences in average values of some parameters between thesettings. Passage network density (the ratio of the cave length to the area of the cave field, km/km2 is one order of magnitudegreater in confined settings than in unconfined (average 167.3 km/km2 versus 16.6 km/km2. Similarly, an order of magnitudedifference is observed in cave porosity (a fraction of the volume of a cave block, occupied by mapped cavities; 5.0 % versus 0.4 %.This illustrates that storage in maturely karstified confined aquifers is generally much greater than in unconfined. The average areal coverage (a fraction of the area of the cave field occupied by passages in a plan view is about 5 times greater in confined settingsthan in unconfined (29.7 % versus 6.4 %. This indicates that conduit permeability in confined aquifers is appreciably easier to targetwith drilling than the widely spaced conduits in unconfined aquifers.

  1. Aquifers

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — This map layer contains the shallowest principal aquifers of the conterminous United States, Hawaii, Puerto Rico, and the U.S. Virgin Islands, portrayed as polygons....

  2. aquifer in ajaokuta, southwestern nigeria

    African Journals Online (AJOL)

    2005-03-08

    Mar 8, 2005 ... (1969) straight line method (observation well) of draw-down analysis in an unconfined aquifer (B=1) yield ... April) and a short wet season (May-September). .... DECOMPOSED. GRANITIC ROCK WITH. QUARTZ VEINS. 13.

  3. Unconfined Groundwater Quality based on the Settlement Unit in Surakarta City

    OpenAIRE

    Munawar Cholil

    2004-01-01

    The quality of groundwater of unonfined aquifer with growing population density is endangered by population. This may cause serious problem as greatest portion of the population utility groundwater of unconfined aquifer as their drinking water. This research is aim at studying the difference in quality of groundwater of unonfined aquifer in Surakarta Munipicality by settlement units, and studying the impact settlement factors and groundwater depth on the quality of groundwater of unonfined aq...

  4. Effects of highway-deicer application on ground-water quality in a part of the Calumet Aquifer, northwestern Indiana

    Science.gov (United States)

    Watson, Lee R.; Bayless, E. Randall; Buszka, Paul M.; Wilson, John T.

    2002-01-01

    The effects of highway-deicer application on ground-water quality were studied at a site in northwestern Indiana using a variety of geochemical indicators. Site characteristics such as high snowfall rates; large quantities of applied deicers; presence of a high-traffic highway; a homogeneous, permeable, and unconfined aquifer; a shallow water table; a known ground-water-flow direction; and minimal potential for other sources of chloride and sodium to complicate source interpretation were used to select a study area where ground water was likely to be affected by deicer application. Forty-three monitoring wells were installed in an unconfined sand aquifer (the Calumet aquifer) near Beverly Shores in northwestern Indiana. Wells were installed along two transects that approximately paralleled groundwater flow in the Calumet aquifer and crossed US?12. US?12 is a highway that receives Indiana?s highest level of maintenance to maintain safe driving conditions. Ground-water quality and water-level data were collected from the monitoring wells, and precipitation and salt-application data were compiled from 1994 through 1997. The water-quality data indicated that chloride was the most easily traced indicator of highway deicers in ground water. Concentration ratios of chloride to iodide and chloride to bromide and Stiff diagrams of major element concentrations indicated that the principal source of chloride and sodium in ground water from the uppermost one-third to one-half of the Calumet relative electromagnetic conductivity defined a distinct plume of deicer-affected water in the uppermost 8 feet of aquifer at about 9 feet horizontally from the paved roadway edge and a zone of higher conductivity than background in the lower one-third of the aquifer. Chloride and sodium in the deep parts of the aquifer originated from natural sources. Chloride and sodium from highway deicers were present in the aquifer throughout the year. The highest concentrations of chloride and sodium

  5. The unconfined quarks and gluons

    International Nuclear Information System (INIS)

    Abdus Salam

    1977-01-01

    The consequences of the lepton-hadron gauge unification hypothesis with unconfined quarks and gluons being the hall-mark are discussed. Quark and gluon decays into leptons are shown to provide a new source of multileptonic production in NN, νN and μN collisions. A theorem is stated and proved which highlights the differences between the dynamics of gauge versus non-gauge 1 - particles. Empirical manifestations of gauge coloured mesons are discussed. The question of exact confinement or not is concluded to be in the end an empirical one and must be settled in the laboratory

  6. A General Solution for Groundwater Flow in Estuarine Leaky Aquifer System with Considering Aquifer Anisotropy

    Science.gov (United States)

    Chen, Po-Chia; Chuang, Mo-Hsiung; Tan, Yih-Chi

    2014-05-01

    In recent years the urban and industrial developments near the coastal area are rapid and therefore the associated population grows dramatically. More and more water demand for human activities, agriculture irrigation, and aquaculture relies on heavy pumping in coastal area. The decline of groundwater table may result in the problems of seawater intrusion and/or land subsidence. Since the 1950s, numerous studies focused on the effect of tidal fluctuation on the groundwater flow in the coastal area. Many studies concentrated on the developments of one-dimensional (1D) and two-dimensional (2D) analytical solutions describing the tide-induced head fluctuations. For example, Jacob (1950) derived an analytical solution of 1D groundwater flow in a confined aquifer with a boundary condition subject to sinusoidal oscillation. Jiao and Tang (1999) derived a 1D analytical solution of a leaky confined aquifer by considered a constant groundwater head in the overlying unconfined aquifer. Jeng et al. (2002) studied the tidal propagation in a coupled unconfined and confined costal aquifer system. Sun (1997) presented a 2D solution for groundwater response to tidal loading in an estuary. Tang and Jiao (2001) derived a 2D analytical solution in a leaky confined aquifer system near open tidal water. This study aims at developing a general analytical solution describing the head fluctuations in a 2D estuarine aquifer system consisted of an unconfined aquifer, a confined aquifer, and an aquitard between them. Both the confined and unconfined aquifers are considered to be anisotropic. The predicted head fluctuations from this solution will compare with the simulation results from the MODFLOW program. In addition, the solutions mentioned above will be shown to be special cases of the present solution. Some hypothetical cases regarding the head fluctuation in costal aquifers will be made to investigate the dynamic effects of water table fluctuation, hydrogeological conditions, and

  7. Groundwater sustainability assessment in coastal aquifers

    Indian Academy of Sciences (India)

    The present work investigates the response of shallow, coastal unconfined aquifers to anticipated overdraft conditions and climate change effect using numerical simulation. The groundwater flow model MODFLOW and variable density groundwater model SEAWAT are used for this investigation. The transmissivity and ...

  8. Implementation of a 3d numerical model of a folded multilayer carbonate aquifer

    Science.gov (United States)

    Di Salvo, Cristina; Guyennon, Nicolas; Romano, Emanuele; Bruna Petrangeli, Anna; Preziosi, Elisabetta

    2016-04-01

    The main objective of this research is to present a case study of the numerical model implementation of a complex carbonate, structurally folded aquifer, with a finite difference, porous equivalent model. The case study aquifer (which extends over 235 km2 in the Apennine chain, Central Italy) provides a long term average of 3.5 m3/s of good quality groundwater to the surface river network, sustaining the minimum vital flow, and it is planned to be exploited in the next years for public water supply. In the downstream part of the river in the study area, a "Site of Community Importance" include the Nera River for its valuable aquatic fauna. However, the possible negative effects of the foreseen exploitation on groundwater dependent ecosystems are a great concern and model grounded scenarios are needed. This multilayer aquifer was conceptualized as five hydrostratigraphic units: three main aquifers (the uppermost unconfined, the central and the deepest partly confined), are separated by two locally discontinuous aquitards. The Nera river cuts through the two upper aquifers and acts as the main natural sink for groundwater. An equivalent porous medium approach was chosen. The complex tectonic structure of the aquifer requires several steps in defining the conceptual model; the presence of strongly dipping layers with very heterogeneous hydraulic conductivity, results in different thicknesses of saturated portions. Aquifers can have both unconfined or confined zones; drying and rewetting must be allowed when considering recharge/discharge cycles. All these characteristics can be included in the conceptual and numerical model; however, being the number of flow and head target scarce, the over-parametrization of the model must be avoided. Following the principle of parsimony, three steady state numerical models were developed, starting from a simple model, and then adding complexity: 2D (single layer), QUASI -3D (with leackage term simulating flow through aquitards) and

  9. Case studies of groundwater- surface water interactions and scale relationships in small alluvial aquifers

    NARCIS (Netherlands)

    Love, Dave; de Hamer, Wouter; Owen, Richard J.S.; Booij, Martijn J.; Uhlenbrook, Stefan; Hoekstra, Arjen Ysbert; van der Zaag, Pieter

    2007-01-01

    An alluvial aquifer can be described as a groundwater system, generally unconfined, that is hosted in laterally discontinuous layers of gravel, sand, silt and clay, deposited by a river in a river channel, banks or flood plain. In semi-arid regions, streams that are associated with alluvial aquifers

  10. Palaeoclimatic trends deduced from the hydrochemistry of a Triassic sandstone aquifer, U.K

    International Nuclear Information System (INIS)

    Bath, A.H.; Edmunds, W.M.; Andrews, J.N.

    1978-01-01

    A detailed geochemical study (elemental, isotopic and dissolved inert gases) of unconfined and confined sections of the Triassic non-marine sandstone aquifer in Eastern England has been undertaken. Aspects of the recharge history of this aquifer over the past 40 000 years are revealed by examination of the data. (orig./HK) [de

  11. Modeling the potential impact of seasonal and inactive multi-aquifer wells on contaminant movement to public water-supply wells

    Science.gov (United States)

    Johnson, R.L.; Clark, B.R.; Landon, M.K.; Kauffman, L.J.; Eberts, S.M.

    2011-01-01

    Wells screened across multiple aquifers can provide pathways for the movement of surprisingly large volumes of groundwater to confined aquifers used for public water supply (PWS). Using a simple numerical model, we examine the impact of several pumping scenarios on leakage from an unconfined aquifer to a confined aquifer and conclude that a single inactive multi-aquifer well can contribute nearly 10% of total PWS well flow over a wide range of pumping rates. This leakage can occur even when the multi-aquifer well is more than a kilometer from the PWS well. The contribution from multi-aquifer wells may be greater under conditions where seasonal pumping (e.g., irrigation) creates large, widespread downward hydraulic gradients between aquifers. Under those conditions, water can continue to leak down a multi-aquifer well from an unconfined aquifer to a confined aquifer even when those multi-aquifer wells are actively pumped. An important implication is that, if an unconfined aquifer is contaminated, multi-aquifer wells can increase the vulnerability of a confined-aquifer PWS well.

  12. Closed-form analytical solutions incorporating pumping and tidal effects in various coastal aquifer systems

    Science.gov (United States)

    Wang, Chaoyue; Li, Hailong; Wan, Li; Wang, Xusheng; Jiang, Xiaowei

    2014-07-01

    Pumping wells are common in coastal aquifers affected by tides. Here we present analytical solutions of groundwater table or head variations during a constant rate pumping from a single, fully-penetrating well in coastal aquifer systems comprising an unconfined aquifer, a confined aquifer and semi-permeable layer between them. The unconfined aquifer terminates at the coastline (or river bank) and the other two layers extend under tidal water (sea or tidal river) for a certain distance L. Analytical solutions are derived for 11 reasonable combinations of different situations of the L-value (zero, finite, and infinite), of the middle layer's permeability (semi-permeable and impermeable), of the boundary condition at the aquifer's submarine terminal (Dirichlet describing direct connection with seawater and no-flow describing the existence of an impermeable capping), and of the tidal water body (sea and tidal river). Solutions are discussed with application examples in fitting field observations and parameter estimations.

  13. Assessing groundwater availability in a folded carbonate aquifer through the development of a numerical model

    Science.gov (United States)

    Di Salvo, Cristina; Romano, Emanuele; Guyennon, Nicolas; Bruna Petrangeli, Anna; Preziosi, Elisabetta

    2015-04-01

    multilayer aquifer was conceptualized as five folded hydrostratigraphic units: three main carbonate aquifers are separated by two aquitards, which can be locally discontinuous, leading to a complicated flow pattern. In general the vertical leakance is upward from the basal aquifer to the unconfined uppermost aquifer. As shown by the increasing discharge from north to south, the Nera river acts as the main sink of the study area, gaining groundwater as it cuts through the folded terrain. The numerical model was implemented using the MODFLOW-2000 code and extends over an area of 235 km2 with a grid spacing of 100 meters in each of the 5 layers. Model calibration was achieved by comparing the model results with observed streamflow of the Nera river (8-10 measures per year during 1991-1993 and 1996-2012) which on the basis of the river hydrograph at gaging locations is considered to be derived entirely from groundwater. The effects of climate variation on groundwater discharge to the river in the past 60 years are analyzed. Key issues related to the elaboration of a numerical model of a folded structure are also described.

  14. Unconfined Groundwater Quality based on the Settlement Unit in Surakarta City

    Directory of Open Access Journals (Sweden)

    Munawar Cholil

    2004-01-01

    Full Text Available The quality of groundwater of unonfined aquifer with growing population density is endangered by population. This may cause serious problem as greatest portion of the population utility groundwater of unconfined aquifer as their drinking water. This research is aim at studying the difference in quality of groundwater of unonfined aquifer in Surakarta Munipicality by settlement units, and studying the impact settlement factors and groundwater depth on the quality of groundwater of unonfined aquifer. The research was executed by a survey methhod, taking 44 units of groundwater of unonfined aquifer samples at stratified proportional random from 44 villages. The samples were analyzed at the laboratory of Local Drinking Water Company (PDAM of Surakarta. Data were analyzed using by stiff diagram, variance analysis, and multiple regression. The research reveals that there is very little differences in the quality of free groundwater in Surakarta, as it is shown by same chemical properties. Several chemical properties were found very high in concentration, but the rest were simultaniously low. On the basis of minimum quality of drinking water coli content have exeeded the allowed limit for drinking water. Among the settlement units observed, there were no significant differences in the physical, chemical (except pH, bacteriological factors. This means that differences among various depth of water. Electrical onductivity (EC, Na, Mg, H2CO3, H2SO4, and NH3 were found different among various depth of water table. Major chemical conentration were significant with geology formation. Population density, built up areas, size of settlement, building density, and the condition of drainage simultaniously affect the quality of free ground water. No differences among settlement units was observed the most important fators determining the free groundwater quality was population density.

  15. Dual Pump Recovery (DPR System to Extract Freshwater in Coastal Aquifers

    Directory of Open Access Journals (Sweden)

    C. Otto

    2002-06-01

    Full Text Available The paper describes the hydraulic theory of recovering a dense plume using a newly devised dual pump recover system (DPR and its feasibility to half the remediation time of a contaminated unconfined aquifer in a coastal urban environment. Although the DPR system was successfully applied to clean up the polluted aquifer, the hydraulic principles and techniques are also applicable to extract fresh groundwater from coastal aquifers without the risk of saltwater incursion.

  16. Vertical contamination in the unconfined groundwater at the Hanford Site, Washington

    International Nuclear Information System (INIS)

    Eddy, P.A.; Myers, D.A.; Raymond, J.R.

    1978-08-01

    Disposal to the ground at Hanford of large volumes of low- and intermediate-level wastes in the local unconfined groundwater flow system has raised concern about the movement and distribution of this waste. Previous work produced information on the horizontal movement of the waste, but little or no information exists on its vertical distribution within the unconfined groundwater flow system. In 1975 Phase I of a study was started to determine the vertical distribution of contaminants in three existing wells (699-28-40, 699-31-31, and 699-37-43). Because of negative results, only one well that produced positive results (699-31-31) was chosen for Phase II. Phase II consisted of tests conducted on this well by a testing company, with samples cross-checked by two different laboratories. Phase III was a cooperative study with Rockwell Hanford Operations, which included the installation, testing, and sampling of piezometers. The data were then analyzed using predictive codes and models in order to determine if vertical movement did occur. The present groundwater flow system shows some vertical contamination. However, concentrations are relatively higher near the surface of the flow system, indicating possible radial flow patterns from the groundwater mounds known to have developed under the chemical processing area disposal sites. Upward flow from deeper aquifers may be diluting the contaminant and masking a possible downward migration of contaminants

  17. Estimating Aquifer Properties Using Sinusoidal Pumping Tests

    Science.gov (United States)

    Rasmussen, T. C.; Haborak, K. G.; Young, M. H.

    2001-12-01

    We develop the theoretical and applied framework for using sinusoidal pumping tests to estimate aquifer properties for confined, leaky, and partially penetrating conditions. The framework 1) derives analytical solutions for three boundary conditions suitable for many practical applications, 2) validates the analytical solutions against a finite element model, 3) establishes a protocol for conducting sinusoidal pumping tests, and 4) estimates aquifer hydraulic parameters based on the analytical solutions. The analytical solutions to sinusoidal stimuli in radial coordinates are derived for boundary value problems that are analogous to the Theis (1935) confined aquifer solution, the Hantush and Jacob (1955) leaky aquifer solution, and the Hantush (1964) partially penetrated confined aquifer solution. The analytical solutions compare favorably to a finite-element solution of a simulated flow domain, except in the region immediately adjacent to the pumping well where the implicit assumption of zero borehole radius is violated. The procedure is demonstrated in one unconfined and two confined aquifer units near the General Separations Area at the Savannah River Site, a federal nuclear facility located in South Carolina. Aquifer hydraulic parameters estimated using this framework provide independent confirmation of parameters obtained from conventional aquifer tests. The sinusoidal approach also resulted in the elimination of investigation-derived wastes.

  18. Alluvial Aquifer

    Data.gov (United States)

    Kansas Data Access and Support Center — This coverage shows the extents of the alluvial aquifers in Kansas. The alluvial aquifers consist of unconsolidated Quaternary alluvium and contiguous terrace...

  19. Transient well flow in vertically heterogeneous aquifers

    Science.gov (United States)

    Hemker, C. J.

    1999-11-01

    A solution for the general problem of computing well flow in vertically heterogeneous aquifers is found by an integration of both analytical and numerical techniques. The radial component of flow is treated analytically; the drawdown is a continuous function of the distance to the well. The finite-difference technique is used for the vertical flow component only. The aquifer is discretized in the vertical dimension and the heterogeneous aquifer is considered to be a layered (stratified) formation with a finite number of homogeneous sublayers, where each sublayer may have different properties. The transient part of the differential equation is solved with Stehfest's algorithm, a numerical inversion technique of the Laplace transform. The well is of constant discharge and penetrates one or more of the sublayers. The effect of wellbore storage on early drawdown data is taken into account. In this way drawdowns are found for a finite number of sublayers as a continuous function of radial distance to the well and of time since the pumping started. The model is verified by comparing results with published analytical and numerical solutions for well flow in homogeneous and heterogeneous, confined and unconfined aquifers. Instantaneous and delayed drainage of water from above the water table are considered, combined with the effects of partially penetrating and finite-diameter wells. The model is applied to demonstrate that the transient effects of wellbore storage in unconfined aquifers are less pronounced than previous numerical experiments suggest. Other applications of the presented solution technique are given for partially penetrating wells in heterogeneous formations, including a demonstration of the effect of decreasing specific storage values with depth in an otherwise homogeneous aquifer. The presented solution can be a powerful tool for the analysis of drawdown from pumping tests, because hydraulic properties of layered heterogeneous aquifer systems with

  20. Deflagration explosion of an unconfined fuel vapor cloud

    International Nuclear Information System (INIS)

    Taki, S.; Ogawa, Y.

    1981-01-01

    In the reported study, explosions are produced by injecting a small amount of liquefied petroleum gas (LPG) into air. The ignition and subsequent evolution of the explosion of the unconfined vapor cloud are observed by the simultaneous use of direct photographs and pressure recording. The intensity of the compression waves generated by unconfined combustion are modeled on the basis of the solution of the conservation equations for the flow associated with a spherically symmetric expanding piston. The obtained results are compared with the measurements. It is pointed out that the development of unconfined fuel vapor cloud explosions can be divided into two stages, including a deflagration propagating in premixed gases, which is followed by a diffusion flame promoted by buoyancy and convection. The experimental result from the pressure measurement is found to be quantitatively consistent with the result obtained from the spherical piston model

  1. Hydromorphology of the Unconfined Groundwater in the South of Klaten District (Data Before Earthquake Mei 27th 2006

    Directory of Open Access Journals (Sweden)

    Langgeng Wahyu Santosa

    2016-05-01

    Full Text Available There are some characteristics and distributions of unconfined groundwater variation in the research area. Those are related to a system of water supply and consumptive use for drinking water. Variation of the groundwater characteristic depends on variation of morphology. Therefore, it is needed to delineate hydromorphology units of the regions as a base on groundwater resources management, especially for drinking water. The aims of the research are: (1 to study of the characteristic and distribution of unconfined groundwater variations base on landform units, (2 to study the factors that affect such variations, and (3 to establish the hydromorphology units of the regions for groundwater resources management, especially for drinking water. The method used in this research is landform approach and field survey. The sampling method is stratified sampling, based on landform as the analysis approach. Result of the research shows that there are some variations of groundwater characteristic at each landform. Landforms which have good groundwater characteristic are Hydromorphology Unit of Fluvio Volcanic Plain of Young Merapi (except Bayat region and Hydromorphology Unit of Volcanic Foot Plain of Young Merapi. At those units, there are good quality of groundwater, bicarbonate water (hydrochemical type I, having low electric conductivity, shallow of water table, low in fluctuation, and middle to fast class in aquifer permeability. Those units are the most potential unconfined groundwater resources management for drinking water. The units which have poor groundwater characteristic are Hidromorphology Unit in Bayat Region, including Undulating Alluvial Plain, Fluvio Volcanic Plain of Young Merapi, and Swamp Alluvial Plain. Generally, the groundwater quality is medium to poor, the hydrochemical type is Va (initiation process of connate water and type III (evaporate water, shallow up to medium of water table, and low to middle class of aquifer permeability

  2. Can Remote Sensing Detect Aquifer Characteristics?: A Case Study in the Guarani Aquifer System

    Science.gov (United States)

    Richey, A. S.; Thomas, B.; Famiglietti, J. S.

    2013-12-01

    Global water supply resiliency depends on groundwater, especially regions threatened by population growth and climate change. Aquifer characteristics, even as basic as confined versus unconfined, are necessary to prescribe regulations to sustainably manage groundwater supplies. A significant barrier to sustainable groundwater management exists in the difficulties associated with mapping groundwater resources and characteristics at a large spatial scale. This study addresses this challenge by investigating if remote sensing, including with NASA's Gravity Recovery and Climate Experiment (GRACE), can detect and quantify key aquifer parameters and characteristics. We explore this through a case study in the Guarani Aquifer System (GAS) of South America, validating our remote sensing-based findings against the best available regional estimates. The use of remote sensing to advance the understanding of large aquifers is beneficial to sustainable groundwater management, especially in a trans-boundary system, where consistent information exchange can occur within hydrologic boundaries instead of political boundaries.

  3. Effect of Short-Circuit Pathways on Water Quality in Selected Confined Aquifers (Invited)

    Science.gov (United States)

    McMahon, P. B.

    2010-12-01

    Confined aquifers in the United States generally contain fewer anthropogenic contaminants than unconfined aquifers because confined aquifers often contain water recharged prior to substantial human development and redox conditions are more reducing, which favors degradation of common contaminants like nitrate and chlorinated solvents. Groundwater in a confined part of the High Plains aquifer near York, Nebraska had an adjusted radiocarbon age of about 2,000 years, and groundwater in a confined part of the Floridan aquifer near Tampa, Florida had apparent ages greater than 60 years on the basis of tritium measurements. Yet compounds introduced more recently into the environment (anthropogenic nitrate and volatile organic compounds) were detected in selected public-supply wells completed in both aquifers. Depth-dependent measurements of flow and chemistry in the pumping supply wells, groundwater age dating, numerical modeling of groundwater flow, and other monitoring data indicated that the confined aquifers sampled by the supply wells were connected to contaminated unconfined aquifers by short-circuit pathways. In the High Plains aquifer, the primary pathways appeared to be inactive irrigation wells screened in both the unconfined and confined aquifers. In the Floridan aquifer, the primary pathways were karst sinkholes and conduits. Heavy pumping in both confined systems exacerbated the problem by reducing the potentiometric surface and increasing groundwater velocities, thus enhancing downward gradients and reducing reaction times for processes like denitrification. From a broader perspective, several confined aquifers in the U.S. have experienced large declines in their potentiometric surfaces because of groundwater pumping and this could increase the potential for contamination in those aquifers, particularly where short-circuit pathways connect them to shallower, contaminated sources of water, such as was observed in York and Tampa.

  4. FEWA: a Finite Element model of Water flow through Aquifers

    International Nuclear Information System (INIS)

    Yeh, G.T.; Huff, D.D.

    1983-11-01

    This report documents the implementation and demonstration of a Finite Element model of Water flow through Aquifers (FEWA). The particular features of FEWA are its versatility and flexibility to deal with as many real-world problems as possible. Point as well as distributed sources/sinks are included to represent recharges/pumpings and rainfall infiltrations. All sources/sinks can be transient or steady state. Prescribed hydraulic head on the Dirichlet boundaries and fluxes on Neumann or Cauchy boundaries can be time-dependent or constant. Source/sink strength over each element and node, hydraulic head at each Dirichlet boundary node, and flux at each boundary segment can vary independently of each other. Either completely confined or completely unconfined aquifers, or partially confined and partially unconfined aquifers can be dealt with effectively. Discretization of a compound region with very irregular curved boundaries is made easy by including both quadrilateral and triangular elements in the formulation. Large-field problems can be solved efficiently by including a pointwise iterative solution strategy as an optional alternative to the direct elimination solution method for the matrix equation approximating the partial differential equation of groundwater flow. FEWA also includes transient flow through confining leaky aquifers lying above and/or below the aquifer of interest. The model is verified against three simple cases to which analytical solutions are available. It is then demonstrated by two examples of how the model can be applied to heterogeneous and anisotropic aquifers with transient boundary conditions, time-dependent sources/sinks, and confining aquitards for a confined aquifer of variable thickness and for a free surface problem in an unconfined aquifer, respectively. 20 references, 25 figures, 8 tables

  5. FEWA: a Finite Element model of Water flow through Aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, G.T.; Huff, D.D.

    1983-11-01

    This report documents the implementation and demonstration of a Finite Element model of Water flow through Aquifers (FEWA). The particular features of FEWA are its versatility and flexibility to deal with as many real-world problems as possible. Point as well as distributed sources/sinks are included to represent recharges/pumpings and rainfall infiltrations. All sources/sinks can be transient or steady state. Prescribed hydraulic head on the Dirichlet boundaries and fluxes on Neumann or Cauchy boundaries can be time-dependent or constant. Source/sink strength over each element and node, hydraulic head at each Dirichlet boundary node, and flux at each boundary segment can vary independently of each other. Either completely confined or completely unconfined aquifers, or partially confined and partially unconfined aquifers can be dealt with effectively. Discretization of a compound region with very irregular curved boundaries is made easy by including both quadrilateral and triangular elements in the formulation. Large-field problems can be solved efficiently by including a pointwise iterative solution strategy as an optional alternative to the direct elimination solution method for the matrix equation approximating the partial differential equation of groundwater flow. FEWA also includes transient flow through confining leaky aquifers lying above and/or below the aquifer of interest. The model is verified against three simple cases to which analytical solutions are available. It is then demonstrated by two examples of how the model can be applied to heterogeneous and anisotropic aquifers with transient boundary conditions, time-dependent sources/sinks, and confining aquitards for a confined aquifer of variable thickness and for a free surface problem in an unconfined aquifer, respectively. 20 references, 25 figures, 8 tables.

  6. Hydrogeology and water quality of glacial-drift aquifers in the Bemidji-Bagley area, Beltrami, Clearwater, Cass, and Hubbard counties, Minnesota

    Science.gov (United States)

    Stark, J.R.; Busch, J.P.; Deters, M.H.

    1991-01-01

    Unconfined and the upper confined aquifers in glacial drift are the primary sources of water in a 1,600 square-mile area including parts of Beltrami, Cass, Clearwater, and Hubbard Counties, Minnesota. The unconfineddrift aquifer consists of coarse sand and gravel in the center of the study area. The total area underlain by the unconfined-drift aquifer is approximately 550 square miles. The unconfined aquifer ranges in thickness from 0 to 130 feet, and is greater than 20 feet thick over an area of 280 square miles. On the basis of scant data, the transmissivity of the unconfined aquifer ranges from less than 70 feet squared per day in the south and west to greater than 8,900 feet squared per day in an area west of Bemidji. Well yields from 10 to 300 gallons per minute are possible in some areas. The unconfined and upper confined-drift aquifers are separated by a fine-grained confining unit of till or lake deposits.

  7. Response of the Water Level in a Well to Earth Tides and Atmospheric Loading Under Unconfined Conditions

    Science.gov (United States)

    Rojstaczer, Stuart; Riley, Francis S.

    1990-08-01

    The response of the water level in a well to Earth tides and atmospheric loading under unconfined conditions can be explained if the water level is controlled by the aquifer response averaged over the saturated depth of the well. Because vertical averaging tends to diminish the influence of the water table, the response is qualitatively similar to the response of a well under partially confined conditions. When the influence of well bore storage can be ignored, the response to Earth tides is strongly governed by a dimensionless aquifer frequency Q'u. The response to atmospheric loading is strongly governed by two dimensionless vertical fluid flow parameters: a dimensionless unsaturated zone frequency, R, and a dimensionless aquifer frequency Qu. The differences between Q'u and Qu are generally small for aquifers which are highly sensitive to Earth tides. When Q'u and Qu are large, the response of the well to Earth tides and atmospheric loading approaches the static response of the aquifer under confined conditions. At small values of Q'u and Qu, well response to Earth tides and atmospheric loading is strongly influenced by water table drainage. When R is large relative to Qu, the response to atmospheric loading is strongly influenced by attenuation and phase shift of the pneumatic pressure signal in the unsaturated zone. The presence of partial penetration retards phase advance in well response to Earth tides and atmospheric loading. When the theoretical response of a phreatic well to Earth tides and atmospheric loading is fit to the well response inferred from cross-spectral estimation, it is possible to obtain estimates of the pneumatic diffusivity of the unsaturated zone and the vertical hydraulic conductivity of the aquifer.

  8. Carbonate aquifers

    Science.gov (United States)

    Cunningham, Kevin J.; Sukop, Michael; Curran, H. Allen

    2012-01-01

    Only limited hydrogeological research has been conducted using ichnology in carbonate aquifer characterization. Regardless, important applications of ichnology to carbonate aquifer characterization include its use to distinguish and delineate depositional cycles, correlate mappable biogenically altered surfaces, identify zones of preferential groundwater flow and paleogroundwater flow, and better understand the origin of ichnofabric-related karst features. Three case studies, which include Pleistocene carbonate rocks of the Biscayne aquifer in southern Florida and Cretaceous carbonate strata of the Edwards–Trinity aquifer system in central Texas, demonstrate that (1) there can be a strong relation between ichnofabrics and groundwater flow in carbonate aquifers and (2) ichnology can offer a useful methodology for carbonate aquifer characterization. In these examples, zones of extremely permeable, ichnofabric-related macroporosity are mappable stratiform geobodies and as such can be represented in groundwater flow and transport simulations.

  9. The structure of the crust and uppermost mantle beneath Madagascar

    Science.gov (United States)

    Andriampenomanana, Fenitra; Nyblade, Andrew A.; Wysession, Michael E.; Durrheim, Raymond J.; Tilmann, Frederik; Julià, Jordi; Pratt, Martin J.; Rambolamanana, Gérard; Aleqabi, Ghassan; Shore, Patrick J.; Rakotondraibe, Tsiriandrimanana

    2017-09-01

    The lithosphere of Madagascar was initially amalgamated during the Pan-African events in the Neoproterozoic. It has subsequently been reshaped by extensional processes associated with the separation from Africa and India in the Jurassic and Cretaceous, respectively, and been subjected to several magmatic events in the late Cretaceous and the Cenozoic. In this study, the crust and uppermost mantle have been investigated to gain insights into the present-day structure and tectonic evolution of Madagascar. We analysed receiver functions, computed from data recorded on 37 broad-band seismic stations, using the H-κ stacking method and a joint inversion with Rayleigh-wave phase-velocity measurements. The thickness of the Malagasy crust ranges between 18 and 46 km. It is generally thick beneath the spine of mountains in the centre part (up to 46 km thick) and decreases in thickness towards the edges of the island. The shallowest Moho is found beneath the western sedimentary basins (18 km thick), which formed during both the Permo-Triassic Karro rifting in Gondwana and the Jurassic rifting of Madagascar from eastern Africa. The crust below the sedimentary basin thickens towards the north and east, reflecting the progressive development of the basins. In contrast, in the east there was no major rifting episode. Instead, the slight thinning of the crust along the east coast (31-36 km thick) may have been caused by crustal uplift and erosion when Madagascar moved over the Marion hotspot and India broke away from it. The parameters describing the crustal structure of Archean and Proterozoic terranes, including average thickness (40 km versus 35 km), Poisson's ratio (0.25 versus 0.26), average shear-wave velocity (both 3.7 km s-1), and thickness of mafic lower crust (7 km versus 4 km), show weak evidence of secular variation. The uppermost mantle beneath Madagascar is generally characterized by shear-wave velocities typical of stable lithosphere (∼4.5 km s-1). However

  10. Effect of Unsaturated Flow on Delayed Response of Unconfined Aquifiers to Pumping

    Science.gov (United States)

    Tartakovsky, G.; Neuman, S. P.

    2005-12-01

    A new analytical solution is presented for the delayed response process characterizing flow to a partially penetrating well in an unconfined aquifer. The new solution generalizes that of Neuman [1972, 1974] by accounting for unsaturated flow above the water table. Axially symmetric three-dimensional flow in the unsaturated zone is described by a linearized version of Richards' equation in which hydraulic conductivity and water content vary exponentially with incremental capillary pressure head relative to its air entry value (defining the interface between the saturated and unsaturated zones). Unsaturated soil properties are characterized by an exponent κ having the dimension of inverse length and a dimensionless exponent κD = κb where b is initial saturated thickness. Our treatment of the unsaturated zone is similar to that of Kroszynski and Dagan [1975] who however have ignored internal (artesian) aquifer storage. It has been suggested by Boulton [1954, 1963, 1970] and Neuman [1972, 1974], and is confirmed by our solution, that internal storage is required to reproduce the early increase in drawdown characterizing delayed response to pumping in typical aquifers. According to our new solution such aquifers are characterized by relatively large κ_ D values, typically 10 or larger; in the limit as κD tends to infinity (the soil unsaturated water retention capacity becomes insignificant and/or aquifer thickness become large), unsaturated flow becomes unimportant and our solution reduces to that of Neuman. In typical cases corresponding to κD larger than or equal to 10, unsaturated flow is found to have little impact on early and late dimensionless time behaviors of drawdown measured wholly or in part at some distance below the water table; unsaturated flow causes drawdown to increase slightly at intermediate dimensionless time values that represent transition from an early artesian dominated to a late water-table dominated flow regime. The increase in drawdown

  11. Three-Dimensional Flow Generated by a Partially Penetrating Well in a Two-Aquifer System

    Science.gov (United States)

    Sepulveda, N.

    2007-12-01

    An analytical solution is presented for three-dimensional (3D) flow in a confined aquifer and the overlying storative semiconfining layer and unconfined aquifer. The equation describing flow caused by a partially penetrating production well is solved analytically to provide a method to accurately determine the hydraulic parameters in the confined aquifer, semiconfining layer, and unconfined aquifer from aquifer-test data. Previous solutions for a partially penetrating well did not account for 3D flow or storativity in the semiconfining unit. The 3D and two- dimensional (2D) flow solutions in the semiconfining layer are compared for various hydraulic conductivity ratios between the aquifer and the semiconfining layer. Analysis of the drawdown data from an aquifer test in central Florida showed that the 3D solution in the semiconfining layer provides a more unique identification of the hydraulic parameters than the 2D solution. The analytical solution could be used to analyze, with higher accuracy, the effect that pumping water from the lower aquifer in a two-aquifer system has on wetlands.

  12. Behaviour of soil-cement specimens in unconfined dynamic compression

    Science.gov (United States)

    Davies, J.; Fendukly, L. M.

    1994-06-01

    The response of the cement-stabilized red marl to dynamic loading in compression has been investigated over a range of cement contents and curing times. Specimens were subjected to different stress levels below unconfined compressive strength, at a frequency of 5 Hz, and a fatigue relationship for the material was developed. The value of resilient modulus was found to be greater than the modulus of elasticity for the same cement content and curing time.

  13. Flow Generated by a Partially Penetrating Well in a Leaky Two-Aquifer System with a Storative Semiconfining Layer

    Science.gov (United States)

    Sepulveda, N.; Rohrer, K.

    2008-05-01

    The permeability of the semiconfining layers of the highly productive Floridan Aquifer System may be large enough to invalidate the assumptions of the leaky aquifer theory. These layers are the intermediate confining and the middle semiconfining units. The analysis of aquifer-test data with analytical solutions of the ground-water flow equation developed with the approximation of a low hydraulic conductivity ratio between the semiconfining layer and the aquifer may lead to inaccurate hydraulic parameters. An analytical solution is presented here for the flow in a confined leaky aquifer, the overlying storative semiconfining layer, and the unconfined aquifer, generated by a partially penetrating well in a two-aquifer system, and allowing vertical and lateral flow components to occur in the semiconfining layer. The equations describing flow caused by a partially penetrating production well are solved analytically to provide a method to accurately determine the hydraulic parameters in the confined aquifer, semiconfining layer, and unconfined aquifer from aquifer-test data. Analysis of the drawdown data from an aquifer test performed in central Florida showed that the flow solution presented here for the semiconfining layer provides a better match and a more unique identification of the hydraulic parameters than an analytical solution that considers only vertical flow in the semiconfining layer.

  14. A Black Hills-Madison Aquifer origin for Dakota Aquifer groundwater in northeastern Nebraska.

    Science.gov (United States)

    Stotler, Randy; Harvey, F Edwin; Gosselin, David C

    2010-01-01

    Previous studies of the Dakota Aquifer in South Dakota attributed elevated groundwater sulfate concentrations to Madison Aquifer recharge in the Black Hills with subsequent chemical evolution prior to upward migration into the Dakota Aquifer. This study examines the plausibility of a Madison Aquifer origin for groundwater in northeastern Nebraska. Dakota Aquifer water samples were collected for major ion chemistry and isotopic analysis ((18)O, (2)H, (3)H, (14)C, (13)C, (34)S, (18)O-SO(4), (87)Sr, (37)Cl). Results show that groundwater beneath the eastern, unconfined portion of the study area is distinctly different from groundwater sampled beneath the western, confined portion. In the east, groundwater is calcium-bicarbonate type, with delta(18)O values (-9.6 per thousand to -12.4 per thousand) similar to local, modern precipitation (-7.4 per thousand to -10 per thousand), and tritium values reflecting modern recharge. In the west, groundwater is calcium-sulfate type, having depleted delta(18)O values (-16 per thousand to -18 per thousand) relative to local, modern precipitation, and (14)C ages 32,000 to more than 47,000 years before present. Sulfate, delta(18)O, delta(2)H, delta(34)S, and delta(18)O-SO(4) concentrations are similar to those found in Madison Aquifer groundwater in South Dakota. Thus, it is proposed that Madison Aquifer source water is also present within the Dakota Aquifer beneath northeastern Nebraska. A simple Darcy equation estimate of groundwater velocities and travel times using reported physical parameters from the Madison and Dakota Aquifers suggests such a migration is plausible. However, discrepancies between (14)C and Darcy age estimates indicate that (14)C ages may not accurately reflect aquifer residence time, due to mixtures of varying aged water.

  15. FEMA: a Finite Element Model of Material Transport through Aquifers

    International Nuclear Information System (INIS)

    Yeh, G.T.; Huff, D.D.

    1985-01-01

    This report documents the construction, verification, and demonstration of a Finite Element Model of Material Transport through Aquifers (FEMA). The particular features of FEMA are its versatility and flexibility to deal with as many real-world problems as possible. Mechanisms included in FEMA are: carrier fluid advection, hydrodynamic dispersion and molecular diffusion, radioactive decay, sorption, source/sinks, and degradation due to biological, chemical as well as physical processes. Three optional sorption models are embodied in FEMA. These are linear isotherm and Freundlich and Langmuir nonlinear isotherms. Point as well as distributed source/sinks are included to represent artificial injection/withdrawals and natural infiltration of precipitation. All source/sinks can be transient or steady state. Prescribed concentration on the Dirichlet boundary, given gradient on the Neumann boundary segment, and flux at each Cauchy boundary segment can vary independently of each other. The aquifer may consist of as many formations as desired. Either completely confined or completely unconfined or partially confined and partially unconfined aquifers can be dealt with effectively. FEMA also includes transient leakage to or from the aquifer of interest through confining beds from or to aquifers lying below and/or above

  16. FEMA: a Finite Element Model of Material Transport through Aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, G.T.; Huff, D.D.

    1985-01-01

    This report documents the construction, verification, and demonstration of a Finite Element Model of Material Transport through Aquifers (FEMA). The particular features of FEMA are its versatility and flexibility to deal with as many real-world problems as possible. Mechanisms included in FEMA are: carrier fluid advection, hydrodynamic dispersion and molecular diffusion, radioactive decay, sorption, source/sinks, and degradation due to biological, chemical as well as physical processes. Three optional sorption models are embodied in FEMA. These are linear isotherm and Freundlich and Langmuir nonlinear isotherms. Point as well as distributed source/sinks are included to represent artificial injection/withdrawals and natural infiltration of precipitation. All source/sinks can be transient or steady state. Prescribed concentration on the Dirichlet boundary, given gradient on the Neumann boundary segment, and flux at each Cauchy boundary segment can vary independently of each other. The aquifer may consist of as many formations as desired. Either completely confined or completely unconfined or partially confined and partially unconfined aquifers can be dealt with effectively. FEMA also includes transient leakage to or from the aquifer of interest through confining beds from or to aquifers lying below and/or above.

  17. Long term rise of a free aquifer in Sahel: hydrodynamic and radioisotopic estimations (3H, 14C) of the recharge in SW Niger

    International Nuclear Information System (INIS)

    Favreau, G.

    2001-01-01

    This article summarizes an hydrodynamic and geochemical survey carried out in SW Niger in order to estimate the impact of rainfall changes and deforestation on the recharge of the uppermost Cretaceous aquifer. 14 C and 3 H activities of the total dissolved inorganic carbon have been used to quantify the long-term recharge of the aquifer. (J.S.)

  18. Ozark Aquifer

    Data.gov (United States)

    Kansas Data Access and Support Center — These digital maps contain information on the altitude of the base and top, the extent, and the potentiometric surface of the Ozark aquifer in Kansas. The Ozark...

  19. Three-dimensional conceptual model for the Hanford Site unconfined aquifer system, FY 1993 status report

    International Nuclear Information System (INIS)

    Thorne, P.D.; Chamness, M.A.; Spane, F.A. Jr.; Vermeul, V.R.; Webber, W.D.

    1993-12-01

    The ground water underlying parts of the Hanford Site (Figure 1.1) contains radioactive and chemical contaminants at concentrations exceeding regulatory standards (Dresel et al. 1993). The Hanford Site Ground-Water Surveillance Project, operated by Pacific Northwest Laboratory (PNL), is responsible for monitoring the movement of these contaminants to ensure that public health and the environment are protected. To support the monitoring effort, a sitewide three-dimensional ground-water flow model is being developed. This report provides an update on the status of the conceptual model that will form the basis for constructing a numerical three-dimensional flow model for, the site. Thorne and Chamness (1992) provide additional information on the initial development of the three-dimensional conceptual model

  20. Saltwater intrusion and water management in the unconfined coastal aquifer of Ravenna (Italy): a numerical model

    NARCIS (Netherlands)

    Giambastiani, Beatrice Maria Sole; Antonellini, Marco; Oude Essink, Gualbert; Stuurman, Roelof J.

    2007-01-01

    The Ravenna pine forests represent an historical landmark in the Po River Plain. They have great environmental, historical and tourist value. The San Vitale pine for- est is located 10 km north of the town. It is surrounded by an urban area, the city indus- trial infrastructure and the waterworks of

  1. Characterising Bedrock Aquifer Systems in Korea Using Paired Water-Level Monitoring Data

    Directory of Open Access Journals (Sweden)

    Jae Min Lee

    2017-06-01

    Full Text Available This study focused on characterising aquifer systems based on water-level changes observed systematically at 159 paired groundwater monitoring wells throughout Korea. Using spectral analysis, principal component analysis (PCA, and cross-correlation analysis with linear regression, aquifer conditions were identified from the comparison of water-level changes in shallow alluvial and deep bedrock monitoring wells. The spectral analysis could identify the aquifer conditions (i.e., unconfined, semi-confined and confined of 58.5% of bedrock wells and 42.8% of alluvial wells: 93 and 68 wells out of 159 wells, respectively. Even among the bedrock wells, 50 wells (53.7% exhibited characteristics of the unconfined condition, implying significant vulnerability of the aquifer to contaminants from the land surface and shallow depths. It appears to be better approach for deep bedrock aquifers than shallow alluvial aquifers. However, significant portions of the water-level changes remained unclear for categorising aquifer conditions due to disturbances in data continuity. For different aquifer conditions, PCA could show typical pattern and factor scores of principal components. Principal component 1 due to wet-and-dry seasonal changes and water-level response time was dominant covering about 55% of total variances of each aquifer conditions, implying the usefulness of supplementary method of aquifer characterisation. Cross-correlation and time-lag analysis in the water-level responses to precipitations clearly show how the water levels in shallow and deep wells correspond in time scale. No significant differences in time-lags was found between shallow and deep wells. However, clear time-lags were found to be increasing from unconfined to confined conditions: from 1.47 to 2.75 days and from 1.78 to 2.75 days for both shallow alluvial and deep bedrock wells, respectively. In combination of various statistical methods, three types of water-level fluctuation

  2. Determination of friction coefficient in unconfined compression of brain tissue.

    Science.gov (United States)

    Rashid, Badar; Destrade, Michel; Gilchrist, Michael D

    2012-10-01

    Unconfined compression tests are more convenient to perform on cylindrical samples of brain tissue than tensile tests in order to estimate mechanical properties of the brain tissue because they allow homogeneous deformations. The reliability of these tests depends significantly on the amount of friction generated at the specimen/platen interface. Thus, there is a crucial need to find an approximate value of the friction coefficient in order to predict a possible overestimation of stresses during unconfined compression tests. In this study, a combined experimental-computational approach was adopted to estimate the dynamic friction coefficient μ of porcine brain matter against metal platens in compressive tests. Cylindrical samples of porcine brain tissue were tested up to 30% strain at variable strain rates, both under bonded and lubricated conditions in the same controlled environment. It was established that μ was equal to 0.09±0.03, 0.18±0.04, 0.18±0.04 and 0.20±0.02 at strain rates of 1, 30, 60 and 90/s, respectively. Additional tests were also performed to analyze brain tissue under lubricated and bonded conditions, with and without initial contact of the top platen with the brain tissue, with different specimen aspect ratios and with different lubricants (Phosphate Buffer Saline (PBS), Polytetrafluoroethylene (PTFE) and Silicone). The test conditions (lubricant used, biological tissue, loading velocity) adopted in this study were similar to the studies conducted by other research groups. This study will help to understand the amount of friction generated during unconfined compression of brain tissue for strain rates of up to 90/s. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Straddle-packer aquifer test analyses of the Snake River Plain aquifer at the Idaho National Engineering Laboratory

    International Nuclear Information System (INIS)

    Johnson, G.S.; Frederick, D.B.

    1997-01-01

    The State of Idaho INEL Oversight Program, with the University of Idaho, Idaho State University, Boise State University, and the Idaho Geologic Survey, used a straddle-packer system to investigate vertical variations in characteristics of the Snake River Plain aquifer at the Idaho National Engineering Laboratory in southeast Idaho. Sixteen single-well aquifer tests were conducted on.isolated intervals in three observation wells. Each of these wells has approximately 200 feet of open borehole below the water table, penetrating the E through G and I basalt flow groups and interbedded sediments of the Snake River Plain aquifer. The success of the aquifer tests was limited by the inability to induce measurable drawdown in several zones. Time-drawdown data from aquifer tests were matched to type curves for 8 of the 16 zones tested. A single aquifer test at the water table exhibited greater curvature than those at depth. The increased degree of curvature suggests an unconfined response and resulted in an estimate of specific yield of 0.03. Aquifer tests below the water table generally yielded time-drawdown graphs with a rapid initial response followed by constant drawdown throughout the duration of the tests; up to several hours in length. The rapid initial response implies that the aquifer responds as a confined system during brief pumping periods. The nearly constant drawdown suggests a secondary source of water, probably vertical flow from overlying and underlying aquifer layers. Three analytical models were applied for comparison to the conceptual model and to provide estimates of aquifer properties. This, Hantush-Jacob leaky aquifer, and the Moench double-porosity fractured rock models were fit to time-drawdown data. The leaky aquifer type curves of Hantush and Jacob generally provided the best match to observed drawdown. A specific capacity regression equation was also used to estimate hydraulic conductivity

  4. Guarani aquifer

    International Nuclear Information System (INIS)

    2007-01-01

    The environmental protection and sustain ability develop project of Guarani Aquifer System is a join work from Argentina, Brazil, Paraguay and Uruguay with a purpose to increase the knowledge resource and propose technical legal and organizational framework for sustainable management between countries.The Universities funds were created as regional universities support in promotion, training and academic research activities related to environmental al social aspects of the Guarani Aquifer System.The aim of the project is the management and protection of the underground waters resources taking advantage and assesment for nowadays and future generations

  5. Ground-water flow directions and estimation of aquifer hydraulic properties in the lower Great Miami River Buried Valley aquifer system, Hamilton Area, Ohio

    Science.gov (United States)

    Sheets, Rodney A.; Bossenbroek, Karen E.

    2005-01-01

    The Great Miami River Buried Valley Aquifer System is one of the most productive sources of potable water in the Midwest, yielding as much as 3,000 gallons per minute to wells. Many water-supply wells tapping this aquifer system are purposely placed near rivers to take advantage of induced infiltration from the rivers. The City of Hamilton's North Well Field consists of 10 wells near the Great Miami River, all completed in the lower Great Miami River Buried Valley Aquifer System. A well-drilling program and a multiple-well aquifer test were done to investigate ground-water flow directions and to estimate aquifer hydraulic properties in the lower part of the Great Miami River Buried Valley Aquifer System. Descriptions of lithology from 10 well borings indicate varying amounts and thickness of clay or till, and therefore, varying levels of potential aquifer confinement. Borings also indicate that the aquifer properties can change dramatically over relatively short distances. Grain-size analyses indicate an average bulk hydraulic conductivity value of aquifer materials of 240 feet per day; the geometric mean of hydraulic conductivity values of aquifer material was 89 feet per day. Median grain sizes of aquifer material and clay units were 1.3 millimeters and 0.1 millimeters, respectively. Water levels in the Hamilton North Well Field are affected by stream stage in the Great Miami River and barometric pressure. Bank storage in response to stream stage is evident. Results from a multiple-well aquifer test at the well field indicate, as do the lithologic descriptions, that the aquifer is semiconfined in some areas and unconfined in others. Transmissivity and storage coefficient of the semiconfined part of the aquifer were 50,000 feet squared per day and 5x10-4, respectively. The average hydraulic conductivity (450 feet per day) based on the aquifer test is reasonable for glacial outwash but is higher than calculated from grain-size analyses, implying a scale effect

  6. Geochemical evolution processes and water-quality observations based on results of the National Water-Quality Assessment Program in the San Antonio segment of the Edwards aquifer, 1996-2006

    Science.gov (United States)

    Musgrove, MaryLynn; Fahlquist, Lynne; Houston, Natalie A.; Lindgren, Richard J.; Ging, Patricia B.

    2010-01-01

    As part of the National Water-Quality Assessment Program, the U.S. Geological Survey collected and analyzed groundwater samples during 1996-2006 from the San Antonio segment of the Edwards aquifer of central Texas, a productive karst aquifer developed in Cretaceous-age carbonate rocks. These National Water-Quality Assessment Program studies provide an extensive dataset of groundwater geochemistry and water quality, consisting of 249 groundwater samples collected from 136 sites (wells and springs), including (1) wells completed in the shallow, unconfined, and urbanized part of the aquifer in the vicinity of San Antonio (shallow/urban unconfined category), (2) wells completed in the unconfined (outcrop area) part of the regional aquifer (unconfined category), and (3) wells completed in and springs discharging from the confined part of the regional aquifer (confined category). This report evaluates these data to assess geochemical evolution processes, including local- and regional-scale processes controlling groundwater geochemistry, and to make water-quality observations pertaining to sources and distribution of natural constituents and anthropogenic contaminants, the relation between geochemistry and hydrologic conditions, and groundwater age tracers and travel time. Implications for monitoring water-quality trends in karst are also discussed. Geochemical and isotopic data are useful tracers of recharge, groundwater flow, fluid mixing, and water-rock interaction processes that affect water quality. Sources of dissolved constituents to Edwards aquifer groundwater include dissolution of and geochemical interaction with overlying soils and calcite and dolomite minerals that compose the aquifer. Geochemical tracers such as magnesium to calcium and strontium to calcium ratios and strontium isotope compositions are used to evaluate and constrain progressive fluid-evolution processes. Molar ratios of magnesium to calcium and strontium to calcium in groundwater typically

  7. Water-quality observations of the San Antonio segment of the Edwards aquifer, Texas, with an emphasis on processes influencing nutrient and pesticide geochemistry and factors affecting aquifer vulnerability, 2010–16

    Science.gov (United States)

    Opsahl, Stephen P.; Musgrove, MaryLynn; Mahler, Barbara J.; Lambert, Rebecca B.

    2018-06-07

    As questions regarding the influence of increasing urbanization on water quality in the Edwards aquifer are raised, a better understanding of the sources, fate, and transport of compounds of concern in the aquifer—in particular, nutrients and pesticides—is needed to improve water management decision-making capabilities. The U.S. Geological Survey, in cooperation with the San Antonio Water System, performed a study from 2010 to 2016 to better understand how water quality changes under a range of hydrologic conditions and in contrasting land-cover settings (rural and urban) in the Edwards aquifer. The study design included continuous hydrologic monitoring, continuous water-quality monitoring, and discrete sample collection for a detailed characterization of water quality at a network of sites throughout the aquifer system. The sites were selected to encompass a “source-to-sink” (that is, from aquifer recharge to aquifer discharge) approach. Network sites were selected to characterize rainfall, recharging surface water, and groundwater; groundwater sites included wells in the unconfined part of the aquifer (unconfined wells) and in the confined part of the aquifer (confined wells) and a major discharging spring. Storm-related samples—including rainfall samples, stormwater-runoff (surface-water) samples, and groundwater samples—were collected to characterize the aquifer response to recharge.Elevated nitrate concentrations relative to national background values and the widespread detection of pesticides indicate that the Edwards aquifer is vulnerable to contamination and that vulnerability is affected by factors such as land cover, aquifer hydrogeology, and changes in hydrologic conditions. Greater vulnerability of groundwater in urban areas relative to rural areas was evident from results for urban groundwater sites, which generally had higher nitrate concentrations, elevated δ15N-nitrate values, a greater diversity of pesticides, and higher pesticide

  8. Unconfined deflagrative explosions without turbulence: experiments and model

    International Nuclear Information System (INIS)

    Lannoy, A.

    1989-01-01

    This paper reviews laboratory, balloon and open field experiments which have been performed to study the deflagration regime in free air. In a first part, are considered different models available to estimate deflagrative unconfined explosions effects, without turbulence. Then, a description is given of the known performed tests, which indicate the effective scale of various experiments, their operating conditions and the type of measurements carried out. Results are presented and discussed. The influence on the explosion force of different parameters (fuel concentration gradients, flammable mixture shape and size, ignition energy) is estimated. The overall conclusion of this survey is that flammable mixtures drifting over open field and ignited, will burn with low flame speed and consequently will generate very weak pressure effects [fr

  9. Distribution of aquifers, liquid-waste impoundments, and municipal water-supply sources, Massachusetts

    Science.gov (United States)

    Delaney, David F.; Maevsky, Anthony

    1980-01-01

    Impoundments of liquid waste are potential sources of ground-water contamination in Massachusetts. The map report, at a scale of 1 inch equals 4 miles, shows the idstribution of aquifers and the locations of municipal water-supply sources and known liquid-waste impoundments. Ground water, an important source of municipal water supply, is produced from shallow sand and gravel aquifers that are generally unconfined, less than 200 feet thick, and yield less than 2,000 gallons per minute to individual wells. These aquifers commonly occupy lowlands and stream valleys and are most extensive in eastern Massachusetts. Surface impoundments of liquid waste are commonly located over these aquifers. These impoundments may leak and allow waste to infiltrate underlying aquifers and alter their water quality. (USGS)

  10. Marine macrofossil communities in the uppermost Maastrichtian chalk of Stevns Klint, Denmark

    DEFF Research Database (Denmark)

    Hansen, Thomas; Surlyk, Finn

    2014-01-01

    Three successive marine habitats and their benthic macrofossil communities have been recognised and assessed in the uppermost Maastrichtian chalk of Stevns Klint, Denmark. The mound-bedded lower Sigerslev Member was deposited below the photic zone under the influence of persistent, non-erosive bo......Three successive marine habitats and their benthic macrofossil communities have been recognised and assessed in the uppermost Maastrichtian chalk of Stevns Klint, Denmark. The mound-bedded lower Sigerslev Member was deposited below the photic zone under the influence of persistent, non...

  11. Inherent mineralization of 2,6-dichlorobenzamide (BAM) in unsaturated zone and aquifers – Effect of initial concentrations and adaptation

    DEFF Research Database (Denmark)

    Janniche, Gry Sander; Clausen, Liselotte; Albrechtsen, Hans-Jørgen

    2011-01-01

    cores with known dichlobenil application were collected from topsoil to 8.5 m below surface resulting in 57 samples hereof 4 aquifer samples. Mineralization was only substantial (>10%) in the uppermost meter of the unsaturated zone. Microbial adaptation, observed as faster mineralization in pre......, in pre-exposed clay mineralization was stimulated at high concentrations. Furthermore BAM was for the first time mineralized in aerobic aquifer sediments from different BAM-contaminated groundwater locations. BAM mineralization in subsurface and groundwater was demonstrated....

  12. An evaluation of slug interference tests for aquifer characterization at the Hanford Site

    International Nuclear Information System (INIS)

    Spane, F.A. Jr.; Thorne, P.D.

    1992-01-01

    Slug interference tests are conducted by instantaneously changing the water level in a well and monitoring the aquifer response at one or more observation wells. The applicability of this method for hydraulic characterization of a high permeability unconfined aquifer at the Hanford Site was evaluated. Analytical techniques were used to predict slug interference responses over a range of aquifer hydraulic conditions and observation well distances. This was followed by a field test of the proposed technique. The results showed that slug interference testing can be used to characterize aquifers having transmissivities up to 10 -1 m 2 /s compared to a maximum transmissivity of about 10 -3 m 2 /s for single-well slug tests. The amplitude of the pressure response measured at the observation well is primarily determined by aquifer storativity, while the time-lag of the pressure peak is mainly controlled by the transmissivity. Several recommendations are made optimizing the results of slug interference tests in higher permeability, unconfined to semiconfined aquifers

  13. Transient well flow in leaky multiple-aquifer systems

    Science.gov (United States)

    Hemker, C. J.

    1985-10-01

    A previously developed eigenvalue analysis approach to groundwater flow in leaky multiple aquifers is used to derive exact solutions for transient well flow problems in leaky and confined systems comprising any number of aquifers. Equations are presented for the drawdown distribution in systems of infinite extent, caused by wells penetrating one or more of the aquifers completely and discharging each layer at a constant rate. Since the solution obtained may be regarded as a combined analytical-numerical technique, a type of one-dimensional modelling can be applied to find approximate solutions for several complicating conditions. Numerical evaluations are presented as time-drawdown curves and include effects of storage in the aquitard, unconfined conditions, partially penetrating wells and stratified aquifers. The outcome of calculations for relatively simple systems compares very well with published corresponding results. The proposed multilayer solution can be a valuable tool in aquifer test evaluation, as it provides the analytical expression required to enable the application of existing computer methods to the determination of aquifer characteristics.

  14. Aquifer test plan for the 100-HR-3 Operable Unit

    International Nuclear Information System (INIS)

    Swanson, L.C.; Hartman, M.J.

    1994-01-01

    This test plan directs hydrologic testing activities planned at three existing Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) wells in the 100-HR-3 Operable Unit of the Hanford Site. Three additional wells will be installed near these existing wells and used as additional testing arid observation points during the field activities. Figure 1 shows the locations of the three test sites. A primary objective of the testing program is to provide more detailed hydraulic characterization information for the unconfined aquifer and targeted test sites than provided by the initial reconnaissance-level slug testing of Vukelich. A second objective is to evaluate the applicability of slug interference and dipole flow tests for detailed hydraulic characterization in an unconfined aquifer. This aquifer testing program will also be useful for substantiating hydraulic conductivities reported from previous slug tests and evaluating the effects of filter pack volume/configuration on slug test data. Vukelich recommended additional testing to address the latter two issues

  15. Recharge and Aquifer Response: Manukan Island’s Aquifer, Sabah, Malaysia

    Directory of Open Access Journals (Sweden)

    Sarva Mangala Praveena

    2010-01-01

    Full Text Available Manukan Island is a small island located in North-West of Sabah, Malaysia was used as a case study area for numerical modeling of an aquifer response to recharge and pumping rates. The results in this study present the variations of recharge into the aquifer under the prediction simulations. The recharge rate increases the water level as indicated by hydraulic heads. This shows that it can alter groundwater of Manukan Island which has been suffering from an overexploration in its unconfined the aquifer. The increase in recharge rate (from 600 mm/year to 750 mm/year increases the water level indicated by hydraulic heads. A reduction in pumping rate (from 0.072 m3/day to 0.058 m3/day not only increases the amount of water levels in aquifer but also reduces the supply hence a deficit in supply. The increase in hydraulic heads depends on the percentage reduction of pumping and recharges rates. The well water has 1978.3 mg/L chloride with current pumping (0.072 m3/day and recharge rates (600 mm/year. However, with an increased of recharge rate and current pumping rate it has decreased about 1.13%. In addition, reduction in pumping rate made the chloride concentration decreased about 2.8%. In general, a reduction in pumping with an increase in recharge rate leads to a decreased in chloride concentrations within the vicinity of cone of depression. Next, to further develop the numerical model, the model should focus on climate change variables such as consequences of climate change are increase in air temperature, increase in sea surface temperature, and more extreme weather conditions. These parameters are considered critical parameters for climate change impact modeling in aquifers. The behavior of the aquifer and its sustainable pumping rate can be done by applying a computer modeling component.

  16. Residence Times in Central Valley Aquifers Recharged by Dammed Rivers

    Science.gov (United States)

    Loustale, M.; Paukert Vankeuren, A. N.; Visser, A.

    2017-12-01

    Groundwater is a vital resource for California, providing between 30-60% of the state's water supply. Recent emphasis on groundwater sustainability has induced a push to characterize recharge rates and residence times for high priority aquifers, including most aquifers in California's Central Valley. Flows in almost all rivers from the western Sierra to the Central Valley are controlled by dams, altering natural flow patterns and recharge to local aquifers. In eastern Sacramento, unconfined and confined shallow aquifers (depth recharged by a losing reach of the Lower American River, despite the presence of levees with slurry cut-off walls.1 Flow in the Lower American River is controlled through the operation of the Folsom and Nimbus Dams, with a minimum flow of 500 cfs. Water table elevation in wells in close proximity to the river are compared to river stage to determine the effect of river stage on groundwater recharge rates. Additionally, Tritium-3Helium dates and stable isotopes (∂18O and ∂2H) have been measured in monitoring wells 200- 2400 ft lateral distance from the river, and depths of 25 -225 feet BGS. Variation in groundwater age in the vertical and horizontal directions are used to determine groundwater flow path and velocity. These data are then used to calculate residence time of groundwater in the unconfined and confined aquifer systems for the Central Valley in eastern Sacramento. Applying groundwater age tracers can benefit future compliance metrics of the California Sustainable Groundwater Resources Act (SGMA), by quantifying river seepage rates and impacts of groundwater management on surface water resources. 1Moran et al., UCRL-TR-203258, 2004.

  17. Assessing the susceptibility to contamination of two aquifer systems used for public water supply in the Modesto and Fresno metropolitan areas, California, 2001 and 2002

    Science.gov (United States)

    Wright, Michael T.; Belitz, Kenneth; Johnson, Tyler D.

    2004-01-01

    Ground-water samples were collected from 90 active public supply wells in the Fresno and Modesto metropolitan areas as part of the California Aquifer Susceptibility (CAS) program. The CAS program was formed to examine the susceptibility to contamination of aquifers that are tapped by public supply wells to serve the citizens of California. The objectives of the program are twofold: (1) to evaluate the quality of ground water used for public supply using volatile organic compound (VOC) concentrations in ground-water samples and (2) to determine if the occurrence and distribution of low level VOCs in ground water and characteristics, such as land use, can be used to predict aquifer susceptibility to contamination from anthropogenic activities occurring at, or near, land surface. An evaluation was made of the relation between VOC occurrence and the explanatory variables: depth to the top of the uppermost well perforation, land use, relative ground-water age, high nitrate concentrations, density of leaking underground fuel tanks (LUFT), and source of recharge water. VOCs were detected in 92 percent of the wells sampled in Modesto and in 72 percent of the wells sampled in Fresno. Trihalomethanes (THM) and solvents were frequently detected in both study areas. Conversely, the gasoline components?benzene, toluene ethylbenzene, and xylenes (BTEX)?were rarely, if at all, detected, even though LUFTs were scattered throughout both study areas. The rare occurrence of BTEX compounds may be the result of their low solubility and labile nature in the subsurface environment. Samples were analyzed for 85 VOCs; 25 were detected in at least one sample. The concentrations of nearly all VOCs detected were at least an order of magnitude below action levels set by drinking water standards. Concentrations of four VOCs exceeded federal and state maximum contaminant levels (MCL): the solvent trichloroethylene (TCE) and the fumigant 1, 2-dibromo-3-chloropropane (DBCP) in Fresno, and the

  18. Aquifer sensitivity to pesticide leaching: Testing a soils and hydrogeologic index method

    Science.gov (United States)

    Mehnert, E.; Keefer, D.A.; Dey, W.S.; Wehrmann, H.A.; Wilson, S.D.; Ray, C.

    2005-01-01

    For years, researchers have sought index and other methods to predict aquifer sensitivity and vulnerability to nonpoint pesticide contamination. In 1995, an index method and map were developed to define aquifer sensitivity to pesticide leaching based on a combination of soil and hydrogeologic factors. The soil factor incorporated three soil properties: hydraulic conductivity, amount of organic matter within individual soil layers, and drainage class. These properties were obtained from a digital soil association map. The hydrogeologic factor was depth to uppermost aquifer material. To test this index method, a shallow ground water monitoring well network was designed, installed, and sampled in Illinois. The monitoring wells had a median depth of 7.6 m and were located adjacent to corn and soybean fields where the only known sources of pesticides were those used in normal agricultural production. From September 1998 through February 2001, 159 monitoring wells were sampled for 14 pesticides but no pesticide metabolites. Samples were collected and analyzed to assess the distribution of pesticide occurrence across three units of aquifer sensitivity. Pesticides were detected in 18% of all samples and nearly uniformly from samples from the three units of aquifer sensitivity. The new index method did not predict pesticide occurrence because occurrence was not dependent on the combined soil and hydrogeologic factors. However, pesticide occurrence was dependent on the tested hydrogeologic factor and was three times higher in areas where the depth to the uppermost aquifer was <6 m than in areas where the depth to the uppermost aquifer was 6 to <15 m. Copyright ?? 2005 National Ground Water Association.

  19. Perched aquifers - their potential impact on contaminant transport in the southern High Plains, Texas

    International Nuclear Information System (INIS)

    Mullican, W.F. III; Fryar, A.E.; Johns, N.D.

    1993-01-01

    Understanding the hydrogeology and hydrochemistry of perched aquifers at potential and known contaminated waste sites has become increasingly important because of the impact these aquifers may have on contaminant transport independent of regional aquifer processes. Investigations of a perched aquifer above the Ogallala aquifer are being conducted in the region of the U.S. Department of Energy's Pantex Plant, a proposed Superfund site, located approximately 20 mi northeast of Amarillo, Texas. Since the early 1950s, a small playa basin located on the Pantex Plant has been used as a waste-water discharge pond with daily discharge rates ranging from 400,000 to 1 million gal. The focus of this investigation is an unconfined, perched aquifer that overlies a thick silty clay sequence within the upper, mostly unsaturated part of the Ogallala Formation (Neogene). In the area of the Pantex Plant, measured depths to the perched aquifer range from 200 to 300 ft below land surface, whereas depth to the regional Ogallala aquifer ranges from 375 to 500 ft. The potentiometric surface of the perched aquifer typically represents groundwater mounds proximal to the playas and thins into trough in the interplaya areas. Hydrologic gradients of the primary mound under investigation are relatively high, ranging from 28 to 45 ft/mi. Calculated transmissivities have a geometric mean of 54 ft 2 /day, with saturated thicknesses ranging from 4 to 1000 ft. Modeling of the perched aquifer was designed to determine how much, if any, discharge to the small playa basin has enhanced recharge to the perched aquifers and increased the vertical and lateral extent of the perched aquifer. Preliminary results indicate that measurements of vertical conductance through the perching silty-clay sequence and recharge rates through playas are critical for calibrating the model. Accurate delineation of rates and flow directions in the perched aquifer is critical to any successful remediation effort

  20. Aquifer Testing And Rebound Study In Support Of The 100-H Deep Chromium Investigation

    International Nuclear Information System (INIS)

    Smoot, J.L.

    2010-01-01

    The 100-HR-3 Groundwater Operable Unit (OU) second Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) 5-year review (DOEIRL-2006-20, The Second CERCLA Five-Year Review Report for the Hanford Site) set a milestone to conduct an investigation of deep hexavalent chromium contamination in the sediments of the Ringold upper mud (RUM) unit, which underlies the unconfined aquifer in the 100-H Area. The 5-year review noted that groundwater samples from one deep well extending below the aquitard (i.e., RUM) exceeded both the groundwater standard of 48 parts per billion (ppb) (Ecology Publication 94-06, Model Toxics Control Act Cleanup Statute and Regulation) and the federal drinking water standard of 100 μg/L for hexavalent chromium. The extent of hexavalent chromium contamination in this zone is not well understood. Action 12-1 from the 5-year review is to perform additional characterization of the aquifer below the initial aquitard. Field characterization and aquifer testing were performed in the Hanford Site's 100-H Area to address this milestone. The aquifer tests were conducted to gather data to answer several fundamental questions regarding the presence of the hexavalent chromium in the deep sediments of the RUM and to determine the extent and magnitude of deeper contamination. The pumping tests were performed in accordance with the Description of Work for Aquifer Testing in Support of the 100-H Deep Chromium Investigation (SGW-41302). The specific objectives for the series of tests were as follows: (1) Evaluate the sustainable production of the subject wells using step-drawdown and constant-rate pumping tests. (2) Collect water-level data to evaluate the degree of hydraulic connection between the RUM and the unconfined (upper) aquifer (natural or induced along the well casing). (3) Evaluate the hydraulic properties of a confined permeable layer within the RUM.; (4) Collect time-series groundwater samples during testing to evaluate

  1. Aquifer test to determine hydraulic properties of the Elm aquifer near Aberdeen, South Dakota

    Science.gov (United States)

    Schaap, Bryan D.

    2000-01-01

    The Elm aquifer, which consists of sandy and gravelly glacial-outwash deposits, is present in several counties in northeastern South Dakota. An aquifer test was conducted northeast of Aberdeen during the fall of 1999 to determine the hydraulic properties of the Elm aquifer in that area. An improved understanding of the properties of the aquifer will be useful in the possible development of the aquifer as a water resource. Historical water-level data indicate that the saturated thickness of the Elm aquifer can change considerably over time. From September 1977 through November 1985, water levels at three wells completed in the Elm aquifer near the aquifer test site varied by 5.1 ft, 9.50 ft, and 11.1 ft. From June 1982 through October 1999, water levels at five wells completed in the Elm aquifer near the aquifer test site varied by 8.7 ft, 11.4 ft, 13.2 ft, 13.8 ft, and 19.7 ft. The water levels during the fall of 1999 were among the highest on record, so the aquifer test was affected by portions of the aquifer being saturated that might not be saturated during drier times. The aquifer test was conducted using five existing wells that had been installed prior to this study. Well A, the pumped well, has an operating irrigation pump and is centrally located among the wells. Wells B, C, D, and E are about 70 ft, 1,390 ft, 2,200 ft, and 3,100 ft, respectively, in different directions from Well A. Using vented pressure transducers and programmable data loggers, water-level data were collected at the five wells prior to, during, and after the pumping, which started on November 19, 1999, and continued a little over 72 hours. Based on available drilling logs, the Elm aquifer near the test area was assumed to be unconfined. The Neuman (1974) method theoretical response curves that most closely match the observed water-level changes at Wells A and B were calculated using software (AQTESOLV for Windows Version 2.13-Professional) developed by Glenn M. Duffield of Hydro

  2. Sn-wave velocity structure of the uppermost mantle beneath the Australian continent

    Science.gov (United States)

    Wei, Zhi; Kennett, Brian L. N.; Sun, Weijia

    2018-06-01

    We have extracted a data set of more than 5000 Sn traveltimes for source-station pairs within continental Australia, with 3-D source relocation using Pn arrivals to improve data consistency. We conduct tomographic inversion for S-wave-speed structure down to 100 km using the Fast Marching Tomography (FMTOMO) method for the whole Australian continent. We obtain a 3-D model with potential resolution of 3.0° × 3.0°. The new S-wave-speed model provides strong constraints on structure in a zone that was previously poorly characterized. The S velocities in the uppermost mantle are rather fast, with patterns of variation generally corresponding to those for Pn. We find strong heterogeneities of Swave speed in the uppermost mantle across the entire continent of Australia with a close relation to crustal geological features. For instance, the cratons in the western Australia usually have high S velocities (>4.70 km s-1), while the volcanic regions on the eastern margin of Australia are characterized by low S velocities (<4.40 km s-1). Exploiting an equivalent Pn inversion, we also determine the Vp/Vs ratios across the whole continent. We find that most of the uppermost mantle has Vp/Vs between 1.65 and 1.85, but with patches in central Australia and in the east with much higher Vp/Vs ratios. Distinctive local anomalies on the eastern margin may indicate the positions of remnants of mantle plumes.

  3. Modelling stream aquifer seepage in an alluvial aquifer: an improved loosing-stream package for MODFLOW

    Science.gov (United States)

    Osman, Yassin Z.; Bruen, Michael P.

    2002-07-01

    Seepage from a stream, which partially penetrates an unconfined alluvial aquifer, is studied for the case when the water table falls below the streambed level. Inadequacies are identified in current modelling approaches to this situation. A simple and improved method of incorporating such seepage into groundwater models is presented. This considers the effect on seepage flow of suction in the unsaturated part of the aquifer below a disconnected stream and allows for the variation of seepage with water table fluctuations. The suggested technique is incorporated into the saturated code MODFLOW and is tested by comparing its predictions with those of a widely used variably saturated model, SWMS_2D simulating water flow and solute transport in two-dimensional variably saturated media. Comparisons are made of both seepage flows and local mounding of the water table. The suggested technique compares very well with the results of variably saturated model simulations. Most currently used approaches are shown to underestimate the seepage and associated local water table mounding, sometimes substantially. The proposed method is simple, easy to implement and requires only a small amount of additional data about the aquifer hydraulic properties.

  4. Application and evaluation of electromagnetic methods for imaging saltwater intrusion in coastal aquifers: Seaside Groundwater Basin, California

    Science.gov (United States)

    Nenna, Vanessa; Herckenrather, Daan; Knight, Rosemary; Odlum, Nick; McPhee, Darcy

    2013-01-01

    Developing effective resource management strategies to limit or prevent saltwater intrusion as a result of increasing demands on coastal groundwater resources requires reliable information about the geologic structure and hydrologic state of an aquifer system. A common strategy for acquiring such information is to drill sentinel wells near the coast to monitor changes in water salinity with time. However, installation and operation of sentinel wells is costly and provides limited spatial coverage. We studied the use of noninvasive electromagnetic (EM) geophysical methods as an alternative to installation of monitoring wells for characterizing coastal aquifers. We tested the feasibility of using EM methods at a field site in northern California to identify the potential for and/or presence of hydraulic communication between an unconfined saline aquifer and a confined freshwater aquifer. One-dimensional soundings were acquired using the time-domain electromagnetic (TDEM) and audiomagnetotelluric (AMT) methods. We compared inverted resistivity models of TDEM and AMT data obtained from several inversion algorithms. We found that multiple interpretations of inverted models can be supported by the same data set, but that there were consistencies between all data sets and inversion algorithms. Results from all collected data sets suggested that EM methods are capable of reliably identifying a saltwater-saturated zone in the unconfined aquifer. Geophysical data indicated that the impermeable clay between aquifers may be more continuous than is supported by current models.

  5. Use of stable and radioactive isotopes in the determination of the recharge rate in Djeffara aquifer system southern Tunisia

    International Nuclear Information System (INIS)

    Trabelisi, R.; Zouari, K.

    2012-12-01

    Southern Tunisia is characterized by the presence of several hydrogeological basins, which extend over Tunisian borders. The Djeffara aquifer is one of the most important aquifer systems n this area and contains several interconnected aquifer levels. Stable (δ 2 H, δ 18 O and δ 13 C) and radioactive isotopes (1 4C , 3 H ) have been used to evaluate recharge mechanisms and groundwater residence time in the Djeffara multi-aquifer. Thesis aquifer presents two compartments, the first one ( west of the Medenine fault system) is unconfined with a well defined isotope fingerprint, the second compartment is deeper and confined multi- tracer results show groundwater of different origins, and ages , and that tectonic features control ground water flows. The unconfined part was mostly recharged during the Holocene. The recharge rates of this aquifer, inferred by 1 4C ages, are variable and could reach 3.5 mm/year. However, stable isotope composition and 1 4 'C content of the confined groundwater indicates carrier recharge during late pelistocene cold periods. (Author)

  6. Geohydrology and water quality of the stratified-drift aquifers in Upper Buttermilk Creek and Danby Creek Valleys, Town of Danby, Tompkins County, New York

    Science.gov (United States)

    Miller, Todd S.

    2015-11-20

    In 2006, the U.S. Geological Survey, in cooperation with the Town of Danby and the Tompkins County Planning Department, began a study of the stratified-drift aquifers in the upper Buttermilk Creek and Danby Creek valleys in the Town of Danby, Tompkins County, New York. In the northern part of the north-draining upper Buttermilk Creek valley, there is only one sand and gravel aquifer, a confined basal unit that overlies bedrock. In the southern part of upper Buttermilk Creek valley, there are as many as four sand and gravel aquifers, two are unconfined and two are confined. In the south-draining Danby Creek valley, there is an unconfined aquifer consisting of outwash and kame sand and gravel (deposited by glacial meltwaters during the late Pleistocene Epoch) and alluvial silt, sand, and gravel (deposited by streams during the Holocene Epoch). In addition, throughout the study area, there are several small local unconfined aquifers where large tributaries deposited alluvial fans in the valley.

  7. Evaluation of blast wave damage from very large unconfined vapour cloud explosions

    International Nuclear Information System (INIS)

    Munday, G.

    1975-01-01

    A mathematical model is described for estimating the damage potential from unconfined vapour cloud explosions. An attempt has been made to cover the salient details of the explosive phenomenon including finite flame accelerations and finite vapour cloud sizes. The model has been evaluated against two industrial incidents and the results extrapolated to large-volume vapour clouds. The authors conclude, on the evidence of this model, that great care must be taken in the evaluation of the explosion hazard from the probable occurrence of very large unconfined explosions even at distances in excess of 1 km from the centre of initiation. (author)

  8. Confining model with composite left-handed and unconfined right-handed particles

    International Nuclear Information System (INIS)

    Bordi, F.; Gatto, R.; Dominici, D.; Florence Univ.

    1982-01-01

    We present a fermionic composite model in which left-handed quarks and leptons transform as bound states of three elementary fermions confined under a subcolor gauge group whereas their right-handed partners are unconfined singlets. All the elementary fermions, confined or unconfined, are classified into a single spinor representation. A mass-mechanism, originating from the breaking of the spinor representation, gives masses to the quarks and leptons, originally massless from the anomaly conditions. A natural mechanism arises for the neutrino mass matrix. (orig.)

  9. Multiple Regression Analysis of Unconfined Compression Strength of Mine Tailings Matrices

    Directory of Open Access Journals (Sweden)

    Mahmood Ali A.

    2017-01-01

    Full Text Available As part of a novel approach of sustainable development of mine tailings, experimental and numerical analysis is carried out on newly formulated tailings matrices. Several physical characteristic tests are carried out including the unconfined compression strength test to ascertain the integrity of these matrices when subjected to loading. The current paper attempts a multiple regression analysis of the unconfined compressive strength test results of these matrices to investigate the most pertinent factors affecting their strength. Results of this analysis showed that the suggested equation is reasonably applicable to the range of binder combinations used.

  10. Analysis of Tide and Offshore Storm-Induced Water Table Fluctuations for Structural Characterization of a Coastal Island Aquifer

    Science.gov (United States)

    Trglavcnik, Victoria; Morrow, Dean; Weber, Kela P.; Li, Ling; Robinson, Clare E.

    2018-04-01

    Analysis of water table fluctuations can provide important insight into the hydraulic properties and structure of a coastal aquifer system including the connectivity between the aquifer and ocean. This study presents an improved approach for characterizing a permeable heterogeneous coastal aquifer system through analysis of the propagation of the tidal signal, as well as offshore storm pulse signals through a coastal aquifer. Offshore storms produce high wave activity, but are not necessarily linked to significant onshore precipitation. In this study, we focused on offshore storm events during which no onshore precipitation occurred. Extensive groundwater level data collected on a sand barrier island (Sable Island, NS, Canada) show nonuniform discontinuous propagation of the tide and offshore storm pulse signals through the aquifer with isolated inland areas showing enhanced response to both oceanic forcing signals. Propagation analysis suggests that isolated inland water table fluctuations may be caused by localized leakage from a confined aquifer that is connected to the ocean offshore but within the wave setup zone. Two-dimensional groundwater flow simulations were conducted to test the leaky confined-unconfined aquifer conceptualization and to identify the effect of key parameters on tidal signal propagation in leaky confined-unconfined coastal aquifers. This study illustrates that analysis of offshore storm signal propagation, in addition to tidal signal propagation, provides a valuable and low resource approach for large-scale characterization of permeable heterogeneous coastal aquifers. Such an approach is needed for the effective management of coastal environments where water resources are threatened by human activities and the changing climate.

  11. Analytical Solution for Time-drawdown Response to Constant Pumping from a Homogeneous, Confined Horizontal Aquifer with Unidirectional Flow

    Science.gov (United States)

    Parrish, K. E.; Zhang, J.; Teasdale, E.

    2007-12-01

    An exact analytical solution to the ordinary one-dimensional partial differential equation is derived for transient groundwater flow in a homogeneous, confined, horizontal aquifer using Laplace transformation. The theoretical analysis is based on the assumption that the aquifer is homogeneous and one-dimensional (horizontal); confined between impermeable formations on top and bottom; and of infinite horizontal extent and constant thickness. It is also assumed that there is only a single pumping well penetrating the entire aquifer; flow is everywhere horizontal within the aquifer to the well; the well is pumping with a constant discharge rate; the well diameter is infinitesimally small; and the hydraulic head is uniform throughout the aquifer before pumping. Similar to the Theis solution, this solution is suited to determine transmissivity and storativity for a two- dimensional, vertically confined aquifer, such as a long vertically fractured zone of high permeability within low permeable rocks or a long, high-permeability trench inside a low-permeability porous media. In addition, it can be used to analyze time-drawdown responses to pumping and injection in similar settings. The solution can also be used to approximate the groundwater flow for unconfined conditions if (1) the variation of transmissivity is negligible (groundwater table variation is small in comparison to the saturated thickness); and (2) the unsaturated flow is negligible. The errors associated with the use of the solution to unconfined conditions depend on the accuracies of the above two assumptions. The solution can also be used to assess the impacts of recharge from a seasonal river or irrigation canal on the groundwater system by assuming uniform, time- constant recharge along the river or canal. This paper presents the details for derivation of the analytical solution. The analytical solution is compared to numerical simulation results with example cases. Its accuracy is also assessed and

  12. Modelling the salinization of a coastal lagoon-aquifer system

    Science.gov (United States)

    Colombani, N.; Mastrocicco, M.

    2017-08-01

    In this study, a coastal area constituted by alternations of saline-brackish lagoons and freshwater bodies was studied and modelled to understand the hydrological processes occurring between the lagoons, the groundwater system of the Po River Delta (Italy) and the Adriatic Sea. The contribution of both evaporation and anthropogenic factors on groundwater salinization was assessed by means of soil, groundwater and surface water monitoring. Highresolution multi-level samplers were used to capture salinity gradients within the aquifer and surface water bodies. Data were employed to calibrate a density-dependent numerical transport model implemented with SEAWAT code along a transect perpendicular to the coast line. The results show that the lagoon is hydraulically well connected with the aquifer, which provides the major source of salinity because of the upcoming of paleo-seawater from the aquitard laying at the base of the unconfined aquifer. On the contrary, the seawater (diluted by the freshwater river outflow) creates only a limited saltwater wedge. The increase in groundwater salinity could be of serious concern, especially for the pinewood located in the dune near the coast, sensitive to salinity increases. This case study represents an interesting paradigm for other similar environmental setting, where the assumption of classical aquifer salinization from a saltwater wedge intruding from the sea is often not representative of the actual aquifer’s salinization mechanisms.

  13. Inverse modelling of aquifer parameters in basaltic rock with the help of pumping test method using MODFLOW software

    Directory of Open Access Journals (Sweden)

    Kanak Moharir

    2017-11-01

    The present study of estimation of aquifer factors such as transmissivity (T and storativity (S are vital for the evaluation of groundwater resources. There are several methods to estimate the accurate aquifer parameters (i.e. hydrograph analysis, pumping test, etc.. In initial days, these parameters are projected either by means of in-situ test or execution test on aquifer well samples carried in the laboratory. The simultaneous information on the hydraulic behavior of the well (borehole that provides on this method, the reservoir and the reservoir boundaries, are important for efficient aquifer and well data management and analysis. The most common in-situ test is pumping test performed on wells, which involves the measurement of the fall and increase of groundwater level with respect to time. The alteration in groundwater level (drawdown/recovery is caused due to pumping of water from the well. Theis (1935 was first to propose method to evaluate aquifer parameters from the pumping test on a bore well in a confined aquifer. It is essential to know the transmissivity (T = Kb, where b is the aquifer thickness; pumping flow rate, Q = TW (dh/dl flow through an aquifer and storativity (confined aquifer: S = bSs, unconfined: S = Sy, for the characterization of the aquifer parameters in an unknown area so as to predict the rate of drawdown of the groundwater table/potentiometric surface throughout the pumping test of an aquifer. The determination of aquifer's parameters is an important basis for groundwater resources evaluation, numerical simulation, development and protection as well as scientific management. For determining aquifer's parameters, pumping test is a main method. A case study shows that these techniques have been fast speed and high correctness. The results of parameter's determination are optimized so that it has important applied value for scientific research and geology engineering preparation.

  14. Dataset of the relationship between unconfined compressive strength and tensile strength of rock mass

    International Nuclear Information System (INIS)

    Sugita, Yutaka; Yui, Mikazu

    2002-02-01

    This report summary the dataset of the relationship between unconfined compressive strength and tensile strength of the rock mass described in supporting report 2; repository design and engineering technology of second progress report (H12 report) on research and development for the geological disposal of HLW in Japan. (author)

  15. The Effect of Polymer-Cement Stabilization on the Unconfined Compressive Strength of Liquefiable Soils

    Directory of Open Access Journals (Sweden)

    Ali Ateş

    2013-01-01

    Full Text Available Soil stabilization has been widely used as an alternative to substitute the lack of suitable material on site. The use of nontraditional chemical stabilizers in soil improvement is growing daily. In this study a laboratory experiment was conducted to evaluate the effects of waterborne polymer on unconfined compression strength and to study the effect of cement grout on pre-venting of liquefiable sandy soils. The laboratory tests were performed including grain size of sandy soil, unit weight, ultrasonic pulse velocity, and unconfined compressive strength test. The sand and various amounts of polymer (1%, 2%, 3%, and 4% and cement (10%, 20%, 30%, and 40% were mixed with all of them into dough using mechanical kneader in laboratory conditions. Grouting experiment is performed with a cylindrical mould of  mm. The samples were subjected to unconfined compression tests to determine their strength after 7 and 14 days of curing. The results of the tests indicated that the waterborne polymer significantly improved the unconfined compression strength of sandy soils which have susceptibility of liquefaction.

  16. A landscape scale valley confinement algorithm: Delineating unconfined valley bottoms for geomorphic, aquatic, and riparian applications

    Science.gov (United States)

    David E. Nagel; John M. Buffington; Sharon L. Parkes; Seth Wenger; Jaime R. Goode

    2014-01-01

    Valley confinement is an important landscape characteristic linked to aquatic habitat, riparian diversity, and geomorphic processes. This report describes a GIS program called the Valley Confinement Algorithm (VCA), which identifies unconfined valleys in montane landscapes. The algorithm uses nationally available digital elevation models (DEMs) at 10-30 m resolution to...

  17. What controls the transition from confined to unconfined flow? : Analysis of hydraulics in a river delta

    NARCIS (Netherlands)

    Hiatt, Matthew; Passalacqua, Paola

    2017-01-01

    Recent field work at the Wax Lake Delta (WLD) in coastal Louisiana indicates lateral outflow from channels to islands upstream of the receiving basin; in this region of the delta the flow transitions from confined to unconfined (i.e., from a uniform discharge profile to a nonuniform discharge

  18. Influence of variables on the consolidation and unconfined compressive strength of crushed salt: Technical report

    International Nuclear Information System (INIS)

    Pfeifle, T.W.; Senseny, P.E.; Mellegard, K.D.

    1987-01-01

    Eight hydrostatic compression creep tests were performed on crushed salt specimens fabricated from Avery Island dome salt. Following the creep test, each specimen was tested in unconfined compression. The experiments were performed to assess the influence of the following four variables on the consolidation and unconfined strength of crushed salt: grain size distribution, temperature, time, and moisture content. The experiment design comprised a half-fraction factorial matrix at two levels. The levels of each variable investigated were grain size distribution, uniform-graded and well-graded (coefficient of uniformity of 1 and 8); temperature 25 0 C and 100 0 C; time, 3.5 x 10 3 s and 950 x 10 3 s (approximately 60 minutes and 11 days, respectively); and moisture content, dry and wet (85% relative humidity for 24 hours). The hydrostatic creep stress was 10 MPa. The unconfined compression tests were performed at an axial strain rate of 1 x 10 -5 s -1 . Results show that the variables time and moisture content have the greatest influence on creep consolidation, while grain size distribution and, to a somewhat lesser degree, temperature have the greatest influence on total consolidation. Time and moisture content and the confounded two-factor interactions between either grain size distribution and time or temperature and moisture content have the greatest influence on unconfined strength. 7 refs., 7 figs., 11 tabs

  19. Preliminary analysis of some waters from the confined aquifers underlying the Hanford site

    International Nuclear Information System (INIS)

    Deju, R.A.

    1978-09-01

    This report presents results of analyses available at this time from waters from some wells sampled in or near the Hanford Site. The analyses of these wells were done for various purposes and are consolidated to help define the nature of the waters found within the Columbia Plateau basaltic sequence. Results of the analyses show the waters from the unconfined aquifers underlying the Hanford Site are characterized by a high calcium--magnesium content. These waters can be described as calcium--magnesium--bicarbonate-type. Waters from deeper basaltic confined aquifers are primarily of the sodium bicarbonate type. Two waters sampled from the Grande Ronde Formation from Rattlesnake Hills Exploratory Well Number 1 are slightly different and can be described as sodium--calcium--bicarbonate--sulfate--chloride-type. Age-dating results for these water samples lead to the conclusions that waters from the confined aquifers were entrapped 15,000 to 23,000 years ago

  20. Managed Aquifer Recharge Using Treated Wastewater: An Option to Manage a Coastal Aquifer In Oman For Better Domestic Water Supply

    Science.gov (United States)

    Al-Maktoumi, Ali; Zekri, Slim; ElRawy, Mustafa

    2016-04-01

    Arid countries, such as the Sultanate of Oman, are facing challenges of water shortages threatening economic development and social stability. Most of those countries are vulnerable to the potential adverse impacts of climate change, the most significant of which are increased average temperatures, less and more erratic precipitation, sea level rise, and desertification. The combined effect of existing adverse conditions and likely impacts of future climate change will make water management even more difficult than what it is today. Tremendous efforts have been devoted to augment the water resources. Managed Aquifer Recharge (MAR) is practiced widely to store water during periods of surpluses and withdraw during deficits from an aquifer. In Muscat, there will be a surplus of >100,000 m3/day of TWW during winter months in the coming few years. The aquifer along the northern coast of Oman (Al-Khawd Aquifer) is conducive for MAR. Data show that TWW volumes will increase from 7.6 Mm3 in 2003 to 70.9 Mm3 in 2035 in Muscat city only. This study assesses, using MODFLOW 2005 numerical code, the impact of MAR using TWW on better management of the Al-Khawd unconfined coastal aquifer for better urban water supply. Specifically, aiming to maximize withdrawals from the domestic wells with minimize adverse effect of seawater intrusion. The model operates under a number of constrains that minimize the loss to the sea and the injected TWW must not migrates upstream (due to developed mound) and reach the wellfields used for domestic supply. The hypothetical injection wells are located downstream the domestic wellfield zone. The results of different managerial scenarios show that MAR produces a hydraulic barrier that decelerates the seawater intrusion which allows higher abstraction of pristine water from the upstream part of the aquifer. MAR along with redistribution/relocation of public wells allows abstraction of 2 times the current abstraction rate (around 6 Mm3/year to 12 Mm3

  1. A mini slug test method for determination of a local hydraulic conductivity of an unconfined sandy aquifer

    DEFF Research Database (Denmark)

    Hinsby, Klaus; Bjerg, Poul Løgstrup; Andersen, Lars J.

    1992-01-01

    distributed measurements of a local hydraulic conductivity at a tracer test site at Vejen, Denmark. The mini slug test results calculated by a modified Dax slug test analysing method, applying the elastic storativity in the Dax equations instead of the specific yield, are in good accordance with the results...

  2. Characterization of the lowland coastal aquifer of Comacchio (Ferrara, Italy): Hydrology, hydrochemistry and evolution of the system

    Science.gov (United States)

    Giambastiani, B. M. S.; Colombani, N.; Mastrocicco, M.; Fidelibus, M. D.

    2013-09-01

    This study delineates the actual hydrogeochemistry and the geological evolution of an unconfined coastal aquifer located in a lowland setting in order to understand the drivers of the groundwater salinization. Physical aquifer parameterization highlights a vertical hydraulic gradient due to the presence of a heavy drainage system, which controls the hydrodynamics of this coastal area, forcing groundwater to flow from the bottom toward the top of the aquifer. As a consequence, relict seawater in stable density stratification, preserved within low permeability sediments in the deepest portion of the aquifer, has been drawn upward. The hydrogeochemical investigations allow identifying the role of seepage and water-sediment interactions in the aquifer salinization process and in the modification of groundwater chemistry. Mixing between freshwater and saltwater occurs; however, it is neither the only nor the dominant process driving groundwater hydrochemistry. In the aquifer several concurring and competing water-sediment interactions - as NaCl solution, ion-exchange, calcite and dolomite dissolution/precipitation, oxidation of organic matter, and sulfate bacterial reduction - are triggered by or overlap freshwater-saltwater mixing The hyper-salinity found in the deepest portion of the aquifer cannot be associated with present seawater intrusion, but suggests the presence of salt water of marine origin, which was trapped in the inter-basin during the Holocene transgression. The results of this study contribute to a better understanding of groundwater dynamics and salinization processes in this lowland coastal aquifer.

  3. The integrated impacts of natural processes and human activities on the origin and processes of groundwater salinization in the coastal aquifers of Beihai, Southern China

    Science.gov (United States)

    Li, Q.; Zhan, Y., , Dr; Chen, W. Ms; Yu, S., , Dr

    2017-12-01

    Salinization in coastal aquifers usually is the results of contamination related to both seawater intrusion and water-rock interaction. The chemical and isotopic methods were combined to identify the origin and processes of groundwater salinization in Daguansha area of Beihai. The concentrations of the major ions that dominate in sea water (Cl-, Na+, Ca2+, Mg2+ and SO2- 4), as well as the isotopic ratios (2H, 18O, 87Sr/86Sr and 13C) suggest that the salinization occurring in the aquifer water of the coastal plain is related to seawater and the prevailing hydrochemical processes are evaporation, mixing, dissolution and ion exchange. For the unconfined aquifer, groundwater salinization occurred in parts of the area, which is significantly influenced by the land-based sea farming. The integrated impacts of seawater intrusion from the Beibuwan Gulf and infiltration of seawater from the culture ponds is identified in the confined aquifer I at site BBW2. In consequence, the leakage from this polluted aquifer causes the salinization of groundwater in the confined aquifer II. At site BBW3, the confined aquifer I and lower confined aquifer II are remarkably contaminated by seawater intrusion. The weak connectivity with upper aquifers and seaward movement of freshwater prevents saltwater from encroaching the confined aquifer III. Above all, understanding of the origin and processes of groundwater salinization will provide essential information for sustainable planning and management of groundwater resources in this region.

  4. Value of information analysis for groundwater quality monitoring network design Case study: Eocene Aquifer, Palestine

    Science.gov (United States)

    Khader, A.; McKee, M.

    2010-12-01

    Value of information (VOI) analysis evaluates the benefit of collecting additional information to reduce or eliminate uncertainty in a specific decision-making context. It makes explicit any expected potential losses from errors in decision making due to uncertainty and identifies the “best” information collection strategy as one that leads to the greatest expected net benefit to the decision-maker. This study investigates the willingness to pay for groundwater quality monitoring in the Eocene Aquifer, Palestine, which is an unconfined aquifer located in the northern part of the West Bank. The aquifer is being used by 128,000 Palestinians to fulfill domestic and agricultural demands. The study takes into account the consequences of pollution and the options the decision maker might face. Since nitrate is the major pollutant in the aquifer, the consequences of nitrate pollution were analyzed, which mainly consists of the possibility of methemoglobinemia (blue baby syndrome). In this case, the value of monitoring was compared to the costs of treating for methemoglobinemia or the costs of other options like water treatment, using bottled water or importing water from outside the aquifer. And finally, an optimal monitoring network that takes into account the uncertainties in recharge (climate), aquifer properties (hydraulic conductivity), pollutant chemical reaction (decay factor), and the value of monitoring is designed by utilizing a sparse Bayesian modeling algorithm called a relevance vector machine.

  5. Software packages for simulating groundwater flow and the spreading of soluble and insoluble admixtures in aquifers

    International Nuclear Information System (INIS)

    Roshal, A.A.; Klein, I.S.; Svishchov, A.M.

    1993-01-01

    Software programs are described designed for solving hydrogeological and environmental problems related to the analysis and prediction of groundwater flow and the spreading of solutes and insolubles in the saturated zones. The software package GWFS (Ground Water Flow Simulation) allows for simulating steady-state and unsteady-state flow in confined, unconfined, and confined-unconfined multi-layer and quasi-3D isotropic and anisotropic aquifer systems. Considered are intra-layer sources and sinks, infiltration, inter-layer leakages, the interrelationships with surface reservoirs and streams, interrelationships with the drains, aquifer discharge to surface sources. The MTS (Mass Transport Simulation) package is designed for solving solute transport problems. Taken into account is convective transport, hydrodynamic dispersion and diffusion, linear equilibrium sorption. The method of characteristics is being implemented here using the ''particles-in-cells'' scheme in which the transport is modeled with the help of tracers. The software package OWFS (Oil-Water Flow Simulation) is designed for the simulation of hydrocarbon (oil-water) migration in aquifers

  6. Delineation of the extent of milling-related contamination in a naturally contaminated aquifer system

    International Nuclear Information System (INIS)

    Downs, William F.; Storms, Erik F.

    1992-01-01

    Uranium mill tailings from the Susquehanna-Western mill near Falls City, Texas, were pumped to tailings ponds located in abandoned open pit uranium mines. The ores from these mines were oxidized. Uranium and the associated hazardous constituents were present in these ores as relatively soluble secondary minerals. Because the tailings piles are located on the outcrops of the units designated as the uppermost aquifer, there is no upgradient aquifer from which to establish 'background' water quality. The widespread mineralization in the area naturally imposes a large variability in water quality in these units. It was necessary to demonstrate to State and Federal regulators that selected downgradient wells were beyond the influence of milling operations, and to develop a series of 'indicator parameters' that could be used to differentiate milling contaminated groundwater from that native to the aquifer. (author)

  7. Managed Aquifer Recharge (MAR in Sustainable Urban Water Management

    Directory of Open Access Journals (Sweden)

    Declan Page

    2018-02-01

    Full Text Available To meet increasing urban water requirements in a sustainable way, there is a need to diversify future sources of supply and storage. However, to date, there has been a lag in the uptake of managed aquifer recharge (MAR for diversifying water sources in urban areas. This study draws on examples of the use of MAR as an approach to support sustainable urban water management. Recharged water may be sourced from a variety of sources and in urban centers, MAR provides a means to recycle underutilized urban storm water and treated wastewater to maximize their water resource potential and to minimize any detrimental effects associated with their disposal. The number, diversity and scale of urban MAR projects is growing internationally due to water shortages, fewer available dam sites, high evaporative losses from surface storages, and lower costs compared with alternatives where the conditions are favorable, including water treatment. Water quality improvements during aquifer storage are increasingly being documented at demonstration sites and more recently, full-scale operational urban schemes. This growing body of knowledge allows more confidence in understanding the potential role of aquifers in water treatment for regulators. In urban areas, confined aquifers provide better protection for waters recharged via wells to supplement potable water supplies. However, unconfined aquifers may generally be used for nonpotable purposes to substitute for municipal water supplies and, in some cases, provide adequate protection for recovery as potable water. The barriers to MAR adoption as part of sustainable urban water management include lack of awareness of recent developments and a lack of transparency in costs, but most importantly the often fragmented nature of urban water resources and environmental management.

  8. Uppermost oceanic crust structure and properties from multichannel seismic data at the Alaska subduction zone

    Science.gov (United States)

    Becel, A.; Carton, H. D.; Shillington, D. J.

    2017-12-01

    The most heterogeneous, porous and permeable layer within a subducting oceanic crust is the uppermost layer called Layer 2A. This layer, made of extrusive basalts, forms at the ridge axis and persists as a thin ( 600 m) low-velocity cap in old crust. Nearing the trench axis, when oceanic plate bends, normal faults can be formed or reactivated at the outer-rise allowing a more vigorous hydrothermal circulation to resume within this layer. Porosity and heterogeneity within this layer are important to assess because these parameters might have a profound impact on subduction zone processes. However, conventional refraction data quality is rarely good enough to look into detail into the properties of the uppermost oceanic layer. Here we use 2D marine long-offset multi-channel seismic (MCS) reflection data collected offshore of the Alaska Peninsula during the ALEUT Program. The dataset was acquired aboard the R/V Marcus Langseth with a 636-channels, 8-km long streamer. We present initial results from three 140 km long profiles across the 52-56Myr old incoming Pacific oceanic crust formed at fast spreading rate: two perpendicular margin and one parallel margin profiles. Those profiles are located outboard of the Shumagin gaps. Outboard of this subduction zone segment, abundant bending related normal faults are imaged and concentrated within 50-60 km of the trench. Long-offset MCS data exhibit a prominent triplication that includes postcritical reflections and turning waves within the upper crust at offsets larger than 3 km. The triplication suggests the presence of a velocity discontinuity within the upper oceanic crust. We follow a systematic and uniform approach to extract upper crustal post-critical reflections and add them to them to the vertical incidence MCS images. Images reveal small-scale variations in the thickness of the Layer 2A and the strength of its base along the profiles. The second step consists of the downward continuation followed by travel

  9. Reliability estimate of unconfined compressive strength of black cotton soil stabilized with cement and quarry dust

    Directory of Open Access Journals (Sweden)

    Dayo Oluwatoyin AKANBI

    2017-06-01

    Full Text Available Reliability estimates of unconfined compressive strength values from laboratory results for specimens compacted at British Standard Light (BSLfor compacted quarry dust treated black cotton soil using cement for road sub – base material was developed by incorporating data obtained from Unconfined compressive strength (UCS test gotten from the laboratory test to produce a predictive model. Data obtained were incorporated into a FORTRAN-based first-order reliability program to obtain reliability index values. Variable factors such as water content relative to optimum (WRO, hydraulic modulus (HM, quarry dust (QD, cement (C, Tri-Calcium silicate (C3S, Di-calcium silicate (C2S, Tri-Calcium Aluminate (C3A, and maximum dry density (MDD produced acceptable safety index value of1.0and they were achieved at coefficient of variation (COV ranges of 10-100%. Observed trends indicate that WRO, C3S, C2S and MDD are greatly influenced by the COV and therefore must be strictly controlled in QD/C treated black cotton soil for use as sub-base material in road pavements. Stochastically, British Standard light (BSL can be used to model the 7 days unconfined compressive strength of compacted quarry dust/cement treated black cotton soil as a sub-base material for road pavement at all coefficient of variation (COV range 10 – 100% because the safety index obtained are higher than the acceptable 1.0 value.

  10. Unconfined Unsteady Laminar Flow of a Power-Law Fluid across a Square Cylinder

    Directory of Open Access Journals (Sweden)

    Asterios Pantokratoras

    2016-11-01

    Full Text Available The flow of a non-Newtonian, power-law fluid, directed normally to a horizontal cylinder with square cross-section (two-dimensional flow is considered in the present paper. The problem is investigated numerically with a very large calculation domain in order that the flow could be considered unconfined. The investigation covers the power-law index from 0.1 up to 2 and the Reynolds number ranges from 60 to 160. Over this range of Reynolds numbers the flow is unsteady. It is found that the drag coefficient and the Strouhal number are higher in a confined flow compared to those of an unconfined flow. In addition some flow characteristics are lost in a confined flow. Complete results for the drag coefficient and Strouhal number in the entire shear-thinning and shear-thickening region have been produced. In shear-thinning fluids chaotic structures exist which diminish at higher values of power-law index. This study represents the first investigation of unsteady, non-Newtonian power-law flow past a square cylinder in an unconfined field.

  11. Identifying Stream/Aquifer Exchange by Temperature Gradient in a Guarani Aquifer System Outcrop Zone

    Science.gov (United States)

    Wendland, E.; Rosa, D. M. S.; Anache, J. A. A.; Lowry, C.; Lin, Y. F. F.

    2017-12-01

    Recharge of the Guarani Aquifer System (GAS) in South America is supposed to occur mainly in the outcrop zones, where the GAS appears as an unconfined aquifer (10% of the 1.2 Million km2 aquifer extension). Previous evaluations of recharge are based essentially on water balance estimates for the whole aquifer area or water table fluctuations in monitoring wells. To gain a more detailed understanding of the recharge mechanisms the present work aimed to study the stream aquifer interaction in a watershed (Ribeirão da Onça) at an outcrop zone. Two Parshall flumes were installed 1.3 km apart for discharge measurement in the stream. Along this distance an optic fiber cable was deployed to identify stretches with gaining and losing behavior. In order to estimate groundwater discharge in specific locations, 8 temperature sticks were set up along the stream reach to measure continuously the vertical temperature gradient. A temperature probe with 4 thermistors was also used to map the shallow streambed temperature gradient manually along the whole distance. The obtained results show a discharge difference of 250 m3/h between both flumes. Since the last significant rainfall (15 mm) in the watershed occurred 3 months ago, this value can be interpreted as the base flow contribution to the stream during the dry season. Given the temperature difference between groundwater ( 24oC) and surface water ( 17oC) the fiber-optic distributed temperature sensing (FO-DTS) allowed the identification of stretches with gaining behavior. Temperature gradients observed at the streambed varied between 0.67 and 14.33 oC/m. The study demonstrated that heat may be used as natural tracer even in tropical conditions, where the groundwater temperature is higher than the surface water temperature during the winter. The obtained results show that the discharge difference between both flumes can not be extrapolated without detailed analysis. Gaining and loosing stretches have to be identified on order

  12. Spatial and temporal small-scale variation in groundwater quality of a shallow sandy aquifer

    DEFF Research Database (Denmark)

    Bjerg, Poul Løgstrup; Christensen, Thomas Højlund

    1992-01-01

    The groundwater quality of a shallow unconfined sandy aquifer has been characterized for pH, alkalinity, chloride, nitrate, sulfate, calcium, magnesium, sodium and potassium in terms of vertical and horizontal variations (350 groundwater samples). The test area is located within a farmland lot....... The geology of the area described on the basis of 31 sediment cores appears relatively homogeneous. Large vertical and horizontal variations were observed. The vertical variations are strongly affected by the deviating composition of the agricultural infiltration water. The horizontal variations show very...

  13. Characteristics of Southern California coastal aquifer systems

    Science.gov (United States)

    Edwards, B.D.; Hanson, R.T.; Reichard, E.G.; Johnson, T.A.

    2009-01-01

    , litany of names for the various formations, lithofacies, and aquifer systems identified within these basins. Despite these nomenclatural problems, available data show that most basins contain similar sequences of deposits and share similar geologic histories dominated by glacio-eustatic sea-level fluctuations, and overprinted by syndepositional and postdepositional tectonic deformation. Impermeable, indurated mid-Tertiary units typically form the base of each siliciclastic groundwater basin. These units are overlain by stacked sequences of Pliocene to Holocene interbedded marine, paralic, fluvial, and alluvial sediment (weakly indurated, folded, and fractured) that commonly contain the historically named "80-foot sand," "200-foot sand," and "400-foot gravel" in the upper part of the section. An unconformity, cut during the latest Pleistocene lowstand (??18O stage 2; ca. 18 ka), forms a major sequence boundary that separates these units from the overlying Holocene fluvial sands and gravels. Unconfined aquifers occur in amalgamated coarse facies near the bounding mountains (forebay area). These units are inferred to become lithologically more complex toward the center of the basins and coast line, where interbedded permeable and low-permeability alluvial, fluvial, paralic, and marine facies contain confined aquifers (pressure area). Coastal bounding faults limit intrabasin and/or interbasin flow in parts of many basins. ?? 2009 Geological Society of America.

  14. DNAPL migration in a coastal plain aquifer

    International Nuclear Information System (INIS)

    DiGuiseppi, W.H.; Jung, A.D.

    1995-01-01

    Soil and ground water at the Dover Gas Light Superfund Site, a former manufactured gas plant (1859 to 1948), are contaminated with polynuclear aromatic hydrocarbons and volatile organic compounds. Contaminants of concern include light aromatics, such as benzene, toluene, ethylbenzene, and xylenes (BTEX), and heavy aromatics, including naphthalene, acenaphthylene, phenanthrene, and benzo(a)pyrene. Although ground-water contaminant levels are elevated near the site, only naphthalene and acenaphthylene are present within an order of magnitude of their solubility limits, indicating the possibility of dense non-aqueous phase liquids (DNAPL) in the subsurface. The unconfined Columbia Aquifer, which is characterized by interfingering and discontinuous sand, silt, and clay Coastal Plain deposits, overlies a clay aquitard at a depth of 60 feet. The ground water beneath the intermediate clay horizon exhibited little or no contamination, even immediately downgradient from the site. The relationship between the more permeable granular sand horizons and the less permeable interfingering clay zones controls the migration of both the aqueous-phase contamination and the DNAPL. A detailed horizontal and vertical characterization of the subsurface stratigraphy was critical to the accurate interpretation of the extent and magnitude of contamination and the identification and delineation of DNAPL zones

  15. Effect Of Coir Fibres On The Compaction And Unconfined Compressive Strength Of Bentonite-Lime-Gypsum Mixture

    Directory of Open Access Journals (Sweden)

    Tilak B. Vidya

    2015-06-01

    Full Text Available This paper presents the effect of coir fibres on the compaction and unconfined compressive strength of a bentonite-lime-gypsum mixture. The coir fiber content varied from 0.5 to 2 %. The results indicated that the dry unit weight and the optimum moisture content of a bentonite – lime mix increased with the addition of gypsum. The unconfined compressive strength of the bentonite increased with the increase in the lime content up to 8 %. Beyond 8 %, the unconfined compressive strength decreased. The dry unit weight of the reference mix decreased, and the optimum moisture content increased with the addition of coir fibre. The unconfined compressive strength of the bentonite + 8 % lime mix increased up to 4 % with the gypsum. Beyond 4 %, the unconfined compressive strength decreased. The unconfined compressive strength of the reference mix increased with the addition of coir fibre up to a fibre content of 1.5 %. The unconfined compressive strength of the reference mix-coir fibre composite was less in comparison to the reference mix. The unconfined compressive strength of the bentonite increased with the addition of lime and gypsum and with the increase in the curing period. The improvement in the post-peak region was better for the reference mix with reinforced coir fibres as compared to the unreinforced reference mix. The improved post-peak behaviour of the bentonite-lime-gypsum-coir fibre mixture could boost the construction of temporary roads on such problematic soils. Further, its use will also provide an environmental motivation for providing a means of consuming large quantities of coir fibres.

  16. Shear velocity structure of the laterally heterogeneous crust and uppermost mantle beneath the Indian region

    Science.gov (United States)

    Mohan, G.; Rai, S. S.; Panza, G. F.

    1997-08-01

    The shear velocity structure of the Indian lithosphere is mapped by inverting regionalized Rayleigh wave group velocities in time periods of 15-60 s. The regionalized maps are used to subdivide the Indian plate into several geologic units and determine the variation of velocity with depth in each unit. The Hedgehog Monte Carlo technique is used to obtain the shear wave velocity structure for each geologic unit, revealing distinct velocity variations in the lower crust and uppermost mantle. The Indian shield has a high-velocity (4.4-4.6 km/s) upper mantle which, however, is slower than other shields in the world. The central Indian platform comprised of Proterozoic basins and cratons is marked by a distinct low-velocity (4.0-4.2 km/s) upper mantle. Lower crustal velocities in the Indian lithosphere generally range between 3.8 and 4.0 km/s with the oceanic segments and the sedimentary basins marked by marginally higher and lower velocities, respectively. A remarkable contrast is observed in upper mantle velocities between the northern and eastern convergence fronts of the Indian plate. The South Bruma region along the eastern subduction front of the Indian oceanic lithosphere shows significant velocity enhancement in the lower crust and upper mantle. High velocities (≈4.8 km/s) are also observed in the upper mantle beneath the Ninetyeast ridge in the northeastern Indian Ocean.

  17. Fate of Arsenic during Red River Water Infiltration into Aquifers beneath Hanoi, Vietnam.

    Science.gov (United States)

    Postma, Dieke; Mai, Nguyen Thi Hoa; Lan, Vi Mai; Trang, Pham Thi Kim; Sø, Helle Ugilt; Nhan, Pham Quy; Larsen, Flemming; Viet, Pham Hung; Jakobsen, Rasmus

    2017-01-17

    Recharge of Red River water into arsenic-contaminated aquifers below Hanoi was investigated. The groundwater age at 40 m depth in the aquifer underlying the river was 1.3 ± 0.8 years, determined by tritium-helium dating. This corresponds to a vertical flow rate into the aquifer of 19 m/year. Electrical conductivity and partial pressure of CO 2 (P CO 2 ) indicate that water recharged from the river is present in both the sandy Holocene and gravelly Pleistocene aquifers and is also abstracted by the pumping station. Infiltrating river water becomes anoxic in the uppermost aquifer due to the oxidation of dissolved organic carbon. Further downward, sedimentary carbon oxidation causes the reduction of As-containing Fe-oxides. Because the release of arsenic by reduction of Fe-oxides is controlled by the reaction rate, arsenic entering the solution becomes highly diluted in the high water flux and contributes little to the groundwater arsenic concentration. Instead, the As concentration in the groundwater of up to 1 μM is due to equilibrium-controlled desorption of arsenic, adsorbed to the sediment before river water started to infiltrate due to municipal pumping. Calculations indicate that it will take several decades of river water infiltration to leach arsenic from the Holocene aquifer to below the World Health Organization limit of 10 μg/L.

  18. Fate of Arsenic during Red River Water Infiltration into Aquifers beneath Hanoi, Vietnam

    Science.gov (United States)

    2016-01-01

    Recharge of Red River water into arsenic-contaminated aquifers below Hanoi was investigated. The groundwater age at 40 m depth in the aquifer underlying the river was 1.3 ± 0.8 years, determined by tritium–helium dating. This corresponds to a vertical flow rate into the aquifer of 19 m/year. Electrical conductivity and partial pressure of CO2 (PCO2) indicate that water recharged from the river is present in both the sandy Holocene and gravelly Pleistocene aquifers and is also abstracted by the pumping station. Infiltrating river water becomes anoxic in the uppermost aquifer due to the oxidation of dissolved organic carbon. Further downward, sedimentary carbon oxidation causes the reduction of As-containing Fe-oxides. Because the release of arsenic by reduction of Fe-oxides is controlled by the reaction rate, arsenic entering the solution becomes highly diluted in the high water flux and contributes little to the groundwater arsenic concentration. Instead, the As concentration in the groundwater of up to 1 μM is due to equilibrium-controlled desorption of arsenic, adsorbed to the sediment before river water started to infiltrate due to municipal pumping. Calculations indicate that it will take several decades of river water infiltration to leach arsenic from the Holocene aquifer to below the World Health Organization limit of 10 μg/L. PMID:27958705

  19. Map showing minimum depth to water in shallow aquifers (1963-72) in the Sugar House quadrangle, Salt Lake County, Utah

    Science.gov (United States)

    Mower, R.W.; Van Horn, Richard

    1973-01-01

    The depth to ground water in shallow aquifers in the Sugar Horse quadrangle ranges from zero in areas of springs and seeps to more than 10 feet beneath most of the area shown on the map. The depth to water differs from place to place because of irregular topography, and the varying capability of different rock materials to transmit water. Ground water also occurs under unconfined and confined conditions in deep aquifers beneath the Sugar Horse quadrangle, as shown by the block diagram and as described by Hely, Mower, and Harr (1971a, p. 17-111).

  20. Groundwater vulnerability mapping in Guadalajara aquifers system (Western Mexico)

    Science.gov (United States)

    Rizo-Decelis, L. David; Marín, Ana I.; Andreo, Bartolomé

    2016-04-01

    Groundwater vulnerability mapping is a practical tool to implement strategies for land-use planning and sustainable socioeconomic development coherent with groundwater protection. The objective of vulnerability mapping is to identify the most vulnerable zones of catchment areas and to provide criteria for protecting the groundwater used for drinking water supply. The delineation of protection zones in fractured aquifers is a challenging task due to the heterogeneity and anisotropy of hydraulic conductivities, which makes difficult prediction of groundwater flow organization and flow velocities. Different methods of intrinsic groundwater vulnerability mapping were applied in the Atemajac-Toluquilla groundwater body, an aquifers system that covers around 1300 km2. The aquifer supplies the 30% of urban water resources of the metropolitan area of Guadalajara (Mexico), where over 4.6 million people reside. Study area is located in a complex neotectonic active volcanic region in the Santiago River Basin (Western Mexico), which influences the aquifer system underneath the city. Previous works have defined the flow dynamics and identified the origin of recharge. In addition, the mixture of fresh groundwater with hydrothermal and polluted waters have been estimated. Two main aquifers compose the multilayer system. The upper aquifer is unconfined and consists of sediments and pyroclastic materials. Recharge of this aquifer comes from rainwater and ascending vertical fluids from the lower aquifer. The lower aquifer consists of fractured basalts of Pliocene age. Formerly, the main water source has been the upper unit, which is a porous and unconsolidated unit, which acts as a semi-isotropic aquifer. Intense groundwater usage has resulted in lowering the water table in the upper aquifer. Therefore, the current groundwater extraction is carried out from the deeper aquifer and underlying bedrock units, where fracture flow predominates. Pollution indicators have been reported in

  1. Effects of Barometric Fluctuations on Well Water-Level Measurements and Aquifer Test Data

    Energy Technology Data Exchange (ETDEWEB)

    FA Spane, Jr.

    1999-12-16

    The Pacific Northwest National Laboratory, as part of the Hanford Groundwater Monitoring Project, examines the potential for offsite migration of contamination within underlying aquifer systems. Well water-level elevation measurements from selected wells within these aquifer systems commonly form the basis for delineating groundwater-flow patterns (i.e., flow direction and hydraulic gradient). In addition, the analysis of water-level responses obtained in wells during hydrologic tests provides estimates of hydraulic properties that are important for evaluating groundwater-flow velocity and transport characteristics. Barometric pressure fluctuations, however, can have a discernible impact on well water-level measurements. These barometric effects may lead to erroneous indications of hydraulic head within the aquifer. Total hydraulic head (i.e., sum of the water-table elevation and the atmospheric pressure at the water-table surface) within the aquifer, not well water-level elevation, is the hydrologic parameter for determining groundwater-flow direction and hydraulic gradient conditions. Temporal variations in barometric pressure may also adversely affect well water-level responses obtained during hydrologic tests. If significant, adjustments or removal of these barometric effects from the test-response record may be required for quantitative hydraulic property determination. This report examines the effects of barometric fluctuations on well water-level measurements and evaluates adjustment and removal methods for determining areal aquifer head conditions and aquifer test analysis. Two examples of Hanford Site unconfined aquifer tests are examined that demonstrate barometric response analysis and illustrate the predictive/removal capabilities of various methods for well water-level and aquifer total head values. Good predictive/removal characteristics were demonstrated with best corrective results provided by multiple-regression deconvolution methods.

  2. Geochemical controls on fluoriferous groundwaters of the Pliocene and the more recent aquifers: The case of Aigion region, Greece

    Science.gov (United States)

    Katsanou, K.; Siavalas, G.; Lambrakis, N.

    2013-12-01

    High fluoride concentrations (> 8 mg/L) in the groundwater of the Plio-Pleistocene sediments are rare; however, this is the case around Aigion town, where teeth fluorosis has been detected since the 80s. Aiming to investigate the origin and the mobility mechanism of fluorine in groundwater and sediments a hydrogeological and geochemical research has been conducted. The hydrogeological research revealed that the Na-HCO3 water type of boreholes aligned along a fault and hosted in the confined aquifers display the higher fluoride content. The unconfined aquifer is mostly dominated by Na-Ca-Mg-HCO3-SO4 water, which displays much lower fluoride concentrations. The most permeable sectors of this aquifer host fresh water of Ca-HCO3 type. The geochemical research revealed significant amount of fluorine in the base of a lignite sequence hosted in the Plio-Pleistocene sediments.

  3. EPA Sole Source Aquifers

    Data.gov (United States)

    U.S. Environmental Protection Agency — Information on sole source aquifers (SSAs) is widely used in assessments under the National Environmental Policy Act and at the state and local level. A national...

  4. Tracers Detect Aquifer Contamination

    National Research Council Canada - National Science Library

    Enfield, Carl

    1995-01-01

    The EPA's National Laboratory (NRMRL) at Ada, OK, along with the University of Florida and the University of Texas, have developed a tracer procedure to detect the amount of contamination in aquifer formations...

  5. New Pn and Sn tomographic images of the uppermost mantle beneath the Mediterranean region

    Science.gov (United States)

    Gil, A.; Díaz, J.; Gallart, J.

    2012-04-01

    We present here new images of the seismic velocity and anisotropy variations in the uppermost mantle beneath the Mediterranean region, compiled from inversion of Pn and Sn phases. The method of Hearn (1996) has been applied to Pn and Sn lectures from the catalogs of the International Seismological Center and the Spanish Instituto Geografico Nacional. A total of 1,172,293 Pn arrivals coming from 16,527 earthquakes recorded at 1,657 stations with epicentral distances between 220 km and 1400 km have been retained (331,567 arrivals from 15,487events at 961 stations for Sn). Our results, grossly consistent with available 3D tomography images, show significant features well correlated with surface geology. The Pn velocities are high (>8.2 km/s) beneath major sedimentary basins (western Alboran Sea, Valencia Trough, Adriatic Sea, Aquitaine, Guadalquivir, Rharb, Aquitaine and Po basins), and low (Islands, probably related to a thermal anomaly associated to the westward displacement of the Alboran block along the Emile Baudot escarpment 16 Ma ago. The Pn anisotropic image shows consistent orientations sub-parallel to major orogenic structures, such as Betics, Apennines, Calabrian Arc and Alps. The station delays beneath Betic and Rif ranges are strongly negative, suggesting the presence of crustal thickening all along the Gibraltar Arc. However, only the Betics have a very strong low-velocity anomaly and a pronounced anisotropy pattern. The Sn tomographic image correlates well with the Pn image, even if some relevant differences can be observed beneath particular regions.

  6. Shape preferred orientation of iron grains compatible with Earth's uppermost inner core hemisphericity

    Science.gov (United States)

    Calvet, Marie; Margerin, Ludovic

    2018-01-01

    Constraining the possible patterns of iron fabrics in the Earth's Uppermost Inner Core (UIC) is key to unravel the mechanisms controlling its growth and dynamics. In the framework of crystalline micro-structures composed of ellipsoidal, aligned grains, we discuss possible textural models of UIC compatible with observations of P-wave attenuation and velocity dispersion. Using recent results from multiple scattering theory in textured heterogeneous materials, we compute the P-wave phase velocity and scattering attenuation as a function of grain volume, shape, and orientation wrt to the propagation direction of seismic P-waves. Assuming no variations of the grain volume between the Eastern and Western hemisphere, we show that two families of texture are compatible with the degree-one structure of the inner core as revealed by the positive correlation between seismic velocity and attenuation. (1) Strong flattening of grains parallel to the Inner Core Boundary in the Western hemisphere and weak anisometry in the Eastern hemisphere. (2) Strong radial elongation of grains in the Western hemisphere and again weak anisometry in the Eastern hemisphere. Both textures can quantitatively explain the seismic data in a limited range of grain volumes. Furthermore, the velocity and attenuation anisotropy locally observed under Africa demands that the grains be locally elongated in the direction of Earth's meridians. Our study demonstrates that the hemispherical seismic structure of UIC can be entirely explained by changes in the shape and orientation of grains, thereby offering an alternative to changes in grain volumes. In the future, our theoretical toolbox could be used to systematically test the compatibility of textures predicted by geodynamical models with seismic observations.

  7. Pumping Test Determination of Unsaturated Aquifer Properties

    Science.gov (United States)

    Mishra, P. K.; Neuman, S. P.

    2008-12-01

    Tartakovsky and Neuman [2007] presented a new analytical solution for flow to a partially penetrating well pumping at a constant rate from a compressible unconfined aquifer considering the unsaturated zone. In their solution three-dimensional, axially symmetric unsaturated flow is described by a linearized version of Richards' equation in which both hydraulic conductivity and water content vary exponentially with incremental capillary pressure head relative to its air entry value, the latter defining the interface between the saturated and unsaturated zones. Both exponential functions are characterized by a common exponent k having the dimension of inverse length, or equivalently a dimensionless exponent kd=kb where b is initial saturated thickness. The authors used their solution to analyze drawdown data from a pumping test conducted by Moench et al. [2001] in a Glacial Outwash Deposit at Cape Cod, Massachusetts. Their analysis yielded estimates of horizontal and vertical saturated hydraulic conductivities, specific storage, specific yield and k . Recognizing that hydraulic conductivity and water content seldom vary identically with incremental capillary pressure head, as assumed by Tartakovsky and Neuman [2007], we note that k is at best an effective rather than a directly measurable soil parameter. We therefore ask to what extent does interpretation of a pumping test based on the Tartakovsky-Neuman solution allow estimating aquifer unsaturated parameters as described by more common constitutive water retention and relative hydraulic conductivity models such as those of Brooks and Corey [1964] or van Genuchten [1980] and Mualem [1976a]? We address this question by showing how may be used to estimate the capillary air entry pressure head k and the parameters of such constitutive models directly, without a need for inverse unsaturated numerical simulations of the kind described by Moench [2003]. To assess the validity of such direct estimates we use maximum

  8. Ogallala Aquifer Mapping Program

    International Nuclear Information System (INIS)

    1984-10-01

    A computerized data file has been established which can be used efficiently by the contour-plotting program SURFACE II to produce maps of the Ogallala aquifer in 17 counties of the Texas Panhandle. The data collected have been evaluated and compiled into three sets, from which SURFACE II can generate maps of well control, aquifer thickness, saturated thickness, water level, and the difference between virgin (pre-1942) and recent (1979 to 1981) water levels. 29 figures, 1 table

  9. The integrated impacts of natural processes and human activities on groundwater salinization in the coastal aquifers of Beihai, southern China

    Science.gov (United States)

    Li, Qinghua; Zhang, Yanpeng; Chen, Wen; Yu, Shaowen

    2018-03-01

    Salinization in coastal aquifers is usually related to both seawater intrusion and water-rock interaction. The results of chemical and isotopic methods were combined to identify the origin and processes of groundwater salinization in Daguansha area of Beihai, southern China. The concentrations of the major ions that dominate in seawater (Cl-, Na+, Ca2+, Mg2+ and SO4 2- ), as well as the isotopic content and ratios (2H, 18O, 87Sr/86Sr and 13C), suggest that the salinization occurring in the aquifer of the coastal plain is related to seawater and that the prevailing hydrochemical processes are evaporation, mixing, dissolution and ion exchange. For the unconfined aquifer, groundwater salinization has occurred in an area that is significantly influenced by land-based sea farming. The integrated impacts of seawater intrusion from the Beibuwan Gulf and infiltration of seawater from the culture ponds are identified in the shallowest confined aquifer (I) in the middle of the area (site BBW2). Leakage from this polluted confined aquifer causes the salinization of groundwater in the underlying confined aquifer (II). At the coastal monitoring site (BBW3), confined aquifer I and lower confined aquifer II are heavily contaminated by seawater intrusion. The weak connectivity between the upper aquifers, and the seaward movement of freshwater, prevents saltwater from encroaching the deepest confined aquifer (III). A conceptual model is presented. Above all, understanding of the origin and processes of groundwater salinization will provide essential information for the planning and sustainable management of groundwater resources in this region.

  10. Saturated-unsaturated flow to a partially penetrating well with storage in a compressible aquifer

    Science.gov (United States)

    Mishra, P. K.; Neuman, S. P.

    2010-12-01

    Mishra and Neuman [2010] developed an analytical solution for flow to a partially penetrating well of zero radius in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from responses recorded in the saturated and/or the unsaturated zone. We extend their solution to the case of a finite diameter pumping well with storage. Both solutions account for horizontal as well as vertical flows throughout the system. We investigate the effects of storage in the pumping well and delayed piezometer response on drawdowns in the saturated and unsaturated zones as functions of position and time; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten - Mualem constitutive model; and use our solution to analyze drawdown data from a pumping test conducted at the Borden site in Ontario, Canada.

  11. Isotopes to Study the coastal aquifer plain, Cap Bon, Tunisia

    International Nuclear Information System (INIS)

    Ben Hamouda, M. F.; Zouari, Kamel; Tarhouni, J.; Gaye, C.B.; Oueslati, M.N.

    2005-01-01

    some sites the presence of bomb-tritium indicates a modern component of recharge in the groundwater. This suggests that the aquifer is unconfined, at least in its upper layer. 14C data will be used to estimate the rate of local recharge. The salinity of the groundwater appears to originate from dissolution of minerals (halite) in the aquifer system. The higher values of the dissolved anions and cations in korba area are due to higher sodium and chloride concentrations coming from mixture with sea water. The changes of the latter concentration seem to be associated with changes of the proportion of local recharge. In general, the oriental coast aquifer system receives relatively a good recharge coming from water of current precipitation. This contribution of current water is shown also on the deep aquifer, in particular on the level of the piedmont. This situation seems to indicate that the reconstitution of the reserves is fast in these areas. The salinity is generally acquired by dissolution associated with a process of evaporation.However for the shallow aquifer a contamination by a mixture with seawater is extremely probable, in particular in the sectors of Korba and Tefelloune, where we observe a negative piezometry and the salinity can reach the 8 g/l

  12. An Experimental Study of Unconfined Hydrogen/Oxygen and Hydrogen/Air Explosions

    Science.gov (United States)

    Richardson, Erin; Skinner, Troy; Blackwood, James; Hays, Michael; Bangham, Mike; Jackson, Austin

    2014-01-01

    Development tests are being conducted to characterize unconfined Hydrogen/air and Hydrogen/Oxygen blast characteristics. Most of the existing experiments for these types of explosions address contained explosions, like shock tubes. Therefore, the Hydrogen Unconfined Combustion Test Apparatus (HUCTA) has been developed as a gaseous combustion test device for determining the relationship between overpressure, impulse, and flame speed at various mixture ratios for unconfined reactions of hydrogen/oxygen and hydrogen/air. The system consists of a central platform plumbed to inject and mix component gasses into an attached translucent bag or balloon while monitoring hydrogen concentration. All tests are ignited with a spark with plans to introduce higher energy ignition sources in the future. Surrounding the platform are 9 blast pressure "Pencil" probes. Two high-speed cameras are used to observe flame speed within the combustion zone. The entire system is raised approx. 6 feet off the ground to remove any ground reflection from the measurements. As of this writing greater than 175 tests have been performed and include Design of Experiments test sets. Many of these early tests have used bags or balloons between approx. 340L and approx. 1850L to quantify the effect of gaseous mixture ratio on the properties of interest. All data acquisition is synchronized between the high-speed cameras, the probes, and the ignition system to observe flame and shock propagation. Successful attempts have been made to couple the pressure profile with the progress of the flame front within the combustion zone by placing a probe within the bag. Overpressure and impulse data obtained from these tests are used to anchor engineering analysis tools, CFD models and in the development of blast and fragment acceleration models.

  13. Experimental Study on Unconfined Compressive Strength of Basalt Fiber Reinforced Clay Soil

    OpenAIRE

    Gao, Lei; Hu, Guohui; Xu, Nan; Fu, Junyi; Xiang, Chao; Yang, Chen

    2015-01-01

    In order to study the mechanism and effect of basalt fiber reinforced clay soil, a series of unconfined compressive strength tests conducted on clay soil reinforced with basalt fiber have been performed under the condition of optimum water content and maximum dry density. Both the content and length of basalt fiber are considered in this paper. When the effect of content is studied, the 12 mm long fibers are dispersed into clay soil at different contents of 0.05%, 0.1%, 0.15%, 0.20%, 0.25%, 0...

  14. Hydrochemistry and Isotope Hydrology for Groundwater Sustainability of the Coastal Multilayered Aquifer System (Zhanjiang, China

    Directory of Open Access Journals (Sweden)

    Pengpeng Zhou

    2017-01-01

    Full Text Available Groundwater sustainability has become a critical issue for Zhanjiang (China because of serious groundwater level drawdown induced by overexploitation of its coastal multilayered aquifer system. It is necessary to understand the origins, material sources, hydrochemical processes, and dynamics of the coastal groundwater in Zhanjiang to support its sustainable management. To this end, an integrated analysis of hydrochemical and isotopic data of 95 groundwater samples was conducted. Hydrochemical analysis shows that coastal groundwater is fresh; however, relatively high levels of Cl−, Mg2+, and total dissolved solid (TDS imply slight seawater mixing with coastal unconfined groundwater. Stable isotopes (δ18O and δ2H values reveal the recharge sources of groundwater in the multilayered aquifer system. The unconfined groundwater originates from local modern precipitation; the confined groundwater in mainland originates from modern precipitation in northwestern mountain area, and the confined groundwater in Donghai and Leizhou is sourced from rainfall recharge during an older period with a colder climate. Ionic relations demonstrate that silicate weathering, carbonate dissolutions, and cation exchange are the primary processes controlling the groundwater chemical composition. Declining trends of groundwater level and increasing trends of TDS of the confined groundwater in islands reveal the landward extending tendency of the freshwater-seawater mixing zone.

  15. Composition of uppermost mantle beneath the Northern Fennoscandia - numerical modeling and petrological interpretation

    Science.gov (United States)

    Virshylo, Ivan; Kozlovskaya, Elena; Prodaivoda, George; Silvennoinen, Hanna

    2013-04-01

    Studying of the uppermost mantle beneath the northern Fennoscandia is based on the data of the POLENET/LAPNET passive seismic array. Firstly, arrivals of P-waves of teleseismic events were inverted into P-wave velocity model using non-linear tomography (Silvennoinen et al., in preparation). The second stage was numerical petrological interpretation of referred above velocity model. This study presents estimation of mineralogical composition of the uppermost mantle as a result of numerical modeling. There are many studies concerning calculation of seismic velocities for polymineral media under high pressure and temperature conditions (Afonso, Fernàndez, Ranalli, Griffin, & Connolly, 2008; Fullea et al., 2009; Hacker, 2004; Xu, Lithgow-Bertelloni, Stixrude, & Ritsema, 2008). The elastic properties under high pressure and temperature (PT) conditions were modelled using the expanded Hook's law - Duhamel-Neumann equation, which allows computation of thermoelastic strains. Furthermore, we used a matrix model with multi-component inclusions that has no any restrictions on shape, orientation or concentration of inclusions. Stochastic method of conditional moment with computation scheme of Mori-Tanaka (Prodaivoda, Khoroshun, Nazarenko, & Vyzhva, 2000) is applied instead of traditional Voigt-Reuss-Hill and Hashin-Shtrikman equations. We developed software for both forward and inverse problem calculation. Inverse algorithm uses methods of global non-linear optimization. We prefer a "model-based" approach for ill-posed problem, which means that the problem is solved using geological and geophysical constraints for each parameter of a priori and final models. Additionally, we are checking at least several different hypothesis explaining how it is possible to get the solution with good fit to the observed data. If the a priori model is close to the real medium, the nearest solution would be found by the inversion. Otherwise, the global optimization is searching inside the

  16. Factors Affecting Water Quality in Domestic Wells in the Upper Floridan Aquifer, Southeastern United States, 1998-2005

    Science.gov (United States)

    Berndt, Marian P.; Crandall, Christy A.; Deacon, Michael; Embry, Teresa L.; Howard, Rhonda S.

    2009-01-01

    The Floridan aquifer system is a highly productive carbonate aquifer that provides drinking water to about 10 million people in Florida, Georgia, and South Carolina. Approximately 1.6 million people rely on domestic wells (privately owned household wells) for drinking water. Withdrawals of water from the Floridan aquifer system have increased by more than 500 percent from 630 million gallons per day (2.38 cubic meters per day) in 1950 to 4,020 million gallons per day (15.2 cubic meters per day) in 2000, largely due to increases in population, tourism, and agriculture production. Water samples were collected from 148 domestic wells in the Upper Floridan aquifer in Florida, Georgia, South Carolina, and Alabama during 1998-2005 as part of the U.S. Geological Survey (USGS) National Water-Quality Assessment Program. The wells were located in different hydrogeologic settings based on confinement of the Upper Floridan aquifer. Five networks of wells were sampled con-sisting of 28 to 30 wells each: two networks were in unconfined areas, two networks were in semiconfined areas, and one network was in the confined area. Physical properties and concentrations of major ions, trace elements, nutrients, radon, and organic compounds (volatile organic compounds and pesticides) were measured in water samples. Concentrations were compared to water-quality benchmarks for human health, either U.S. Environmental Protection Agency (USEPA) Maximum Contaminant Levels (MCLs) for public water supplies or USGS Health-Based Screening Levels (HBSLs). The MCL for fluoride of 4 milligrams per liter (mg/L) was exceeded for two samples (about 1 percent of samples). A proposed MCL for radon of 300 picocuries per liter was exceeded in about 40 percent of samples. Nitrate concentrations in the Upper Floridan aquifer ranged from less than the laboratory reporting level of 0.06 to 8 mg/L, with a median nitrate concentration less than 0.06 mg/L (as nitrogen). Nitrate concentrations did not exceed the

  17. The stability of clay using mount Sinabung ash with unconfined compression test (uct) value

    Science.gov (United States)

    Puji Hastuty, Ika; Roesyanto; Hutauruk, Ronny; Simanjuntak, Oberlyn

    2018-03-01

    The soil has a important role as a highway’s embankment material (sub grade). Soil conditions are very different in each location because the scientifically soil is a very complex and varied material and the located on the field is very loose or very soft, so it is not suitable for construction, then the soil should be stabilized. The additive material commonly used for soil stabilization includes cement, lime, fly ash, rice husk ash, and others. This experiment is using the addition of volcanic ash. The purpose of this study was to determine the Index Properties and Compressive Strength maximum value with Unconfined Compression Test due to the addition of volcanic ash as a stabilizing agent along with optimum levels of the addition. The result showed that the original soil sample has Water Content of 14.52%; the Specific Weight of 2.64%; Liquid limit of 48.64% and Plasticity Index of 29.82%. Then, the Compressive Strength value is 1.40 kg/cm2. According to USCS classification, the soil samples categorized as the (CL) type while based on AASHTO classification, the soil samples are including as the type of A-7-6. After the soil is stabilized with a variety of volcanic ash, can be concluded that the maximum value occurs at mixture variation of 11% Volcanic Ash with Unconfined Compressive Strength value of 2.32 kg/cm2.

  18. Reflections about the modelling of unconfined explosions of air-hydrocarbon mixtures

    International Nuclear Information System (INIS)

    Hendrickx, S.; Lannoy, A.

    1983-01-01

    To design nuclear power plants structures, an evaluation of hazards which can be induced by the industrial activities is needed. These hazards namely involve explosions of flamable air-hydrocarbon gas clouds. Such clouds can drift before ignition, and, when ignited, the generated pressure wave can cause serious damage, even far from the initial accident location. When the designs an industrial plant, the designer has to predict the overpressures capable of jeopardizing the safety functions of the plant. The analysis of real accidental explosions which have actually occurred, on the basis of a total explosion yield and the TNT equivalency concept, is a first step. Indeed, it allows a total explosion yield to be calculated, an empirical TNT equivalent of hydrocarbon to be deducted. Unfortunately, this TNT equivalency concept is scientifically not satisfying. The modelling of an unconfined air-hydrocarbon detonation can be used for safety analysis, if we assume that an unconfined explosion can be a detonation, which is unlikely. (orig./WL)

  19. Approaches to the simulation of unconfined flow and perched groundwater flow in MODFLOW

    Science.gov (United States)

    Bedekar, Vivek; Niswonger, Richard G.; Kipp, Kenneth; Panday, Sorab; Tonkin, Matthew

    2012-01-01

    Various approaches have been proposed to manage the nonlinearities associated with the unconfined flow equation and to simulate perched groundwater conditions using the MODFLOW family of codes. The approaches comprise a variety of numerical techniques to prevent dry cells from becoming inactive and to achieve a stable solution focused on formulations of the unconfined, partially-saturated, groundwater flow equation. Keeping dry cells active avoids a discontinuous head solution which in turn improves the effectiveness of parameter estimation software that relies on continuous derivatives. Most approaches implement an upstream weighting of intercell conductance and Newton-Raphson linearization to obtain robust convergence. In this study, several published approaches were implemented in a stepwise manner into MODFLOW for comparative analysis. First, a comparative analysis of the methods is presented using synthetic examples that create convergence issues or difficulty in handling perched conditions with the more common dry-cell simulation capabilities of MODFLOW. Next, a field-scale three-dimensional simulation is presented to examine the stability and performance of the discussed approaches in larger, practical, simulation settings.

  20. A practical method for estimating maximum shear modulus of cemented sands using unconfined compressive strength

    Science.gov (United States)

    Choo, Hyunwook; Nam, Hongyeop; Lee, Woojin

    2017-12-01

    The composition of naturally cemented deposits is very complicated; thus, estimating the maximum shear modulus (Gmax, or shear modulus at very small strains) of cemented sands using the previous empirical formulas is very difficult. The purpose of this experimental investigation is to evaluate the effects of particle size and cement type on the Gmax and unconfined compressive strength (qucs) of cemented sands, with the ultimate goal of estimating Gmax of cemented sands using qucs. Two sands were artificially cemented using Portland cement or gypsum under varying cement contents (2%-9%) and relative densities (30%-80%). Unconfined compression tests and bender element tests were performed, and the results from previous studies of two cemented sands were incorporated in this study. The results of this study demonstrate that the effect of particle size on the qucs and Gmax of four cemented sands is insignificant, and the variation of qucs and Gmax can be captured by the ratio between volume of void and volume of cement. qucs and Gmax of sand cemented with Portland cement are greater than those of sand cemented with gypsum. However, the relationship between qucs and Gmax of the cemented sand is not affected by the void ratio, cement type and cement content, revealing that Gmax of the complex naturally cemented soils with unknown in-situ void ratio, cement type and cement content can be estimated using qucs.

  1. Prediction of zeolite-cement-sand unconfined compressive strength using polynomial neural network

    Science.gov (United States)

    MolaAbasi, H.; Shooshpasha, I.

    2016-04-01

    The improvement of local soils with cement and zeolite can provide great benefits, including strengthening slopes in slope stability problems, stabilizing problematic soils and preventing soil liquefaction. Recently, dosage methodologies are being developed for improved soils based on a rational criterion as it exists in concrete technology. There are numerous earlier studies showing the possibility of relating Unconfined Compressive Strength (UCS) and Cemented sand (CS) parameters (voids/cement ratio) as a power function fits. Taking into account the fact that the existing equations are incapable of estimating UCS for zeolite cemented sand mixture (ZCS) well, artificial intelligence methods are used for forecasting them. Polynomial-type neural network is applied to estimate the UCS from more simply determined index properties such as zeolite and cement content, porosity as well as curing time. In order to assess the merits of the proposed approach, a total number of 216 unconfined compressive tests have been done. A comparison is carried out between the experimentally measured UCS with the predictions in order to evaluate the performance of the current method. The results demonstrate that generalized polynomial-type neural network has a great ability for prediction of the UCS. At the end sensitivity analysis of the polynomial model is applied to study the influence of input parameters on model output. The sensitivity analysis reveals that cement and zeolite content have significant influence on predicting UCS.

  2. Estimation of the recharge area contributing water to a pumped well in a glacial-drift, river-valley aquifer

    Science.gov (United States)

    Morrissey, Daniel J.

    1989-01-01

    The highly permeable, unconfined, glacial-drift aquifers that occupy most New England river valleys constitute the principal source of drinking water for many of the communities that obtain part or all of their public water supply from ground water. Recent events have shown that these aquifers are highly susceptible to contamination that results from a number of sources, such as seepage from wastewater lagoons, leaking petroleum-product storage tanks, and road salting. To protect the quality of water pumped from supply wells in these aquifers, it is necessary to ensure that potentially harmful contaminants do not enter the ground in the area that contributes water to the well. A high degree of protection can be achieved through the application of appropriate land-use controls within the contributing area. However, the contributing areas for most supply wells are not known. This report describes the factors that affect the size and shape of contributing areas to public supply wells and evaluates several methods that may be used to delineate contributing areas of wells in glacial-drift, river-valley aquifers. Analytical, two-dimensional numerical, and three-dimensional numerical models were used to delineate contributing areas. These methods of analysis were compared by applying them to a hypothetical aquifer having the dimensions and geometry of a typical glacial-drift, river-valley aquifer. In the model analyses, factors that control the size and shape of a contributing area were varied over ranges of values common to glacial-drift aquifers in New England. The controlling factors include the rate of well discharge, rate of recharge to the aquifer from precipitation and from adjacent till and bedrock uplands, distance of a pumping well from a stream or other potential source of induced recharge, degree of hydraulic connection of the aquifer with a stream, horizontal hydraulic conductivity of the aquifer, ratio of horizontal to vertical hydraulic conductivity, and

  3. Evaluation of availability of water from drift aquifers near the Pomme de Terre and Chippewa rivers, western Minnesota

    Science.gov (United States)

    Delin, G.N.

    1987-01-01

    Ground-water flow in the confined- and unconfined-drift aquifers near Appleton and Benson, Minnesota, was simulated with a three-dimensional finite-difference ground-water-flow model. Model results indicate that 98 percent of the total inflow to the modeled area is from precipitation. Of the total outflow, 38 percent is ground-water discharge to the Pom me de Terre and Chippewa Rivers, 36 percent is evapotranspiration, 17 percent is ground-water pumpage, and 8 percent is ground-water discharge to the Minnesota River.

  4. Estimating hydraulic parameters of the Açu-Brazil aquifer using the computer analysis of micrographs

    Science.gov (United States)

    de Lucena, Leandson R. F.; da Silva, Luis R. D.; Vieira, Marcela M.; Carvalho, Bruno M.; Xavier Júnior, Milton M.

    2016-04-01

    The conventional way of obtaining hydraulic parameters of aquifers is through the interpretation of aquifer tests that requires a fairly complex logistics in terms of equipment and personnel. On the other way, the processing and analysis of digital images of two-dimensional rock sample micrographs presents itself as a promising (simpler and cheaper) alternative procedure for obtaining estimates for hydraulics parameters. This methodology involves the sampling of rocks, followed by the making and imaging of thin rock samples, image segmentation, three-dimensional reconstruction and flow simulation. This methodology was applied to the outcropping portion of the Açu aquifer in the northeast of Brazil, and the computational analyses of the thin rock sections of the acquired samples produced effective porosities between 11.2% and 18.5%, and permeabilities between 52.4 mD and 1140.7 mD. Considering that the aquifer is unconfined, these effective porosity values can be used effectively as storage coefficients. The hydraulic conductivities produced by adopting different water dynamic viscosities at the temperature of 28 °C in the conversion of the permeabilities result in values in the range of [ 6.03 ×10-7, 1.43 ×10-5 ] m/s, compatible with the local hydrogeology.

  5. Transient well flow in layered aquifer systems: the uniform well-face drawdown solution

    Science.gov (United States)

    Hemker, C. J.

    1999-11-01

    Previously a hybrid analytical-numerical solution for the general problem of computing transient well flow in vertically heterogeneous aquifers was proposed by the author. The radial component of flow was treated analytically, while the finite-difference technique was used for the vertical flow component only. In the present work the hybrid solution has been modified by replacing the previously assumed uniform well-face gradient (UWG) boundary condition in such a way that the drawdown remains uniform along the well screen. The resulting uniform well-face drawdown (UWD) solution also includes the effects of a finite diameter well, wellbore storage and a thin skin, while partial penetration and vertical heterogeneity are accommodated by the one-dimensional discretization. Solutions are proposed for well flow caused by constant, variable and slug discharges. The model was verified by comparing wellbore drawdowns and well-face flux distributions with published numerical solutions. Differences between UWG and UWD well flow will occur in all situations with vertical flow components near the well, which is demonstrated by considering: (1) partially penetrating wells in confined aquifers, (2) fully penetrating wells in unconfined aquifers with delayed response and (3) layered aquifers and leaky multiaquifer systems. The presented solution can be a powerful tool for solving many well-hydraulic problems, including well tests, flowmeter tests, slug tests and pumping tests. A computer program for the analysis of pumping tests, based on the hybrid analytical-numerical technique and UWG or UWD conditions, is available from the author.

  6. Reactive transport modelling of groundwater chemistry in a chalk aquifer at the watershed scale.

    Science.gov (United States)

    Mangeret, A; De Windt, L; Crançon, P

    2012-09-01

    This study investigates thermodynamics and kinetics of water-rock interactions in a carbonate aquifer at the watershed scale. A reactive transport model is applied to the unconfined chalk aquifer of the Champagne Mounts (France), by considering both the chalk matrix and the interconnected fracture network. Major element concentrations and main chemical parameters calculated in groundwater and their evolution along flow lines are in fair agreement with field data. A relative homogeneity of the aquifer baseline chemistry is rapidly reached in terms of pH, alkalinity and Ca concentration since calcite equilibrium is achieved over the first metres of the vadose zone. However, incongruent chalk dissolution slowly releases Ba, Mg and Sr in groundwater. Introducing dilution effect by rainwater infiltration and a local occurrence of dolomite improves the agreement between modelling and field data. The dissolution of illite and opal-CT, controlling K and SiO(2) concentrations in the model, can be approximately tackled by classical kinetic rate laws, but not the incongruent chalk dissolution. An apparent kinetic rate has therefore been fitted on field data by inverse modelling: 1.5×10(-5) mol(chalk)L (-1) water year (-1). Sensitivity analysis indicates that the CO(2) partial pressure of the unsaturated zone is a critical parameter for modelling the baseline chemistry over the whole chalk aquifer. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Aquifer characterization and groundwater modeling in support of remedial actions at the Weldon Spring Site

    International Nuclear Information System (INIS)

    Durham, L.A.; Carman, J.D.

    1993-01-01

    Aquifer characterization studies were performed to develop a hydrogeologic understanding of an unconfined shallow aquifer at the Weldon Spring site west of St. Louis, Missouri. The 88-ha site became contaminated because of uranium and thorium processing and disposal activities that took place from the 1940s through the 1960s. Slug and pumping tests provided valuable information on the lateral distribution of hydraulic conductivities, and packer tests and lithologic information were used to determine zones of contrasting hydrologic properties within the aquifer. A three-dimensional, finite- element groundwater flow model was developed and used to simulate the shallow groundwater flow system at the site. The results of this study show that groundwater flow through the system is predominantly controlled by a zone of fracturing and weathering in the upper portion of the limestone aquifer. The groundwater flow model, developed and calibrated from field investigations, improved the understanding of the hydrogeology and supported decisions regarding remedial actions at the site. The results of this study illustrate the value, in support of remedial actions, of combining field investigations with numerical modeling to develop an improved understanding of the hydrogeology at the site

  8. Geohydrology of the valley-fill aquifer in the Corning area, Steuben County, New York

    Science.gov (United States)

    Miller, Todd S.; Belli, J.L.; Allen, R.V.

    1982-01-01

    This report is the seventh in a series of 11 map sets depicting geohydrologic conditions in selected aquifers in upstate New York. Geohydrologic data are compiled on six maps at 1:24,000 scale. Together, the maps provide a comprehensive overview of a major valley-fill aquifer in southeastern Steuben County. The maps include surficial geology, geologic sections, water-infiltration potential of soil zone, aquifer thickness, potentiometric-surface elevations, and land use. The valley-fill deposits consist of alluvial silt, sand, and gravel, glacial-outwash (sand and gravel), till, and lacustrine silt and clay. The sand and gravel beds have relatively high permeabilities, whereas the till and silt deposits have relatively low permeabilities. Water-table conditions prevail in unconfined sand and gravel along the valley margin. Artesian conditions are found locally in sand and gravel confined under silt and clay in the middle of the valley. Recharge occurs nearly everywhere on the valley floor, but principally along the margin of the valley, where highly permeable land surface conditions exist, and runoff from the hillsides is concentrated. The use of land overlying the aquifer is a mixture of residential, commercial, agricultural, and industrial uses. (USGS)

  9. Identification of aquifer potential in Karanganyar city by using vertical electrical sounding method

    Science.gov (United States)

    Marfuatik, L.; Koesuma, S.; Legowo, B.; Darsono

    2018-03-01

    The identification of aquifer was done by using Vertical Electrical Sounding (VES) method. This research aims to identify potential and depth of the aquifers. The locations of surveys are at ten points,namely TS1 (Alastuwo), TS2 (Wonorejo), TS3 (Kaling), TS4 (Kaling), TS5 (Buran), TS6 (Wonolopo), TS7 (Buran), TS8 (Ngijo), TS9 (Jati), and TS10 (Suruhkalang) where all located in Karanganyar regency. The survey path is about 500-600 meters length which can penetrate current to 100 – 200 meters in depth. The measurement was done by using OYO Mc OHM-EL Model 2119C. Geoelectrical data analysis was processed using Progress version 3.0 Software. The interpretation result shows that the locations of research area are included in Lawu-volcano rock formation which is breccias, lava, and tuff as the constituents. We found that unconfined aquifer in all of locations with different depth and confined aquifer just 7 locations start from 25.04 meters.

  10. Potential Risks of Freshwater Aquifer Contamination with Geosequestration

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, Robert

    2013-09-30

    Substantial leakage of CO{sub 2} from deep geological strata to shallow potable aquifers is likely to be rare, but chemical detection of potential leakage nonetheless remains an integral component of any safe carbon capture and storage system. CO{sub 2} that infiltrates an unconfined freshwater aquifer will have an immediate impact on water chemistry by lowering pH in most cases and by altering the concentration of total dissolved solids. Chemical signatures in affected waters provide an important opportunity for early detection of leaks. In the presence of CO{sub 2}, trace elements such as Mn, Fe, and Ca can increase by an order of magnitude or more above control concentrations within 100 days. Therefore, these and other elements should be monitored along with pH as geochemical markers of potential CO{sub 2} leaks. Dissolved inorganic carbon and alkalinity can also be rapidly responsive to CO{sub 2} and are stable indicators of a leak. Importantly, such changes may be detectable long before direct changes in CO{sub 2} are observed. The experimental results also suggest that the relative severity of the impact of leaks on overlying drinking-water aquifers should be considered in the selection of CO{sub 2} sequestration sites. One primary selection criteria should be metal and metalloid availability, such as uranium and arsenic abundance, to carefully monitor chemical species that could trigger changes above maximum contaminant levels (MCLs). Overall, the risks of leakage from underground CO{sub 2} storage are real but appear to be manageable if systems are closely monitored.

  11. Estimation of hydraulic properties and development of a layered conceptual model for the Snake River plain aquifer at the Idaho National Engineering Laboratory, Idaho

    International Nuclear Information System (INIS)

    Frederick, D.B.; Johnson, G.S.

    1996-02-01

    The Idaho INEL Oversight Program, in association with the University of Idaho, Idaho Geological Survey, Boise State University, and Idaho State University, developed a research program to determine the hydraulic properties of the Snake River Plain aquifer and characterize the vertical distribution of contaminants. A straddle-packer was deployed in four observation wells near the Idaho Chemical Processing Plant at the Idaho National Engineering Laboratory. Pressure transducers mounted in the straddle-packer assembly were used to monitor the response of the Snake River Plain aquifer to pumping at the ICPP production wells, located 2600 to 4200 feet from the observation wells. The time-drawdown data from these tests were used to evaluate various conceptual models of the aquifer. Aquifer properties were estimated by matching time-drawdown data to type curves for partially penetrating wells in an unconfined aquifer. This approach assumes a homogeneous and isotropic aquifer. The hydraulic properties of the aquifer obtained from the type curve analyses were: (1) Storativity = 3 x 10 -5 , (2) Specific Yield = 0.01, (3) Transmissivity = 740 ft 2 /min, (4) Anisotropy (Kv:Kh)= 1:360

  12. New methodology to investigate potential contaminant mass fluxes at the stream-aquifer interface by combining integral pumping tests and streambed temperatures

    International Nuclear Information System (INIS)

    Kalbus, E.; Schmidt, C.; Bayer-Raich, M.; Leschik, S.; Reinstorf, F.; Balcke, G.U.; Schirmer, M.

    2007-01-01

    The spatial pattern and magnitude of mass fluxes at the stream-aquifer interface have important implications for the fate and transport of contaminants in river basins. Integral pumping tests were performed to quantify average concentrations of chlorinated benzenes in an unconfined aquifer partially penetrated by a stream. Four pumping wells were operated simultaneously for a time period of 5 days and sampled for contaminant concentrations. Streambed temperatures were mapped at multiple depths along a 60 m long stream reach to identify the spatial patterns of groundwater discharge and to quantify water fluxes at the stream-aquifer interface. The combined interpretation of the results showed average potential contaminant mass fluxes from the aquifer to the stream of 272 μg m -2 d -1 MCB and 71 μg m -2 d -1 DCB, respectively. This methodology combines a large-scale assessment of aquifer contamination with a high-resolution survey of groundwater discharge zones to estimate contaminant mass fluxes between aquifer and stream. - We provide a new methodology to quantify the potential contaminant mass flux from an aquifer to a stream

  13. Hydrogeology and water quality of the stratified-drift aquifer in the Pony Hollow Creek Valley, Tompkins County, New York

    Science.gov (United States)

    Bugliosi, Edward F.; Miller, Todd S.; Reynolds, Richard J.

    2014-01-01

    The lithology, areal extent, and the water-table configuration in stratified-drift aquifers in the northern part of the Pony Hollow Creek valley in the Town of Newfield, New York, were mapped as part of an ongoing aquifer mapping program in Tompkins County. Surficial geologic and soil maps, well and test-boring records, light detection and ranging (lidar) data, water-level measurements, and passive-seismic surveys were used to map the aquifer geometry, construct geologic sections, and determine the depth to bedrock at selected locations throughout the valley. Additionally, water-quality samples were collected from selected streams and wells to characterize the quality of surface and groundwater in the study area. Sedimentary bedrock underlies the study area and is overlain by unstratified drift (till), stratified drift (glaciolacustrine and glaciofluvial deposits), and recent post glacial alluvium. The major type of unconsolidated, water-yielding material in the study area is stratified drift, which consists of glaciofluvial sand and gravel, and is present in sufficient amounts in most places to form an extensive unconfined aquifer throughout the study area, which is the source of water for most residents, farms, and businesses in the valleys. A map of the water table in the unconfined aquifer was constructed by using (1) measurements made between the mid-1960s through 2010, (2) control on the altitudes of perennial streams at 10-foot contour intervals from lidar data collected by Tompkins County, and (3) water surfaces of ponds and wetlands that are hydraulically connected to the unconfined aquifer. Water-table contours indicate that the direction of groundwater flow within the stratified-drift aquifer is predominantly from the valley walls toward the streams and ponds in the central part of the valley where groundwater then flows southwestward (down valley) toward the confluence with the Cayuta Creek valley. Locally, the direction of groundwater flow is radially

  14. New isotopic evidence for the origin of groundwater from the Nubian Sandstone Aquifer in the Negev, Israel

    Science.gov (United States)

    Vengosh, A.; Hening, S.; Ganor, J.; Mayer, B.; Weyhenmeyer, C.E.; Bullen, T.D.; Paytan, A.

    2007-01-01

    The geochemistry and isotopic composition (H, O, S, Osulfate, C, Sr) of groundwater from the Nubian Sandstone (Kurnub Group) aquifer in the Negev, Israel, were investigated in an attempt to reconstruct the origin of the water and solutes, evaluate modes of water-rock interactions, and determine mean residence times of the water. The results indicate multiple recharge events into the Nubian sandstone aquifer characterized by distinctive isotope signatures and deuterium excess values. In the northeastern Negev, groundwater was identified with deuterium excess values of ???16???, which suggests local recharge via unconfined areas of the aquifer in the Negev anticline systems. The ??18OH2O and ??2H values (-6.5??? and -35.4???) of this groundwater are higher than those of groundwater in the Sinai Peninsula and southern Arava valley (-7.5??? and -48.3???) that likewise have lower deuterium excess values of ???10???. Based on the geochemical differences between groundwater in the unconfined and confined zones of the aquifer, a conceptual geochemical model for the evolution of the groundwater in the Nubian sandstone aquifer has been reconstructed. The isotopic composition of shallow groundwater from the unconfined zone indicates that during recharge oxidation of pyrite to SO4 (??34SSO4 ???-13???; ??18OSO4 ???+7.7???) and dissolution of CaCO3 (87Sr/86Sr ???0.70787; ??13CDIC = -3.7???) occur. In the confined zone of the aquifer, bacterial SO4 reduction removes a significant part of dissolved SO42 -, thereby modifying its isotopic composition (??34SSO4 ???-2???; ??18OSO4 ???+8.5???) and liberating dissolved inorganic C that contains little or no radiocarbon (14C-free) with low ??13CDIC values (contribution of external groundwater sources to the Nubian Sandstone aquifer, resulting in further modifications of the groundwater chemical and isotopic signatures. In the northeastern Negev, it is shown that SO4-rich groundwater from the underlying Jurassic aquifer contributes

  15. Unconfined twist : a simple method to prepare ultrafine grained metallic materials.

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Y. (Yonghao); Liao, Xiaozhou; Zhu, Y. T. (Yuntian Theodore)

    2004-01-01

    A new simple method - unconfined twist was employed to prepare ultrafine grained (UFG) Fe,wire. A coarse grained (CG) Fe wire with a diameter of 0.85 mm was fixed at one end, and twisted at the other end. After maximum twist before fracture, in the cross-sectional plane, concentrically deformed layers with a width of several micrometers formed surrounding the center axis of the wire. The near-surface deformed layers consist of lamella grains with a width in submicrometer range. In the longitudinal plane, deformed bands (with a width of several micrometers) formed uniformly, which were composed of lamella crystallites (with a width in submicrometer range). The tensile yield strength and ultimate strength of the twisted Fe wire are increased by about 150% and 100% compared with the values of its CG counterpart.

  16. ΔT=1/2 rule in quark models with unconfined colour

    International Nuclear Information System (INIS)

    Arbuzov, B.A.; Kompaneetz, F.F.; Tikhonin, F.F.

    1977-01-01

    In the triplet quark model with unconfined colour a weak hadronic current is obtained with the following properties: a) it satisfies weak SU(2) algebra; b) the neutral current is completely diagonal and coincides with electromagnetic one in the quark structure ; c) the ''white'' part of the current possesses the properties of the Cabbibo current. The properties of the ''white'' part of nonleptonic Lagrangian derived from this current are : a)between the coefficients of the transition amplitudes ΔT=1/2 and ΔT=3/2 there is a ratio approximately 25 corresponding to experiment; b) there are no transitions ΔS=2; c) the values for the transitions ΔT=0,1,2 of the Lagrangian without changes of strangeness are compatible with each other

  17. Influence of Nanolime and Curing Period on Unconfined Compressive Strength of Soil

    Directory of Open Access Journals (Sweden)

    Panbarasi Govindasamy

    2017-01-01

    Full Text Available This paper presents the improvement of the unconfined compressive strength (UCS of soil by mixing different percentages of nanolime and 5% lime with soil. The UCS of treated soil increased significantly over curing time with increasing percentage of nanolime. The optimum results were reached at only 0.5% nanolime admixtures which were much higher than 5% lime admixture. This may be due to higher ability of nanolime to flocculate and agglomerate the soil particles compared with the lime. In addition, the lime could fill only the micropores while nanolime could fill the micro- and nanopores as well. The strength gain is inversely proportional to the remolded moisture content and curing period. However, when the content of nanolime used is larger than 0.5%, nanolime particles are not uniformly dispersed. Therefore, a weak area in the form of voids is created, consequently the homogeneous hydrated microstructure cannot be formed, and finally the strength will decrease.

  18. Correlation between nitrate concentration in groundwater and parameters affecting aquifer intrinsic vulnerability

    Science.gov (United States)

    Debernardi, Laura; de Luca, Domenico Antonio; Lasagna, Manuela

    2008-08-01

    This paper is the result of a study which was carried out in order to verify if the traditional methods to evaluate the intrinsic vulnerability or vulnerability related parameters, are able to clarify the problem of nitrate pollution in groundwater. In particular, the aim was to evaluate limitations and problems connected to aquifer vulnerability methods applied to nitrate contamination prevision in groundwater. The investigation was carried out by comparing NO3 - concentrations, measured in March and November 2004 in the shallow aquifer, and the vulnerability classes, obtained by using GOD and TOT methods. Moreover, it deals with a comparison between NO3 - concentrations and single parameters (depth to water table, land use and nitrogen input). The study area is the plain sector of Piemonte (Northern Italy), where an unconfined aquifer nitrate contamination exists. In this area the anthropogenic presence is remarkable and the input of N-fertilizers and zootechnical effluents to the soil cause a growing amount of nitrates in groundwater. This approach, used in a large area (about 10,000 km2) and in several monitoring wells (about 500), allowed to compare the efficiency of different vulnerability methods and to verify the importance of every parameter on the nitrate concentrations in the aquifer. Furthermore it allowed to obtain interesting correlations in different hydrogeological situations. Correlations between depth to water table, land use and nitrogen input to the soil with nitrate concentrations in groundwater show unclear situations: in fact these comparisons describe the phenomenon trend and highlight the maximum nitrate concentrations for each circumstance but often show wide ranges of possible nitrate concentrations. The same situation could be observed by comparing vulnerability indexes and nitrate concentrations in groundwater. These results suggest that neither single parameters nor vulnerability methods (GOD and TOT) are able to describe individually

  19. Bed stability in unconfined gravel bed mountain streams: With implications for salmon spawning viability in future climates

    Science.gov (United States)

    Jim McKean; Daniele Tonina

    2013-01-01

    Incubating eggs of autumn-spawning Chinook salmon (Oncorhynchus tshawytscha) could be at risk of midwinter high flows and substrate scour in a changing climate. A high-spatial-resolution multidimensional hydrodynamics model was used to assess the degree of scour risk in low-gradient unconfined gravel bed channels that are the favored environment for autumn-spawning...

  20. Electrical Resistivity Imaging and the Saline Water Interface in High-Quality Coastal Aquifers

    Science.gov (United States)

    Costall, A.; Harris, B.; Pigois, J. P.

    2018-07-01

    Population growth and changing climate continue to impact on the availability of natural resources. Urbanization of vulnerable coastal margins can place serious demands on shallow groundwater. Here, groundwater management requires definition of coastal hydrogeology, particularly the seawater interface. Electrical resistivity imaging (ERI) appears to be ideally suited for this purpose. We investigate challenges and drivers for successful electrical resistivity imaging with field and synthetic experiments. Two decades of seawater intrusion monitoring provide a basis for creating a geo-electrical model suitable for demonstrating the significance of acquisition and inversion parameters on resistivity imaging outcomes. A key observation is that resistivity imaging with combinations of electrode arrays that include dipole-dipole quadrupoles can be configured to illuminate consequential elements of coastal hydrogeology. We extend our analysis of ERI to include a diverse set of hydrogeological settings along more than 100 km of the coastal margin passing the city of Perth, Western Australia. Of particular importance are settings with: (1) a classic seawater wedge in an unconfined aquifer, (2) a shallow unconfined aquifer over an impermeable substrate, and (3) a shallow multi-tiered aquifer system over a conductive impermeable substrate. We also demonstrate a systematic increase in the landward extent of the seawater wedge at sites located progressively closer to the highly urbanized center of Perth. Based on field and synthetic ERI experiments from a broad range of hydrogeological settings, we tabulate current challenges and future directions for this technology. Our research contributes to resolving the globally significant challenge of managing seawater intrusion at vulnerable coastal margins.

  1. River Intrusion in Karst Springs in Eogenetic Aquifers: Implications for Speleogenesis

    Science.gov (United States)

    Martin, J. B.; Gulley, J.; Screaton, E. J.

    2008-12-01

    Conceptual models of speleogenesis generally assume uni-directional transport in integrated conduit systems from discrete recharge points to discharge at karst springs. Estavelles, however, are karst springs that function intermittently as discrete recharge points when river stage rises more rapidly than local aquifer heads. As river water chemistry changes between baseflow and floods, estavelles should influence mass transport through (e.g. organic carbon, nutrients, and oxygen) and speleogenesis within karst systems. Estavelles are common in our study area in north-central Florida, particularly along the lower reaches of the Santa Fe River, where it flows across the unconfined karstic Floridan aquifer. River stage in this unconfined region can rise much faster than aquifer heads when large amounts of rain fall on the confined regions in its upper reaches. Backflooding into the estavelles during elevated river stage drives river water into the ground, causing some springs to reverse and other springs to recirculate large volumes of river water. Floodwaters originating in the confined region are highly undersaturated with respect to calcite, and thus river water transitions from slightly supersaturated to highly undersaturated with respect to calcite during flood events. As a result, conduits connected to estavelles are continuously enlarged as springs reverse or recirculate calcite-undersaturated river water. It has been suggested that currently flooded caves (i.e. karst conduits) associated with springs in Florida formed entirely underwater because speleothems, which are prevalent in flooded caves in the Yucatan and Bahamas, have not been observed by cave divers. Results of this study indicate that the absence of speleothems does not necessarily provide evidence of a continuous phreatic history for underwater caves. Instead speleothems that formed in caves while dry could have been dissolved by backflooding of estavelles with undersaturated water

  2. Electrical Resistivity Imaging and the Saline Water Interface in High-Quality Coastal Aquifers

    Science.gov (United States)

    Costall, A.; Harris, B.; Pigois, J. P.

    2018-05-01

    Population growth and changing climate continue to impact on the availability of natural resources. Urbanization of vulnerable coastal margins can place serious demands on shallow groundwater. Here, groundwater management requires definition of coastal hydrogeology, particularly the seawater interface. Electrical resistivity imaging (ERI) appears to be ideally suited for this purpose. We investigate challenges and drivers for successful electrical resistivity imaging with field and synthetic experiments. Two decades of seawater intrusion monitoring provide a basis for creating a geo-electrical model suitable for demonstrating the significance of acquisition and inversion parameters on resistivity imaging outcomes. A key observation is that resistivity imaging with combinations of electrode arrays that include dipole-dipole quadrupoles can be configured to illuminate consequential elements of coastal hydrogeology. We extend our analysis of ERI to include a diverse set of hydrogeological settings along more than 100 km of the coastal margin passing the city of Perth, Western Australia. Of particular importance are settings with: (1) a classic seawater wedge in an unconfined aquifer, (2) a shallow unconfined aquifer over an impermeable substrate, and (3) a shallow multi-tiered aquifer system over a conductive impermeable substrate. We also demonstrate a systematic increase in the landward extent of the seawater wedge at sites located progressively closer to the highly urbanized center of Perth. Based on field and synthetic ERI experiments from a broad range of hydrogeological settings, we tabulate current challenges and future directions for this technology. Our research contributes to resolving the globally significant challenge of managing seawater intrusion at vulnerable coastal margins.

  3. Structural Control and Groundwater Flow in the Nubian Aquifer

    Science.gov (United States)

    Fathy, K.; Sultan, M.; Ahmed, M.; Save, H.; Emil, M. K.; Elkaliouby, B.

    2017-12-01

    An integrated research approach (remote sensing, field, geophysics) was conducted to investigate the structural control on groundwater flow in large aquifers using the less studied Nubian Sandstone Aquifer System (NSAS) of NE Africa as a test site. The aquifer extends over 2.2 x 106 km2 in Egypt, Libya, Chad, and Sudan and consists of thick (> 3 kms), water-bearing, Paleozoic and Mesozoic sandstone with intercalations of Tertiary shale and clay. It is subdivided into three sub-basins (Northern Sudan Platform [NSP], Dakhla [DAS], and Kufra) that are separated by basement uplifts (e.g., E-W trending Uweinat-Aswan uplift that separates DAS from the NSP). Aquifer recharge occurs in the south (NSP and southern Kufra) where the aquifer is unconfined and precipitation is high (Average Annual Precipitation [AAP]: 117 mm/yr.) and discharge is concentrated in the north (DAS and northern Kufra). Our approach is a three-fold exercise. Firstly, we compared GOCE-based Global Geopotential Models (GGMs) to terrestrial gravity anomalies for 21262 sites to select the optimum model for deriving Bouguer gravity anomalies. Secondly, structures and uplifts were mapped using hill shade images and their extension in the subsurface were mapped using the Eigen_6C4 model-derived Bouguer anomalies and their Tilt Derivative products (TDR). Thirdly, hydrological analysis was conducted using GRACE CSR 1° x 1° mascon solutions to investigate the mass variations in relation to the mapped structures. Our findings include: (1) The Eigen-6C4 is the optimum model having the lowest deviation (9.122 mGal) from the terrestrial gravity anomalies; (2) the surface expressions of structures matched fairly well with their postulated extensions in the subsurface; (3) identified fault systems include: Red Sea rift-related N-S to NW-SE trending grabens formed by reactivating basement structures during Red Sea opening and Syrian arc-related NE-SW trending dextral shear systems; (4) TWS patterns are uniform

  4. Rice HOX12 Regulates Panicle Exsertion by Directly Modulating the Expression of ELONGATED UPPERMOST INTERNODE1[OPEN

    Science.gov (United States)

    Gao, Shaopei; Fang, Jun; Xu, Fan; Wang, Wei

    2016-01-01

    Bioactive gibberellins (GAs) are key endogenous regulators of plant growth. Previous work identified ELONGATED UPPERMOST INTERNODE1 (EUI1) as a GA-deactivating enzyme that plays an important role in panicle exsertion from the flag leaf sheath in rice (Oryza sativa). However, the mechanism that regulates EUI1 activity during development is still largely unexplored. In this study, we identified the dominant panicle enclosure mutant regulator of eui1 (ree1-D), whose phenotype is caused by the activation of the homeodomain-leucine zipper transcription factor HOX12. Diminished HOX12 expression by RNA interference enhanced panicle exsertion, mimicking the eui1 phenotype. HOX12 knockdown plants contain higher levels of the major biologically active GAs (such as GA1 and GA4) than the wild type. The expression of EUI1 is elevated in the ree1-D mutant but reduced in HOX12 knockdown plants. Interestingly, both HOX12 and EUI1 are predominantly expressed in panicles, where GA4 is highly accumulated. Yeast one-hybrid, electrophoretic mobility shift assay, and chromatin immunoprecipitation analyses showed that HOX12 physically interacts with the EUI1 promoter both in vitro and in vivo. Furthermore, plants overexpressing HOX12 in the eui1 mutant background retained the elongated uppermost internode phenotype. These results indicate that HOX12 acts directly through EUI1 to regulate panicle exsertion in rice. PMID:26977084

  5. Heterogeneous seismic anisotropy in the transition zone and uppermost lower mantle: evidence from South America, Izu-Bonin and Japan

    Science.gov (United States)

    Lynner, Colton; Long, Maureen D.

    2015-06-01

    Measurements of seismic anisotropy are commonly used to constrain deformation in the upper mantle. Observations of anisotropy at mid-mantle depths are, however, relatively sparse. In this study we probe the anisotropic structure of the mid-mantle (transition zone and uppermost lower mantle) beneath the Japan, Izu-Bonin, and South America subduction systems. We present source-side shear wave splitting measurements for direct teleseismic S phases from earthquakes deeper than 300 km that have been corrected for the effects of upper mantle anisotropy beneath the receiver. In each region, we observe consistent splitting with delay times as large as 1 s, indicating the presence of anisotropy at mid-mantle depths. Clear splitting of phases originating from depths as great as ˜600 km argues for a contribution from anisotropy in the uppermost lower mantle as well as the transition zone. Beneath Japan, fast splitting directions are perpendicular or oblique to the slab strike and do not appear to depend on the propagation direction of the waves. Beneath South America and Izu-Bonin, splitting directions vary from trench-parallel to trench-perpendicular and have an azimuthal dependence, indicating lateral heterogeneity. Our results provide evidence for the presence of laterally variable anisotropy and are indicative of variable deformation and dynamics at mid-mantle depths in the vicinity of subducting slabs.

  6. 3D Crust and Uppermost Mantle Structure beneath Tian Shan Region from ambient noise and earthquake surface waves

    Science.gov (United States)

    Xiao, X.; Wen, L.

    2017-12-01

    As a typical active intracontinental mountain range in Central Asia, Tian Shan Mt serves as the prototype in studying geodynamic processes and mechanism of intracontinental mountain building. We study 3D crust and the uppermost mantle structure beneath Tian Shan region using ambient noise and earthquake surface waves. Our dataset includes vertical component records of 62 permanent broadband seismic stations operated by the Earthquake Administration of China. Firstly, we calculate two-year stacked Cross-Correlation Functions (CCFs) of ambient noise records between the stations. The CCFs are treated as the Empirical Green's Functions (EGFs) of each station pair, from which we measured phase velocities of fundamental-mode Rayleigh wave in the period of 3-40 s using a frequency-time analysis method. Secondly, we collect surface wave data from tele-seismic events with Mw > 5.5 and depth shallower than 200 km and measure phase velocities of the fundamental-mode of Rayleigh wave in the period of 30-150 s using a two-station method. Finally, we combine the phase velocity measurements from ambient noise and earthquake surface waves, obtain lateral isotropic phase velocity maps at different periods based on tomography and invert a 3D Vsv model of crust and uppermost mantle down to about 150 km using a Monte Carlo Inversion method. We will discuss our inversion results in detail, as well as their implications to the tectonics in the region.

  7. Geohydrology of the valley-fill aquifer in the Endicott-Johnson City area, Broome County, New York

    Science.gov (United States)

    Holecek, Thomas J.; Randall, A.D.; Belli, J.L.; Allen, R.V.

    1982-01-01

    This report is the tenth in a series of 11 map sets depicting geohydrologic conditions in selected aquifers in upstate New York. Geohydrologic data are compiled on five maps at 1:24,000 scale. Together, the maps provide a comprehensive overview of a major valley-fill aquifer in southwestern Broome County. The maps include surficial geology, geologic sections, aquifer thickness, water-infiltration potential of soil zone, potentiometric-surface altitude, and land use. The valley-fill deposits consist of alluvial silt and sand, glacial outwash (sand and gravel), ice-contact sand and gravel, till, and lacustrine silt and clay. The sand and gravel beds have relatively high permeabilities whereas the till, silt, and clay deposits have relatively low permeabilities. Water-table conditions are found in unconfined sand and gravel, whereas artesian conditions prevail within sand and gravel confined by silty deposits. Recharge occurs over the entire surface of the aquifer, due to permeable land-surface conditions, but is greatest along the margin of the valley, where runoff from the hillsides is concentrated, and near streams. The use of land overlying the aquifer is predominantly commercial and residential with lesser amounts of agricultural and industrial uses. (USGS)

  8. Geohydrology of the valley-fill aquifer in the South Fallsburgh-Woodbourne area, Sullivan County, New York

    Science.gov (United States)

    Anderson, H.R.; Dineen, R.J.; Stelz, W.G.; Belli, J.L.

    1982-01-01

    This report is the ninth in a series of map sets depicting geohydrologic conditions in selected aquifers in upstate New York. Geohydrologic data are compiled on six maps at 1:24,000 scale. Together the maps provide a comprehensive overview of a major valley-fill aquifer in southeastern Sullivan County. The maps include surficial geology, geologic sections, aquifer thickness, water-infiltration potential of soil zone, potentiometric surface elevations, well yields, and land use. The valley-fill deposits consist of alluvial silt and sand, glacial outwash (sand and gravel), ice-contact sand and gravel, till, and lacustrine silt and clay. The sand and gravel beds have relatively high permeabilities whereas the till, silt, and clay deposits have relatively low permeabilities. Water-table conditions prevail in unconfined sand and gravel whereas artesian conditions prevail within sand and gravel confined by silty deposits. The aquifer is recharged throughout, where the land surface is most permeable and is greatest along the margin of the valley, where runoff from the hillsides is concentrated. The use of land overlying the aquifer is predominantly commercial, agricultural, and residential with lesser industrial uses. (USGS)

  9. Geohydrology of the valley-fill aquifer in the Ramapo and Mahwah rivers area, Rockland County, New York

    Science.gov (United States)

    Moore, Richard Bridge; Cadwell, D.H.; Stelz, W.G.; Belli, J.L.

    1982-01-01

    This report is the eighth in a series of 11 map sets depicting geohydrologic conditions in selected aquifers in upstate New York. Geohydrologic data are compiled on six maps at 1:24,000 scale. Together, the maps provide a comprehensive overview of a major valley-fill aquifer in southeastern Rockland County. The maps include surficial geology, geologic sections, water-infiltration potential of soil zone, aquifer thickness, water-table elevations, well yields, and land use. The valley-fill deposits consists of alluvial silt and sand, glacial outwash (sand and gravel), ice-contact sand and gravel, till, and lacustrine silt and clay. The sand and gravel beds have relatively high permeabilities, whereas the till, silt, and clay deposits have relatively low permeabilities. Water-table conditions prevail in unconfined sand and gravel along the Ramapo River valley and much of the Mahwah River valley. Artesian conditions prevail in confined sand and gravel buried under silt and clay and till in parts of the Mahway valley. The aquifer is recharged throughout, where the land surface is most permeable and is greatest along the margin of the valley, where runoff from the hillsides is concentrated. The use of land overlying the aquifer is predominantly commercial, agricultural and residential, with lesser industrial uses. (USGS)

  10. Descriptions and characterizations of water-level data and groundwater flow for the Brewster Boulevard and Castle Hayne Aquifer Systems and the Tarawa Terrace Aquifer

    Science.gov (United States)

    Faye, Robert E.; Jones, L. Elliott; Suárez-Soto, René J.

    2013-01-01

    This supplement of Chapter A (Supplement 3) summarizes results of analyses of groundwater-level data and describes corresponding elements of groundwater flow such as vertical hydraulic gradients useful for groundwater-flow model calibration. Field data as well as theoretical concepts indicate that potentiometric surfaces within the study area are shown to resemble to a large degree a subdued replica of surface topography. Consequently, precipitation that infiltrates to the water table flows laterally from highland to lowland areas and eventually discharges to streams such as Northeast and Wallace Creeks and New River. Vertically downward hydraulic gradients occur in highland areas resulting in the transfer of groundwater from shallow relatively unconfined aquifers to underlying confined or semi-confined aquifers. Conversely, in the vicinity of large streams such as Wallace and Frenchs Creeks, diffuse upward leakage occurs from underlying confined or semi-confined aquifers. Point water-level data indicating water-table altitudes, water-table altitudes estimated using a regression equation, and estimates of stream levels determined from a digital elevation model (DEM) and topographic maps were used to estimate a predevelopment water-table surface in the study area. Approximate flow lines along hydraulic gradients are shown on a predevelopment potentiometric surface map and extend from highland areas where potentiometric levels are greatest toward streams such as Wallace Creek and Northeast Creek. The distribution of potentiometric levels and corresponding groundwater-flow directions conform closely to related descriptions of the conceptual model.

  11. Ground-water-quality assessment of the Central Oklahoma Aquifer, Oklahoma: geochemical and geohydrologic investigations

    Science.gov (United States)

    Parkhurst, David L.; Christenson, Scott C.; Breit, George N.

    1993-01-01

    the most likely source of bromide and chloride in the aquifer.The dominant reaction in recharge is the uptake of carbon dioxide gas from the unsaturated zone (about 2.0 to 4.0 millimoles per liter) and the dissolution of dolomite (about 0.3 to 1.0 millimoles per liter). This reaction generates calcium, magnesium, and bicarbonate water composition. If dolomite does not dissolve to equilibrium, pH values range from 6.0 to 7.3; if dolomite dissolves to equilibrium, pH values are about 7.5. By the time recharge enters the deeper flow system, all ground water is saturated or supersaturated with dolomite and calcite.After carbonate-mineral equilibration has occurred, cation exchange of calcium and magnesium for sodium is the dominant geochemical reaction, which occurs to a substantial extent only in parts of the aquifer. Mass transfers of cation exchange greater than 2.0 millimoles per liter occur in the confined part of the Garber Sandstone and Wellington Formation and in parts of the Chase, Council Grove, and Admire Groups. Associated with cation exchange is dissolution of small quantities of dolomite, calcite, biotite, chlorite, plagioclase, or potassium feldspar, which produces pH values that range from 8.6 to 9.1.Large tritium concentrations indicate ground-water ages of less than about 40 years for most samples of recharge. Carbon-14 ages for samples from the unconfined aquifer generally are less than 10,000 years. Carbon-14 ages of ground water in the confined part of the aquifer range from about 10,000 to 30,000 years or older. These ages produce a time trend in deuterium values that qualitatively is consistent with the timing of the transition from the last glacial maximum to the present interglacial period.The most transmissive geologic units in the Central Oklahoma aquifer are the Garber Sandstone and Wellington Formation and the alluvium and terrace deposits; the Chase, Council Grove, and Admire Groups are less transmissive on the basis of available specific

  12. Simulated effects of groundwater withdrawals from the Kirkwood-Cohansey aquifer system and Piney Point aquifer, Maurice and Cohansey River Basins, Cumberland County and vicinity, New Jersey

    Science.gov (United States)

    Gordon, Alison D.; Buxton, Debra E.

    2018-05-10

    The U.S. Geological Survey, in cooperation with the New Jersey Department of Environmental Protection, conducted a study to simulate the effects of withdrawals from the Kirkwood-Cohansey aquifer system on streamflow and groundwater flow and from the Piney Point aquifer on water levels in the Cohansey and Maurice River Basins in Cumberland County and surrounding areas. The aquifer system consists of gravel, sand, silt, and clay sediments of the Cohansey Sand and Kirkwood Formation that dip and thicken to the southeast. The aquifer system is generally an unconfined aquifer, but semi-confined and confined conditions exist within the Cumberland County study area. The Kirkwood-Cohansey aquifer system is present throughout Cumberland County and is the principal source of groundwater for public, domestic, agricultural-irrigation, industrial, and commercial water uses. In 2008, reported groundwater withdrawals from the Kirkwood-Cohansey aquifer system in the study area totaled about 21,700 million gallons—about 36 percent for public supply; about 49 percent for agricultural irrigation; and about 15 percent for industrial, commercial, mining by sand and gravel companies, and non-agricultural irrigation uses. A transient numerical groundwater-flow model of the Kirkwood-Cohansey aquifer system was developed and calibrated by incorporating monthly recharge, base-flow estimates, water-level data, surface-water diversions and discharges, and groundwater withdrawals from 1998 to 2008.The groundwater-flow model was used to simulate five withdrawal scenarios to observe the effects of additional groundwater withdrawals on the Kirkwood-Cohansey aquifer system and streams. These scenarios include (1) average 1998 to 2008 monthly groundwater withdrawals (baseline scenario); (2) monthly full-allocation groundwater withdrawals, but agricultural-irrigation withdrawals were decreased for October through March; (3) monthly full-allocation groundwater withdrawals; (4) estimated monthly

  13. Analytical solutions for recession analyses of sloping aquifers - applicability on relict rock glaciers in alpine catchments

    Science.gov (United States)

    Pauritsch, Marcus; Birk, Steffen; Hergarten, Stefan; Kellerer-Pirklbauer, Andreas; Winkler, Gerfried

    2014-05-01

    model was then compared to the analytical solution based on the one dimensional Boussinesq equation for unconfined flow in sloping aquifers. Field observations as well as results from the numerical model suggest that the rock glacier has a complex internal structure with zones of low hydraulic conductivity and a high conductive layer on top. The analytical solution attempts to represent this heterogeneous aquifer by an equivalent homogeneous medium. However, as the relative contribution of the different aquifer components varies throughout the recession, the parameter estimates are not easily interpreted in terms of actual aquifer properties. Employing analytical solutions for recession analysis in this type of setting therefore requires a sound understanding of the internal structure and its influence on the flow and storage processes within the rock glacier.

  14. Glacial recharge, salinisation and anthropogenic contamination in the coastal aquifers of Recife (Brazil)

    Energy Technology Data Exchange (ETDEWEB)

    Chatton, E., E-mail: eliot.chatton@gmail.com [Géosciences Rennes, Université Rennes 1-CNRS, UMR 6118, adress: 263 av du général Leclerc, Campus de Beaulieu, bat 15, 35042 Rennes Cedex (France); Aquilina, L., E-mail: luc.aquilina@univ-rennes1.fr [Géosciences Rennes, Université Rennes 1-CNRS, UMR 6118, adress: 263 av du général Leclerc, Campus de Beaulieu, bat 15, 35042 Rennes Cedex (France); Pételet-Giraud, E., E-mail: e.petelet@brgm.fr [Bureau de Recherches Géologiques et Minières (BRGM), adress: 3 avenue Claude-Guillemin, BP 36009, 45060 Orléans Cedex 2 (France); Cary, L., E-mail: l.cary@brgm.fr [Bureau de Recherches Géologiques et Minières (BRGM), adress: 3 avenue Claude-Guillemin, BP 36009, 45060 Orléans Cedex 2 (France); Bertrand, G., E-mail: guillaume353@gmail.com [Instituto de Geociências, CEPAS (Groundwater Research Center), University of São Paulo, adress: Rua do lago 562, 05508-080 Sao Paulo (Brazil); Labasque, T., E-mail: thierry.labasque@univ-rennes1.fr [Géosciences Rennes, Université Rennes 1-CNRS, UMR 6118, adress: 263 av du général Leclerc, Campus de Beaulieu, bat 15, 35042 Rennes Cedex (France); and others

    2016-11-01

    Implying large residence times and complex water origins deep coastal aquifers are of particular interest as they are remarkable markers of climate, water use and land use changes. Over the last decades, the Metropolitan Region of Recife (Brazil) went through extensive environmental changes increasing the pressure on water resources and giving rise to numerous environmental consequences on the coastal groundwater systems. We analysed the groundwater of the deep aquifers Cabo and Beberibe that are increasingly exploited. The processes potentially affecting groundwater residence times and flow paths have been studied using a multi-tracer approach (CFCs, SF6, noble gases, 14C, 2H and 18O). The main findings of these investigations show that: (1) Groundwaters of the Cabo and Beberibe aquifers have long residence times and were recharged about 20,000 years ago. (2) Within these old groundwaters we can find palaeo-climate evidences from the last glacial period at the tropics with lower temperatures and dryer conditions than the present climate. (3) Recently, the natural slow dynamic of these groundwater systems was significantly affected by mixing processes with contaminated modern groundwater coming from the shallow unconfined Boa Viagem aquifer. (4) The large exploitation of these aquifers leads to a modification of the flow directions and causes the intrusion through palaeo-channels of saline water probably coming from the Capibaribe River and from the last transgression episodes. These observations indicate that the current exploitation of the Cabo and Beberibe aquifers is unsustainable regarding the long renewal times of these groundwater systems as well as their ongoing contamination and salinisation. The groundwater cycle being much slower than the human development rhythm, it is essential to integrate the magnitude and rapidity of anthropogenic impacts on this extremely slow cycle to the water management concepts. - Highlights: • Study of anthropogenic impacts

  15. Glacial recharge, salinisation and anthropogenic contamination in the coastal aquifers of Recife (Brazil)

    International Nuclear Information System (INIS)

    Chatton, E.; Aquilina, L.; Pételet-Giraud, E.; Cary, L.; Bertrand, G.; Labasque, T.

    2016-01-01

    Implying large residence times and complex water origins deep coastal aquifers are of particular interest as they are remarkable markers of climate, water use and land use changes. Over the last decades, the Metropolitan Region of Recife (Brazil) went through extensive environmental changes increasing the pressure on water resources and giving rise to numerous environmental consequences on the coastal groundwater systems. We analysed the groundwater of the deep aquifers Cabo and Beberibe that are increasingly exploited. The processes potentially affecting groundwater residence times and flow paths have been studied using a multi-tracer approach (CFCs, SF6, noble gases, 14C, 2H and 18O). The main findings of these investigations show that: (1) Groundwaters of the Cabo and Beberibe aquifers have long residence times and were recharged about 20,000 years ago. (2) Within these old groundwaters we can find palaeo-climate evidences from the last glacial period at the tropics with lower temperatures and dryer conditions than the present climate. (3) Recently, the natural slow dynamic of these groundwater systems was significantly affected by mixing processes with contaminated modern groundwater coming from the shallow unconfined Boa Viagem aquifer. (4) The large exploitation of these aquifers leads to a modification of the flow directions and causes the intrusion through palaeo-channels of saline water probably coming from the Capibaribe River and from the last transgression episodes. These observations indicate that the current exploitation of the Cabo and Beberibe aquifers is unsustainable regarding the long renewal times of these groundwater systems as well as their ongoing contamination and salinisation. The groundwater cycle being much slower than the human development rhythm, it is essential to integrate the magnitude and rapidity of anthropogenic impacts on this extremely slow cycle to the water management concepts. - Highlights: • Study of anthropogenic impacts

  16. Seismic and thermal structure of the crust and uppermost mantle beneath Antarctica from inversion of multiple seismic datasets

    Science.gov (United States)

    Wiens, D.; Shen, W.; Anandakrishnan, S.; Aster, R. C.; Gerstoft, P.; Bromirski, P. D.; Dalziel, I.; Hansen, S. E.; Heeszel, D.; Huerta, A. D.; Nyblade, A.; Stephen, R. A.; Wilson, T. J.; Winberry, J. P.; Stern, T. A.

    2017-12-01

    Since the last decade of the 20th century, over 200 broadband seismic stations have been deployed across Antarctica (e.g., temporary networks such as TAMSEIS, AGAP/GAMSEIS, POLENET/ANET, TAMNNET and RIS/DRIS by U.S. geoscientists as well as stations deployed by Japan, Britain, China, Norway, and other countries). In this presentation, we discuss our recent efforts to build reference crustal and uppermost mantle shear velocity (Vs) and thermal models for continental Antarctica based on those seismic arrays. By combing the high resolution Rayleigh wave dispersion maps derived from both ambient noise and teleseismic earthquakes, together with P receiver function waveforms, we develop a 3-D Vs model for the crust and uppermost mantle beneath Central and West Antarctica to a depth of 200 km. Additionally, using this 3-D seismic model to constrain the crustal structure, we re-invert for the upper mantle thermal structure using the surface wave data within a thermodynamic framework and construct a 3-D thermal model for the Antarctic lithosphere. The final product, a high resolution thermal model together with associated uncertainty estimates from the Monte Carlo inversion, allows us to derive lithospheric thickness and surface heat flux maps for much of the continent. West Antarctica shows a much thinner lithosphere ( 50-90 km) than East Antarctica ( 130-230 km), with a sharp transition along the Transantarctic Mountains (TAM). A variety of geological features, including a slower/hotter but highly heterogeneous West Antarctica and a much faster/colder East Antarctic craton, are present in the 3-D seismic/thermal models. Notably, slow seismic velocities observed in the uppermost mantle beneath the southern TAM are interpreted as a signature of lithospheric foundering and replacement with hot asthenosphere. The high resolution image of these features from the 3-D models helps further investigation of the dynamic state of Antarctica's lithosphere and underlying asthenosphere

  17. Arsenic levels in groundwater aquifer

    African Journals Online (AJOL)

    Miodrag Jelic

    resistance (ρ); dielectric constant (ε); magnetic permeability (η); electrochemical activity ..... comprises grey sands of different particle size distribution ..... groundwater: testing pollution mechanisms for sedimentary aquifers in. Bangladesh.

  18. EPA Region 1 Sole Source Aquifers

    Data.gov (United States)

    U.S. Environmental Protection Agency — This coverage contains boundaries of EPA-approved sole source aquifers. Sole source aquifers are defined as an aquifer designated as the sole or principal source of...

  19. Acoustic and Petrophysical Evolution of Organic-Rich Chalk Following Maturation Induced by Unconfined Pyrolysis

    Science.gov (United States)

    Shitrit, Omri; Hatzor, Yossef H.; Feinstein, Shimon; Vinegar, Harold J.

    2017-12-01

    Thermal maturation is known to influence the rock physics of organic-rich rocks. While most studies were performed on low-porosity organic-rich shales, here we examine the effect of thermal maturation on a high-porosity organic-rich chalk. We compare the physical properties of native state immature rock with the properties at two pyrolysis-simulated maturity levels: early-mature and over-mature. We further evaluate the applicability of results from unconfined pyrolysis experiments to naturally matured rock properties. Special attention is dedicated to the elastic properties of the organic phase and the influence of bitumen and kerogen contents. Rock physics is studied based on confined petrophysical measurements of porosity, density and permeability, and measurements of bedding-normal acoustic velocities at estimated field stresses. Geochemical parameters like total organic carbon (TOC), bitumen content and thermal maturation indicators are used to monitor variations in density and volume fraction of each phase. We find that porosity increases significantly upon pyrolysis and that P wave velocity decreases in accordance. Solids density versus TOC relationships indicate that the kerogen increases its density from 1.43 to 1.49 g/cc at the immature and early-mature stages to 2.98 g/cc at the over-mature stage. This density value is unusually high, although increase in S wave velocity and backscatter SEM images of the over-mature samples verify that the over-mature kerogen is significantly denser and stiffer. Using the petrophysical and acoustic properties, the elastic moduli of the rock are estimated by two Hashin-Shtrikman (HS)-based models: "HS + BAM" and "HS kerogen." The "HS + BAM" model is calibrated to the post-pyrolysis measurements to describe the mechanical effect of the unconfined pyrolysis on the rock. The absence of compaction in the pyrolysis process causes the post-pyrolysis samples to be extremely porous. The "HS kerogen" model, which simulates a

  20. Information content of slug tests for estimating hydraulic properties in realistic, high-conductivity aquifer scenarios

    Science.gov (United States)

    Cardiff, Michael; Barrash, Warren; Thoma, Michael; Malama, Bwalya

    2011-06-01

    SummaryA recently developed unified model for partially-penetrating slug tests in unconfined aquifers ( Malama et al., in press) provides a semi-analytical solution for aquifer response at the wellbore in the presence of inertial effects and wellbore skin, and is able to model the full range of responses from overdamped/monotonic to underdamped/oscillatory. While the model provides a unifying framework for realistically analyzing slug tests in aquifers (with the ultimate goal of determining aquifer properties such as hydraulic conductivity K and specific storage Ss), it is currently unclear whether parameters of this model can be well-identified without significant prior information and, thus, what degree of information content can be expected from such slug tests. In this paper, we examine the information content of slug tests in realistic field scenarios with respect to estimating aquifer properties, through analysis of both numerical experiments and field datasets. First, through numerical experiments using Markov Chain Monte Carlo methods for gauging parameter uncertainty and identifiability, we find that: (1) as noted by previous researchers, estimation of aquifer storage parameters using slug test data is highly unreliable and subject to significant uncertainty; (2) joint estimation of aquifer and skin parameters contributes to significant uncertainty in both unless prior knowledge is available; and (3) similarly, without prior information joint estimation of both aquifer radial and vertical conductivity may be unreliable. These results have significant implications for the types of information that must be collected prior to slug test analysis in order to obtain reliable aquifer parameter estimates. For example, plausible estimates of aquifer anisotropy ratios and bounds on wellbore skin K should be obtained, if possible, a priori. Secondly, through analysis of field data - consisting of over 2500 records from partially-penetrating slug tests in a

  1. Nature of the uppermost mantle below the Porcupine Basin, offshore Ireland: new insights from seismic refraction and gravity data modeling

    Science.gov (United States)

    Prada, M.; Watremez, L.; Chen, C.; O'Reilly, B.; Minshull, T. A.; Reston, T. J.; Wagner, G.; Gaw, V.; Klaeschen, D.; Shannon, P.

    2015-12-01

    The Porcupine Basin is a tongue-shaped basin SW of Ireland formed during the opening of the North Atlantic Ocean. Its history of sedimentation reveals several rifting and subsidence phases during the Late Paleozoic and Cenozoic, with a particular major rift phase occurring in Late Jurassic-Early Cretaceous times. Previous work, focused on seismic and gravity data, suggest the presence of major crustal faulting and uppermost mantle serpentinization in the basin. Serpentinization is a key factor in lithospheric extension since it reduces the strength of mantle rocks, and hence, influences the tectonics of the lithosphere. Besides reducing the seismic velocity of the rock, serpentinization decreases mantle rock density favoring isostatic rebound and basin uplift, thus affecting the tectonic and thermal evolution of the basin. Here we characterize the deep structure of the Porcupine Basin from wide-angle seismic (WAS) and gravity data, with especial emphasis on the nature of the underlying mantle. The WAS data used were acquired along a 300 km long transect across the northern region of the basin. We used a travel time inversion method to model the data and obtain a P-wave velocity (Vp) model of the crust and uppermost mantle, together with the geometry of the main geological interfaces. The crustal structure along the model reveals a maximum stretching factor of ~5-6. These values are well within the range of crustal extension at which the crust becomes entirely brittle allowing the formation of major crustal faulting and serpentinization of the mantle. To further constrain the seismic structure and hence the nature of the mantle we assess the Vp uncertainty of the model by means of a Monte Carlo analysis and perform gravity modeling to test different interpretations regarding mantle rock nature. This project is funded by the Irish Shelf Petroleum Studies Group (ISPSG) of the Irish Petroleum Infrastructure Programme Group 4.

  2. Thermo-mechanical cementation effects in bentonite investigated by unconfined compression tests

    International Nuclear Information System (INIS)

    Dueck, Ann

    2010-01-01

    Results from the project LOT showed that specimens exposed to warm conditions had a significantly reduced strain at failure compared to reference material. The objective of the present study was to investigate the impact of parameters such as temperature, density, water content and degree of saturation on the occurrence of brittleness at failure of bentonite specimens. To quantify the influence of the different parameters the unconfined compression test was used on specimens with a height and diameter of 20 mm. In this test the relation between stress and strain is determined from axial compression of a cylindrical specimen. Brittle failure is in this investigation mainly seen on specimens having a density of ρ ≥ 2,060 kg/m 3 or on specimens exposed to high temperature T ≥ 150 deg C in the laboratory. Brittle failure behaviour was also seen on unsaturated specimens with a degree of saturation less than Sr i = 0% before saturation, on specimens with a final degree of saturation of S r ≤ 97% and also on one specimen subjected to consolidation during preparation. Brittle failure and reduced strain were noticed in the heated field exposed material in the LOT project. Similar behaviour was also observed in the present short term laboratory tests. However, the specimens in the present study showing this behaviour had higher density, lower degree of saturation or were exposed to higher temperatures than the field exposed specimens

  3. Experimental Study on Unconfined Compressive Strength of Basalt Fiber Reinforced Clay Soil

    Directory of Open Access Journals (Sweden)

    Lei Gao

    2015-01-01

    Full Text Available In order to study the mechanism and effect of basalt fiber reinforced clay soil, a series of unconfined compressive strength tests conducted on clay soil reinforced with basalt fiber have been performed under the condition of optimum water content and maximum dry density. Both the content and length of basalt fiber are considered in this paper. When the effect of content is studied, the 12 mm long fibers are dispersed into clay soil at different contents of 0.05%, 0.1%, 0.15%, 0.20%, 0.25%, 0.30%, and 0.35%. When the effect of length is researched, different lengths of basalt fibers with 4 mm, 8 mm, 12 mm, and 15 mm are put into soil at the same content of 0.05%. Experimental results show that basalt fiber can effectively improve the UCS of clay soil. And the best content and length are 0.25% and 12 mm, respectively. The results also show that the basalt fiber reinforced clay soil has the “poststrong” characteristic. About the reinforcement mechanism, the fiber and soil column-net model is proposed in this paper. Based on this model and SEM images, the effect of fiber content and length is related to the change of fiber-soil column and formation of effective fiber-soil net.

  4. Interaction of Aquifer and River-Canal Network near Well Field.

    Science.gov (United States)

    Ghosh, Narayan C; Mishra, Govinda C; Sandhu, Cornelius S S; Grischek, Thomas; Singh, Vikrant V

    2015-01-01

    The article presents semi-analytical mathematical models to asses (1) enhancements of seepage from a canal and (2) induced flow from a partially penetrating river in an unconfined aquifer consequent to groundwater withdrawal in a well field in the vicinity of the river and canal. The nonlinear exponential relation between seepage from a canal reach and hydraulic head in the aquifer beneath the canal reach is used for quantifying seepage from the canal reach. Hantush's (1967) basic solution for water table rise due to recharge from a rectangular spreading basin in absence of pumping well is used for generating unit pulse response function coefficients for water table rise in the aquifer. Duhamel's convolution theory and method of superposition are applied to obtain water table position due to pumping and recharge from different canal reaches. Hunt's (1999) basic solution for river depletion due to constant pumping from a well in the vicinity of a partially penetrating river is used to generate unit pulse response function coefficients. Applying convolution technique and superposition, treating the recharge from canal reaches as recharge through conceptual injection wells, river depletion consequent to variable pumping and recharge is quantified. The integrated model is applied to a case study in Haridwar (India). The well field consists of 22 pumping wells located in the vicinity of a perennial river and a canal network. The river bank filtrate portion consequent to pumping is quantified. © 2014, National GroundWater Association.

  5. AQUIFER IN AJAOKUTA, SOUTHWESTERN NIGERIA

    African Journals Online (AJOL)

    2005-03-08

    Mar 8, 2005 ... To establish the feasibility of water supply in a basement complex area ofAjaokuta, Southwestern Nigeria, pumping test results were used to investigate the storage properties and groundwater potential of the aquifer. The aquifer system consists of weathered and weathered/fractured zone of decomposed ...

  6. Variably-saturated groundwater modeling for optimizing managed aquifer recharge using trench infiltration

    Science.gov (United States)

    Heilweil, Victor M.; Benoit, Jerome; Healy, Richard W.

    2015-01-01

    Spreading-basin methods have resulted in more than 130 million cubic meters of recharge to the unconfined Navajo Sandstone of southern Utah in the past decade, but infiltration rates have slowed in recent years because of reduced hydraulic gradients and clogging. Trench infiltration is a promising alternative technique for increasing recharge and minimizing evaporation. This paper uses a variably saturated flow model to further investigate the relative importance of the following variables on rates of trench infiltration to unconfined aquifers: saturated hydraulic conductivity, trench spacing and dimensions, initial water-table depth, alternate wet/dry periods, and number of parallel trenches. Modeling results showed (1) increased infiltration with higher hydraulic conductivity, deeper initial water tables, and larger spacing between parallel trenches, (2) deeper or wider trenches do not substantially increase infiltration, (3) alternating wet/dry periods result in less overall infiltration than keeping the trenches continuously full, and (4) larger numbers of parallel trenches within a fixed area increases infiltration but with a diminishing effect as trench spacing becomes tighter. An empirical equation for estimating expected trench infiltration rates as a function of hydraulic conductivity and initial water-table depth was derived and can be used for evaluating feasibility of trench infiltration in other hydrogeologic settings

  7. Optical transitions involving unconfined energy states in In/sub x/Ga/sub 1-//sub x/As/GaAs multiple quantum wells

    International Nuclear Information System (INIS)

    Ji, G.; Dobbelaere, W.; Huang, D.; Morkoc, H.

    1989-01-01

    Optical transitions with energies higher than that of the GaAs band gap in highly strained In/sub x/Ga/sub 1-//sub x/As/GaAs multiple--quantum-well structures have been observed in photoreflectance spectra. In some samples as many as seven such structures were present. We identify them as transitions between the unconfined electron states and the confined heavy-hole states. For energies below the GaAs signal, intense transitions corresponding to such unconfined electron subbands were also observed. The intensity of the transitions involving unconfined electron subbands decreases with increasing well width, but is weakly dependent on the mole fraction x. The transmission coefficients are calculated in order to locate the positions of the unconfined electron subband energies. Good agreement is obtained between the experimental data and the theoretical calculation

  8. The interaction between the unsaturated zone, aquifer, and stream during a period of groundwater withdrawal

    DEFF Research Database (Denmark)

    Poulsen, Søren Erbs; Christensen, Steen; Rasmussen, Keld Rømer

    2011-01-01

    drainage responses to water-table drawdown. The responses can be sufficiently modeled by estimating the specific yield and five exponential time constants of a Moench/Boulton type model of delayed drainage. The average specific yield is thus estimated to 0.24 which is in agreement with previous small scale......; in the second case the estimate (0.17) is in better agreement with core and previous estimates (0.24). The analysis indicates that relatively fast drainage, and the existence of two drawdown dependent sources of groundwater recharge (the storage and the stream), complicates pumping test design to obtain unique...... parameter estimation. The analysis supports that an essential factor in parameter estimation by pumping test analysis for (at least some) unconfined aquifers is the use of a model that accounts for time-varying drainage from the vadose zone. Finally, when predicting stream depletion beyond 1. day of pumping...

  9. The study of using earth tide response of groundwater level and rainfall recharge to identify groundwater aquifer

    Science.gov (United States)

    Huang, W. J.; Hsu, C. H.; Chang, L. C.; Chiang, C. J.; Wang, Y. S.; Lu, W. C.

    2017-12-01

    Hydrogeological framework is the most important basis for groundwater analysis and simulation. Conventionally, the core drill is a most commonly adopted skill to acquire the core's data with the help of other research methods to artificially determine the result. Now, with the established groundwater station network, there are a lot of groundwater level information available. Groundwater level is an integrated presentation of the hydrogeological framework and the external pumping and recharge system. Therefore, how to identify the hydrogeological framework from a large number of groundwater level data is an important subject. In this study, the frequency analysis method and rainfall recharge mechanism were used to identify the aquifer where the groundwater level's response frequency and amplitude react to the earth tide. As the earth tide change originates from the gravity caused by the paths of sun and moon, it leads to soil stress and strain changes, which further affects the groundwater level. The scale of groundwater level's change varies with the influence of aquifer pressure systems such as confined or unconfined aquifers. This method has been applied to the identification of aquifers in the Cho-Shui River Alluvial Fan. The results of the identification are compared to the records of core drill and they both are quite consistent. It is shown that the identification methods developed in this study can considerably contribute to the identification of hydrogeological framework.

  10. Quantification of the specific yield in a two-layer hard-rock aquifer model

    Science.gov (United States)

    Durand, Véronique; Léonardi, Véronique; de Marsily, Ghislain; Lachassagne, Patrick

    2017-08-01

    Hard rock aquifers (HRA) have long been considered to be two-layer systems, with a mostly capacitive layer just below the surface, the saprolite layer, and a mainly transmissive layer underneath, the fractured layer. Although this hydrogeological conceptual model is widely accepted today within the scientific community, it is difficult to quantify the respective storage properties of each layer with an equivalent porous medium model. Based on an HRA field site, this paper attempts to quantify in a distinct manner the respective values of the specific yield (Sy) in the saprolite and the fractured layer, with the help of a deterministic hydrogeological model. The study site is the Plancoët migmatitic aquifer located in north-western Brittany, France, with piezometric data from 36 observation wells surveyed every two weeks for eight years. Whereas most of the piezometers (26) are located where the water table lies within the saprolite, thus representing the specific yield of the unconfined layer (Sy1), 10 of them are representative of the unconfined fractured layer (Sy2), due to their position where the saprolite is eroded or unsaturated. The two-layer model, based on field observations of the layer geometry, runs with the MODFLOW code. 81 values of the Sy1/Sy2 parameter sets were tested manually, as an inverse calibration was not able to calibrate these parameters. In order to calibrate the storage properties, a new quality-of-fit criterion called ;AdVar; was also developed, equal to the mean squared deviation of the seasonal piezometric amplitude variation. Contrary to the variance, AdVar is able to select the best values for the specific yield in each layer. It is demonstrated that the saprolite layer is about 2.5 times more capacitive than the fractured layer, with Sy1 = 10% (7% < Sy1 < 15%) against Sy2 = 2% (1% < Sy2 < 3%), in this particular example.

  11. Role of upper-most crustal composition in the evolution of the Precambrian ocean-atmosphere system

    Science.gov (United States)

    Large, R. R.; Mukherjee, I.; Zhukova, I.; Corkrey, R.; Stepanov, A.; Danyushevsky, L. V.

    2018-04-01

    Recent research has emphasized the potential relationships between supercontinent cycles, mountain building, nutrient flux, ocean-atmosphere chemistry and the origin of life. The composition of the Upper-Most Continental Crust (UMCC) also figures prominently in these relationships, and yet little detailed data on each component of this complex relationship has been available for assessment. Here we provide a new set of data on the trace element concentrations, including the Rare Earth Elements (REE), in the matrix of 52 marine black shale formations spread globally through the Archean and Proterozoic. The data support previous studies on the temporal geochemistry of shales, but with some important differences. Results indicate a change in provenance of the black shales (upper-most crustal composition), from more mafic in the Archean prior to 2700 Ma, to more felsic from 2700 to 2200 Ma, followed by a return to mafic compositions from 2200 to 1850 Ma. Around 1850 to 1800 Ma there is a rapid change to uniform felsic compositions, which remained for a billion years to 800 Ma. The shale matrix geochemistry supports the assertion that the average upper-most continental source rocks for the shales changed from a mix of felsic, mafic and ultramafic prior to 2700 Ma to more felsic after 1850 Ma, with an extended transition period between. The return to more mafic UMCC from 2200 to 1850 Ma is supported by the frequency of Large Igneous Provinces (LIPs) and banded iron formations, which suggest a peak in major mantle-connected plume events and associated Fe-rich hydrothermal activity over this period. Support for the change to felsic UMCC around 1850 Ma is provided by previous geological data which shows that felsic magmas, including, A-type granites and K-Th-U-rich granites intruded vast areas of the continental crust, peaking around 1850 Ma and declining to 1000 Ma. The implications of this change in UMCC are far reaching and may go some way to explain the distinct

  12. Thermo-mechanical cementation effects in bentonite investigated by unconfined compression tests

    International Nuclear Information System (INIS)

    Dueck, Ann; Boergesson, Lennart; Karnland, Ola

    2010-01-01

    Document available in extended abstract form only. Mechanical properties of buffer material are included in the model used for predicting the physical behaviour of saturated buffer in the final disposal of spent nuclear fuel. One simple test where the mechanical properties can be quantified is the unconfined compression test. In this type of test the relation between stress and strain are determined from axial compression of a cylindrical specimen. In the project LOT the unconfined compression test was used to study the mechanical properties on field exposed buffer material. The results from these test series showed that specimens exposed to warm conditions had a significantly reduced strain at failure compared to reference material. Changes in mechanical properties may be due to incipient chemical changes in the material. However, the present study focuses on other possible sources for brittle failure behaviour. In this study the objective was to experimentally investigate if deviating stress-strain behaviour measured after temperature exposure could be explained by Thermo-Hydro-Mechanical processes. The word cementation is used as a general term for the process involving a change in mechanical properties including brittleness at failure. A relatively large number of specimens were tested representing sodium dominated and calcium dominated bentonites. Cylindrical specimens were compacted from air dry powder to a height and diameter of 20 mm. The main part of the specimens was put in a saturation device prior to the tests in order to ensure full saturation. After the saturation each sample was placed in a mechanical press where a constant rate of strain was applied axially to the specimens having no radial confinement. During the test the deformation and the applied force were measured by means of force and strain transducers. After failure the water content and density were determined. Test series were carried out for investigating the influence of for example

  13. Thermo-mechanical cementation effects in bentonite investigated by unconfined compression tests

    Energy Technology Data Exchange (ETDEWEB)

    Dueck, Ann (Clay Technology AB, Lund (Sweden))

    2010-01-15

    Results from the project LOT showed that specimens exposed to warm conditions had a significantly reduced strain at failure compared to reference material. The objective of the present study was to investigate the impact of parameters such as temperature, density, water content and degree of saturation on the occurrence of brittleness at failure of bentonite specimens. To quantify the influence of the different parameters the unconfined compression test was used on specimens with a height and diameter of 20 mm. In this test the relation between stress and strain is determined from axial compression of a cylindrical specimen. Brittle failure is in this investigation mainly seen on specimens having a density of rho >= 2,060 kg/m3 or on specimens exposed to high temperature T >= 150 deg C in the laboratory. Brittle failure behaviour was also seen on unsaturated specimens with a degree of saturation less than Sr < 90%. Failure at reduced strain was seen in this investigation on specimens exposed to T = 150 deg C, on specimens having a water content of w{sub i} = 0% before saturation, on specimens with a final degree of saturation of S{sub r} <= 97% and also on one specimen subjected to consolidation during preparation. Brittle failure and reduced strain were noticed in the heated field exposed material in the LOT project. Similar behaviour was also observed in the present short term laboratory tests. However, the specimens in the present study showing this behaviour had higher density, lower degree of saturation or were exposed to higher temperatures than the field exposed specimens

  14. Experimental Study on Unconfined Compressive Strength of Organic Polymer Reinforced Sand

    Directory of Open Access Journals (Sweden)

    Jin Liu

    2018-01-01

    Full Text Available The natural sand is loose in structure with a small cohesive force. Organic polymer can be used to reinforce this sand. To assess the effectiveness of organic polymer as soil stabilizer (PSS, a series of unconfined compressive strength tests have been performed on reinforced sand. The focus of this study was to determine a curing method and a mix design to stabilize sand. The curing time, PSS concentration, and sand density were considered as variables in this study. The reinforcement mechanism was analyzed with images of scanning electron microscope (SEM. The results indicated that the strength of stabilized sand increased with the increase in the curing time, concentration, and sand density. The strength plateaus are at about curing time of 48 h. The UCS of samples with density of 1.4 g/cm3 at 10%, 20%, 30%, 40%, and 50% PSS concentration are 62.34 kPa, 120.83 kPa, 169.22 kPa, 201.94 kPa, and 245.28 kPa, respectively. The UCS of samples with PSS concentration of 30% at 1.4 g/cm3, 1.5 g/cm3, and 1.6 g/cm3 density are 169.22 kPa, 238.6 kPa 5, and 281.69 kPa, respectively. The chemical reaction between PSS and sand particle is at its microlevel, which improves the sand strength by bonding its particles together and filling the pore spaces. In comparison with the traditional reinforcement methods, PSS has the advantages of time saving, lower cost, and better environment protection. The research results can be useful for practical engineering applications, especially for reinforcement of foundation, embankment, and landfill.

  15. Quaternary stratigraphy, sediment characteristics and geochemistry of arsenic-contaminated alluvial aquifers in the Ganges-Brahmaputra floodplain in central Bangladesh.

    Science.gov (United States)

    Shamsudduha, M; Uddin, A; Saunders, J A; Lee, M-K

    2008-07-29

    This study focuses on the Quaternary stratigraphy, sediment composition, mineralogy, and geochemistry of arsenic (As)-contaminated alluvial aquifers in the Ganges-Brahmaputra floodplain in the central Bangladesh. Arsenic concentrations in 85 tubewells in Manikganj area, 70 km northwest of Dhaka City, range from 0.25 microg/L to 191 microg/L with a mean concentration of 33 microg/L. Groundwater is mainly Ca-HCO(3) type with high concentrations of dissolved As, Fe, and Mn, but low level of SO(4). The uppermost aquifer occurs between 10 m and 80 m below the surface that has a mean arsenic concentration of 35 microg/L. Deeper aquifer (>100 m depth) has a mean arsenic concentration of 18 microg/L. Sediments in the upper aquifer are mostly gray to dark-gray, whereas sediments in the deep aquifer are mostly yellowing-gray to brown. Quartz, feldspar, mica, hornblende, garnet, kyanite, tourmaline, magnetite, ilmenite are the major minerals in sediments from both aquifers. Biotite and potassium feldspar are dominant in shallow aquifer, although plagioclase feldspar and garnet are abundant in deep aquifer sediments. Sediment composition suggests a mixed provenance with sediment supplies from both orogenic belts and cratons. High arsenic concentrations in sediments are found within the upper 50 m in drilled core samples. Statistical analysis shows that As, Fe, Mn, Ca, and P are strongly correlated in sediments. Concentrations of Cd, Cu, Ni, Zn, and Bi also show strong correlations with arsenic in the Manikganj sediment cores. Authigenic goethite concretions, possibly formed by bacteria, are found in the shallow sediments, which contain arsenic of a concentration as high as 8.8 mg/kg. High arsenic concentrations in aquifers are associated with fine-grained sediments that were derived mostly from the recycled orogens and relatively rapidly deposited mainly by meandering channels during the Early to Middle Holocene rising sea-level conditions.

  16. Conceptual Models for Migration of Key Groundwater Contaminants Through the Vadose Zone and Into the Upper Unconfined Aquifer Below the B-Complex

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R. Jeffrey; Bjornstad, Bruce N.; Keller, Jason M.; Thorne, Paul D.; Lanigan, David C.; Christensen, J. N.; Thomas, Gregory S.

    2010-07-01

    The B-Complex contains 3 major crib and trench disposal sites and 3 SST farms that have released nearly 346 mega-liters of waste liquids containing the following high groundwater risk drivers: ~14,000 kg of CN, 29,000 kg of Cr, 12,000 kg of U and 145 Ci of Tc-99. After a thorough review of available vadose zone sediment and pore water, groundwater plume, field gamma logging, field electrical resistivity studies, we developed conceptual models for which facilities have been the significant sources of the contaminants in the groundwater and estimated the masses of these contaminants remaining in the vadose zone and currently present in the groundwater in comparison to the totals released. This allowed us to make mass balance calculations on how consistent our knowledge is on the current deep vadose zone and groundwater distribution of contaminants. Strengths and weaknesses of the conceptual models are discussed as well as implications on future groundwater and deep vadose zone remediation alternatives. Our hypothesized conceptual models attribute the source of all of the cyanide and most of the Tc-99 currently in the groundwater to the BY cribs. The source of the uranium is the BX-102 tank overfill event and the source of most of the chromium is the B-7-A&B and B-8 cribs. Our mass balance estimates suggest that there are much larger masses of U, CN, and Tc remaining in the deep vadose zone within ~20 ft of the water table than is currently in the groundwater plumes below the B-Complex. This hypothesis needs to be carefully considered before future remediation efforts are chosen. The masses of these groundwater risk drivers in the the groundwater plumes have been increasing over the last decade and the groundwater plumes are migrating to the northwest towards the Gable Gap. The groundwater flow rate appears to flucuate in response to seasonal changes in hydraulic gradient. The flux of contaminants out of the deep vadose zone from the three proposed sources also appears to be transient such that the evolution of the contaminant plumes is transient.

  17. Effectiveness of a physical barrier for contaminant control in an unconfined coastal plain aquifer: the case study of the former industrial site of Bagnoli (Naples, southern Italy).

    Science.gov (United States)

    Arienzo, Michele; Allocca, Vincenzo; Manna, Ferdinando; Trifuoggi, Marco; Ferrara, Luciano

    2015-12-01

    A vertical engineered barrier (VEB) coupled with a water treatment plant was surveyed in the framework of a vast remedial action at the brownfield site of the former ILVA of Bagnoli steel making facility located in western Naples, Italy. The VEB was put in place to minimize contaminant migration from the brownfield site toward the sea at the shorelines sites of Bagnoli and Coroglio. The efficiency of the VEB was monitored through 12 piezometers, 8 at the Bagnoli shoreline and 4 at the Coroglio shoreline. Concentrations of inorganic and organic pollutants were examined in upstream and downstream groundwater relative to the VEB. The mean levels of Al, As, Fe, and Mn largely exceeded the legal limits, 10-15-fold, whereas that of Hg was up to 3-fold the rules. The VEB decreased the outlet concentrations only at certain specific location of the barrier, four times for Al, 6-fold for Hg, and by 20% for Mn with means largely exceeding the rules. At the other sites, the downstream water showed marked increases of the pollutants up to 3-fold. Outstanding levels of the hydrocarbons > 12 were detected in the inlet water with means of some hundred times the limits at both sites. Likewise most of screened inorganic pollutants, the downstream water showed marked increases of the hydrocarbons up to ~113%. The treatment plant was very effective, with removal efficiencies >80% for As, Al, Fe, and Mn. The study evidenced the need to put alternative groundwater remedial actions.

  18. Water balance in the Guarani Aquifer outcrop zone based on hydrogeologic monitoring

    Science.gov (United States)

    Wendland, E.; Barreto, C.; Gomes, L. H.

    2007-09-01

    SummaryMain objective of this work was the study of the infiltration and recharge mechanisms in the Guarani Aquifer System (GAS) outcrop zone. The study was based on hydrogeologic monitoring, evapotranspiration and water balance in a pilot watershed. The pilot watershed (Ribeirão da Onça) is situated in the outcrop zone of the Guarani Aquifer between parallels 22°10' and 22°15' (south latitude) and meridians 47°55' and 48°00' (west longitude). For the execution of the research project, a monitoring network (wells, rain gauge and linigraph) was installed in the watershed. Data have been systematically collected during the period of a hydrological year. Water level fluctuation has been used to estimate deep recharge and subsurface storage variation. The method used to estimate the direct recharge adopted the hypothesis that the recession of the groundwater level obeys a function of power law type. Direct recharge is obtained through the difference between the actual level of an unconfined aquifer and the level indicated by extrapolation of the recession curve, in a given period. Base outflow is estimated through a mixed function (linear and exponential). Outflow in the creek has been measured with current meter and monitored continuously with a linigraph. The annual infiltration in 2005 was estimated to be 350 mm, while the deep recharge, based on water balance, appears to be 3.5% of the precipitation (1410 mm). These results indicate that the estimated long term water availability of the Guarani Aquifer System should be studied more carefully.

  19. Gravimetry contributions to the study of the complex western Haouz aquifer (Morocco): Structural and hydrogeological implications

    Science.gov (United States)

    Chouikri, Ibtissam; el Mandour, Abdennabi; Jaffal, Mohammed; Baudron, Paul; García-Aróstegui, José-Luis; Manar, Ahmed; Casas, Albert

    2016-03-01

    This study provides new elements that illustrate the benefits of combining gravity, structural, stratigraphic and piezometric data for hydrogeological purposes. A combined methodology was applied to the western Haouz aquifer (Morocco), one of the main sources of water for irrigation and human consumption in the Marrakech region. First, a residual anomaly map was calculated from the Bouguer anomaly data. The computed map provided information on the ground density variation, revealing a strong control by a regional gradient. We then used various filtering techniques to delineate the major geological structures such as faults and basins: vertical and horizontal derivatives and upward continuation. This technique highlighted news structures and provided information on their dip. The gravity anomalies perfectly delineated the basement uplifts and the sedimentary thickening in depressions and grabens. The interpretation of gravimetric filtering, geological and hydrogeological data then highlighted two types of groundwater reservoirs, an unconfined aquifer hosted in conglomeratic mio-pliocene and quaternary rocks, covering the entire western Haouz and a deep confined aquifer contained in cenomanian-turonian limestone and eocene dolomitic formations in the south. Combining piezometric and residual anomaly maps revealed that groundwater flow and storage was in perfect agreement with the structures showing a negative anomaly, while structures with positive anomalies corresponded to groundwater divides. The study of gravity gradient zones by contact analysis enhanced the existing structural pattern of the study area and highlighted new structures, mainly oriented N70 and N130. The results of this study present a common framework and provide a notable step forward in the knowledge of the geometry and the groundwater flow pattern of the western Haouz aquifer, and will serve as a solid basis for a better water resource management.

  20. Inherent mineralization of 2,6-dichlorobenzamide (BAM) in unsaturated zone and aquifers - Effect of initial concentrations and adaptation

    Energy Technology Data Exchange (ETDEWEB)

    Janniche, Gry Sander, E-mail: gsja@env.dtu.dk [DTU Environment, Technical University of Denmark, Building 113, DK-2800 Kgs. Lyngby (Denmark); Clausen, Liselotte; Albrechtsen, Hans-Jorgen [DTU Environment, Technical University of Denmark, Building 113, DK-2800 Kgs. Lyngby (Denmark)

    2011-10-15

    The dichlobenil metabolite BAM (2,6-dichlorobenzamide) is frequently detected in aquifers e.g. in Denmark despite the mother compound dichlobenil was banned here since 1997. BAM mineralization was investigated at environmentally relevant concentrations in sediment samples. Undisturbed sediment cores with known dichlobenil application were collected from topsoil to 8.5 m below surface resulting in 57 samples hereof 4 aquifer samples. Mineralization was only substantial (>10%) in the uppermost meter of the unsaturated zone. Microbial adaptation, observed as faster mineralization in pre-exposed than in pristine sediments from the same location, was only evident in sandy sediment where dichlobenil was still present, but not in clayey sediments. Higher initial concentrations (1-5000 {mu}g/kg) did not stimulate mineralization in pristine clayey or sandy sediments, or in pre-exposed sand. However, in pre-exposed clay mineralization was stimulated at high concentrations. Furthermore BAM was for the first time mineralized in aerobic aquifer sediments from different BAM-contaminated groundwater locations. - Highlights: > BAM mineralized in BAM-contaminated aerobic aquifer sediments. > In subsurface, fastest BAM mineralization in pre-exposed sandy sediments. > Increased mineralization (adaptation) only observed in contaminated sandy sediment. > In pristine sediments mineralization ratio increased with decreasing concentrations. - BAM mineralization in subsurface and groundwater was demonstrated.

  1. Field-Derived Hydraulic Properties for Perched-Water Aquifer Wells 299-E33-350 and 299-E33-351, Hanford Site B-Complex Area

    Energy Technology Data Exchange (ETDEWEB)

    Newcomer, Darrell R.

    2014-07-01

    During February and March 2014, Pacific Northwest National Laboratory conducted hydraulic (slug) tests at 200-DV-1 Operable Unit wells 299-E33-350 (C8914) and 299-E33-351 (C8915) as part of B-Complex Area Perched-Water characterization activities at the Hanford Site 200-East Area. During the construction/completion phase of each well, two overlapping depth intervals were tested within the unconfined perched-water aquifer contained in the silty-sand subunit of the Cold Creek Unit. The purpose of the slug-test characterization was to provide estimates of transmissivity and hydraulic conductivity for the perched-water aquifer at these selected well locations.

  2. EPA Region 1 Sole Source Aquifers

    Science.gov (United States)

    This coverage contains boundaries of EPA-approved sole source aquifers. Sole source aquifers are defined as an aquifer designated as the sole or principal source of drinking water for a given aquifer service area; that is, an aquifer which is needed to supply 50% or more of the drinking water for the area and for which there are no reasonable alternative sources should the aquifer become contaminated.The aquifers were defined by a EPA hydrogeologist. Aquifer boundaries were then drafted by EPA onto 1:24000 USGS quadrangles. For the coastal sole source aquifers the shoreline as it appeared on the quadrangle was used as a boundary. Delineated boundaries were then digitized into ARC/INFO.

  3. Anatomy and osteohistology of the basal hadrosaurid dinosaur Eotrachodon from the uppermost Santonian (Cretaceous of southern Appalachia

    Directory of Open Access Journals (Sweden)

    Albert Prieto-Márquez

    2016-04-01

    Full Text Available The cranial and postcranial anatomy of the basal hadrosaurid dinosaur Eotrachodon orientalis, from the uppermost Santonian of southern Appalachia (southeastern U.S.A., is described in detail. This animal is the only known pre-Campanian non-lambeosaurine hadrosaurid, and the most complete hadrosauroid known from Appalachia. E. orientalis possesses a mosaic of plesiomorphic and derived characters in the context of Hadrosauroidea. Characters shared with basal hadrosauroids include a short and sloping maxillary ectopterygoid shelf, caudally prominent maxillary jugal process, one functional tooth per alveolus on the maxillary occlusal plane, a jugal rostral process with a shallow caudodorsal margin and medioventrally facing articular facet, a vertical dentary coronoid process with a poorly expanded apex, and tooth crowns with accessory ridges. Derived characters shared with other hadrosaurids include a circumnarial depression compartmented into three fossae (as in brachylophosaurins and Edmontosaurus, a thin everted premaxillary oral margin (as in Gryposaurus, Prosaurolophus, and Saurolophus, and a maxilla with a deep and rostrocaudally extensive rostrodorsal region with a steeply sloping premaxillary margin (as in Gryposaurus. Eotrachodon orientalis differs primarily from the other hadrosauroid from the Mooreville Chalk of Alabama, Lophorhothon atopus, in having a slender and crestless nasal whose caudodorsal margin is not invaded by the circumnarial depression. Hadrosaurus foulkii, the only other known hadrosaurid from Appalachia, is distinct from E. orientalis in having dentary teeth lacking accessory ridges and a dorsally curved shaft of the ischium. A histological section of the tibia of the E. orientalis holotype (MSC 7949 suggests that this individual was actively growing at the time of death and, thus, had the potential to become a larger animal later in development.

  4. Anatomy and osteohistology of the basal hadrosaurid dinosaur Eotrachodon from the uppermost Santonian (Cretaceous) of southern Appalachia.

    Science.gov (United States)

    Prieto-Márquez, Albert; Erickson, Gregory M; Ebersole, Jun A

    2016-01-01

    The cranial and postcranial anatomy of the basal hadrosaurid dinosaur Eotrachodon orientalis, from the uppermost Santonian of southern Appalachia (southeastern U.S.A.), is described in detail. This animal is the only known pre-Campanian non-lambeosaurine hadrosaurid, and the most complete hadrosauroid known from Appalachia. E. orientalis possesses a mosaic of plesiomorphic and derived characters in the context of Hadrosauroidea. Characters shared with basal hadrosauroids include a short and sloping maxillary ectopterygoid shelf, caudally prominent maxillary jugal process, one functional tooth per alveolus on the maxillary occlusal plane, a jugal rostral process with a shallow caudodorsal margin and medioventrally facing articular facet, a vertical dentary coronoid process with a poorly expanded apex, and tooth crowns with accessory ridges. Derived characters shared with other hadrosaurids include a circumnarial depression compartmented into three fossae (as in brachylophosaurins and Edmontosaurus), a thin everted premaxillary oral margin (as in Gryposaurus, Prosaurolophus, and Saurolophus), and a maxilla with a deep and rostrocaudally extensive rostrodorsal region with a steeply sloping premaxillary margin (as in Gryposaurus). Eotrachodon orientalis differs primarily from the other hadrosauroid from the Mooreville Chalk of Alabama, Lophorhothon atopus, in having a slender and crestless nasal whose caudodorsal margin is not invaded by the circumnarial depression. Hadrosaurus foulkii, the only other known hadrosaurid from Appalachia, is distinct from E. orientalis in having dentary teeth lacking accessory ridges and a dorsally curved shaft of the ischium. A histological section of the tibia of the E. orientalis holotype (MSC 7949) suggests that this individual was actively growing at the time of death and, thus, had the potential to become a larger animal later in development.

  5. Petrogenesis of the NE Gondwanan uppermost Ediacaran-Lower Cretaceous siliciclastic sequence of Jordan: Provenance, tectonic, and climatic implications

    Science.gov (United States)

    Amireh, Belal S.

    2018-04-01

    Detrital framework modes of the NE Gondwanan uppermost Ediacaran-Lower Cretaceous siliciclastic sequence of Jordan are determined employing the routine polarized light microscope. The lower part of this sequence constitutes a segment of the vast lower Paleozoic siliciclastic sheet flanking the northern Gondwana margin that was deposited over a regional unconformity truncating the outskirts of the East African orogen in the aftermath of the Neoproterozoic amalgamation of Gondwana. The research aims to evaluate the factors governing the detrital light mineral composition of this sandstone. The provenance terranes of the Arabian craton controlled by plate tectonics appear to be the primary factor in most of the formations, which could be either directly inferred employing Dickinson's compositional triangles or implied utilizing the petrographic data achieved and the available tectonic and geological data. The Arabian-Nubian Shield constitutes invariably the craton interior or the transitional provenance terrane within the NE Gondwana continental block that consistently supplied sandy detritus through northward-flowing braided rivers to all the lower Paleozoic formations. On the other hand, the Lower Cretaceous Series received siliciclastic debris, through braided-meandering rivers having same northward dispersal direction, additionally from the lower Paleozoic and lower-middle Mesozoic platform strata in the Arabian Craton. The formations making about 50% of the siliciclastic sequence represent a success for Dickinson's plate tectonics-provenance approach in attributing the detrital framework components primarily to the plate tectonic setting of the provenance terranes. However, even under this success, the varying effects of the other secondary sedimentological and paleoclimatological factors are important and could be crucial. The inapplicability of this approach to infer the appropriate provenance terranes of the remaining formations could be ascribed either to the

  6. Uppermost mantle seismic velocity and anisotropy in the Euro-Mediterranean region from Pn and Sn tomography

    Science.gov (United States)

    Díaz, J.; Gil, A.; Gallart, J.

    2013-01-01

    In the last 10-15 years, the number of high quality seismic stations monitoring the Euro-Mediterranean region has increased significantly, allowing a corresponding improvement in structural constraints. We present here new images of the seismic velocity and anisotropy variations in the uppermost mantle beneath this complex area, compiled from inversion of Pn and Sn phases sampling the whole region. The method of Hearn has been applied to the traveltime arrivals of the International Seismological Center catalogue for the time period 1990-2010. A total of 579 753 Pn arrivals coming from 12 377 events recorded at 1 408 stations with epicentral distances between 220 km and 1 400 km have been retained after applying standard quality criteria (maximum depth, minimum number of recordings, maximum residual values …). Our results show significant features well correlated with surface geology and evidence the heterogeneous character of the Euro-Mediterranean lithosphere. The station terms reflect the existence of marked variations in crustal thickness, consistent with available Moho depths inferred from active seismic experiments. The highest Pn velocities are observed along a continuous band from the Po Basin to the northern Ionian Sea. Other high velocity zones include the Ligurian Basin, the Valencia Trough, the southern Alboran Sea and central part of the Algerian margin. Most significant low-velocity values are associated to orogenic belts (Betics, Pyrenees, Alps, Apennines and Calabrian Arc, Dinarides-Hellenides), and low-velocity zones are also identified beneath Sardinia and the Balearic Islands. The introduction of an anisotropic term enhances significantly the lateral continuity of the anomalies, in particular in the most active tectonic areas. Pn anisotropy shows consistent orientations subparallel to major orogenic structures, such as Betics, Apennines, Calabrian Arc and Alps. The Sn tomographic image has lower resolution but confirms independently most of the

  7. High-resolution surface wave tomography of the European crust and uppermost mantle from ambient seismic noise

    Science.gov (United States)

    Lu, Yang; Stehly, Laurent; Paul, Anne; AlpArray Working Group

    2018-05-01

    Taking advantage of the large number of seismic stations installed in Europe, in particular in the greater Alpine region with the AlpArray experiment, we derive a new high-resolution 3-D shear-wave velocity model of the European crust and uppermost mantle from ambient noise tomography. The correlation of up to four years of continuous vertical-component seismic recordings from 1293 broadband stations (10° W-35° E, 30° N-75° N) provides Rayleigh wave group velocity dispersion data in the period band 5-150 s at more than 0.8 million virtual source-receiver pairs. Two-dimensional Rayleigh wave group velocity maps are estimated using adaptive parameterization to accommodate the strong heterogeneity of path coverage. A probabilistic 3-D shear-wave velocity model, including probability densities for the depth of layer boundaries and S-wave velocity values, is obtained by non-linear Bayesian inversion. A weighted average of the probabilistic model is then used as starting model for the linear inversion step, providing the final Vs model. The resulting S-wave velocity model and Moho depth are validated by comparison with previous geophysical studies. Although surface-wave tomography is weakly sensitive to layer boundaries, vertical cross-sections through our Vs model and the associated probability of presence of interfaces display striking similarities with reference controlled-source (CSS) and receiver-function sections across the Alpine belt. Our model even provides new structural information such as a ˜8 km Moho jump along the CSS ECORS-CROP profile that was not imaged by reflection data due to poor penetration across a heterogeneous upper crust. Our probabilistic and final shear wave velocity models have the potential to become new reference models of the European crust, both for crustal structure probing and geophysical studies including waveform modeling or full waveform inversion.

  8. Ground-Water Flow Model for the Spokane Valley-Rathdrum Prairie Aquifer, Spokane County, Washington, and Bonner and Kootenai Counties, Idaho

    Science.gov (United States)

    Hsieh, Paul A.; Barber, Michael E.; Contor, Bryce A.; Hossain, Md. Akram; Johnson, Gary S.; Jones, Joseph L.; Wylie, Allan H.

    2007-01-01

    approximately 326 square miles. For the most part, the model extent coincides with the 2005 revised extent of the Spokane Valley-Rathdrum Prairie aquifer as defined in a previous report. However, the model excludes Spirit and Hoodoo Valleys because of uncertainties about the ground-water flow directions in those valleys and the degree of hydraulic connection between the valleys and northern Rathdrum Prairie. The SVRP aquifer is considered to be a single hydrogeologic unit except in Hillyard Trough and the Little Spokane River Arm. In those areas, a continuous clay layer divides the aquifer into an upper, unconfined unit and a lower, confined unit. The model includes all known components of inflows to and outflows from the aquifer. Inflows to the SVRP aquifer include (1) recharge from precipitation, (2) inflows from tributary basins and adjacent uplands, (3) subsurface seepage and surface overflows from lakes that border the aquifer, (4) flow from losing segments of the Spokane River to the aquifer, (5) return percolation from irrigation, and (6) effluent from septic systems. Outflows from the SVRP aquifer include (1) ground-water withdrawals from wells, (2) flow from the aquifer to gaining segments of the Spokane River, (3) aquifer discharge to the Little Spokane River, and (4) subsurface outflow from the lower unit at the western limit of the model area near Long Lake. These inflow and outflow components are represented in the model by using MODFLOW-2000 packages. The parameter-estimation program PEST was used to calibrate the SVRP aquifer model. PEST implements a nonlinear least-squares regression method to estimate model parameters so that the differences between measured and simulated quantities are minimized with respect to an optimal criterion. Calibration data include 1,573 measurements of water levels and 313 measurements of streamflow gains and losses along segments of the Spokane and Little Spokane Rivers. Model parameters estimated during calib

  9. Estimating Groundwater Mounding in Sloping Aquifers for Managed Aquifer Recharge.

    Science.gov (United States)

    Zlotnik, Vitaly A; Kacimov, Anvar; Al-Maktoumi, Ali

    2017-11-01

    Design of managed aquifer recharge (MAR) for augmentation of groundwater resources often lacks detailed data, and simple diagnostic tools for evaluation of the water table in a broad range of parameters are needed. In many large-scale MAR projects, the effect of a regional aquifer base dip cannot be ignored due to the scale of recharge sources (e.g., wadis, streams, reservoirs). However, Hantush's (1967) solution for a horizontal aquifer base is commonly used. To address sloping aquifers, a new closed-form analytical solution for water table mound accounts for the geometry and orientation of recharge sources at the land surface with respect to the aquifer base dip. The solution, based on the Dupiuit-Forchheimer approximation, Green's function method, and coordinate transformations is convenient for computing. This solution reveals important MAR traits in variance with Hantush's solution: mounding is limited in time and space; elevation of the mound is strongly affected by the dip angle; and the peak of the mound moves over time. These findings have important practical implications for assessment of various MAR scenarios, including waterlogging potential and determining proper rates of recharge. Computations are illustrated for several characteristic MAR settings. © 2017, National Ground Water Association.

  10. Characterising aquifer treatment for pathogens in managed aquifer recharge.

    Science.gov (United States)

    Page, D; Dillon, P; Toze, S; Sidhu, J P S

    2010-01-01

    In this study the value of subsurface treatment of urban stormwater during Aquifer Storage Transfer Recovery (ASTR) is characterised using quantitative microbial risk assessment (QMRA) methodology. The ASTR project utilizes a multi-barrier treatment train to treat urban stormwater but to date the role of the aquifer has not been quantified. In this study it was estimated that the aquifer barrier provided 1.4, 2.6, >6.0 log(10) removals for rotavirus, Cryptosporidium and Campylobacter respectively based on pathogen diffusion chamber results. The aquifer treatment barrier was found to vary in importance vis-à-vis the pre-treatment via a constructed wetland and potential post-treatment options of UV-disinfection and chlorination for the reference pathogens. The risk assessment demonstrated that the human health risk associated with potable reuse of stormwater can be mitigated (disability adjusted life years, DALYs aquifer is integrated with suitable post treatment options into a treatment train to attenuate pathogens and protect human health.

  11. A series solution for horizontal infiltration in an initially dry aquifer

    Science.gov (United States)

    Furtak-Cole, Eden; Telyakovskiy, Aleksey S.; Cooper, Clay A.

    2018-06-01

    The porous medium equation (PME) is a generalization of the traditional Boussinesq equation for hydraulic conductivity as a power law function of height. We analyze the horizontal recharge of an initially dry unconfined aquifer of semi-infinite extent, as would be found in an aquifer adjacent a rising river. If the water level can be modeled as a power law function of time, similarity variables can be introduced and the original problem can be reduced to a boundary value problem for a nonlinear ordinary differential equation. The position of the advancing front is not known ahead of time and must be found in the process of solution. We present an analytical solution in the form of a power series, with the coefficients of the series given by a recurrence relation. The analytical solution compares favorably with a highly accurate numerical solution, and only a small number of terms of the series are needed to achieve high accuracy in the scenarios considered here. We also conduct a series of physical experiments in an initially dry wedged Hele-Shaw cell, where flow is modeled by a special form of the PME. Our analytical solution closely matches the hydraulic head profiles in the Hele-Shaw cell experiment.

  12. Investigating sources and pathways of perfluoroalkyl acids (PFAAs) in aquifers in Tokyo using multiple tracers

    International Nuclear Information System (INIS)

    Kuroda, Keisuke; Murakami, Michio; Oguma, Kumiko; Takada, Hideshige; Takizawa, Satoshi

    2014-01-01

    We employed a multi-tracer approach to investigate sources and pathways of perfluoroalkyl acids (PFAAs) in urban groundwater, based on 53 groundwater samples taken from confined aquifers and unconfined aquifers in Tokyo. While the median concentrations of groundwater PFAAs were several ng/L, the maximum concentrations of perfluorooctane sulfonate (PFOS, 990 ng/L), perfluorooctanoate (PFOA, 1800 ng/L) and perfluorononanoate (PFNA, 620 ng/L) in groundwater were several times higher than those of wastewater and street runoff reported in the literature. PFAAs were more frequently detected than sewage tracers (carbamazepine and crotamiton), presumably owing to the higher persistence of PFAAs, the multiple sources of PFAAs beyond sewage (e.g., surface runoff, point sources) and the formation of PFAAs from their precursors. Use of multiple methods of source apportionment including principal component analysis–multiple linear regression (PCA–MLR) and perfluoroalkyl carboxylic acid ratio analysis highlighted sewage and point sources as the primary sources of PFAAs in the most severely polluted groundwater samples, with street runoff being a minor source (44.6% sewage, 45.7% point sources and 9.7% street runoff, by PCA–MLR). Tritium analysis indicated that, while young groundwater (recharged during or after the 1970s, when PFAAs were already in commercial use) in shallow aquifers (< 50 m depth) was naturally highly vulnerable to PFAA pollution, PFAAs were also found in old groundwater (recharged before the 1950s, when PFAAs were not in use) in deep aquifers (50–500 m depth). This study demonstrated the utility of multiple uses of tracers (pharmaceuticals and personal care products; PPCPs, tritium) and source apportionment methods in investigating sources and pathways of PFAAs in multiple aquifer systems. - Highlights: • Aquifers in Tokyo had high levels of perfluoroalkyl acids (up to 1800 ng/L). • PFAAs were more frequently detected than sewage

  13. Investigating sources and pathways of perfluoroalkyl acids (PFAAs) in aquifers in Tokyo using multiple tracers

    Energy Technology Data Exchange (ETDEWEB)

    Kuroda, Keisuke, E-mail: keisukekr@gmail.com [Department of Urban Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Murakami, Michio [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Oguma, Kumiko [Department of Urban Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Takada, Hideshige [Laboratory of Organic Geochemistry (LOG), Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509 (Japan); Takizawa, Satoshi [Department of Urban Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan)

    2014-08-01

    We employed a multi-tracer approach to investigate sources and pathways of perfluoroalkyl acids (PFAAs) in urban groundwater, based on 53 groundwater samples taken from confined aquifers and unconfined aquifers in Tokyo. While the median concentrations of groundwater PFAAs were several ng/L, the maximum concentrations of perfluorooctane sulfonate (PFOS, 990 ng/L), perfluorooctanoate (PFOA, 1800 ng/L) and perfluorononanoate (PFNA, 620 ng/L) in groundwater were several times higher than those of wastewater and street runoff reported in the literature. PFAAs were more frequently detected than sewage tracers (carbamazepine and crotamiton), presumably owing to the higher persistence of PFAAs, the multiple sources of PFAAs beyond sewage (e.g., surface runoff, point sources) and the formation of PFAAs from their precursors. Use of multiple methods of source apportionment including principal component analysis–multiple linear regression (PCA–MLR) and perfluoroalkyl carboxylic acid ratio analysis highlighted sewage and point sources as the primary sources of PFAAs in the most severely polluted groundwater samples, with street runoff being a minor source (44.6% sewage, 45.7% point sources and 9.7% street runoff, by PCA–MLR). Tritium analysis indicated that, while young groundwater (recharged during or after the 1970s, when PFAAs were already in commercial use) in shallow aquifers (< 50 m depth) was naturally highly vulnerable to PFAA pollution, PFAAs were also found in old groundwater (recharged before the 1950s, when PFAAs were not in use) in deep aquifers (50–500 m depth). This study demonstrated the utility of multiple uses of tracers (pharmaceuticals and personal care products; PPCPs, tritium) and source apportionment methods in investigating sources and pathways of PFAAs in multiple aquifer systems. - Highlights: • Aquifers in Tokyo had high levels of perfluoroalkyl acids (up to 1800 ng/L). • PFAAs were more frequently detected than sewage

  14. Quantifying an aquifer nitrate budget and future nitrate discharge using field data from streambeds and well nests

    Science.gov (United States)

    Gilmore, Troy E.; Genereux, David P.; Solomon, D. Kip; Farrell, Kathleen M.; Mitasova, Helena

    2016-11-01

    Novel groundwater sampling (age, flux, and nitrate) carried out beneath a streambed and in wells was used to estimate (1) the current rate of change of nitrate storage, dSNO3/dt, in a contaminated unconfined aquifer, and (2) future [NO3-]FWM (the flow-weighted mean nitrate concentration in groundwater discharge) and fNO3 (the nitrate flux from aquifer to stream). Estimates of dSNO3/dt suggested that at the time of sampling (2013) the nitrate storage in the aquifer was decreasing at an annual rate (mean = -9 mmol/m2yr) equal to about one-tenth the rate of nitrate input by recharge. This is consistent with data showing a slow decrease in the [NO3-] of groundwater recharge in recent years. Regarding future [NO3-]FWM and fNO3, predictions based on well data show an immediate decrease that becomes more rapid after ˜5 years before leveling out in the early 2040s. Predictions based on streambed data generally show an increase in future [NO3-]FWM and fNO3 until the late 2020s, followed by a decrease before leveling out in the 2040s. Differences show the potential value of using information directly from the groundwater—surface water interface to quantify the future impact of groundwater nitrate on surface water quality. The choice of denitrification kinetics was similarly important; compared to zero-order kinetics, a first-order rate law levels out estimates of future [NO3-]FWM and fNO3 (lower peak, higher minimum) as legacy nitrate is flushed from the aquifer. Major fundamental questions about nonpoint-source aquifer contamination can be answered without a complex numerical model or long-term monitoring program.

  15. Quantifying aquifer properties and freshwater resource in coastal barriers: a hydrogeophysical approach applied at Sasihithlu (Karnataka state, India)

    Science.gov (United States)

    Vouillamoz, J.-M.; Hoareau, J.; Grammare, M.; Caron, D.; Nandagiri, L.; Legchenko, A.

    2012-11-01

    Many human communities living in coastal areas in Africa and Asia rely on thin freshwater lenses for their domestic supply. Population growth together with change in rainfall patterns and sea level will probably impact these vulnerable groundwater resources. Spatial knowledge of the aquifer properties and creation of a groundwater model are required for achieving a sustainable management of the resource. This paper presents a ready-to-use methodology for estimating the key aquifer properties and the freshwater resource based on the joint use of two non-invasive geophysical tools together with common hydrological measurements. We applied the proposed methodology in an unconfined aquifer of a coastal sandy barrier in South-Western India. We jointly used magnetic resonance and transient electromagnetic soundings and we monitored rainfall, groundwater level and groundwater electrical conductivity. The combined interpretation of geophysical and hydrological results allowed estimating the aquifer properties and mapping the freshwater lens. Depending on the location and season, we estimate the freshwater reserve to range between 400 and 700 L m-2 of surface area (± 50%). We also estimate the recharge using time lapse geophysical measurements with hydrological monitoring. After a rainy event close to 100% of the rain is reaching the water table, but the net recharge at the end of the monsoon is less than 10% of the rain. Thus, we conclude that a change in rainfall patterns will probably not impact the groundwater resource since most of the rain water recharging the aquifer is flowing towards the sea and the river. However, a change in sea level will impact both the groundwater reserve and net recharge.

  16. Quantifying aquifer properties and freshwater resource in coastal barriers: a hydrogeophysical approach applied at Sasihithlu (Karnataka state, India

    Directory of Open Access Journals (Sweden)

    J.-M. Vouillamoz

    2012-11-01

    Full Text Available Many human communities living in coastal areas in Africa and Asia rely on thin freshwater lenses for their domestic supply. Population growth together with change in rainfall patterns and sea level will probably impact these vulnerable groundwater resources. Spatial knowledge of the aquifer properties and creation of a groundwater model are required for achieving a sustainable management of the resource. This paper presents a ready-to-use methodology for estimating the key aquifer properties and the freshwater resource based on the joint use of two non-invasive geophysical tools together with common hydrological measurements.

    We applied the proposed methodology in an unconfined aquifer of a coastal sandy barrier in South-Western India. We jointly used magnetic resonance and transient electromagnetic soundings and we monitored rainfall, groundwater level and groundwater electrical conductivity. The combined interpretation of geophysical and hydrological results allowed estimating the aquifer properties and mapping the freshwater lens. Depending on the location and season, we estimate the freshwater reserve to range between 400 and 700 L m−2 of surface area (± 50%. We also estimate the recharge using time lapse geophysical measurements with hydrological monitoring. After a rainy event close to 100% of the rain is reaching the water table, but the net recharge at the end of the monsoon is less than 10% of the rain. Thus, we conclude that a change in rainfall patterns will probably not impact the groundwater resource since most of the rain water recharging the aquifer is flowing towards the sea and the river. However, a change in sea level will impact both the groundwater reserve and net recharge.

  17. Aquifers Characterization and Productivity in Ellala Catchment ...

    African Journals Online (AJOL)

    user

    Aquifers Characterization and Productivity in Ellala Catchment, Tigray, ... using geological and hydrogeological methods in Ellala catchment (296.5km. 2. ) ... Current estimates put the available groundwater ... Aquifer characterization takes into.

  18. Geohydrology of the stratified-drift aquifer system in the lower Sixmile Creek and Willseyville Creek trough, Tompkins County, New York

    Science.gov (United States)

    Miller, Todd S.; Karig, Daniel E.

    2010-01-01

    In 2002, the U.S. Geological Survey, in cooperation with the Tompkins County Planning Department began a series of studies of the stratified-drift aquifers in Tompkins County to provide geohydrologic data for planners to develop a strategy to manage and protect their water resources. This aquifer study in lower Sixmile Creek and Willseyville Creek trough is the second in a series of aquifer studies in Tompkins County. The study area is within the northern area of the Appalachian Plateau and extends about 9 miles from the boundary between Tompkins County and Tioga County in the south to just south of the City of Ithaca in the north. In lower Sixmile Creek and Willseyville Creek trough, confined sand and gravel aquifers comprise the major water-bearing units while less extensive unconfined units form minor aquifers. About 600 people who live in lower Sixmile Creek and Willseyville Creek trough rely on groundwater from the stratified-drift aquifer system. In addition, water is used by non-permanent residents such as staff at commercial facilities. The estimated total groundwater withdrawn for domestic use is about 45,000 gallons per day (gal/d) or 0.07 cubic foot per second (ft3/s) based on an average water use of 75 gal/d per person for self-supplied water systems in New York. Scouring of bedrock in the preglacial lower Sixmile Creek and Willseyville Creek valleys by glaciers and subglacial meltwaters truncated hillside spurs, formed U-shaped, transverse valley profiles, smoothed valley walls, and deepened the valleys by as much as 300 feet (ft), forming a continuous trough. The unconsolidated deposits in the study area consist mostly of glacial drift, both unstratified drift (till) and stratified drift (laminated lake, deltaic, and glaciofluvial sediments), as well as some post-glacial stratified sediments (lake-bottom sediments that were deposited in reservoirs, peat and muck that were deposited in wetlands, and alluvium deposited by streams). Multiple advances and

  19. VS of the uppermost crust structure of the Campi Flegrei caldera (southern Italy) from ambient noise Rayleigh wave analysis

    Science.gov (United States)

    Costanzo, M. R.; Nunziata, C.; Strollo, R.

    2017-11-01

    Shear wave velocities (VS) are defined in the uppermost 1-2 km of the Campi Flegrei caldera through the non-linear inversion of the group velocity dispersion curves of fundamental-mode Rayleigh waves extracted from ambient noise cross-correlations between two receivers. Noise recordings, three months long, at 12 seismic stations are cross-correlated between all couples of stations. The experiment provided successful results along 54 paths (inter-stations distance), of which 27 sampled a depth > 1 km. VS contour lines are drawn from 0.06 km b.s.l. to 1 km depth b.s.l. and show difference between the offshore (gulf of Pozzuoli and coastline) and the onshore areas. At 0.06 km b.s.l., the gulf of Pozzuoli and the coastline are characterized by VS of 0.3-0.5 km/s and of 0.5-0.7 km/s, respectively. Such velocities are typical of Neapolitan pyroclastic soils and fractured or altered tuffs. The inland shows VS in the range 0.7-0.9 km/s, typical of Neapolitan compact tuffs. Velocities increase with depth and, at 1 km depth b.s.l., velocities lower than 1.5 km/s are still present in the gulf and along the coastline while velocities higher than 1.9 km/s characterize the eastern sector (grossly coincident with the Neapolitan Yellow Tuff caldera rim), the S. Vito plain and the area between Solfatara and SW of Astroni. Such features are much more evident along two cross-sections drawn in the offshore and onshore sectors by integrating our VS models with literature data. Our models join previous noise cross-correlation studies at greater scale at depths of 0.7-0.8 km, hence the picture of the Campi Flegrei caldera is shown up to a depth of 15 km. VS of about 1.7 km/s, corresponding to compression velocities (VP) of about 3 km/s (computed by using the VP/VS ratio resulted in the inversion), are found at depths of 1.1 km, in the centre of the gulf of Pozzuoli, and at a depth of about 0.7 km b.s.l. onshore. An increment of VS velocity ( 1.9-2.0 km/s) is locally observed onshore

  20. Bedrock topography beneath uppermost part of Aletsch glacier, Central Swiss Alps, revealed from cosmic-ray muon radiography

    Science.gov (United States)

    Nishiyama, Ryuichi; Ariga, Akitaka; Ariga, Tomoko; Käser, Samuel; Lechmann, Alessandro; Mair, David; Scampoli, Paola; Vladymyrov, Mykhailo; Ereditato, Antonio; Schlunegger, Fritz

    2017-04-01

    absorption rate enabled us to image a three-dimensional boundary shape between dense granite bedrock (˜ 2.7 g/cm3) and light ice part (˜ 0.8 g/cm3) in the very uppermost part of Aletsch glacier. This is the first application of muon radiography to cryogenic science. Further measurements are presently ongoing to image inside a much larger edifice of Eiger glacier, which straddles on the western flank of the famous Eiger mountain. References: Ambrosino et al. (2015), J. Geophys. Res. Solid Earth, 120, 7290-7307. Jourde et al. (2016), Scientific Reports, 6, 33406. Nishiyama et al. (2016), Pure Appl. Geophys., doi:10.1007/s00024-016-1430-9. Tanaka et al. (2011), Earth Planet Sci. Lett., 306, 156-162.

  1. Hydrogeology of Two Areas of the Tug Hill Glacial-Drift Aquifer, Oswego County, New York

    Science.gov (United States)

    Miller, Todd S.; Bugliosi, Edward F.; Hetcher-Aguila, Kari K.; Eckhardt, David A.

    2007-01-01

    slightly exceeded the U.S. Environmental Protection Agency?s Secondary Maximum Contaminant Level in three of the four samples. The relatively small concentrations of major ions and nutrients in the samples indicate that there is no contamination from septic-tank effluent and dissolved road salt in the ground water at the Village of Pulaski well field. Three of the four samples were analyzed for total coliform bacteria and Escherichia coli (E. coli), and only total coliform bacteria were detected in all three samples. E. coli was not detected in any samples. The Villages of Sandy Creek and Lacona use about 270,000 gallons of water per day for public consumption?alternating withdrawals from northern and southern well fields located in glaciolacustrine beach, glaciofluvial outwash, and alluvial inwash deposits consisting mostly of silty sand and gravel. Four test wells were drilled, hydraulic heads were measured, and water samples collected between 2001 and 2003 and analyzed for physical properties, inorganic constituents, nutrients, bacteria, tritium, dissolved gases, and chlorofluorocarbons. The aquifer in the Sandy Creek/Lacona area is highly susceptible to contamination because the aquifer (1) is unconfined, (2) is highly transmissive, (3) is thin (10 to 25 feet) and narrow (about 0.5 miles wide), and (4) has relatively short ground-water flowpaths from recharge to discharge areas (including wells). Additionally, drainage ditches east of the southern well field intercept westward-flowing ground water, which then is routed to an area just upgradient from the production wells where some of the water seeps back into the aquifer and is captured by these wells, effectively shortcircuiting the ground-water-flow system. Water-quality samples collected from three wells in the Sandy Creek/Lacona southern well field indicate that the ground water is a sodium-bicarbonate/sulfate type and of good quality; however, in one water sample, the sodium concentration of 6

  2. Two-dimensional finite element solution for the simultaneous transport of water and solutes through a nonhomogeneous aquifer under transient saturated unsaturated flow conditions

    International Nuclear Information System (INIS)

    Gureghian, A.B.

    1979-01-01

    A mathematical model of ground water transport through an aquifer is presented. The solute of interest is a metal tracer or radioactive material which may undergo decay through a sorbing unconfined aquifer. The subject is developed under the following headings: flow equation, solute equation, boundary conditions, finite element formulation, element formulation, solution scheme (flow equation, solute equation), results and discussions, water movement in a ditch drained aquifer under transient state, water and solute movement in a homogeneous and unsaturated soil, transport of 226 Ra in nonhomogeneous aquifer, tailings pond lined, and tailings pond unlined. It is concluded that this mathematical model may have a wide variety of applications. The uranium milling industry may find it useful to evaluate the hydrogeological suitability of their disposal sites. It may prove suited for the design of clay disposal ponds destined to hold hazardous liquids. It may also provide a means of estimating the long-term impact of radionuclides or other pollutants on the quality of ground water. 31 references, 9 figures, 3 tables

  3. Palaeoclimatic trends deduced from the hydrochemistry of a Triassic sandstone aquifer, United Kingdom

    International Nuclear Information System (INIS)

    Bath, A.H.; Edmunds, W.M.; Andrews, J.N.

    1979-01-01

    A detailed geochemical study (elemental, isotopic and dissolved inert gases) of unconfined and confined sections of the Triassic non-marine sandstone aquifer in eastern England has been undertaken. Aspects of the recharge history of this aquifer over the past 40,000 years are revealed by examination of the data. 14 C activity and delta 13 C values show downgradient decrease and increase, respectively, the latter from -12 to -13 per mille (PDB) at outcrop to -8.5 per mille in deep confined groundwaters, indicating a continuing reaction between water and carbonate mineral phases. Although the bulk carbonate contained in sandstone samples gives delta 13 C around -7 per mille, modelling of the carbon isotopic evolution and consideration of the resulting 14 C age corrections suggest that a carbonate with delta 13 C closer to 0 per mille has played a major role in at least the earlier stages of hydrochemical evolution. The corrected radiocarbon age ranges, generated by the computer program WATEQF-ISOTOP, are used as a framework in which the palaeo-environmental information from oxygen and hydrogen isotope data, inert gas contents, and chloride levels are discussed. The measurement of dissolved helium levels demonstrates an excess of 4 He in many samples, which correlates with radiocarbon ages. The assumption of bulk chemical and physical properties for the aquifer rock allows independent 'excess 4 He' ages to be computed, which are mostly in excess of the corrected 14 C ages. The trend of delta 18 O is from about -8 per mille at outcrop to -9.7 per mille (SMOW) downgradient, which is significantly more depleted than has been found in previous studies of UK basins. The delta 2 H and delta 18 O values are related by the regression line delta 2 H=6.6delta 18 O+1; data from other UK studies also lie close to this trend

  4. Hydrogeology, water quality, and microbial assessment of a coastal alluvial aquifer in western Saudi Arabia: potential use of coastal wadi aquifers for desalination water supplies [Hydrogéologie, qualité de l’eau et évaluation microbienne d’un aquifère côtier alluvial dans l’Ouest de l’Arabie Saoudite: utilisation potentielle des aquifères côtiers des oueds pour l’alimentation en eau après désalinisation] [Hidrogeologia, qualidade da água e avaliação microbiológica de um aquífero costeiro no oeste da Arábia Saudita: uso potencial de aquíferos de wadi costeiros para dessalinização de águas destinadas a abastecimento] [Hidrogeología, calidad de agua y evaluación microbiana de un acuífero costero aluvial en Arabia Saudita occidental: uso potencial de acuíferos costeros uadis para la desalinización de los abastecimientos de agua

    KAUST Repository

    Missimer, Thomas M.

    2014-07-20

    Wadi alluvial aquifers located along coastal areas of the Middle East have been assumed to be suitable sources of feed water for seawater reverse osmosis facilities based on high productivity, connectedness to the sea for recharge, and the occurrence of seawater with chemistry similar to that in the adjacent Red Sea. An investigation of the intersection of Wadi Wasimi with the Red Sea in western Saudi Arabia has revealed that the associated predominantly unconfined alluvial aquifer divides into two sand-and-gravel aquifers at the coast, each with high productivity (transmissivity = 42,000 m2/day). This aquifer system becomes confined near the coast and contains hypersaline water. The hydrogeology of Wadi Wasimi shows that two of the assumptions are incorrect in that the aquifer is not well connected to the sea because of confinement by very low hydraulic conductivity terrigenous and marine muds and the aquifer contains hypersaline water as a result of a hydraulic connection to a coastal sabkha. A supplemental study shows that the aquifer system contains a diverse microbial community composed of predominantly of Proteobacteria with accompanying high percentages of Gammaproteobacteria, Alphaproteobacteria and Deltaproteobacteria.

  5. Hydrogeology and water quality of the Floridan aquifer system and effects of Lower Floridan aquifer pumping on the Upper Floridan aquifer at Fort Stewart, Georgia

    Science.gov (United States)

    Clarke, John S.; Cherry, Gregory C.; Gonthier, Gerard

    2011-01-01

    Test drilling, field investigations, and digital modeling were completed at Fort Stewart, GA, during 2009?2010, to assess the geologic, hydraulic, and water-quality characteristics of the Floridan aquifer system and evaluate the effect of Lower Floridan aquifer (LFA) pumping on the Upper Floridan aquifer (UFA). This work was performed pursuant to the Georgia Environmental Protection Division interim permitting strategy for new wells completed in the LFA that requires simulation to (1) quantify pumping-induced aquifer leakage from the UFA to LFA, and (2) identify the equivalent rate of UFA pumping that would produce the same maximum drawdown in the UFA that anticipated pumping from LFA well would induce. Field investigation activities included (1) constructing a 1,300-foot (ft) test boring and well completed in the LFA (well 33P028), (2) constructing an observation well in the UFA (well 33P029), (3) collecting drill cuttings and borehole geophysical logs, (4) collecting core samples for analysis of vertical hydraulic conductivity and porosity, (5) conducting flowmeter and packer tests in the open borehole within the UFA and LFA, (6) collecting depth-integrated water samples to assess basic ionic chemistry of various water-bearing zones, and (7) conducting aquifer tests in new LFA and UFA wells to determine hydraulic properties and assess interaquifer leakage. Using data collected at the site and in nearby areas, model simulation was used to assess the effects of LFA pumping on the UFA. Borehole-geophysical and flowmeter data indicate the LFA at Fort Stewart consists of limestone and dolomitic limestone between depths of 912 and 1,250 ft. Flowmeter data indicate the presence of three permeable zones at depth intervals of 912-947, 1,090-1,139, and 1,211?1,250 ft. LFA well 33P028 received 50 percent of the pumped volume from the uppermost permeable zone, and about 18 and 32 percent of the pumped volume from the middle and lowest permeable zones, respectively. Chemical

  6. Aquifer thermal energy stores in Germany

    International Nuclear Information System (INIS)

    Kabus, F.; Seibt, P.; Poppei, J.

    2000-01-01

    This paper describes the state of essential demonstration projects of heat and cold storage in aquifers in Germany. Into the energy supply system of the buildings of the German Parliament in Berlin, there are integrated both a deep brine-bearing aquifer for the seasonal storage of waste heat from power and heat cogeneration and a shallow-freshwater bearing aquifer for cold storage. In Neubrandenburg, a geothermal heating plant which uses a 1.200 m deep aquifer is being retrofitted into an aquifer heat storage system which can be charged with the waste heat from a gas and steam cogeneration plant. The first centralised solar heating plant including an aquifer thermal energy store in Germany was constructed in Rostock. Solar collectors with a total area of 1000m 2 serve for the heating of a complex of buildings with 108 flats. A shallow freshwater-bearing aquifer is used for thermal energy storage. (Authors)

  7. Biostratigraphy and carbon isotope stratigraphy of uppermost Cretaceous-lower Cenozoic Muzzle Group in middle Clarence valley, New Zealand

    International Nuclear Information System (INIS)

    Hollis, C.J.; Field, B.D.; Jones, C.M.; Strong, C.P.; Wilson, G.J.; Dickens, G.R.

    2005-01-01

    Muzzle Group strata exposed along southeast-flowing tributaries of the Clarence River valley, Marlborough, record hemipelagic-pelagic sedimentation across a high latitude (c. 55 degrees S), terrigenous sediment-starved, continental margin from latest Cretaceous to middle Eocene times. Studies of dinoflagellates, foraminifera, calcareous nannofossils, and radiolarians have been integrated with bulk carbonate δ 13 C profiles to establish the chronostratigraphy for two stratigraphic sections along Bluff and Muzzle Streams, middle Clarence valley. The two sections comprise similar successions. Uppermost Cretaceous (upper Haumurian) micritic limestone of Mead Hill Formation is overlain unconformably by Teredo Limestone, a c. 0.25 m thick bed of highly glauconitic, calcareous sandstone. This unit, the basal member of Amuri Limestone, is overlain conformably by c. 15 m thick Lower Limestone, micritic limestone that is glauconitic at base and progressively more marl-rich in its upper part. Lower Limestone grades up into Lower Marl, a poorly exposed, 40-70 m thick unit of alternating marl and micritic limestone beds. Biostratigraphy indicates that the base of Amuri Limestone is younger at Bluff Stream (earliest Eocene, early Waipawan) than at Muzzle Stream (late Paleocene, late Teurian). In the condensed (12 m) upper Paleocene-lower Eocene Amuri Limestone sequence at Muzzle Stream, a trend in δ 13 C from high (≥2.4 permille) to low (≤1 permille) values is consistent with global records across three major climate or carbon cycle perturbations: the late Paleocene carbon isotope maximum (PCIM, 59-56 Ma), the initial Eocene thermal maximum (IETM, 55.5 Ma), and the early Eocene climatic optimum (EECO, 53-50 Ma). Probably only the upper PCIM is preserved in the 4 m thick siliceous limestone interval overlying Teredo Limestone. The IETM is well-defined by a 1 permille negative δ 13 C excursion at the base of a 0.8 m thick marl-rich unit (Dee Marl), 5 m above the base of

  8. Simulation of flow in the Edwards Aquifer, San Antonio region, Texas, and refinement of storage and flow concepts

    Science.gov (United States)

    Maclay, Robert W.; Land, Larry F.

    1988-01-01

    The Edwards aquifer is a complexly faulted, carbonate aquifer lying within the Balcones fault zone of south-central Texas. The aquifer consists of thin- to massive-bedded limestone and dolomite, most of which is in the form of mudstones and wackestones. Well-developed secondary porosity has formed in association with former erosional surfaces within the carbonate rocks, within dolomitized-burrowed tidal and evaporitic deposits, and along inclined fractures to produce an aquifer with transmissivities greater than 100 ft2/s. The aquifer is recharged mainly by streamflow losses in the outcrop area of the Edwards aquifer and is discharged by major springs located at considerable distances, as much as 150 mi, from the areas of recharge and by wells. Ground-water flow within the Edwards aquifer of the San Antonio region was simulated to investigate concepts relating to the storage and flow characteristics. The concepts of major interest were the effects of barrier faults on flow direction, water levels, springflow, and storage within the aquifer. A general-purpose, finite-difference model, modified to provide the capability of representing barrier faults, was used to simulate ground-water flow and storage in the aquifer. The approach in model development was to conduct a series of simulations beginning with a simple representation of the aquifer framework and then proceeding to subsequent representations of increasing complexity. The simulations investigated the effects of complex geologic structures and of significant changes in transmissivity, anisotropy, and storage coefficient. Initial values of transmissivity, anisotropy, and storage coefficient were estimated based on concepts developed in previous studies. Results of the simulations confirmed the original estimates of transmissivity values (greater than 100 square feet/s) in the confined zone of the aquifer between San Antonio and Comal Springs. A storage coefficient of 0.05 in the unconfined zone of the aquifer

  9. Application of a Density-Dependent Numerical Model (MODHMS) to Assess Salinity Intrusion in the Biscayne Aquifer, North Miami-Dade County, Florida

    Science.gov (United States)

    Guha, H.; Panday, S.

    2005-05-01

    Miami-Dade County is located at the Southeastern part of the State of Florida adjoining the Atlantic coast. The sole drinking water source is the Biscayne Aquifer, which is an unconfined freshwater aquifer, composed of marine limestone with intermediate sand lenses. The aquifer is highly conductive with hydraulic conductivity values ranging from 1,000 ft/day to over 100,000 ft/day in some areas. Saltwater intrusion from the coast is an immediate threat to the freshwater resources of the County. Therefore, a multilayer density-dependent transient groundwater model was developed to evaluate the saltwater intrusion characteristics of the system. The model was developed using MODHMS, a finite difference, fully coupled groundwater and surface water flow and transport model. The buoyancy term is included in the equation for unconfined flow and the flow and transport equations are coupled using an iterative scheme. The transport equation was solved using an adaptive implicit total variation diminishing (TVD) scheme and anisotropy of dispersivity was included for longitudinal, transverse, vertical transverse, and vertical longitudinal directions. The model eastern boundaries extended approximately 3.5 miles into the Atlantic Ocean while the western boundary extended approximately 27 miles inland from the coast. The northern and southern boundaries extend 6 miles into Broward County and up to the C-100 canal in Miami-Dade County respectively. Close to 2 million active nodes were simulated, with horizontal discretization of 500 feet. A total of nine different statistical analyses were conducted with observed and simulated hydraulic heads. The analysis indicates that the model simulated hydraulic heads matched closely with the observed heads across the model domain. In general, the model reasonably simulated the inland extent of saltwater intrusion within the aquifer, and matched relatively well with limited observed chloride data from monitoring wells along the coast

  10. Hydro geochemistry and isotopic approach of coastal aquifer systems of Cap Bon : The case of tablecloths and the eastern coast of El Haourai - Tunisia

    International Nuclear Information System (INIS)

    Ben Hammouda, Fethi

    2008-01-01

    As many other semi-arid regions, the Cap Bon peninsula (N.E. Tunisia) shows a parallel increase in overexploitation and mineralization of groundwater resources. In the eastern coast and El Haouaria aquifers, the groundwater quality is threatened. Surveys including level measurements, water sampling, chemical analysis (ions Na+, Cl., Ca2+, Mg2+, Br.) and sotopes (18O, 2H, 3H, 13C, 14C) were performed in 2001, 2002 and 2003. Several analysis types were conducted and results are compared with the hydrodynamic information for identifying the main processes involved in the mineralization increase. Particularly, the isotopes were permitting the understanding of the hydrogeological of the concerned aquifers and the localization of the recharge zones. Because the regional situation along the seashore, the seawater intrusion in the unconfined Plio-quaternary aquifer, resulting from the groundwater overexploitation, and obvious explanation for the rising salinity is identified but is not the only cause of the qualitative degradation: the irrigation development that induces the soil leaching and the fertilizers transfer to groundwater over the whole aquifer extent is another major reason of the mineralization increase. Piezometric and salinity maps of the Plio-quaternary aquifer were established. The continuous increase in pumping has created several depressions in the water table, up to 12 m below msl and induced a deterioration of the water quality. The temporal changes in water-table level and salinity are often similar which suggests a strong link between them. Several geochemical approaches were performed to identify the importance of the marine intrusion in the increase in mineralization. The salinity of the groundwater appears to originate from dissolution of minerals in the aquifer system

  11. Accounting for pore water pressure and confined aquifers in assessing the stability of slopes: a Limit Equilibrium analysis carried out through the Minimum Lithostatic Deviation method

    Science.gov (United States)

    Ausilia Paparo, Maria; Tinti, Stefano

    2015-04-01

    The model we introduce is an implementation of the Minimum Lithostatic Deviation (MLD) method, developed by Tinti and Manucci (Tinti and Manucci 2006; 2008), that makes use of the limit equilibrium (LE) theory to estimate the stability of a slope. The main purpose here is to analyse the role of a confined aquifer on the value of the Safety Factor (F), the parameter that in the LE is used to determine if a slope is stable or unstable. The classical LE methods treat unconfined aquifers by including the water pore pressure in the Mohr-Coulomb failure formula: since the water decreases the friction shear strength, the soil above the sliding surface turns out to be more prone to instability. In case of a confined aquifer, however, due to a presence of impermeable layers, the water is not free to flow into the matrix of the overlying soil. We consider here the assumption of a permeable soil sliding over an impermeable layer, which is an occurrence that is found in several known landslide cases (e.g. Person, 2008; Strout and Tjeltja, 2008; Morgan et al., 2010 for offshore slides; and Palladino and Peck, 1972; Miller and Sias, 1998; Jiao et al. 2005; Paparo et al., 2013 for slopes in proximity of artificial or natural water basins) where clay beds form the potential sliding surface: the water, confined below, pushes along these layers and acts on the sliding body as an external bottom load. We modify the MLD method equations in order to take into account the load due to a confined aquifer and apply the new model to the Vajont case, where many have hypothesised the contribution of a confined aquifer to the failure. Our calculations show that the rain load i) infiltrating directly into the soil body and ii) penetrating into the confined aquifer below the clay layers, in addition with the lowering of the reservoir level, were key factors of destabilization of the Mt Toc flank and caused the disastrous landslide.

  12. Function of a deltaic silt deposit as a repository and long-term source of sulfate and related weathering products in a glaciofluvial aquifer derived from organic-rich shale (North Dakota, USA)

    Science.gov (United States)

    Schuh, W. M.; Bottrell, S. H.

    2014-05-01

    A shallow unconfined glaciofluvial aquifer in North Dakota (USA) has largest groundwater sulfate concentrations near the bottom boundary. A deltaic silt layer underlying the aquifer, at >16 m, is the modern proximate sulfate source for the aquifer. The original sulfate source was pyrite in the organic-rich shale component of the aquifer and silt grain matrix. An oxidizing event occurred during which grain-matrix pyrite sulfur was oxidized to sulfate. Thereafter the silt served as a "conserving" layer, slowly feeding sulfate into the lower part of the aquifer and the underlying till. A method was developed for estimating the approximate initial sulfate concentration in the source layer and the redistribution time since the oxidizing event, using a semi-generic convection-dispersion model. The convection-dispersion model and a model for the evolution of modern sulfate δ 34S in silt-layer pore water from the initial grain-matrix pyrite δ 34S, both estimated that the oxidizing event occurred several thousand years ago, and was likely related to the dry conditions of the Hypsithermal Interval. The silt layer also serves as an arsenic source. Results indicate that deltaic silts derived from organic-rich shale parent materials in a glacial environment can provide long-term sources for sulfate and arsenic and possibly other related oxidative weathering products.

  13. Using artificial sweeteners to identify contamination sources and infiltration zones in a coupled river-aquifer system

    Science.gov (United States)

    Bichler, Andrea; Muellegger, Christian; Hofmann, Thilo

    2014-05-01

    In shallow or unconfined aquifers the infiltration of contaminated river water might be a major threat to groundwater quality. Thus, the identification of possible contamination sources in coupled surface- and groundwater systems is of paramount importance to ensure water quality. Micropollutants like artificial sweeteners are promising markers for domestic waste water in natural water bodies. Compounds, such as artificial sweeteners, might enter the aquatic environment via discharge of waste water treatment plants, leaky sewer systems or septic tanks and are ubiquitously found in waste water receiving waters. The hereby presented field study aims at the (1) identification of contamination sources and (2) delineation of infiltration zones in a connected river-aquifer system. River bank filtrate in the groundwater body was assessed qualitatively and quantitatively using a combined approach of hydrochemical analysis and artificial sweeteners (acesulfame ACE) as waste water markers. The investigated aquifer lies within a mesoscale alpine head water catchment and is used for drinking water production. It is hypothesized that a large proportion of the groundwater flux originates from bank filtrate of a nearby losing stream. Water sampling campaigns in March and July 2012 confirmed the occurrence of artificial sweeteners at the investigated site. The municipal waste water treatment plant was identified as point-source for ACE in the river network. In the aquifer ACE was present in more than 80% of the monitoring wells. In addition, water samples were classified according to their hydrochemical composition, identifying two predominant types of water in the aquifer: (1) groundwater influenced by bank filtrate and (2) groundwater originating from local recharge. In combination with ACE concentrations a third type of water could be discriminated: (3) groundwater influence by bank filtrate but infiltrated prior to the waste water treatment plant. Moreover, the presence of ACE

  14. Geochemical characterization and heavy metal migration in a coastal polluted aquifer incorporating tidal effects: field investigation in Chongming Island, China.

    Science.gov (United States)

    Liu, Shuguang; Tan, Bo; Dai, Chaomeng; Lou, Sha; Tao, An; Zhong, Guihui

    2015-12-01

    The occurrence and migration of heavy metal in coastal aquifer incorporating tidal effects were investigated in detail by the field geological survey and observation. The continuous groundwater sampling, field observation (for groundwater potentiometric surface elevation, pH, dissolved oxygen, temperature, and salinity), and laboratory analysis (for Cr, Ni, Cu, Zn, Cd, and Pb concentration) were conducted through eight monitoring wells located around the landfill in the northern part of Chongming Island, China. The results showed that the unconfined aquifer medium was estuary-littoral facies deposit of Holocene, mainly gray clayey silt and grey sandy silt, and the groundwater flow was mainly controlled by topography condition of the aquifer formation strike. The background values of Cr, Ni, Cu, Zn, Cd, and Pb in Chongming Island were 3.10 ± 3.09, 0.81 ± 0.25, 1.48 ± 1.09, 43.32 ± 33.06, 0.08 ± 0.16, and 0.88 ± 1.74 μg/L, respectively. Compared with the groundwater samples around the study area, the drinking water was qualified and was free from the seawater intrusion/estuarine facies contaminant encroachment. Pollutant discharge was reflected in water quality parameters, the Cr and Cu concentrations elevated to the peak of 50.07 and 46.00 μg/L, respectively, and meanwhile specific migration regularity was embodied in observation time series as well as other elements. This migration regularity was not fully identical according to correlations between these analyzed elements. Ambient watery environment, anthropogenic disturbance, regional hydrogeological condition, and biogeochemical reactivity on heavy metals reduced/altered the significance of elements correlation in the migration pathway in coastal aquifer.

  15. Potential shallow aquifers characterization through an integrated geophysical method: multivariate approach by means of k-means algorithms

    Directory of Open Access Journals (Sweden)

    Stefano Bernardinetti

    2017-06-01

    Full Text Available The need to obtain a detailed hydrogeological characterization of the subsurface and its interpretation for the groundwater resources management, often requires to apply several and complementary geophysical methods. The goal of the approach in this paper is to provide a unique model of the aquifer by synthesizing and optimizing the information provided by several geophysical methods. This approach greatly reduces the degree of uncertainty and subjectivity of the interpretation by exploiting the different physical and mechanic characteristics of the aquifer. The studied area, into the municipality of Laterina (Arezzo, Italy, is a shallow basin filled by lacustrine and alluvial deposits (Pleistocene and Olocene epochs, Quaternary period, with alternated silt, sand with variable content of gravel and clay where the bottom is represented by arenaceous-pelitic rocks (Mt. Cervarola Unit, Tuscan Domain, Miocene epoch. This shallow basin constitutes the unconfined superficial aquifer to be exploited in the nearly future. To improve the geological model obtained from a detailed geological survey we performed electrical resistivity and P wave refraction tomographies along the same line in order to obtain different, independent and integrable data sets. For the seismic data also the reflected events have been processed, a remarkable contribution to draw the geologic setting. Through the k-means algorithm, we perform a cluster analysis for the bivariate data set to individuate relationships between the two sets of variables. This algorithm allows to individuate clusters with the aim of minimizing the dissimilarity within each cluster and maximizing it among different clusters of the bivariate data set. The optimal number of clusters “K”, corresponding to the individuated geophysical facies, depends to the multivariate data set distribution and in this work is estimated with the Silhouettes. The result is an integrated tomography that shows a finite

  16. Hydrogeology, groundwater levels, and generalized potentiometric-surface map of the Green River Basin lower Tertiary aquifer system, 2010–14, in the northern Green River structural basin

    Science.gov (United States)

    Bartos, Timothy T.; Hallberg, Laura L.; Eddy-Miller, Cheryl

    2015-07-14

    In cooperation with the Bureau of Land Management, groundwater levels in wells located in the northern Green River Basin in Wyoming, an area of ongoing energy development, were measured by the U.S. Geological Survey from 2010 to 2014. The wells were completed in the uppermost aquifers of the Green River Basin lower Tertiary aquifer system, which is a complex regional aquifer system that provides water to most wells in the area. Except for near perennial streams, groundwater-level altitudes in most aquifers generally decreased with increasing depth, indicating a general downward potential for groundwater movement in the study area. Drilled depth of the wells was observed as a useful indicator of depth to groundwater such that deeper wells typically had a greater depth to groundwater. Comparison of a subset of wells included in this study that had historical groundwater levels that were measured during the 1960s and 1970s and again between 2012 and 2014 indicated that, overall, most of the wells showed a net decline in groundwater levels.

  17. Geohydrology of the Unconsolidated Valley-Fill Aquifer in the Meads Creek Valley, Schuyler and Steuben Counties, New York

    Science.gov (United States)

    Miller, Todd S.; Bugliosi, Edward F.; Reddy, James E.

    2008-01-01

    The Meads Creek valley encompasses 70 square miles of predominantly forested uplands in the upper Susquehanna River drainage basin. The valley, which was listed as a Priority Waterbody by the New York State Department of Environmental Conservation in 2004, is prone to periodic flooding, mostly in its downstream end, where development is occurring most rapidly. Hydraulic characteristics of the unconsolidated valley-fill aquifer were evaluated, and seepage rates in losing and gaining tributaries were calculated or estimated, in an effort to delineate the aquifer geometry and identify the factors that contribute to flooding. Results indicated that (1) Meads Creek gained about 61 cubic feet of flow per second (about 6.0 cubic feet per second per mile of stream channel) from ground-water discharge and inflow from tributaries in its 10.2-mile reach between the northernmost and southernmost measurement sites; (2) major tributaries in the northern part of the valley are not significant sources of recharge to the aquifer; and (3) major tributaries in the central and southern part of the valley provide recharge to the aquifer. The ground-water portion of streamflow in Meads Creek (excluding tributary inflow) was 11.3 cubic feet per second (ft3/s) in the central part of the valley and 17.2 ft3/s in the southern part - a total of 28.5 ft3/s. Ground-water levels were measured in 29 wells finished in unconfined deposits for construction of a potentiometric-surface map to depict directions of ground-water flow within the valley. In general, ground water flows from the edges of the valley toward Meads Creek and ultimately discharges to it. The horizontal hydraulic gradient for the entire 12-mile-long aquifer averages about 30 feet per mile, whereas the gradient in the southern fourth of the valley averages about half that - about 17 feet per mile. A water budget for the aquifer indicated that 28 percent of recharge was derived from precipitation that falls on the aquifer, 32

  18. A Simplified Methodology For Risk Assessment of The Oolitic Limestone Aquifer, West of Alexandria Coastal Zone

    International Nuclear Information System (INIS)

    Sadek, M.A.; Hussein, R.A.

    2013-01-01

    Groundwater risk analysis helps to assess the effects of contaminants reach to specific position in groundwater system after introduction at some location above the uppermost aquifer. This provides a basis for initiating protective and mitigation measures for important groundwater resources. An attempt has been made in the present study to assess the risk of diffuse groundwater pollution at the north western coast of Alexandria against landfill waste disposal as well as agricultural pollutants leachates which are the main land use in the studied area. A simplified weighing/ rating approach have been functioned for this purpose, Slovene methodology, which is relevant for fissured carbonate aquifers that characterize the studied area. This method is based on an origin-pathway-target model, which applies for both resource and source protection. Conservative values for the intrinsic geological, hydrogeological, geo morphological and climatological parameters have been reviewed and determined for assessment of the source and resource vulnerability, hazards and risk (lithology, texture and structure of soil zone, lithology and thickness of the unsaturated zone and aquifer conditions, morphological features, slope and vegetation cover, average annual stormy days, travel time and karst network , the fertilizers and pesticide used for agriculture, the volume of unlined waste disposal site). The methodology applied in the present study emphasizes how the physical properties of the hydrological system can be integrated in an index that reflects the level of risk of a diffuse pollution to groundwater. This aligns with the prospective of site safety evaluation around risky installations such as a nuclear power plants or waste disposal facilities where assurance should be done that the risk to the public and environment is acceptably low. According to the functioned methodology, the fissured limestone under study is low vulnerable and highly protectable against surface diffuse

  19. Arsenic, microbes and contaminated aquifers

    Science.gov (United States)

    Oremland, Ronald S.; Stolz, John F.

    2005-01-01

    The health of tens of millions of people world-wide is at risk from drinking arsenic-contaminated well water. In most cases this arsenic occurs naturally within the sub-surface aquifers, rather than being derived from identifiable point sources of pollution. The mobilization of arsenic into the aqueous phase is the first crucial step in a process that eventually leads to human arsenicosis. Increasing evidence suggests that this is a microbiological phenomenon.

  20. ELONGATED UPPERMOST INTERNODE Encodes a Cytochrome P450 Monooxygenase That Epoxidizes Gibberellins in a Novel Deactivation Reaction in RiceW⃞

    Science.gov (United States)

    Zhu, Yongyou; Nomura, Takahito; Xu, Yonghan; Zhang, Yingying; Peng, Yu; Mao, Bizeng; Hanada, Atsushi; Zhou, Haicheng; Wang, Renxiao; Li, Peijin; Zhu, Xudong; Mander, Lewis N.; Kamiya, Yuji; Yamaguchi, Shinjiro; He, Zuhua

    2006-01-01

    The recessive tall rice (Oryza sativa) mutant elongated uppermost internode (eui) is morphologically normal until its final internode elongates drastically at the heading stage. The stage-specific developmental effect of the eui mutation has been used in the breeding of hybrid rice to improve the performance of heading in male sterile cultivars. We found that the eui mutant accumulated exceptionally large amounts of biologically active gibberellins (GAs) in the uppermost internode. Map-based cloning revealed that the Eui gene encodes a previously uncharacterized cytochrome P450 monooxygenase, CYP714D1. Using heterologous expression in yeast, we found that EUI catalyzed 16α,17-epoxidation of non-13-hydroxylated GAs. Consistent with the tall and dwarfed phenotypes of the eui mutant and Eui-overexpressing transgenic plants, respectively, 16α,17-epoxidation reduced the biological activity of GA4 in rice, demonstrating that EUI functions as a GA-deactivating enzyme. Expression of Eui appeared tightly regulated during plant development, in agreement with the stage-specific eui phenotypes. These results indicate the existence of an unrecognized pathway for GA deactivation by EUI during the growth of wild-type internodes. The identification of Eui as a GA catabolism gene provides additional evidence that the GA metabolism pathway is a useful target for increasing the agronomic value of crops. PMID:16399803

  1. Aquifer thermal-energy-storage modeling

    Science.gov (United States)

    Schaetzle, W. J.; Lecroy, J. E.

    1982-09-01

    A model aquifer was constructed to simulate the operation of a full size aquifer. Instrumentation to evaluate the water flow and thermal energy storage was installed in the system. Numerous runs injecting warm water into a preconditioned uniform aquifer were made. Energy recoveries were evaluated and agree with comparisons of other limited available data. The model aquifer is simulated in a swimming pool, 18 ft by 4 ft, which was filled with sand. Temperature probes were installed in the system. A 2 ft thick aquifer is confined by two layers of polyethylene. Both the aquifer and overburden are sand. Four well configurations are available. The system description and original tests, including energy recovery, are described.

  2. Groundwater-flow modeling in the Yucatan karstic aquifer, Mexico

    Science.gov (United States)

    González-Herrera, Roger; Sánchez-y-Pinto, Ismael; Gamboa-Vargas, José

    2002-09-01

    The current conceptual model of the unconfined karstic aquifer in the Yucatan Peninsula, Mexico, is that a fresh-water lens floats above denser saline water that penetrates more than 40 km inland. The transmissivity of the aquifer is very high so the hydraulic gradient is very low, ranging from 7-10 mm/km through most of the northern part of the peninsula. The computer modeling program AQUIFER was used to investigate the regional groundwater flow in the aquifer. The karstified zone was modeled using the assumption that it acts hydraulically similar to a granular, porous medium. As part of the calibration, the following hypotheses were tested: (1) karstic features play an important role in the groundwater-flow system; (2) a ring or belt of sinkholes in the area is a manifestation of a zone of high transmissivity that facilitates the channeling of groundwater toward the Gulf of Mexico; and (3) the geologic features in the southern part of Yucatan influence the groundwater-flow system. The model shows that the Sierrita de Ticul fault, in the southwestern part of the study area, acts as a flow barrier and head values decline toward the northeast. The modeling also shows that the regional flow-system dynamics have not been altered despite the large number of pumping wells because the volume of water pumped is small compared with the volume of recharge, and the well-developed karst system of the region has a very high hydraulic conductivity. Résumé. Le modèle conceptuel classique de l'aquifère karstique libre de la péninsule du Yucatan (Mexique) consiste en une lentille d'eau douce flottant sur une eau salée plus dense qui pénètre à plus de 40 km à l'intérieur des terres. La transmissivité de l'aquifère est très élevée, en sorte que le gradient hydraulique est très faible, compris entre 7 et 10 mm/km dans la plus grande partie du nord de la péninsule. Le modèle AQUIFER a été utilisé pour explorer les écoulements souterrains régionaux dans cet

  3. Hydrochemistry of New Zealand's aquifers

    International Nuclear Information System (INIS)

    Rosen, M.R.

    2001-01-01

    Groundwater chemistry on a national scale has never been studied in New Zealand apart from a few studies on nitrate concentrations and pesticides. These studies are covered in Chapter 8 of this book. However general studies of groundwater chemistry, groundwater-rock interaction and regional characteristics of water quality have not been previously addressed in much detail. This is partly because New Zealand aquifers are relatively small on a world scale and are geologically and tectonically diverse (see Chapter 3). But New Zealand has also recently lacked a centralised agency responsible for groundwater quality, and therefore, no national assessments have been undertaken. In recent years, the Institute of Geological and Nuclear Sciences has managed a programme of collecting and analysing the groundwater chemistry of key New Zealand aquifers. This programme is called the National Groundwater Monitoring Programme (NGMP) and is funded by the New Zealand Public Good Science Fund. The programme started in 1990 using only 22 wells, with four regional authorities of the country participating. The NGMP now includes all 15 regional and unitary authorities that use groundwater and over 100 monitoring sites. The NGMP is considered a nationally significant database by the New Zealand Foundation for Research Science and Technology. The NGMP allows a national comparison of aquifer chemistries because the samples are all analysed at one laboratory in a consistent manner and undergo stringent quality control checks. Poor quality analyses are thus minimised. In addition, samples are collected quarterly so that long-term seasonal trends in water quality can be analysed, and the effects of changes in land use and the vulnerability of aquifers to contaminant leaching can be assessed. This chapter summarises the water quality data collected for the NGMP over the past 10 years. Some records are much shorter than others, but most are greater than three years. Additional information is

  4. Aquifer Characterization and Groundwater Potential Assessment

    African Journals Online (AJOL)

    Timothy Ademakinwa

    Keywords: Aquifer Characterization, Groundwater Potential, Electrical Resistivity, Lithologic Logs ... State Water Corporation currently cannot meet the daily water ... METHOD OF STUDY ... sections which were constrained with the available.

  5. Distribution of effluent injected into the Boulder Zone of the Floridan aquifer system at the North District Wastewater Treatment Plant, southeastern Florida, 1997–2011

    Science.gov (United States)

    King, Jeffrey N.; Decker, Jeremy D.

    2018-02-09

    Nonhazardous, secondarily treated, domestic wastewater (effluent) has been injected about 1 kilometer below land surface into the Boulder Zone of the Floridan aquifer system at the North District Wastewater Treatment Plant in southeastern Florida. The Boulder Zone contains saline, nonpotable water. Effluent transport out of the injection zone is a risk of underground effluent injection. At the North District Wastewater Treatment Plant, injected effluent was detected outside the Boulder Zone. The U.S. Geological Survey, in cooperation with Miami-Dade Water and Sewer Department, investigated effluent transport from the Boulder Zone to overlying permeable zones in the Floridan aquifer system.One conceptual model is presented to explain the presence of effluent outside of the injection zone in which effluent injected into the Boulder Zone was transported to the Avon Park permeable zone, forced by buoyancy and injection pressure. In this conceptual model, effluent injected primarily into the Boulder Zone reaches a naturally occurring feature (a karst-collapse structure) near an injection well, through which the effluent is transported vertically upward to the uppermost major permeable zone of the Lower Floridan aquifer. The effluent is then transported laterally through the uppermost major permeable zone of the Lower Floridan aquifer to another naturally occurring feature northwest of the North District Wastewater Treatment Plant, through which it is then transported vertically upward into the Avon Park permeable zone. In addition, a leak within a monitoring well, between monitoring zones, allowed interflow between the Avon Park permeable zone and the Upper Floridan aquifer. A groundwater flow and effluent transport simulation of the hydrogeologic system at the North District Wastewater Treatment Plant, based on the hypothesized and non-unique conceptualization of the subsurface hydrogeology and flow system, generally replicated measured effluent constituent

  6. Assessment of groundwater availability in the Northern Atlantic Coastal Plain aquifer system From Long Island, New York, to North Carolina

    Science.gov (United States)

    Masterson, John P.; Pope, Jason P.; Fienen, Michael N.; Monti, Jr., Jack; Nardi, Mark R.; Finkelstein, Jason S.

    2016-08-31

    interstate aquifer management issues. Regional water-resources managers in the northern Atlantic Coastal Plain physiographic province face challenges beyond competing local domestic, industrial, agricultural, and environmental demands for water. Large changes in regional water use have made the State-level management of aquifer resources more difficult because of hydrologic effects that extend beyond State boundaries.The northern Atlantic Coastal Plain physiographic province is underlain by a wedge of unconsolidated to partially consolidated sediments that are typically thousands of feet thick along the coastline with a maximum thickness of about 10,000 ft near the edge of the continental shelf. The NACP aquifer system consists of nine confined aquifers and nine confining units capped by an unconfined surficial aquifer that is bounded laterally from the west by the contact between Coastal Plain sediments and the upland Piedmont bedrock. This aquifer system extends to the east to the limit of the Continental Shelf, however, the boundary between fresh and saline groundwater is considered to be much closer to the shoreline and varies vertically by aquifer.Precipitation over the region for average conditions from 2005 to 2009 is about 61,800 Mgal/d, but about 70 percent of it is lost to evapotranspiration resulting in an inflow of about 19,600 Mgal/d entering the groundwater system as aquifer recharge. Most of this recharge enters the aquifer system and flows through the shallow unconfined aquifer and either discharges to streams or directly to coastal waters without reaching the deep, confined aquifer system. In addition to recharge from precipitation, other sources of water include the return of wastewater from domestic septic systems of about 240 Mgal/d, about 60 Mgal/d of water released from storage in the confined system, and about 30 Mgal/d of lateral inflow at the boundary between freshwater and saltwater in response to pumping for conditions in 2013.The outflow needed to

  7. Drainage estimation to aquifer and water use irrigation efficiency in semi-arid zone for a long period of time

    Science.gov (United States)

    Jiménez-Martínez, J.; Molinero-Huguet, J.; Candela, L.

    2009-04-01

    Water requirements for different crop types according to soil type and climate conditions play not only an important role in agricultural efficiency production, though also for water resources management and control of pollutants in drainage water. The key issue to attain these objectives is the irrigation efficiency. Application of computer codes for irrigation simulation constitutes a fast and inexpensive approach to study optimal agricultural management practices. To simulate daily water balance in the soil, vadose zone and aquifer the VisualBALAN V. 2.0 code was applied to an experimental area under irrigation characterized by its aridity. The test was carried out in three experimental plots for annual row crops (lettuce and melon), perennial vegetables (artichoke), and fruit trees (citrus) under common agricultural practices in open air for October 1999-September 2008. Drip irrigation was applied to crops production due to the scarcity of water resources and the need for water conservation. Water level change was monitored in the top unconfined aquifer for each experimental plot. Results of water balance modelling show a good agreement between observed and estimated water level values. For the study period, mean drainage obtained values were 343 mm, 261 mm and 205 mm for lettuce and melon, artichoke and citrus respectively. Assessment of water use efficiency was based on the IE indicator proposed by the ASCE Task Committee. For the modelled period, water use efficiency was estimated as 73, 71 and 78 % of the applied dose (irrigation + precipitation) for lettuce and melon, artichoke and citrus, respectively.

  8. Assessment of groundwater exploitation in an aquifer using the random walk on grid method: a case study at Ordos, China

    Science.gov (United States)

    Nan, Tongchao; Li, Kaixuan; Wu, Jichun; Yin, Lihe

    2018-04-01

    Sustainability has been one of the key criteria of effective water exploitation. Groundwater exploitation and water-table decline at Haolebaoji water source site in the Ordos basin in NW China has drawn public attention due to concerns about potential threats to ecosystems and grazing land in the area. To better investigate the impact of production wells at Haolebaoji on the water table, an adapted algorithm called the random walk on grid method (WOG) is applied to simulate the hydraulic head in the unconfined and confined aquifers. This is the first attempt to apply WOG to a real groundwater problem. The method can not only evaluate the head values but also the contributions made by each source/sink term. One is allowed to analyze the impact of source/sink terms just as if one had an analytical solution. The head values evaluated by WOG match the values derived from the software Groundwater Modeling System (GMS). It suggests that WOG is effective and applicable in a heterogeneous aquifer with respect to practical problems, and the resultant information is useful for groundwater management.

  9. Radiocarbon ages of ground water as a basis for the determination of safe limits of aquifer exploitation

    International Nuclear Information System (INIS)

    Tamers, M.A.; Stipp, J.J.; Weiner, R.

    1975-01-01

    Deep ground waters of the Biscayne aquifer of south Florida were studied with radiocarbon dating techniques. Dissolved carbonates served as the material for the age determinations. Limestone dilution corrections of the measured carbon-14 activities were made by comparison of the relative concentrations of bicarbonate and total carbonates. The deep well waters of the southern portion of the deposit have corrected radiocarbon contents indicating thermonuclear weapon testing contamination; they are, therefore, less than 20 years old. The ages of the ground waters generally increase in the northern direction. This is interpreted as due to the greater depth of the deposit of that region. A model is formulated for ground water movement in an unconfined producing hydrological unit and applied to the radiocarbon results of the most intensively exploited zone of the Biscayne aquifer. It is shown that the water which is extracted by the municipal wells in this area is limited to the bottom third of the deposit. The avoidance of pollution from the surrounding septic tanks in the shallower depths of the area is explained in this way. The model leads to an objective estimation of the safe limit for the ground water extraction rate in the zone. By application of radiocarbon dating, it is possible to obtain useful information without disturbing the water supply

  10. Analysis of Aquifer Response, Groundwater Flow, and PlumeEvolution at Site OU 1, Former Fort Ord, California

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, Preston D.; Oldenburg, Curtis M.; Su, Grace W.

    2005-02-24

    This report presents a continuation from Oldenburg et al. (2002) of analysis of the hydrogeology, In-Situ Permeable Flow Sensor (ISPFS) results, aquifer response, and changes in the trichloroethylene (TCE) groundwater plume at Operational Unit 1 (OU 1) adjacent to the former Fritzsche Army Airfield at the former Fort Ord Army Base, located on Monterey Bay in northern Monterey County. Fuels and solvents were burned on a portion of OU 1 called the Fire Drill Area (FDA) during airport fire suppression training between 1962 and 1985. This activity resulted in soil and groundwater contamination in the unconfined A-aquifer. In the late 1980's, soil excavation and bioremediation were successful in remediating soil contamination at the site. Shortly thereafter, a groundwater pump, treat, and recharge system commenced operation. This system has been largely successful at remediating groundwater contamination at the head of the groundwater plume. However, a trichloroethylene (TCE) groundwater plume extends approximately 3000 ft (900 m) to the northwest away from the FDA. In the analyses presented here, we augment our prior work (Oldenburg et al., 2002) with new information including treatment-system totalizer data, recent water-level and chemistry data, and data collected from new wells to discern trends in contaminant migration and groundwater flow that may be useful for ongoing remediation efforts. Some conclusions from the prior study have been modified based on these new analyses, and these are pointed out clearly in this report.

  11. Groundwater conservation and monitoring activities in the middle Brenta River plain (Veneto Region, Northern Italy: preliminary results about aquifer recharge

    Directory of Open Access Journals (Sweden)

    Andrea Sottani

    2014-09-01

    Full Text Available In the middle Brenta River plain there is a unconfined aquifer that represents an important groundwater resource in Veneto region. In this area the main groundwater recharge factor is related to the stream seepage: the water dispersion from the Brenta river is active with variable intensity from the foothill to the alignment Nove di Bassano - Cartigliano (Province of Vicenza. In order to mitigate the expected groundwater effects, due to future important waterworks withdrawals provided by the regional water resources management plans, an experimental project of Managed Aquifer Recharge has started, by means of the realization of some river transversal ramps. The construction of pilot works, partially completed, were preceded by a specific hydrogeological monitoring program, aimed to the evaluation of the effectiveness of the MAR actions in terms of comparison between pre-and post-operam conditions. Thanks to the development of a site-specific methodology, aimed to the quantification of the artificial infiltration rate, and after some years of monitoring controls of the hydrological and hydrogeological regimes, it is now possible to evaluate the extent and the rate of the recharge effects in groundwater due to ramps realization. The monitoring plan will be continued in the medium-long term. Some innovative approaches, based for example on the use of groundwater temperature measurements as recharge tracer, will help to validate the preliminary results.

  12. Fine crustal and uppermost mantle S-wave velocity structure beneath the Tengchong volcanic area inferred from receiver function and surface-wave dispersion: constraints on magma chamber distribution

    Science.gov (United States)

    Li, Mengkui; Zhang, Shuangxi; Wu, Tengfei; Hua, Yujin; Zhang, Bo

    2018-03-01

    The Tengchong volcanic area is located in the southeastern margin of the collision zone between the Indian and Eurasian Plates. It is one of the youngest intraplate volcano groups in mainland China. Imaging the S-wave velocity structure of the crustal and uppermost mantle beneath the Tengchong volcanic area is an important means of improving our understanding of its volcanic activity and seismicity. In this study, we analyze teleseismic data from nine broadband seismic stations in the Tengchong Earthquake Monitoring Network. We then image the crustal and uppermost mantle S-wave velocity structure by joint analysis of receiver functions and surface-wave dispersion. The results reveal widely distributed low-velocity zones. We find four possible magma chambers in the upper-to-middle crust and one in the uppermost mantle. The chamber in the uppermost mantle locates in the depth range from 55 to 70 km. The four magma chambers in the crust occur at different depths, ranging from the depth of 7 to 25 km in general. They may be the heat sources for the high geothermal activity at the surface. Based on the fine crustal and uppermost mantle S-wave velocity structure, we propose a model for the distribution of the magma chambers.

  13. Transmissivity of the Upper Floridan aquifer in Florida and parts of Georgia, South Carolina, and Alabama

    Science.gov (United States)

    Kuniansky, Eve L.; Bellino, Jason C.; Dixon, Joann F.

    2012-01-01

    The Floridan aquifer system (FAS) covers an area of approximately 100,000 square miles in Florida and parts of Georgia, South Carolina, Alabama, and Mississippi. Groundwater wells for water supply were first drilled in the late 1800s and by the year 2000, the FAS was the primary source of drinking water for about 10 million people. One of the methods for assessing groundwater availability is the development of regional or subregional groundwater flow models of the aquifer system that can be used to develop water budgets spatially and temporally, as well as evaluate the groundwater resource change over time. Understanding the distribution of transmissivity within the FAS is critical to the development of groundwater flow models. The map presented herein differs from previously published maps of the FAS in that it is based on interpolation of 1,487 values of transmissivity. The transmissivity values in the dataset range from 8 to 9,000,000 feet squared per day (ft2/d) with the majority of the values ranging from 10,000 to 100,000 ft2/d. The wide range in transmissivity (6 orders of magnitude) is typical of carbonate rock aquifers, which are characterized by a wide range in karstification. Commonly, the range in transmissivity is greatest in areas where groundwater flow creates conduits in facies that dissolve more readily or areas of high porosity units that have interconnected vugs, with diameters greater than 0.1 foot. These are also areas where transmissivity is largest. Additionally, first magnitude springsheds and springs are shown because in these springshed areas, the estimates of transmissivity from interpolation may underestimate the actual range in transmissivity. Also shown is an area within the Gulf Trough in Georgia where high yielding wells are unlikely to be developed in the Upper Floridan aquifer. The interpolated transmissivity ranges shown on this map reflect the geologic structure and karstified areas. Transmissivity is large in the areas where the

  14. Numerical simulation of groundwater movement and managed aquifer recharge from Sand Hollow Reservoir, Hurricane Bench area, Washington County, Utah

    Science.gov (United States)

    Marston, Thomas M.; Heilweil, Victor M.

    2012-01-01

    The Hurricane Bench area of Washington County, Utah, is a 70 square-mile area extending south from the Virgin River and encompassing Sand Hollow basin. Sand Hollow Reservoir, located on Hurricane Bench, was completed in March 2002 and is operated primarily as a managed aquifer recharge project by the Washington County Water Conservancy District. The reservoir is situated on a thick sequence of the Navajo Sandstone and Kayenta Formation. Total recharge to the underlying Navajo aquifer from the reservoir was about 86,000 acre-feet from 2002 to 2009. Natural recharge as infiltration of precipitation was approximately 2,100 acre-feet per year for the same period. Discharge occurs as seepage to the Virgin River, municipal and irrigation well withdrawals, and seepage to drains at the base of reservoir dams. Within the Hurricane Bench area, unconfined groundwater-flow conditions generally exist throughout the Navajo Sandstone. Navajo Sandstone hydraulic-conductivity values from regional aquifer testing range from 0.8 to 32 feet per day. The large variability in hydraulic conductivity is attributed to bedrock fractures that trend north-northeast across the study area.A numerical groundwater-flow model was developed to simulate groundwater movement in the Hurricane Bench area and to simulate the movement of managed aquifer recharge from Sand Hollow Reservoir through the groundwater system. The model was calibrated to combined steady- and transient-state conditions. The steady-state portion of the simulation was developed and calibrated by using hydrologic data that represented average conditions for 1975. The transient-state portion of the simulation was developed and calibrated by using hydrologic data collected from 1976 to 2009. Areally, the model grid was 98 rows by 76 columns with a variable cell size ranging from about 1.5 to 25 acres. Smaller cells were used to represent the reservoir to accurately simulate the reservoir bathymetry and nearby monitoring wells; larger

  15. Groundwater and surface-water interaction and effects of pumping in a complex glacial-sediment aquifer, phase 2, east-central Massachusetts

    Science.gov (United States)

    Eggleston, Jack R.; Zarriello, Phillip J.; Carlson, Carl S.

    2015-12-31

    The U.S. Geological Survey, in cooperation with the Town of Framingham, Massachusetts, has investigated the potential of proposed groundwater withdrawals at the Birch Road well site to affect nearby surface water bodies and wetlands, including Lake Cochituate, the Sudbury River, and the Great Meadows National Wildlife Refuge in east-central Massachusetts. In 2012, the U.S. Geological Survey developed a Phase 1 numerical groundwater model of a complex glacial-sediment aquifer to synthesize hydrogeologic information and simulate potential future pumping scenarios. The model was developed with MODFLOW-NWT, an updated version of a standard USGS numerical groundwater flow modeling program that improves solution of unconfined groundwater flow problems. The groundwater model and investigations of the aquifer improved understanding of groundwater–surface-water interaction and the effects of groundwater withdrawals on surface-water bodies and wetlands in the study area. The initial work also revealed a need for additional information and model refinements to better understand this complex aquifer system.

  16. Diagnosis of the Ghiss Nekor aquifer in order to elaborate the aquifer contract

    Science.gov (United States)

    Baite, Wissal; Boukdir, A.; Zitouni, A.; Dahbi, S. D.; Mesmoudi, H.; Elissami, A.; Sabri, E.; Ikhmerdi, H.

    2018-05-01

    The Ghiss-Nekor aquifer, located in the north-east of the action area of the ABHL, plays a strategic role in the drinkable water supply of the city of Al Hoceima and of the neighboring urban areas. It also participates in the irrigation of PMH. However, this aquifer has problems such as over-exploitation and pollution. In the face of these problems, the only Solution is the establishment of a new mode of governance, which privileges the participation, the involvement and the responsibility of the actors concerned in a negotiated contractual framework, namely the aquifer contract. The purpose of this study is to diagnose the current state of the Ghiss Nekor aquifer, the hydrogeological characterization of the aquifer, the use of the waters of the aquifer, the Problem identification and the introduction of the aquifer contract, which aims at the participatory and sustainable management of underground water resources in the Ghiss- Nekor plain, to ensure sustainable development.

  17. Geohydrology of the Cerro Prieto geothermal aquifer

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez R, J.; de la Pena L, A.

    1981-01-01

    The most recent information on the Cerro Prieto geothermal aquifer is summarized, with special emphasis on the initial production zone where the wells completed in the Alpha aquifer are located. These wells produce steam for power plant units 1 and 2. Brief comments also are made on the Beta aquifer, which underlies the Alpha aquifer in the Cerro Prieto I area and which extends to the east to what is known as the Cerro Prieto II and Cerro Prieto III areas. The location of the area studied is shown. The Alpha and Beta aquifers differ in their mineralogy and cementing mineral composition, temperatures, and piezometric levels. The difference in piezometric levels indicates that there is no local communication between the two aquifers. This situation has been verified by a well interference test, using well E-1 as a producer in the Beta aquifer and well M-46 as the observation well in the Alpha aquifer. No interference between them was observed. Information on the geology, geohydrology, and geochemistry of Cerro Prieto is presented.

  18. Geochemistry of the Arbuckle-Simpson Aquifer

    Science.gov (United States)

    Christenson, Scott; Hunt, Andrew G.; Parkhurst, David L.; Osborn, Noel I.

    2009-01-01

    The Arbuckle-Simpson aquifer in south-central Oklahoma provides water for public supply, farms, mining, wildlife conservation, recreation, and the scenic beauty of springs, streams, and waterfalls. A new understanding of the aquifer flow system was developed as part of the Arbuckle-Simpson Hydrology Study, done in 2003 through 2008 as a collaborative research project between the State of Oklahoma and the Federal government. The U.S. Geological Survey collected 36 water samples from 32 wells and springs in the Arbuckle-Simpson aquifer in 2004 through 2006 for geochemical analyses of major ions, trace elements, isotopes of oxygen and hydrogen, dissolved gases, and dating tracers. The geochemical analyses were used to characterize the water quality in the aquifer, to describe the origin and movement of ground water from recharge areas to discharge at wells and springs, and to determine the age of water in the aquifer.

  19. Characterization of deep aquifer dynamics using principal component analysis of sequential multilevel data

    Directory of Open Access Journals (Sweden)

    D. Kurtzman

    2012-03-01

    Full Text Available Two sequential multilevel profiles were obtained in an observation well opened to a 130-m thick, unconfined, contaminated aquifer in Tel Aviv, Israel. While the general profile characteristics of major ions, trace elements, and volatile organic compounds were maintained in the two sampling campaigns conducted 295 days apart, the vertical locations of high concentration gradients were shifted between the two profiles. Principal component analysis (PCA of the chemical variables resulted in a first principal component which was responsible for ∼60% of the variability, and was highly correlated with depth. PCA revealed three distinct depth-dependent water bodies in both multilevel profiles, which were found to have shifted vertically between the sampling events. This shift cut across a clayey bed which separated the top and intermediate water bodies in the first profile, and was located entirely within the intermediate water body in the second profile. Continuous electrical conductivity monitoring in a packed-off section of the observation well revealed an event in which a distinct water body flowed through the monitored section (v ∼ 150 m yr−1. It was concluded that the observed changes in the profiles result from dominantly lateral flow of water bodies in the aquifer rather than vertical flow. The significance of this study is twofold: (a it demonstrates the utility of sequential multilevel observations from deep wells and the efficacy of PCA for evaluating the data; (b the fact that distinct water bodies of 10 to 100 m vertical and horizontal dimensions flow under contaminated sites, which has implications for monitoring and remediation.

  20. Potential for isoproturon, atrazine and mecoprop to be degraded within a chalk aquifer system

    Science.gov (United States)

    Johnson, Andrew C.; White, Craig; Lal Bhardwaj, C.

    2000-06-01

    The potential for herbicide degradation in an unconfined chalk aquifer was examined by collecting and spiking fresh samples and incubating them in the laboratory. The microcosms were incubated at 20°C under aerobic conditions and spiked with either isoproturon, atrazine or mecoprop at a concentration of 100 μg/l. The samples were obtained from a single fieldsite within the Upper Chalk aquifer in Hampshire, UK. Groundwater samples required the presence of sterile chalk in a ratio of at least 1:13 to promote isoproturon degradation. An isoproturon degradation potential existed in the soil, and the chalk unsaturated and saturated zones. However, no degradation of isoproturon in the unsaturated zone was observed when a more appropriate simulation of in-situ moisture conditions was carried out. Apart from the soil, no potential for atrazine or mecoprop degradation could be detected in the same samples over a 200-day incubation. In a series of groundwater samples taken from different boreholes, 10-300 m apart, large differences in isoproturon degradation potential were observed. Removal rates for 100 μg/l isoproturon varied from 83-425 ng/day, but in some samples no degradation potential could be detected. The primary metabolite which could be distinguished from isoproturon degradation in chalk and groundwater was monodesmethyl-isoproturon. When a chalk groundwater sample was spiked with isoproturon at 0.9 μg/l, this was not degraded over a 300-day incubation period. Further experiments with fresh groundwater from a Triassic Sandstone site illustrated that groundwater bacteria could degrade isoproturon at the more realistic temperature of 10°C as well as at 20°C.

  1. Economics of Managed Aquifer Recharge

    Directory of Open Access Journals (Sweden)

    Robert G. Maliva

    2014-05-01

    Full Text Available Managed aquifer recharge (MAR technologies can provide a variety of water resources management benefits by increasing the volume of stored water and improving water quality through natural aquifer treatment processes. Implementation of MAR is often hampered by the absence of a clear economic case for the investment to construct and operate the systems. Economic feasibility can be evaluated using cost benefit analysis (CBA, with the challenge of monetizing benefits. The value of water stored or treated by MAR systems can be evaluated by direct and indirect measures of willingness to pay including market price, alternative cost, value marginal product, damage cost avoided, and contingent value methods. CBAs need to incorporate potential risks and uncertainties, such as failure to meet performance objectives. MAR projects involving high value uses, such as potable supply, tend to be economically feasible provided that local hydrogeologic conditions are favorable. They need to have low construction and operational costs for lesser value uses, such as some irrigation. Such systems should therefore be financed by project beneficiaries, but dichotomies may exist between beneficiaries and payers. Hence, MAR projects in developing countries may be economically viable, but external support is often required because of limited local financial resources.

  2. Groundwater Flow Model of Göksu Delta Coastal Aquifer System

    Science.gov (United States)

    Erdem Dokuz, Uǧur; Çelik, Mehmet; Arslan, Şebnem; Engin, Hilal

    2016-04-01

    the conceptual hydrogeological model of Göksu Delta coastal aquifer system, Göksu Delta is restricted by limestones from north and northwest and reaches up to 250 m in thickness in the southern part. Moreover, a combined aquifer system of confined and unconfined layers has been developed within the delta. The groundwater flow direction is towards south and southeast to the Mediterranean Sea. Data from this study were used to calibrate the flow model under steady-state and transient conditions by using MOFLOW. According to the calibrated model, alluvium aquifer is primarily recharged by limestone aquifer and partially by Göksu River. Discharge from the aquifer is generally towards the Mediterranean Sea and in part to Göksu River in the southern part of the delta. Transient calibration of the model for the year 2012 indicates that Göksu Delta groundwater system is extremely sensitive for groundwater exploitation for agricultural purposes.

  3. Hydrochemical zonation of the western part of Göksu Delta aquifer system, Southern Turkey

    Science.gov (United States)

    Dokuz, U. E.; Çelik, M.; Arslan, Ş.; Engin, H.

    2012-04-01

    In general, coastal areas are preferred places for human settlement, especially at places where infrastructure routes benefit from rivers, streets, or harbours. As a result, these areas usually suffer from rising population and endure increasingly high demand on natural resources like water. Göksu Delta, located in southern Turkey, is one of the important wetland areas of Turkey at the Mediterranean coast. It is divided into two parts by Göksu River. The western part of the delta, which is the subject matter of this study, hosts fertile agricultural fields, touristic places and a Special Environmental Protection Area. These properties of the region lead to a water-dependent ecosystem where groundwater has widely been used for agricultural and domestic purposes. When the exploitation of groundwater peaked in the middle of 1990s, the groundwater levels dropped and seawater intruded. General Directorate of State Hydraulic Works tried to stop seawater intrusion by building irrigation channels connected to Göksu River and banned drilling of new wells for groundwater exploitation, although it is hard to control the drilling of wells without official permit. Geological studies show that the delta is composed of terrestrial sediments including clay to coarse sand deposited during Quaternary. The heterogeneous sediments of Göksu Delta cause hydrogeological features of the aquifer systems to be heterogeneous and anisotropic. Hydrogeological investigations, therefore, indicate mainly two different aquifers, shallow and deep, separated by an aquitard. The shallow aquifer is under unconfined to confined conditions from north to south while the deep aquifer is under confined conditions. This study focuses on hydrogeochemical zonation in terms of hydrochemical processes that affect the Göksu Delta aquifer systems. For this purpose, hydrogeochemical and isotopic studies are conducted to understand the salinisation and softening processes of groundwater. The physicochemical

  4. Air Sparging Versus Gas Saturated Water Injection for Remediation of Volatile LNAPL in the Borden Aquifer

    Science.gov (United States)

    Barker, J.; Nelson, L.; Doughty, C.; Thomson, N.; Lambert, J.

    2009-05-01

    In the shallow, rather homogeneous, unconfined Borden sand aquifer, field trials of air sparging (Tomlinson et al., 2003) and pulsed air sparging (Lambert et al., 2009) have been conducted, the latter to remediate a residual gasoline source emplaced below the water table. As well, a supersaturated (with CO2) water injection (SWI) technology, using the inVentures inFusion system, has been trialed in two phases: 1. in the uncontaminated sand aquifer to evaluate the radius of influence, extent of lateral gas movement and gas saturation below the water table, and 2. in a sheet pile cell in the Borden aquifer to evaluate the recovery of volatile hydrocarbon components (pentane and hexane) of an LNAPL emplaced below the water table (Nelson et al., 2008). The SWI injects water supersaturated with CO2. The supersaturated injected water moves laterally away from the sparge point, releasing CO2 over a wider area than does gas sparging from a single well screen. This presentation compares these two techniques in terms of their potential for remediating volatile NAPL components occurring below the water table in a rather homogeneous sand aquifer. Air sparging created a significantly greater air saturation in the vicinity of the sparge well than did the CO2 system (60 percent versus 16 percent) in the uncontaminated Borden aquifer. However, SWI pushed water, still supersaturated with CO2, up to about 2.5 m from the injection well. This would seem to provide a considerable advantage over air sparging from a point, in that gas bubbles are generated at a much larger radius from the point of injection with SWI and so should involve additional gas pathways through a residual NAPL. Overall, air sparging created a greater area of influence, defined by measurable air saturation in the aquifer, but air sparging also injected about 12 times more gas than was injected in the SWI trials. The pulsed air sparging at Borden (Lambert et al.) removed about 20 percent (4.6 kg) of gasoline

  5. Assessment of Aquifer Age and Replenishment Rate by Utilizing 36Cl-Pulse

    International Nuclear Information System (INIS)

    Challan, M.B.; Challan, M.B.; Labib, A.A.; Labib, A.A.

    2015-01-01

    The present study aims at estimating the residence-time of groundwater based on bomb-produced 36 Cl. Water samples were collected from some selected wells located around Al-Zulfi province, Riyadh central region, Saudi Arabia. 36 The Cl/Cl ratios in the water samples were determined by Inductively Coupled Plasma Mass Spectrometry (ICPMS) and Liquid Scintillation Counting(LSC). 36 The Cl/Cl ratios in the groundwater were estimated to be 1.0-2.0×10 -10 . The shallow unconfined aquifer of the area is mainly replenished by the water infiltration from the seasonal rains. Estimates of residence time were obtained by comparing the measured bomb-derived 36 Cl concentrations in groundwater with the background reference. Dating based on a 36 Cl bomb pulse may be more reliable and sensitive for groundwater recharged before 1975, back as far as the mid-1950s.The above 36 Cl-background concentration was deduced by determining accurately the background corrected Dye-3 ice core data from the frozen Arctic Data, according to the estimated total 3 '6Cl resources, including bomb-produced '3 6 Cl fallout. An estimated residence time of 7.81×10 4 y was obtained from extrapolated flow velocity. It was noticed that 36 Cl concentration in groundwater does not reflect the input of bomb pulse 36 Cl, it belongs to the era before 1950

  6. Origin, process and migration of nitrate compounds in the aquifers of Dakar region, Senegal

    International Nuclear Information System (INIS)

    Tandia, A.A.; Gaye, C.B.; Faye, A.

    1998-01-01

    Dakar is a peninsula inhabited by a population of about 2 million people in 1996. With population growth, water demand has increased, inducing seawater intrusion in some dug wells and piezometers of the peninsula. The NO 3 content in the groundwater is above the WHO allowable concentration of 50 mg/l. In the unconfined part of the aquifer, all the samples from wells are contaminated by high NO 3 contents which rose from 100 mg/l in 1987 to more than significant correlation between Cl and NO 3 in the unsaturated zone indicates an anthropogenic pollution, a fact which indicates the increasing risk of pollution of potable water resources. Studies in the unsaturated zone and familiarity with the sanitation practices in the area indicate that the horizontal and vertical flux are linked mainly to the defective septic tanks and direct organic waste elimination into the soil by more than 40% of the inhabitants. The correlation between tritium values and nitrate shows that the source of nitrate is recent. (author)

  7. Radium mobility and the age of groundwater in public-drinking-water supplies from the Cambrian-Ordovician aquifer system, north-central USA

    Science.gov (United States)

    Stackelberg, Paul E.; Szabo, Zoltan; Jurgens, Bryant C.

    2018-01-01

    High radium (Ra) concentrations in potable portions of the Cambrian-Ordovician (C-O) aquifer system were investigated using water-quality data and environmental tracers (3H, 3Hetrit, SF6, 14C and 4Herad) of groundwater age from 80 public-supply wells (PSWs). Groundwater ages were estimated by calibration of tracers to lumped parameter models and ranged from modern (1 Myr) in the most downgradient, confined portions of the potable system. More than 80 and 40 percent of mean groundwater ages were older than 1000 and 50,000 yr, respectively. Anoxic, Fe-reducing conditions and increased mineralization develop with time in the aquifer system and mobilize Ra into solution resulting in the frequent occurrence of combined Ra (Rac = 226Ra + 228Ra) at concentrations exceeding the USEPA MCL of 185 mBq/L (5 pCi/L). The distribution of the three Ra isotopes comprising total Ra (Rat = 224Ra + 226Ra + 228Ra) differed across the aquifer system. The concentrations of 224Ra and 228Ra were strongly correlated and comprised a larger proportion of the Rat concentration in samples from the regionally unconfined area, where arkosic sandstones provide an enhanced source for progeny from the 232Th decay series. 226Ra comprised a larger proportion of the Ratconcentration in samples from downgradient confined regions. Concentrations of Rat were significantly greater in samples from the regionally confined area of the aquifer system because of the increase in 226Ra concentrations there as compared to the regionally unconfined area. 226Ra distribution coefficients decreased substantially with anoxic conditions and increasing ionic strength of groundwater (mineralization), indicating that Ra is mobilized to solution from solid phases of the aquifer as adsorption capacity is diminished. The amount of 226Ra released from solid phases by alpha-recoil mechanisms and retained in solution increases relative to the amount of Ra sequestered by adsorption processes or co

  8. Constraints of costal aquifer functioning in a deeply antropized area through a multi-isotope fingerprinting (Recife, Brazil)

    Science.gov (United States)

    Petelet-Giraud, Emmanuelle; Cary, Lise; Bertrand, Guillaume; Hirata, Ricardo; Martins, Veridiana; Montenegro, Suzana; Pauwels, Hélène; Kloppmann, Wolfram; Aquilina, Luc

    2014-05-01

    The Metropolitan Region of Recife (RMR) went through large changes of water and land uses over the last decades due to an increasing demographic pressure (1.5 M of inhabitants). These evolutions gave rise to numerous environmental consequences, such as a dramatic decline of the water levels, groundwater salinization and contamination. This degradation of natural resources is linked to the increase of water demand that is also punctually amplified by drought periods, inducing the construction of thousands of private wells. Recife city was built on an estuarine area, at the geological limits of the two sedimentary basins of Pernambuco (north of the city) and Paraíba (south of the city) separated by a famous shear zone (the Pernambuco lineament). Tectonic and sedimentary events involved in the genesis and evolution of these basins were mainly controlled by the opening of the Atlantic Ocean leading to the deposition of cretaceous sediments which now constitute the two main exploited aquifers, the Beberibe and Cabo aquifers. These two deep aquiferous formations are topped by the unconfined Boa Viagem aquifer of quaternary sediments. It is the most directly exposed to contamination, since it is connected to mangroves, rivers, estuaries and highly urbanized areas. Both the Beberibe and Cabo aquifers contain large clay levels and are separated by a rather continuous clayed formation which seems to play a consistent role of screen and to interfere in the hydraulic connections between the three aquifers. Previous isotopic studies have shown that recharge processes are similar in the aquifers, suggesting that exchanges may occur and may be modified or amplified by overexploitation. This very complex aquifer system is studied through more than 60 water samples, including some surface water samples from the main rivers. A methodology based on multi-isotopes fingerprinting is applied, including stable isotopes of the water molecule, strontium isotopes, boron isotopes, sulfur

  9. Combining sound science, legal action and stakeholder involvement to protect a vulnerable coastal aquifer on the island of St. Kitts

    Science.gov (United States)

    Sahely, H.; Nettles, S.; Burrowes, R.; Haas, G.

    2011-12-01

    Water resources in small island developing states (SIDS), especially those in the Caribbean are among the most vulnerable systems to human activities and climate change. This vulnerability is exacerbated by a fragmented approach to water resources management. The unconfined coastal aquifer underlying the Basseterre Valley is a significant asset for the people of St. Kitts-Nevis. The potable water extracted from this aquifer represents over 40% of the total water supply for St. Kitts. The area is subject to urban encroachment, inappropriate land use and threats from pollution. A project was implemented using an integrated approach to help government and communities take practical actions to protect this vulnerable aquifer by demonstrating proper management on three fronts: mitigation of threats from contaminants, protection of the aquifer and improved water resources management. The project is funded by the Global Environment Facility (GEF) as part of the Integrating Watershed and Coastal Areas Management (IWCAM) project for Caribbean Small Island States. A comprehensive hydrogeologic evaluation of the aquifer was undertaken in order to aid in the development of a water resources management strategy for the Basseterre Valley Aquifer. Multi-electrode electrical resistivity (MER), a novel surface geophysical technique, was used to delineate the thickness and distribution of sediments throughout the aquifer, zones of increased porosity, zones of possible contamination and the fresh/salt water interface. Together with slowly declining static water levels and elevated dissolved solids levels, the early stages of salt water intrusion have been documented. Groundwater modelling suggests that adjusting the pumping regime, redeveloping some of the existing wells and relocating other wells is a viable option for increasing efficiency and preventing long term dewatering. Overall, the study has provided a wealth of new information about the aquifer for a reasonable cost. A

  10. Monitoring a pilot CO2 injection experiment in a shallow aquifer using 3D cross-well electrical resistance tomography

    Science.gov (United States)

    Yang, X.; Lassen, R. N.; Looms, M. C.; Jensen, K. H.

    2014-12-01

    Three dimensional electrical resistance tomography (ERT) was used to monitor a pilot CO2 injection experiment at Vrøgum, Denmark. The purpose was to evaluate the effectiveness of the ERT method for monitoring the two opposing effects from gas-phase and dissolved CO2 in a shallow unconfined siliciclastic aquifer. Dissolved CO2 increases water electrical conductivity (EC) while gas phase CO2 reduce EC. We injected 45kg of CO2 into a shallow aquifer for 48 hours. ERT data were collected for 50 hours following CO2 injection. Four ERT monitoring boreholes were installed on a 5m by 5m square grid and each borehole had 24 electrodes at 0.5 m electrode spacing at depths from 1.5 m to 13 m. ERT data were inverted using a difference inversion algorithm for bulk EC. 3D ERT successfully detected the CO2 plume distribution and growth in the shallow aquifer. We found that the changes of bulk EC were dominantly positive following CO2 injection, indicating that the effect of dissolved CO2 overwhelmed that of gas phase CO2. The pre-injection baseline resistivity model clearly showed a three-layer structure of the site. The electrically more conductive glacial sand layer in the northeast region are likely more permeable than the overburden and underburden and CO2 plumes were actually confined in this layer. Temporal bulk EC increase from ERT agreed well with water EC and cross-borehole ground penetrating radar data. ERT monitoring offers a competitive advantage over water sampling and GPR methods because it provides 3D high-resolution temporal tomographic images of CO2 distribution and it can also be automated for unattended operation. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC. LLNL IM release#: LLNL-PROC-657944.

  11. Hydrology of the Claiborne aquifer and interconnection with the Upper Floridan aquifer in southwest Georgia

    Science.gov (United States)

    Gordon, Debbie W.; Gonthier, Gerard

    2017-04-24

    The U.S. Geological Survey conducted a study, in cooperation with the Georgia Environmental Protection Division, to define the hydrologic properties of the Claiborne aquifer and evaluate its connection with the Upper Floridan aquifer in southwest Georgia. The effort involved collecting and compiling hydrologic data from the aquifer in subarea 4 of southwestern Georgia. Data collected for this study include borehole geophysical logs in 7 wells, and two 72-hour aquifer tests to determine aquifer properties.The top of the Claiborne aquifer extends from an altitude of about 200 feet above the North American Vertical Datum of 1988 (NAVD 88) in Terrell County to 402 feet below NAVD 88 in Decatur County, Georgia. The base of the aquifer extends from an altitude of about 60 feet above NAVD 88 in eastern Sumter County to about 750 feet below NAVD 88 in Decatur County. Aquifer thickness ranges from about 70 feet in eastern Early County to 400 feet in Decatur County.The transmissivity of the Claiborne aquifer, determined from two 72-hour aquifer tests, was estimated to be 1,500 and 700 feet squared per day in Mitchell and Early Counties, respectively. The storage coefficient was estimated to be 0.0006 and 0.0004 for the same sites, respectively. Aquifer test data from Mitchell County indicate a small amount of leakage occurred during the test. Groundwater-flow models suggest that the source of the leakage was the underlying Clayton aquifer, which produced about 2.5 feet of drawdown in response to pumping in the Claiborne aquifer. The vertical hydraulic conductivity of the confining unit between the Claiborne and Clayton aquifers was simulated to be about 0.02 foot per day.Results from the 72-hour aquifer tests run for this study indicated no interconnection between the Claiborne and overlying Upper Floridan aquifers at the two test sites. Additional data are needed to monitor the effects that increased withdrawals from the Claiborne aquifer may have on future water resources.

  12. Geochemical Investigation of the Arbuckle-Simpson Aquifer, South-Central Oklahoma, 2004-06

    Science.gov (United States)

    Christenson, Scott; Hunt, Andrew G.; Parkhurst, David L.

    2009-01-01

    A geochemical reconnaissance investigation of the Arbuckle-Simpson aquifer in south-central Oklahoma was initiated in 2004 to characterize the ground-water quality at an aquifer scale, to describe the chemical evolution of ground water as it flows from recharge areas to discharge in wells and springs, and to determine the residence time of ground water in the aquifer. Thirty-six water samples were collected from 32 wells and springs distributed across the aquifer for chemical analysis of major ions, trace elements, isotopes of oxygen and hydrogen, dissolved gases, and age-dating tracers. In general, the waters from wells and springs in the Arbuckle-Simpson aquifer are chemically suitable for all regulated uses, such as public supplies. Dissolved solids concentrations are low, with a median of 347 milligrams per liter (mg/L). Two domestic wells produced water with nitrate concentrations that exceeded the U.S. Environmental Protection Agency's nitrate maximum contaminant level (MCL) of 10 mg/L. Samples from two wells in the confined part of the aquifer exceeded the secondary maximum contaminant level (SMCL) for chloride of 250 mg/L and the SMCL of 500 mg/L for dissolved solids. Water samples from these two wells are not representative of water samples from the other wells and springs completed in the unconfined part of the aquifer. No other water samples from the Arbuckle-Simpson geochemical reconnaissance exceeded MCLs or SMCLs, although not every chemical constituent for which the U.S. Environmental Protection Agency has established a MCL or SMCL was analyzed as part of the Arbuckle-Simpson geochemical investigation. The major ion chemistry of 34 of the 36 samples indicates the water is a calcium bicarbonate or calcium magnesium bicarbonate water type. Calcium bicarbonate water type is found in the western part of the aquifer, which is predominantly limestone. Calcium magnesium bicarbonate water is found in the eastern part of the aquifer, which is predominantly a

  13. Evidence for thermal convection in the deep carbonate aquifer of the eastern sector of the Po Plain, Italy

    Science.gov (United States)

    Pasquale, V.; Chiozzi, P.; Verdoya, M.

    2013-05-01

    Temperatures recorded in wells as deep as 6 km drilled for hydrocarbon prospecting were used together with geological information to depict the thermal regime of the sedimentary sequence of the eastern sector of the Po Plain. After correction for drilling disturbance, temperature data were analyzed through an inversion technique based on a laterally constant thermal gradient model. The obtained thermal gradient is quite low within the deep carbonate unit (14 mK m- 1), while it is larger (53 mK m- 1) in the overlying impermeable formations. In the uppermost sedimentary layers, the thermal gradient is close to the regional average (21 mK m- 1). We argue that such a vertical change cannot be ascribed to thermal conductivity variation within the sedimentary sequence, but to deep groundwater flow. Since the hydrogeological characteristics (including litho-stratigraphic sequence and structural setting) hardly permit forced convection, we suggest that thermal convection might occur within the deep carbonate aquifer. The potential of this mechanism was evaluated by means of the Rayleigh number analysis. It turned out that permeability required for convection to occur must be larger than 3 10- 15 m2. The average over-heat ratio is 0.45. The lateral variation of hydrothermal regime was tested by using temperature data representing the aquifer thermal conditions. We found that thermal convection might be more developed and variable at the Ferrara High and its surroundings, where widespread fracturing may have increased permeability.

  14. First-order shallow aquifer characteristics across Europe: The International Hydrogeological Map of Europe at scale 1:1.5 Million (IHME1500)

    Science.gov (United States)

    Günther, Andreas; Duscher, Klaus; Broda, Stefan; Clos, Patrick; Reichling, Jörg

    2017-04-01

    Since the mid of the last century, pan-European hydrogeological overview-mapping is conducted at the scale 1 : 1.5 Million following common standards and guidelines to interpret suitable geologic mapping units in terms of potential uppermost aquifer (or non-aquifer) characteristics. These comprises potential aquifer productivities and general hydrogeological aquifer conditions (fissured vs. porous). The printed IHME1500 dataset successively elaborated and published from 1970 - 2013 consists of 25 individual map sheets. Besides the potential aquifer characterization grouped in six classes, IHME1500 offers a complete coverage of lithological material properties of potential shallow aquifer assemblages, and tracelines of major fault structures. Regional information on groundwater surfaces, aquifer thicknesses and depths, locations and characteristics of groundwater springs and other punctual information related to European groundwater resources is present for some areas in selected map sheets, however not digitally available. Synoptic IHME1500 vector data consists of a topographically corrected, seamless and harmonized polygon layer with attribute information on potential aquifer productivity and lithology. While the standardized aquifer-classification is relatively easy to harmonize across the entire mapped area, the lithological information of IHME1500 is presented using sheet-specific legend information resulting in more than 1000 aquifer lithology classes. An attempt was made to harmonize this information utilizing a specifically developed taxonomic scheme, treating consolidated, partly consolidated and unconsolidated materials separately. The translation of the original lithological information into this scheme allows for a hierarchical grouping of the mapping units into five generalization levels, where the highest aggregation level displays a ternary map showing the distribution of consolidated, partially consolidated and unconsolidated aquifer materials. The

  15. Temporal and spatial variations in groundwater quality resulting from policy-induced reductions in nitrate leaching to the Rabis Creek aquifer, Denmark

    Science.gov (United States)

    Jessen, Søren; Engesgaard, Peter; Thorling, Lærke; Müller, Sascha; Leskelä, Jari; Postma, Dieke

    2016-04-01

    Twenty-five years of annual groundwater quality monitoring data from the sandy unconfined Rabis Creek aquifer were used to assess the effects of political actions aimed to reduce nitrate leaching to the aquifer. Data were collected from eight multilevel samplers along a ˜3 km transect, which follows the general direction of groundwater flow. Each multilevel sampler comprises 20 screens placed with a 1 m vertical distance from near the water table downwards. The transect covers areas of livestock, plantation & heath, and agriculture. The history of nitrate leaching to the aquifer was assessed using data from screens close to the water table of multilevel samplers placed within agricultural areas. According to these data, nitrate concentrations of infiltrating 'agricultural' water peaked at 2-3 mM (120-180 mg/L) in the year 1989, and then gradually decreased and stabilized at 0.25-1.0 mM (15-60 mg/L) from year 2000. Local farmers declare having used the maximum fertilization rate allowed during the period. The timing of the observed decrease therefore suggests a direct link to the political action plans implemented in the same period. Parallel to the development in nitrate leaching, although with a transport time lag, the average concentration of nitrate in the oxic zone of the aquifer was roughly halved between 2000 and 2013. As a response to political initiatives of the late 1980'ies, part of the area covering the aquifer was changed from agriculture to non-fertilized grass for livestock; the data shows that this effectively remediated the aquifer underneath in less than 20 years, to become nitrate-free and attain background sulfate levels. The oxidized and pyritic reduced zone of the aquifer is separated by a <1 m redoxcline. Denitrification by the pyrite releases sulfate that is retained down-gradient as a tracer for historical nitrate loading to the aquifer. Thus sulfate concentrations currently increase in the multilevel samplers positioned furthest down

  16. Development and Modelling of a High-Resolution Aquifer Analog in the Guarani Aquifer (Brazil)

    OpenAIRE

    Höyng, Dominik

    2014-01-01

    A comprehensive and detailed knowledge about the spatial distribution of physical and chemical properties in heterogeneous porous aquifers plays a decisive role for a realistic representation of governing parameters in mathematical models. Models allow the simulation, prediction and reproduction of subsurface flow and transport characteristics. This work explains the identification, characterization and effects of small-scale aquifer heterogeneities in the Guarani Aquifer System (GAS) in S...

  17. Characterizing Structural and Stratigraphic Heterogeneities in a Faulted Aquifer Using Pump Tests with an Array of Westbay Multilevel Monitoring Wells

    Science.gov (United States)

    Johnson, B.; Zhurina, E. N.

    2001-12-01

    We are developing and assessing field testing and analysis methodologies for quantitative characterization of aquifer heterogenities using data measured in an array of multilevel monitoring wells (MLW) during pumping and recovery well tests. We have developed a unique field laboratory to determine the permeability field in a 20m by 40m by 70m volume in the fault partitioned, siliciclastic Hickory aquifer system in central Texas. The site incorporates both stratigraphic variations and a normal fault system that partially offsets the aquifer and impedes cross-fault flow. We constructed a high-resolution geologic model of the site based upon 1050 m of core and a suite of geophysical logs from eleven, closely spaced (3-10m), continuously cored boreholes to depths of 125 m. Westbay multilevel monitoring systems installed in eight holes provide 94 hydraulically isolated measurement zones and 25 injection zones. A good geologic model is critical to proper installation of the MLW. Packers are positioned at all significant fault piercements and selected, laterally extensive, clay-rich strata. Packers in adjacent MLW bracket selected hydrostratigraphic intervals. Pump tests utilized two, uncased, fully penetrating irrigation wells that straddle the fault system and are in close proximity (7 to 65 m) to the MLW. Pumping and recovery transient pressure histories were measured in 85 zones using pressure transducers with a resolution of 55 Pa (0.008 psi). The hydraulic response is that of an anisotropic, unconfined aquifer. The transient pressure histories vary significantly from zone to zone in a single MLW as well as between adjacent MLW. Derivative plots are especially useful for differentiating details of pressure histories. Based on the geologic model, the derivative curve of a zone reflects its absolute vertical position, vertical stratigraphic position, and proximity to either a fault or significant stratigraphic heterogeneity. Additional forward modeling is needed to

  18. Comparison of aquifer characteristics derived from local and regional aquifer tests.

    Science.gov (United States)

    Randolph, R.B.; Krause, R.E.; Maslia, M.L.

    1985-01-01

    A comparison of the aquifer parameter values obtained through the analysis of a local and a regional aquifer test involving the same area in southeast Georgia is made in order to evaluate the validity of extrapolating local aquifer-test results for use in large-scale flow simulations. Time-drawdown and time-recovery data were analyzed by using both graphical and least-squares fitting of the data to the Theis curve. Additionally, directional transmissivity, transmissivity tensor, and angle of anisotropy were computed for both tests. -from Authors Georgia drawdown transmissivity regional aquifer tests

  19. Conceptual model of fractured aquifer of Uranium Deposit in Caetité, Bahia: implications for groundwater flow

    International Nuclear Information System (INIS)

    Silva, Liliane Ferreira da

    2015-01-01

    The studied area is represented by the uraniferous district of Lagoa Real, located in the center-south of Bahia State, Brazil. The region is set in a semiarid climate context, with hot and dry weather parameters, with hydric deficit along all months of the year and high aridity index. Rural population is affected on drought periods since small agriculture and animal rearing are the main economic activities which are vulnerable in dry seasons. Groundwater represents the main supply source considering that most surface water sources are temporary and only exhibit flow in rainy periods. The main aquifer system present on the region is fractured, and the presence of groundwater flow occurs through the discontinuities of the rock considering that the rock mass corresponds to the set formed by the rock matrix and all its discontinuities (fractures, foliations, discordance, etc). In this sense, the main purpose of this Master Dissertation was to develop a conceptual model for the aquifer system, through the geotechnical characterization of discontinuities, once these structures allow the secondary porosity of the medium. Hydrochemical data hand out as complement for physical characterization for the behavioral interpretation of the aquifer. The aquifer system is unconfined, however, presents points of stagnation of flow forming compartments without communication with the surrounding areas. According to the International Society of Rock Mechanics ISRM method, which consist on qualitative and quantitative characterization of discontinuities of rock mass scanlines were constructed, systematically, describing, the following structure parameters: attitude, spacing, persistence, openness, infilling and roughness. From the results analysis it could be concluded that the aquifer system is composed of three discontinuities sets: one set which dips to NE, second set dipping to SW-W-NW and the last set sub-horizontal. The first and second sets are responsible for the aquifer

  20. 3-D structure of the crust and uppermost mantle at the junction between the Southeastern Alps and External Dinarides from ambient noise tomography

    Science.gov (United States)

    Guidarelli, Mariangela; Aoudia, Abdelkrim; Costa, Giovanni

    2017-12-01

    We use ambient noise tomography to investigate the crust and the uppermost mantle structure beneath the junction between the Southern Alps, the Dinarides and the Po Plain. We obtained Rayleigh wave empirical Green's functions from cross-correlation of vertical component seismic recordings for three years (2010-2012) using stations from networks in Italy, Slovenia, Austria, Croatia, Serbia and Switzerland. We measure group and phase velocity dispersion curves from the reconstructed Rayleigh waves in the period range 5-30 and 8-37 s, respectively, and we invert the surface wave velocities for tomographic images on a grid of 0.1° × 0.1°. After the tomography, the group velocities are then inverted to compute the 3-D shear wave velocity model of the crust and the upper mantle beneath the region. Our shear wave velocity model provides the 3-D image of the structure in the region between Northeastern Italy, Slovenia and Austria. The velocity variations at shallow depths correlate with known geological and tectonic domains. We find low velocities below the Po Plain, the northern tip of the Adriatic and the Pannonian Basin, whereas higher velocities characterize the Alpine chain. The vertical cross-sections reveal a clear northward increase of the crustal thickness with a sharp northward dipping of the Moho that coincides at the surface with the leading edge of the Alpine thrust front adjacent to the Friuli Plain in Northeastern Italy. This geometry of the Moho mimics fairly well the shallow north dipping geometry of the decollement inferred from permanent GPS velocity field where high interseismic coupling is reported. From the northern Adriatic domain up to the Idrija right lateral strike-slip fault system beneath Western Slovenia, the crustal thickness is more uniform. Right across Idrija fault, to the northeast, and along its strike, we report a clear change of the physical properties of the crust up to the uppermost mantle as reflected by the lateral distribution

  1. Steam Injection For Soil And Aquifer Remediation

    Science.gov (United States)

    The purpose of this Issue Paper is to provide to those involved in assessing remediation technologies for specific sites basic technical information on the use of steam injection for the remediation of soils and aquifers that are contaminated by...

  2. Hydrogeologic characterization of devonian aquifers in Uruguay

    International Nuclear Information System (INIS)

    Massa, E.

    1988-01-01

    This article carried out the assistance research project implementation in devonian sedimentary units as a potentials aquifers and their best use to school supplying and rural population in central area of Uruguay.

  3. Aquifer parameter identification and interpretation with different ...

    African Journals Online (AJOL)

    unfortunately, field data deviations from the model type curves are not considered in ... Such an extensive Study can only he done when there is a set of aquifer test data with main and .... 1990; 1995) methods are employed for qualitative.

  4. Geologic and hydrogeologic frameworks of the Biscayne aquifer in central Miami-Dade County, Florida

    Science.gov (United States)

    Wacker, Michael A.; Cunningham, Kevin J.; Williams, John H.

    2014-01-01

    related vugs, or irregular vugs. Flow zones with a mean hydraulic conductivity of 2,600 feet per day are present within the middle semiconfining unit, but none of the flow zones are continuous across the study area. The lower Biscayne aquifer flow unit comprises a group of flow zones in the lower part of the aquifer. These flow zones are present in the lower part of the Fort Thompson Formation and in some cases within the limestone or sandstone or both in the uppermost part of the Pinecrest Sand Member of the Tamiami Formation. The mean hydraulic conductivity of major flow zones within the lower Biscayne aquifer flow unit is 5,900 feet per day, and the mean value for minor flow zones is 2,900 feet per day. A semiconfining unit is present beneath the Biscayne aquifer. The boundary between the two hydrologic units is at the top or near the top of the Pinecrest Sand Member of the Tamiami Formation. The lower semiconfining unit has a hydraulic conductivity of less than 350 feet per day. The most productive zones of groundwater flow within the two Biscayne aquifer flow units have a characteristic pore system dominated by stratiform megaporosity related to selective dissolution of an Ophiomorpha-dominated ichnofabric. In the upper flow unit, decimeter-scale vertical solution pipes that are common in some areas of the SCWF study area contribute to high vertical permeability compared to that in areas without the pipes. Cross-hole flowmeter data collected from the SCWF test coreholes show that the distribution of vuggy porosity, matrix porosity, and permeability within the Biscayne aquifer of the SCWF is highly heterogeneous and anisotropic. Groundwater withdrawals from production well fields in southeastern Florida may be inducing recharge of the Biscayne aquifer from canals near the well fields that are used for water-management functions, such as flood control and well-field pumping. The SCWF was chosen as a location within Miami-Dade County to study the potential for such

  5. Hydrodynamic Analysis of the Jaruco-Aguacate Aquifer; Analisis hidrodinamico del acuifero Jaurco-Aguacate

    Energy Technology Data Exchange (ETDEWEB)

    Dilla Salvador, Felix [Centro de Investigaciones Hidraulicas (Cuba)

    2002-03-01

    The paper shows the hydrodynamic analysis of the Jaruco-Aguacate aquifer using an unsteady groundwater flow mathematical model. The simulation includes conditions before and after pumping from a well filed, called El Gato, which is considered, as the most important water source for Havana city. The system is closed to the sea and conformed by an unconfined karstic aquifer with a well defined storage zone; its natural discharge flows through two spring groups. Results obtained with the model for the main spring discharge are near to the measured values, i. e. around 5 m{sup 3}/dec as the mean value for the period without main pumping station. Flow is reduced to 2.5-1.5 m{sup 3}/sec during pumping period but there are no data to confirm this result. Besides, a detailed study of the open boundary of the system is done when piezometric head variation in time is known. The mathematical modelling has been able to simulate the aquifer in its most general conception, in its regional as well as local representation, with a mean deviation of simulated head from observed values less than one meter in both analysed simulated periods. [Spanish] El objetivo del trabajo fue realizar un analisis hidrodinamico del acuifero Jaruco-Aguacate antes y despues de la puesta en marcha del acueducto el Gato, una de las fuentes de abasto mas importantes de la ciudad de La Habana, Cuba, basado en un modelo matematico de simulacion de flujo subterraneo transitorio bidimensional. El acuifero es una llanura carstica cerrada al mar y libre; hacia su centro, la zona de almacenamiento esta bien definida; el sistema de descarga natural realiza por medio de dos grupos de manantiales. El resultado obtenido para el gasto del manantial coincide con los valores aforados para un valor medio de 5 m{sup 3}/seg en el periodo analizado antes del funcionamiento del acueducto, pero su valor se reduce, variando desde 2.5 a 1.5 m{sup 3}/seg, en el periodo posterior, sin embargo, no existe informacion para

  6. Hydrology of the Ferron sandstone aquifer and effects of proposed surface-coal mining in Castle Valley, Utah, with sections on stratigraphy and leaching of overburden

    Science.gov (United States)

    Lines, Gregory C.; Morrissey, Daniel J.; Ryer, Thomas A.; Fuller, Richard H.

    1983-01-01

    Coal in the Ferron Sandstone Member of the Mancos Shale of Cretaceous age has traditionally been mined by underground techniques in the Emery Coal Field in the southern end of Castle Valley in east-central Utah. However, approximately 99 million tons are recoverable by surface mining. Ground water in the Ferron is the sole source of supply for the town of Emery, but the aquifer is essentially untapped outside the Emery area.The Ferron Sandstone Member crops out along the eastern edge of Castle Valley and generally dips 2 ? to 10 ? to the northwest. Sandstones in the Ferron are enclosed between relatively impermeable shale in the Tununk and Blue Gate Members of the Mancos Shale. Along the outcrop, the Ferron ranges in thickness from about 80 feet in the northern part of Castle Valley to 850 feet in the southern part. The Ferron also generally thickens in the subsurface downdip from the outcrop. Records from wells and test holes indicate that the full thickness of the Ferron is saturated with water in most areas downdip from the outcrop area.Tests in the Emery area indicate that transmissivity of the Ferron sandstone aquifer ranges from about 200 to 700 feet squared per day where the Ferron is fully saturated. Aquifer transmissivity is greatest near the Paradise Valley-Joes Valley fault system where permeability has been increased by fracturing. Storage coefficient ranges from about 10 .6 to 10 -3 where the Ferron sandstone aquifer is confined and probably averages 5 x 10-2 where it is unconfined.

  7. The Next Generation in Subsidence and Aquifer-System Compaction Modeling within the MODFLOW Software Family: A New Package for MODFLOW-2005 and MODFLOW-OWHM

    Science.gov (United States)

    Boyce, S. E.; Leake, S. A.; Hanson, R. T.; Galloway, D. L.

    2015-12-01

    The Subsidence and Aquifer-System Compaction Packages, SUB and SUB-WT, for MODFLOW are two currently supported subsidence packages within the MODFLOW family of software. The SUB package allows the calculation of instantaneous and delayed releases of water from distributed interbeds (relatively more compressible fine-grained sediments) within a saturated aquifer system or discrete confining beds. The SUB-WT package does not include delayed releases, but does perform a more rigorous calculation of vertical stresses that can vary the effective stress that causes compaction. This calculation of instantaneous compaction can include the effect of water-table fluctuations for unconfined aquifers on effective stress, and can optionally adjust the elastic and inelastic storage properties based on the changes in effective stress. The next generation of subsidence modeling in MODFLOW is under development, and will merge and enhance the capabilities of the SUB and SUB-WT Packages for MODFLOW-2005 and MODFLOW-OWHM. This new version will also provide some additional features such as stress dependent vertical hydraulic conductivity of interbeds, time-varying geostatic loads, and additional attributes related to aquifer-system compaction and subsidence that will broaden the class of problems that can be simulated. The new version will include a redesigned source code, a new user friendly input file structure, more output options, and new subsidence solution options. This presentation will discuss progress in developing the new package and the new features being implemented and their potential applications. By Stanley Leake, Scott E. Boyce, Randall T. Hanson, and Devin Galloway

  8. Differentiation of naturally-occurring vs. artificial hydrocarbons in a landfill groundwater investigation

    International Nuclear Information System (INIS)

    Beaver, J.L.; Hartness, J.A.; Breeding, L.B.; Buchanan, D.M.

    1994-01-01

    Interpretation of groundwater sampling data at a large municipal/industrial landfill indicates contamination by both artificial and naturally-occurring hydrocarbons. Site hydrogeology consists of three different water bearing zones. The uppermost (shallow) aquifer is an unconfined unit consisting of silt, clay, and sand deposits. An intermediate depth semiconfined aquifer underlies the unconfined unit, and consists of a chert rubble zone and the upper portion of a fractured and solution-enhanced limestone formation. A regionally-extensive organic-rich shale underlies the semiconfined aquifer and separates it from the deep confined aquifer, which also consists of limestone. Groundwater investigations at the landfill have detected chlorinated and non-chlorinated hydrocarbons in the different aquifer intervals. Chlorinated hydrocarbons detected include tetrachloroethene, dichloroethene, and vinyl chloride and occur almost exclusively in the shallow aquifer. Aromatic hydrocarbons detected include benzene, toluene, ethylbenzene, and xylene (BTEX) and-occur in the intermediate and deep aquifers. The landfill was originally interpreted as the source of the contaminants. The observation of free-phase liquid hydrocarbons in the intermediate aquifer at the site, and high dissolved BTEX levels in the deep and intermediate aquifers upgradient of the landfill suggest that the aromatics were derived from a source other than the landfill. A potential source of BTEX contamination may be abandoned (pre-1930) natural gas wells located near the landfill. An additional BTEX source may be the organic-rich shale formation (a documented petroleum source rock)

  9. Geomorphic effects, flood power, and channel competence of a catastrophic flood in confined and unconfined reaches of the upper Lockyer valley, southeast Queensland, Australia

    Science.gov (United States)

    Thompson, Chris; Croke, Jacky

    2013-09-01

    Flooding is a persistent natural hazard, and even modest changes in future climate are believed to lead to large increases in flood magnitude. Previous studies of extreme floods have reported a range of geomorphic responses from negligible change to catastrophic channel change. This paper provides an assessment of the geomorphic effects of a rare, high magnitude event that occurred in the Lockyer valley, southeast Queensland in January 2011. The average return interval of the resulting flood was ~ 2000 years in the upper catchment and decreased to ~ 30 years downstream. A multitemporal LiDAR-derived DEM of Difference (DoD) is used to quantify morphological change in two study reaches with contrasting valley settings (confined and unconfined). Differences in geomorphic response between reaches are examined in the context of changes in flood power, channel competence and degree of valley confinement using a combination of one-dimensional (1-D) and two-dimensional (2-D) hydraulic modelling. Flood power peaked at 9800 W m- 2 along the confined reach and was 2-3 times lower along the unconfined reach. Results from the DoD confirm that the confined reach was net erosional, exporting ~ 287,000 m3 of sediment whilst the unconfined reach was net depositional gaining ~ 209,000 m3 of sediment, 70% of the amount exported from the upstream, confined reach. The major sources of eroded sediment in the confined reach were within channel benches and macrochannel banks resulting in a significant increase of channel width. In the unconfined reach, the benches and floodplains were the major loci for deposition, whilst the inner channel exhibited minor width increases. The presence of high stream power values, and resultant high erosion rates, within the confined reach is a function of the higher energy gradient of the steeper channel that is associated with knickpoint development. Dramatic differences in geomorphic responses were observed between the two adjacent reaches of

  10. Decreased panicle-derived indole-3-acetic acid reduces gibberellin A1 level in the uppermost internode, causing panicle enclosure in male sterile rice Zhenshan 97A.

    Science.gov (United States)

    Yin, Changxi; Gan, Lijun; Ng, Denny; Zhou, Xie; Xia, Kai

    2007-01-01

    Cytoplasmic male sterile (CMS) rice Zhenshan 97A (ZS97A) has been widely used in hybrid rice production in China. However, ZS97A suffers from serious panicle enclosure, which blocks normal pollination and greatly reduces seed production of hybrid rice. Little is known about the cause of panicle closure in ZS97A. In this study, it was found that the occurrence of cytoplasmic male sterility caused a deficiency of indole-3-acetic acid (IAA) in ZS97A panicles, and less IAA was provided to the uppermost internode (UI). Further, it was found that the decreased panicle-derived IAA caused a gibberellin A(1) (GA(1)) deficiency in the UI by the down-regulation of OsGA3ox2 transcript level. Reduced GA(1) level in the UI led to decreases of both cell number and cell elongation, resulting in a shortened UI. The shortened UI was unable to push the panicle out of the flag leaf sheath that remained normal, which resulted in panicle enclosure in ZS97A. These findings suggest that decreased panicle-derived IAA reduces the GA(1) level in the UI, causing panicle enclosure in CMS rice ZS97A.

  11. Relation between sedimentary framework and hydrogeology in the Guarani Aquifer System in São Paulo state, Brazil

    Science.gov (United States)

    Hirata, Ricardo; Gesicki, Ana; Sracek, Ondra; Bertolo, Reginaldo; Giannini, Paulo César; Aravena, Ramón

    2011-04-01

    This paper presents the results of a new investigation of the Guarani Aquifer System (SAG) in São Paulo state. New data were acquired about sedimentary framework, flow pattern, and hydrogeochemistry. The flow direction in the north of the state is towards the southwest and not towards the west as expected previously. This is linked to the absence of SAG outcrop in the northeast of São Paulo state. Both the underlying Pirambóia Formation and the overlying Botucatu Formation possess high porosity (18.9% and 19.5%, respectively), which was not modified significantly by diagenetic changes. Investigation of sediments confirmed a zone of chalcedony cement close to the SAG outcrop and a zone of calcite cement in the deep confined zone. The main events in the SAG post-sedimentary history were: (1) adhesion of ferrugineous coatings on grains, (2) infiltration of clays in eodiagenetic stage, (3) regeneration of coatings with formation of smectites, (4) authigenic overgrowth of quartz and K-feldspar in advanced eodiagenetic stage, (5) bitumen cementation of Pirambóia Formation in mesodiagenetic stage, (6) cementation by calcite in mesodiagenetic and telodiagenetic stages in Pirambóia Formation, (7) formation of secondary porosity by dissolution of unstable minerals after appearance of hydraulic gradient and penetration of the meteoric water caused by the uplift of the Serra do Mar coastal range in the Late Cretaceous, (8) authigenesis of kaolinite and amorphous silica in unconfined zone of the SAG and cation exchange coupled with the dissolution of calcite at the transition between unconfined and confined zone, and (9) authigenesis of analcime in the confined SAG zone. The last two processes are still under operation. The deep zone of the SAG comprises an alkaline pH, Na-HCO 3 groundwater type with old water and enriched δ 13C values (-18.8) close to the SAG outcrop. This is consistent with a conceptual geochemical model of the SAG, suggesting dissolution of calcite

  12. Guarani aquifer hydrogeological synthesis of the Guarani aquifer system. Edicion bilingue

    International Nuclear Information System (INIS)

    2009-01-01

    This work represents the synthesis of current knowledge of the Guarani Aquifer System, based on technical products made by different companies and consultants who participated in the framework of the Project for Environmental Protection and Sustainable Development of the Guarani Aquifer.

  13. Electromagnetic methods for rapidly characterizing porosity distributions in the upper part of the Biscayne aquifer, southern Florida

    Science.gov (United States)

    Mount, G. J.; Comas, X.; Cunningham, K. J.

    2010-12-01

    Gregory J. Mount1, Xavier Comas1, and Kevin J. Cunningham2 1Department of Geosciences, Florida Atlantic University, Boca Raton, Florida 33431 2U.S. Geological Survey, 3110 SW 9th Avenue, Fort Lauderdale, Florida 33315 Although conventional hydrological techniques of aquifer characterization, which rely on data obtained from boreholes and wells can provide very valuable direct information about porosity, storativity and transmissivity, they are invasive and can often become time consuming and relatively expensive. Near-surface electromagnetic techniques, such as ground penetrating radar (GPR), provide indirect measurements of aquifer properties that complement traditional point measurements and provide a laterally continuous subsurface image in an efficient and cost effective manner with a minimal impact on the environment. We investigated the carbonate rocks of the uppermost part (3-5 meters) of the Biscayne aquifer in Everglades National Park to better understand the distribution of karst features that can create concentrated flow of groundwater, nutrients, and contaminants. As the Biscayne aquifer is the primary source of drinking water for millions of people in southern Palm Beach, Broward, and Miami-Dade counties, knowledge about these features could create a more complete understanding of a critical natural resource. These macroporous elements contribute to the overall storage, permeability, and transmissivity of the aquifer and for that reason, delineation of their distribution and areal extent should aid in the development of more accurate groundwater flow models. The macroporous elements create numerous hyperbolic diffractions in GPR common offset profiles, and these diffractions are used directly used to estimate two-dimensional (2D) models of electromagnetic (EM) wave velocity in the subsurface. Such models are further contrasted with one-dimensional (1D) velocity models using GPR common mid-point surveys at selected locations. In order to estimate

  14. Vertical small scale variations of sorption and mineralization of three herbicides in subsurface limestone and sandy aquifer

    Science.gov (United States)

    Janniche, G. S.; Mouvet, C.; Albrechtsen, H.-J.

    2011-04-01

    Vertical variation in sorption and mineralization potential of mecoprop (MCPP), isoproturon and acetochlor were investigated at low concentrations (μg-range) at the cm-scale in unsaturated sub-surface limestone samples and saturated sandy aquifer samples from an agricultural catchment in Brévilles, France. From two intact core drills, four heterogenic limestone sections were collected from 4.50 to 26.40 m below surface (mbs) and divided into 12 sub-samples of 8-25 cm length, and one sandy aquifer section from 19.20 to 19.53 m depth divided into 7 sub-samples of 4-5 cm length. In the sandy aquifer section acetochlor and isoproturon sorption increased substantially with depth; in average 78% (acetochlor) and 61% (isoproturon) per 5 cm. Also the number of acetochlor and isoproturon degraders (most-probable-number) was higher in the bottom half of the aquifer section (93-> 16 000/g) than in the upper half (4-71/g). One 50 cm long limestone section with a distinct shift in color showed a clear shift in mineralization, number of degraders and sorption: In the two brown, uppermost samples, up to 31% mecoprop and up to 9% isoproturon was mineralized during 231 days, the numbers of mecoprop and isoproturon degraders were 1300 to > 16 000/g, and the sorption of both isoproturon and acetochlor was more than three times higher, compared to the two deeper, grayish samples just below where mineralization (≤ 4%) and numbers of degraders (1-520/g) were low for all three herbicides. In both unsaturated limestone and sandy aquifer, variations and even distinct shifts in both mineralization, number of specific degraders and sorption were seen within just 4-15 cm of vertical distance. A simple conceptual model of herbicides leaching to groundwater through a 10 m unsaturated limestone was established, and calculations showed that a 30 cm active layer with the measured sorption and mineralization values hardly impacted the fate of the investigated herbicides, whereas a total

  15. Aquifer response to earth tides

    International Nuclear Information System (INIS)

    Kanehiro, B.Y.; Narasimhan, T.N.

    1981-01-01

    The relation presented in the first part of this paper are applicable to packed-off wells and other situations where appreciable flow to the well does not exist. Comparisons of aquifer properties determined from the response to earth tides and from the more standard pumping tests for the two California fields are reasonably good. The case of an open well makes the problem more complicated, since there may be an appreciable amount of flow to the well. This flow to the well is seen as either a phase lag or as a difference in the ratio of the well signal to the tide for the semidiurnal and diurnal components of the tide. The latter is probably the better and more accurate indicator of flow to the well. Analyses of such situations, however, become involved and are probably best done as case-by-case studies. The numerical solutions show that treating the inverse problem through numerical modeling is at least feasible for any individual situation. It may be possible to simplify the inverse problem through the generation of type curves, but general type curves that are applicable to diverse situations are not likely to be practical. 7 figures

  16. Aquifer Storage Recovery (ASR) of chlorinated municipal drinking water in a confined aquifer

    Science.gov (United States)

    Izbicki, John A.; Petersen, Christen E.; Glotzbach, Kenneth J.; Metzger, Loren F.; Christensen, Allen H.; Smith, Gregory A.; O'Leary, David R.; Fram, Miranda S.; Joseph, Trevor; Shannon, Heather

    2010-01-01

    About 1.02 x 106 m3 of chlorinated municipal drinking water was injected into a confined aquifer, 94-137 m below Roseville, California, between December 2005 and April 2006. The water was stored in the aquifer for 438 days, and 2.64 x 106 m3 of water were extracted between July 2007 and February 2008. On the basis of Cl data, 35% of the injected water was recovered and 65% of the injected water and associated disinfection by-products (DBPs) remained in the aquifer at the end of extraction. About 46.3 kg of total trihalomethanes (TTHM) entered the aquifer with the injected water and 37.6 kg of TTHM were extracted. As much as 44 kg of TTHMs remained in the aquifer at the end of extraction because of incomplete recovery of injected water and formation of THMs within the aquifer by reactions with freechlorine in the injected water. Well-bore velocity log data collected from the Aquifer Storage Recovery (ASR) well show as much as 60% of the injected water entered the aquifer through a 9 m thick, high-permeability layer within the confined aquifer near the top of the screened interval. Model simulations of ground-water flow near the ASR well indicate that (1) aquifer heterogeneity allowed injected water to move rapidly through the aquifer to nearby monitoring wells, (2) aquifer heterogeneity caused injected water to move further than expected assuming uniform aquifer properties, and (3) physical clogging of high-permeability layers is the probable cause for the observed change in the distribution of borehole flow. Aquifer heterogeneity also enhanced mixing of native anoxic ground water with oxic injected water, promoting removal of THMs primarily through sorption. A 3 to 4-fold reduction in TTHM concentrations was observed in the furthest monitoring well 427 m downgradient from the ASR well, and similar magnitude reductions were observed in depth-dependent water samples collected from the upper part of the screened interval in the ASR well near the end of the extraction

  17. Review of Aquifer Storage and Recovery Performance in the Upper Floridan Aquifer in Southern Florida

    Science.gov (United States)

    Reese, Ronald S.

    2006-01-01

    Introduction: Interest and activity in aquifer storage and recovery (ASR) in southern Florida has increased greatly during the past 10 to 15 years. ASR wells have been drilled to the carbonate Floridan aquifer system at 30 sites in southern Florida, mostly by local municipalities or counties located in coastal areas. The primary storage zone at these sites is contained within the brackish to saline Upper Floridan aquifer of the Floridan aquifer system. The strategy for use of ASR in southern Florida is to store excess freshwater available during the wet season in an aquifer and recover it during the dry season when needed for supplemental water supply. Each ASR cycle is defined by three periods: recharge, storage, and recovery. This fact sheet summarizes some of the findings of a second phase retrospective assessment of existing ASR facilities and sites.

  18. Hydrological connectivity of perched aquifers and regional aquifers in semi-arid environments: a case study from Namibia

    Science.gov (United States)

    Hamutoko, J. T.; Wanke, H.

    2017-12-01

    Integrated isotopic and hydrological tracers along with standard hydrological data are used to understand complex dry land hydrological processes on different spatial and temporal scales. The objective of this study is to analyse the relationship between the perched aquifers and the regional aquifer using hydrochemical data and isotopic composition in the Cuvelai-Etosha Basin in Namibia. This relation between the aquifers will aid in understanding groundwater recharge processes and flow dynamics. Perched aquifers are discontinuous shallow aquifers with water level ranging from 0 to 30 meters below ground level. The regional aquifer occurs in semi-consolidated sandstone at depths between about 60 and 160 meters below ground level. Water samples were collected from both aquifers in 10 villages and were analysed for major ions and stable isotopes. The results show overlapping hydrochemistry and isotopic compositions of both aquifers in 8 villages which suggest the possibility of perched aquifer water infiltrating into the regional aquifer. In two villages the hydrochemistry and isotopic composition of the aquifers are totally different and this suggests that there is no interaction between this aquifers. Areas where perched aquifers are connected to regional aquifers maybe recharge zones. These finding have important implications for groundwater resource management.

  19. Ground-water flow in the surficial aquifer system and potential movement of contaminants from selected waste-disposal sites at Cecil Field Naval Air Station, Jacksonville, Florida

    Science.gov (United States)

    Halford, K.J.

    1998-01-01

    As part of the Installation Restoration Program, Cecil Field Naval Air Station, Jacksonville, Florida, is considering remedialaction alternatives to control the possible movement of contaminants from sites that may discharge to the surface. This requires a quantifiable understanding of ground-water flow through the surficial aquifer system and how the system will respond to any future stresses. The geologic units of interest in the study area consist of sediments of Holocene to Miocene age that extend from land surface to the base of the Hawthorn Group. The hydrogeology within the study area was determined from gamma-ray and geologists? logs. Ground-water flow through the surficial aquifer system was simulated with a seven-layer, finite-difference model that extended vertically from the water table to the top of the Upper Floridan aquifer. Results from the calibrated model were based on a long-term recharge rate of 6 inches per year, which fell in the range of 4 to 10 inches per year, estimated using stream hydrograph separation methods. More than 80 percent of ground-water flow circulates within the surficial-sand aquifer, which indicates that most contaminant movement also can be expected to move through the surficial-sand aquifer alone. The surficial-sand aquifer is the uppermost unit of the surficial aquifer system. Particle-tracking results showed that the distances of most flow paths were 1,500 feet or less from a given site to its discharge point. For an assumed effective porosity of 20 percent, typical traveltimes are 40 years or less. At all of the sites investigated, particles released 10 feet below the water table had shorter traveltimes than those released 40 feet below the water table. Traveltimes from contaminated sites to their point of discharge ranged from 2 to 300 years. The contributing areas of the domestic supply wells are not very extensive. The shortest traveltimes for particles to reach the domestic supply wells from their respective

  20. Development of K-Basin High-Strength Homogeneous Sludge Simulants and Correlations Between Unconfined Compressive Strength and Shear Strength

    Energy Technology Data Exchange (ETDEWEB)

    Onishi, Yasuo; Baer, Ellen BK; Chun, Jaehun; Yokuda, Satoru T.; Schmidt, Andrew J.; Sande, Susan; Buchmiller, William C.

    2011-02-20

    K-Basin sludge will be stored in the Sludge Transport and Storage Containers (STSCs) at an interim storage location on Central Plateau before being treated and packaged for disposal. During the storage period, sludge in the STSCs may consolidate/agglomerate, potentially resulting in high-shear-strength material. The Sludge Treatment Project (STP) plans to use water jets to retrieve K-Basin sludge after the interim storage. STP has identified shear strength to be a key parameter that should be bounded to verify the operability and performance of sludge retrieval systems. Determining the range of sludge shear strength is important to gain high confidence that a water-jet retrieval system can mobilize stored K-Basin sludge from the STSCs. The shear strength measurements will provide a basis for bounding sludge properties for mobilization and erosion. Thus, it is also important to develop potential simulants to investigate these phenomena. Long-term sludge storage tests conducted by Pacific Northwest National Laboratory (PNNL) show that high-uranium-content K-Basin sludge can self-cement and form a strong sludge with a bulk shear strength of up to 65 kPa. Some of this sludge has 'paste' and 'chunks' with shear strengths of approximately 3-5 kPa and 380-770 kPa, respectively. High-uranium-content sludge samples subjected to hydrothermal testing (e.g., 185 C, 10 hours) have been observed to form agglomerates with a shear strength up to 170 kPa. These high values were estimated by measured unconfined compressive strength (UCS) obtained with a pocket penetrometer. Due to its ease of use, it is anticipated that a pocket penetrometer will be used to acquire additional shear strength data from archived K-Basin sludge samples stored at the PNNL Radiochemical Processing Laboratory (RPL) hot cells. It is uncertain whether the pocket penetrometer provides accurate shear strength measurements of the material. To assess the bounding material strength and

  1. Groundwater vulnerability mapping of Qatar aquifers

    Science.gov (United States)

    Baalousha, Husam Musa

    2016-12-01

    Qatar is one of the most arid countries in the world with limited water resources. With little rainfall and no surface water, groundwater is the only natural source of fresh water in the country. Whilst the country relies mainly on desalination of seawater to secure water supply, groundwater has extensively been used for irrigation over the last three decades, which caused adverse environmental impact. Vulnerability assessment is a widely used tool for groundwater protection and land-use management. Aquifers in Qatar are carbonate with lots of fractures, depressions and cavities. Karst aquifers are generally more vulnerable to contamination than other aquifers as any anthropogenic-sourced contaminant, especially above a highly fractured zone, can infiltrate quickly into the aquifer and spread over a wide area. The vulnerability assessment method presented in this study is based on two approaches: DRASTIC and EPIK, within the framework of Geographical Information System (GIS). Results of this study show that DRASTIC vulnerability method suits Qatar hydrogeological settings more than EPIK. The produced vulnerability map using DRASTIC shows coastal and karst areas have the highest vulnerability class. The southern part of the country is located in the low vulnerability class due to occurrence of shale formation within aquifer media, which averts downward movement of contaminants.

  2. Distribution of {sup 36}Cl/Cl in a river-recharged aquifer: Implications for the fallout rate of bomb-produced {sup 36}Cl

    Energy Technology Data Exchange (ETDEWEB)

    Tosaki, Yuki, E-mail: tosaki@tac.tsukuba.ac.j [Sustainable Environmental Studies, Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572 (Japan); Massmann, Gudrun [Institute of Geological Sciences, Department of Earth Sciences, Freie Universitaet Berlin, Malteserstrasse 74-100, 12249 Berlin (Germany); Tase, Norio [Sustainable Environmental Studies, Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572 (Japan); Sasa, Kimikazu; Takahashi, Tsutomu [Tandem Accelerator Complex, Research Facility Center for Science and Technology, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan); Matsushi, Yuki [Department of Nuclear Engineering and Management, School of Engineering, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032 (Japan); Tamari, Michiko [Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571 (Japan); Nagashima, Yasuo [Tandem Accelerator Complex, Research Facility Center for Science and Technology, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan); Bessho, Kotaro; Matsumura, Hiroshi [Radiation Science Center, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2010-04-15

    Distribution of {sup 36}Cl/Cl ratios in a river-recharged aquifer was investigated in the Oderbruch area, northeastern Germany. The aquifer is confined up to 3.5-4 km inland, where it changes to an unconfined condition. The {sup 36}Cl/Cl ratios in the confined area were in the range between 4.6 x 10{sup -14} and 23.1 x 10{sup -14}, showing a peak at 2-3 km away from the river. A plot of {sup 36}Cl/Cl vs. reciprocal Cl{sup -} concentrations indicated possible effect of the Cl{sup -} concentration variation on the observed {sup 36}Cl/Cl ratios. After accounting for this effect, the estimated {sup 36}Cl fallout rates for the last 30 yrs show reasonable agreement with the Dye-3 data and the mid-latitude background value. The results suggest that a local {sup 36}Cl fallout curve can be constructed from groundwater when dispersive mixing is of minor importance.

  3. Timing of the deposition of uppermost Cretaceous and Paleocene coal-bearing deposits in the Greater Glendive area, Montana and North Dakota

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-02-01

    With the aid of a grant from the National Geographic Society, a cooperative agreement with the State University of New York at Stony Brook, and contract with the U.S. Department of Energy, Late Cretaceous and Paleocene geologic and paleontologic field studies were undertaken in Makoshika, State Park and vicinity, Dawson County, Montana. This region was chosen as a study area because of its potential for yielding new fossil localities and extensive exposures both above and below the K/T boundary, as suggested by previous research by David W. Krause and Joseph H. Hartman. Related field studies were also undertaken in areas adjacent to the Cedar Creek Anticline in North Dakota. This work was part of ongoing research to document change in the composition of mammalian and molluscan faunas during the Late Cretaceous and Paleocene and to relate observed patterns to floral and invertebrate changes in composition. This study focuses on the record of mammals and mollusks in the Makoshika stratigraphic section and places old and new observations into a paleomagnetic and palynomorph framework. Of particular interest is the appearance and diversification of archaic ungulate mammals. Simultaneous dinosaur extinction with ungulate radiation has been invoked in gradual, as opposed to catastrophic, models of faunal change at the K/T boundary. However, supposed Cretaceous localities bearing archaic ungulates and other mammals of {open_quotes}Paleocene aspect{close_quotes} may be the product of faunal reworking. Elsewhere in the Williston Basin (e.g., Garfield and McCone Counties, Montana), the molluscan record of uppermost Cretaceous and Paleocene strata indicates the extinction of all of the highly sculptured unionid bivalves just prior to the onset of coal swamps and subsequent coal formation.

  4. Chernobyl fallout in the uppermost (0-3 cm) humus layer of forest soil in Finland, North East Russia and the Baltic countries in 2000--2003.

    Science.gov (United States)

    Ylipieti, J; Rissanen, K; Kostiainen, E; Salminen, R; Tomilina, O; Täht, K; Gilucis, A; Gregorauskiene, V

    2008-12-15

    The situation resulting from the Chernobyl fallout in 1987 was compared to that in 2000--2001 in Finland and NW Russia and that in 2003 in the Baltic countries. 786 humus (0-3 cm layer) samples were collected during 2000--2001 in the Barents Ecogeochemistry Project, and 177 samples in the Baltic countries in 2003. Nuclides emitting gamma-radiation in the 0-3 cm humus layer were measured by the Radiation and Nuclear Safety Authority-STUK in Finland. In 1987 the project area was classified by the European Commission into four different fallout classes. 137Cs inventory Bg/m2 levels measured in 2000--2003 were compared to the EU's class ranges. Fitting over the whole project area was implemented by generalizing the results for samples from the Baltic countries, for which Bq/m2 inventories could be calculated. A rough estimation was made by comparing the mass of organic matter and humus with 137Cs concentrations in these two areas. Changes in 137Cs concentration levels are illustrated in both thematic maps and tables. Radionuclide 137Cs concentrations (Bq/kg d.w.) were detected in the humus layer at all the 988 sampling sites. 134Cs was still present in 198 sites 15 years after the nuclear accident in Chernobyl. No other anthropogenic nuclides emitting gamma-radiation were detected, but low levels of 60Co, 125Sb and 154Eu isotopes were found in 14 sites. Fifteen years after the Chernobyl accident, the radioactive nuclide 137Cs was and still is the most significant fallout radionuclide in the environment and in food chains. The results show that the fallout can still be detected in the uppermost humus layer in North East Europe.

  5. Unravelling the stratigraphy and sedimentation history of the uppermost Cretaceous to Eocene sediments of the Kuching Zone in West Sarawak (Malaysia), Borneo

    Science.gov (United States)

    Breitfeld, H. Tim; Hall, Robert; Galin, Thomson; BouDagher-Fadel, Marcelle K.

    2018-07-01

    The Kuching Zone in West Sarawak consists of two different sedimentary basins, the Kayan and Ketungau Basins. The sedimentary successions in the basins are part of the Kuching Supergroup that extends into Kalimantan. The uppermost Cretaceous (Maastrichtian) to Lower Eocene Kayan Group forms the sedimentary deposits directly above a major unconformity, the Pedawan Unconformity, which marks the cessation of subduction-related magmatism beneath SW Borneo and the Schwaner Mountains, due to termination of the Paleo-Pacific subduction. The successions consist of the Kayan and Penrissen Sandstones and are dominated by fluvial channels, alluvial fans and floodplain deposits with some deltaic to tidally-influenced sections in the Kayan Sandstone. In the late Early or early Middle Eocene, sedimentation in this basin ceased and a new basin, the Ketungau Basin, developed to the east. This change is marked by the Kayan Unconformity. Sedimentation resumed in the Middle Eocene (Lutetian) with the marginal marine, tidal to deltaic Ngili Sandstone and Silantek Formation. Upsequence, the Silantek Formation is dominated by floodplain and subsidiary fluvial deposits. The Bako-Mintu Sandstone, a potential lateral equivalent of the Silantek Formation, is formed of major fluvial channels. The top of the Ketungau Group in West Sarawak is formed by the fluvially-dominated Tutoop Sandstone. This shows a transition of the Ketungau Group in time towards terrestrial/fluvially-dominated deposits. Paleocurrent measurements show river systems were complex, but reveal a dominant southern source. This suggests uplift of southern Borneo initiated in the region of the present-day Schwaner Mountains from the latest Cretaceous onwards. Additional sources were local sources in the West Borneo province, Mesozoic melanges to the east and potentially the Malay Peninsula. The Ketungau Group also includes reworked deposits of the Kayan Group. The sediments of the Kuching Supergroup are predominantly

  6. 40 CFR 147.502 - Aquifer exemptions. [Reserved

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 22 2010-07-01 2010-07-01 false Aquifer exemptions. [Reserved] 147.502... (CONTINUED) STATE, TRIBAL, AND EPA-ADMINISTERED UNDERGROUND INJECTION CONTROL PROGRAMS Florida § 147.502 Aquifer exemptions. [Reserved] ...

  7. Simulation of seawater intrusion in coastal aquifers: Some typical ...

    Indian Academy of Sciences (India)

    Springer Verlag Heidelberg #4 2048 1996 Dec 15 10:16:45

    Seawater intrusion; coastal aquifers; density-dependent flow and ... The seawater intrusion mechanism in coastal aquifers generally causes the occurrence of ... (4) The dynamic viscosity of the fluid does not change with respect to salinity and.

  8. Ground Water movement in crystalline rock aquifers

    International Nuclear Information System (INIS)

    Serejo, A.N.C.; Freire, C.; Siqueira, H.B. de; Frischkorn, H.; Torquato, J.R.F.; Santiago, M.M.F.; Barbosa, P.C.

    1984-01-01

    Ground water movement studies were performed in crystalline rock aquifers from the upper Acarau River hydrographic basin, state of Ceara, Brazil. The studies included carbon-14, 18 O/ 16 O and tritium measurements as well as chemical analysis. A total of 35 wells were surveyed during drought seasons. Carbon-14 values displayed little variation which implied that the water use was adequate despite of the slower recharge conditions. Fairly constant isotopic 18 O/ 16 O ratio values in the wells and their similarity with rainwater values indicated that the recharge is done exclusively by pluvial waters. A decreasing tendency within the tritium concentration values were interpreted as a periodic rainwater renewal for these aquifers. The chemical analysis demonstrated that there is in fact no correlation between salinity and the time the water remains in the aquifer itself. (D.J.M.) [pt

  9. Unconsolidated Aquifers in Tompkins County, New York

    Science.gov (United States)

    Miller, Todd S.

    2000-01-01

    Unconsolidated aquifers consisting of saturated sand and gravel are capable of supplying large quantities of good-quality water to wells in Tompkins County, but little published geohydrologic inform ation on such aquifers is available. In 1986, the U.S.Geological Survey (USGS) began collecting geohydrologic information and well data to construct an aquifer map showing the extent of unconsolidated aquifers in Tompkins county. Data sources included (1) water-well drillers. logs; (2) highway and other construction test-boring logs; (3) well data gathered by the Tompkins County Department of Health, (4) test-well logs from geohydrologic consultants that conducted projects for site-specific studies, and (5) well data that had been collected during past investigations by the USGS and entered into the National Water Information System (NWIS) database. In 1999, the USGS, in cooperation with the Tompkins County Department of Planning, compiled these data to construct this map. More than 600 well records were entered into the NWIS database in 1999 to supplement the 350 well records already in the database; this provided a total of 950 well records. The data were digitized and imported into a geographic information system (GIS) coverage so that well locations could be plotted on a map, and well data could be tabulated in a digital data base through ARC/INFO software. Data on the surficial geology were used with geohydrologic data from well records and previous studies to delineate the extent of aquifers on this map. This map depicts (1) the extent of unconsolidated aquifers in Tompkins County, and (2) locations of wells whose records were entered into the USGS NWIS database and made into a GIS digital coverage. The hydrologic information presented here is generalized and is not intended for detailed site evaluations. Precise locations of geohydrologic-unit boundaries, and a description of the hydrologic conditions within the units, would require additional detailed, site

  10. Aquifer thermal energy storage. International symposium: Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-05-01

    Aquifers have been used to store large quantities of thermal energy to supply process cooling, space cooling, space heating, and ventilation air preheating, and can be used with or without heat pumps. Aquifers are used as energy sinks and sources when supply and demand for energy do not coincide. Aquifer thermal energy storage may be used on a short-term or long-term basis; as the sole source of energy or as a partial storage; at a temperature useful for direct application or needing upgrade. The sources of energy used for aquifer storage are ambient air, usually cold winter air; waste or by-product energy; and renewable energy such as solar. The present technical, financial and environmental status of ATES is promising. Numerous projects are operating and under development in several countries. These projects are listed and results from Canada and elsewhere are used to illustrate the present status of ATES. Technical obstacles have been addressed and have largely been overcome. Cold storage in aquifers can be seen as a standard design option in the near future as it presently is in some countries. The cost-effectiveness of aquifer thermal energy storage is based on the capital cost avoidance of conventional chilling equipment and energy savings. ATES is one of many developments in energy efficient building technology and its success depends on relating it to important building market and environmental trends. This paper attempts to provide guidance for the future implementation of ATES. Individual projects have been processed separately for entry onto the Department of Energy databases.

  11. Modelling contaminant transport in saturated aquifers

    International Nuclear Information System (INIS)

    Lakshminarayana, V.; Nayak, T.R.

    1990-01-01

    With the increase in population and industrialization the problem of pollution of groundwater has become critical. The present study deals with modelling of pollutant transport through saturated aquifers. Using this model it is possible to predict the concentration distribution, spatial as well as temporal, in the aquifer. The paper also deals with one of the methods of controlling the pollutant movement, namely by pumping wells. A simulation model is developed to determine the number, location and rate of pumping of a number of wells near the source of pollution so that the concentration is within acceptable limits at the point of interest. (Author) (18 refs., 14 figs., tab.)

  12. Comparison of groundwater flow in Southern California coastal aquifers

    Science.gov (United States)

    Hanson, Randall T.; Izbicki, John A.; Reichard, Eric G.; Edwards, Brian D.; Land, Michael; Martin, Peter

    2009-01-01

    Development of the coastal aquifer systems of Southern California has resulted in overdraft, changes in streamflow, seawater intrusion, land subsidence, increased vertical flow between aquifers, and a redirection of regional flow toward pumping centers. These water-management challenges can be more effectively addressed by incorporating new understanding of the geologic, hydrologic, and geochemical setting of these aquifers.

  13. Spore-forming, Desulfosporosinus-like sulphate-reducing bacteria from a shallow aquifer contaminated with gasoline.

    Science.gov (United States)

    Robertson, W J; Franzmann, P D; Mee, B J

    2000-02-01

    Previous studies on the geochemistry of a shallow unconfined aquifer contaminated with hydrocarbons suggested that the degradation of some hydrocarbons was linked to bacterial sulphate reduction. There was attenuation of naphthalene, 1,3,5-trimethylbenzene (TMB), toluene, p-xylene and ethylbenzene in the groundwater with concomitant loss of sulphate. Here, the recovery of eight strains of sulphate-reducing bacteria (SRB) from the contaminated site is reported. All were straight or curved rod-shaped cells which formed endospores. Amplification and sequencing of the 16S rDNA indicated that the strains were all sulphate reducers of the Gram-positive line of descent, and were most closely related to Desulfosporosinus (previously Desulfotomaculum) orientis DSM 8344 (97-98.9% sequence similarity). The strains clustered in three phylogenetic groups based on 16S rRNA sequences. Whole cell fatty acid compositions were similar to those of D. orientis DSM 8344, and were consistent with previous studies of fatty acids in soil and groundwater from the site. Microcosms containing groundwater from this aquifer indicated a role for sulphate reduction in the degradation of [ring-UL-14C]toluene, but not for the degradation of [UL-14C]benzene which could also be degraded by the microcosms. Adding one of the strains that was isolated from the groundwater (strain T2) to sulphate-enriched microcosms increased the rate of toluene degradation four- to 10-fold but had no effect on the rate of benzene degradation. The addition of molybdate, an inhibitor of sulphate reduction, to the groundwater samples decreased the rate of toluene mineralization. There was no evidence to support the mineralization of [UL-14C]benzene, [ring-UL-14C]toluene or unlabelled m-xylene, p-xylene, ethylbenzene, TMB or naphthalene by any of the strains in pure culture. Growth of all the strains was completely inhibited by 100 micromol l-1 TMB.

  14. Hydrochemical and Isotopic Investigation of Groundwater in the Hammamet-Nabeul Aquifer System, North-Eastern Tunisia

    Energy Technology Data Exchange (ETDEWEB)

    Ben Moussa, A.; Zouari, K. [Laboratory of Radio-Analysis and Environment, ENIS, Sfax (Tunisia); Kurttas, T. [Isotope Hydrology Section, International Atomic Energy Agency, Vienna (Austria)

    2013-07-15

    The combination of major element geochemistry, stable ({delta}{sup 18}O, {delta}{sup 2}H) and radioactive ({sup 3}H, {sup 14}C) isotopes has provided a comprehensive understanding of the natural and anthropogenic processes that control groundwater mineralization as well as the sources of different groundwater bodies within the Hammamet-Nabeul unconfined aquifer (Cap Bon peninsula, northeastern Tunisia). The geochemical examination shows the dominance of Na-Cl and Ca-SO{sub 4} water types resulting from the dissolution of halite and gypsum, the dedolomitization and the cation exchange process. Additionally, the return flow process in relation with the long term flood irrigation practice contributes to the mineralization by producing high amounts of nitrate. The stable isotope signatures reveal the existence of two groundwater groups. The non-evaporated groundwaters with relatively depleted contents, reflecting recharge at higher altitudes; and evaporated groundwaters with enriched contents highlighting the influence of return flow of irrigation waters. Tritium contents in these two groups provide evidence of the presence of pre- 1950 and post-1960 recharge periods. Carbon-14 activities in shallow wells, in spite of their contamination by organic {sup 14}C, confirm the recent origin of the groundwaters in the study area. (author)

  15. In situ bioreduction of technetium and uranium in a nitrate-contaminated aquifer

    International Nuclear Information System (INIS)

    IstokD, Jonathan; Senko, J.M.; Krumholz, Lee R.; Watson, David B.; Bogle, Mary Anna; Peacock, Aaron D.; Change, Y.J.; White, David C.

    2004-01-01

    The potential to stimulate an indigenous microbial community to reduce a mixture of U(VI) and Tc(VII) in the presence of high (120 mM) initial NO 3 - co-contamination was evaluated in a shallow unconfined aquifer using a series of single-well, push-pull tests. In the absence of added electron donor, NO 3 - , Tc(VII), and U(VI) reduction was not detectable. However, in the presence of added ethanol, glucose, or acetate to serve as electron donor, rapid NO 3 - utilization was observed. The accumulation of NO 2 - , the absence of detectable NH 4 + accumulation, and the production of N 2 O during in situ acetylene-block experiments suggest that NO 3 - was being consumed via denitrification. Tc(VII) reduction occurred concurrently with NO 3 - reduction, but U(VI) reduction was not observed until two or more donor additions resulted in iron-reducing conditions, as detected by the production of Fe(II). Reoxidation/remobilization of U(IV) was also observed in tests conducted with high (120 mM) but not low (1 mM) initial NO 3 - concentrations and not during acetylene-block experiments conducted with high initial NO 3 - . These results suggest that NO 3 - -dependent microbial U(IV) oxidation may inhibit or reverse U(VI) reduction and decrease the stability of U(IV) in this environment. Changes in viable biomass, community composition, metabolic status, and respiratory state of organisms harvested from down-well microbial samplers deployed during these tests were consistent with the conclusions that electron donor additions resulted in microbial growth, the creation of anaerobic conditions, and an increase in activity of metal-reducing organisms (e.g., Geobacter). The results demonstrate that it is possible to stimulate the simultaneous bioreduction of U(VI) and Tc(VII) mixtures commonly found with NO 3 - co-contamination at radioactive waste sites.

  16. Forecasting monthly groundwater level fluctuations in coastal aquifers using hybrid Wavelet packet–Support vector regression

    Directory of Open Access Journals (Sweden)

    N. Sujay Raghavendra

    2015-12-01

    Full Text Available This research demonstrates the state-of-the-art capability of Wavelet packet analysis in improving the forecasting efficiency of Support vector regression (SVR through the development of a novel hybrid Wavelet packet–Support vector regression (WP–SVR model for forecasting monthly groundwater level fluctuations observed in three shallow unconfined coastal aquifers. The Sequential Minimal Optimization Algorithm-based SVR model is also employed for comparative study with WP–SVR model. The input variables used for modeling were monthly time series of total rainfall, average temperature, mean tide level, and past groundwater level observations recorded during the period 1996–2006 at three observation wells located near Mangalore, India. The Radial Basis function is employed as a kernel function during SVR modeling. Model parameters are calibrated using the first seven years of data, and the remaining three years data are used for model validation using various input combinations. The performance of both the SVR and WP–SVR models is assessed using different statistical indices. From the comparative result analysis of the developed models, it can be seen that WP–SVR model outperforms the classic SVR model in predicting groundwater levels at all the three well locations (e.g. NRMSE(WP–SVR = 7.14, NRMSE(SVR = 12.27; NSE(WP–SVR = 0.91, NSE(SVR = 0.8 during the test phase with respect to well location at Surathkal. Therefore, using the WP–SVR model is highly acceptable for modeling and forecasting of groundwater level fluctuations.

  17. Aquifer geochemistry at potential aquifer storage and recovery sites in coastal plain aquifers in the New York city area, USA

    Science.gov (United States)

    Brown, C.J.; Misut, P.E.

    2010-01-01

    The effects of injecting oxic water from the New York city (NYC) drinking-water supply and distribution system into a nearby anoxic coastal plain aquifer for later recovery during periods of water shortage (aquifer storage and recovery, or ASR) were simulated by a 3-dimensional, reactive-solute transport model. The Cretaceous aquifer system in the NYC area of New York and New Jersey, USA contains pyrite, goethite, locally occurring siderite, lignite, and locally varying amounts of dissolved Fe and salinity. Sediment from cores drilled on Staten Island and western Long Island had high extractable concentrations of Fe, Mn, and acid volatile sulfides (AVS) plus chromium-reducible sulfides (CRS) and low concentrations of As, Pb, Cd, Cr, Cu and U. Similarly, water samples from the Lloyd aquifer (Cretaceous) in western Long Island generally contained high concentrations of Fe and Mn and low concentrations of other trace elements such as As, Pb, Cd, Cr, Cu and U, all of which were below US Environmental Protection Agency (USEPA) and NY maximum contaminant levels (MCLs). In such aquifer settings, ASR operations can be complicated by the oxidative dissolution of pyrite, low pH, and high concentrations of dissolved Fe in extracted water.The simulated injection of buffered, oxic city water into a hypothetical ASR well increased the hydraulic head at the well, displaced the ambient groundwater, and formed a spheroid of injected water with lower concentrations of Fe, Mn and major ions in water surrounding the ASR well, than in ambient water. Both the dissolved O2 concentrations and the pH of water near the well generally increased in magnitude during the simulated 5-a injection phase. The resultant oxidation of Fe2+ and attendant precipitation of goethite during injection provided a substrate for sorption of dissolved Fe during the 8-a extraction phase. The baseline scenario with a low (0.001M) concentration of pyrite in aquifer sediments, indicated that nearly 190% more water

  18. Combining lead isotopes and cluster analysis to distinguish the Guarani and Serra Geral Aquifer Systems and contaminated waters in a highly industrialized area in Southern Brazil.

    Science.gov (United States)

    Kuhn, Isadora Aumond; Roisenberg, Ari

    2017-10-01

    The Rio dos Sinos Watershed area is located at the Middle-West region of the Rio Grande do Sul State, Southern Brazil, along thirty two municipalities and affecting 1.5 million inhabitants and many important industrial centers. Three main aquifers are recognized in the study area: the unconfined-fractured Serra Geral Aquifer System, the porous Guarani Aquifer System, and the Permian Aquitard. This study aims to understand groundwater, surface water and human activity interactions in the Rio dos Sinos Watershed, evaluating the application of stable lead isotopic ratios analyzed for this propose. Thirty six groundwater samples, 8 surface water samples and 5 liquid effluents of tanneries and landfills samples were measured using a Thermal Ionization Mass Spectrometer Thermo-Finnigan and a Neptune Multi-Collector Inductively Coupled Plasma Mass Spectrometer. Groundwater isotopic ratios have a wider range compared to the surface water, with less radiogenic averages 208 Pb/ 204 Pb = 38.1837 vs 38.4050 (standard deviation = 0.2921 vs 0.1343) and 206 Pb/ 204 Pb = 18.2947 vs 18.4766 (standard deviation = 0.2215 vs 0.1059), respectively. Industrial liquid effluents (tanneries and industrial landfill) have averages 208 Pb/ 204 Pb = 38.1956 and 206 Pb/ 204 Pb = 18.3169, distinct from effluent samples of domestic sanitary landfill (averages 208 Pb/ 204 Pb = 38.2353 and 206 Pb/ 204 Pb = 18.6607). Hierarchical cluster analysis led to distinguish six groups of groundwater, representing the three aquifers that occur in the area, two clusters suggesting groundwater mixtures and one demonstrating a highly contaminated groundwater. By analyzing the cluster results and wells' stratigraphic profiles it was possible to distinguish the different aquifers in the area. The Serra Geral Aquifer System has 206 Pb/ 204 Pb ratios between 18.4718 and 18.7089; 207 Pb/ 204 Pb between 15.6692 and 15.6777; 208 Pb/ 204 Pb between 38.6826 and 38.7616; 207 Pb/ 206 Pb between 0.8372 and 0

  19. Investigating river–aquifer relations using water temperature in an anthropized environment (Motril-Salobreña aquifer)

    DEFF Research Database (Denmark)

    Duque, Carlos; Calvache, Marie; Engesgaard, Peter Knudegaard

    2010-01-01

    Heat was applied as a tracer for determining river–aquifer relations in the Motril-Salobreña aquifer (S Spain). The aquifer has typically been recharged by River Guadalfeo infiltration, nevertheless from 2005 a dam was constructed changing the traditional dynamic river flow and recharge events...

  20. Guidelines for the development and environmental protection of the outcrop area in the Guarani aquifer system in Sao Paulo State, Brazil; Diretrizes para o desenvolvimento e protecao ambiental da area de afloramento do Sistema Aquifero Guarani no estado de Sao Paulo, Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Alburquerque Filho, J. L.; Carvalho, A. M. de; Ikematsu, P.; Costa Barbosa, M.; Iritani, M.; Nogueira Pressinoti, M. M.; Rocha, G.; Pereira Militao da Silva, M.; Theodorovicz, A.

    2012-11-01

    The Guarani aquifer system (GAS) is an important public water source. The unconfined areas are those where the aquifer is more vulnerable to contamination, justifying the creation of a Protection and Recovery Source Area (Area de Protecao e Recuperacao de Manancial - APRM), as established in Act 9.866/97 of Sao Paulo State. We present here the results of the project Environmental Diagnosis in Support of the Plan for the Development and Environmental Protection Plan of the Outcrop Area of the Guarani Aquifer System in Sao Paulo State (Plano de Desenvolvimento e Protecao Ambiental da Area de Afloramento do Sistema Aquifero Guarani no Estado de Sao Paulo PDPA-SAG) and describe the areas of intervention defined by this law. The characterization of the area studied focuses on the physical and socio-economic aspects of the region, in addition to the pertinent legislation. Partial results indicate that the condition of the aquifer is satisfactory, but territorial discipline continues to be of prime importance. (Author)

  1. Hydrological controls on transient aquifer storage in a karst watershed

    Science.gov (United States)

    Spellman, P.; Martin, J.; Gulley, J. D.

    2017-12-01

    While surface storage of floodwaters is well-known to attenuate flood peaks, transient storage of floodwaters in aquifers is a less recognized mechanism of flood peak attenuation. The hydraulic gradient from aquifer to river controls the magnitude of transient aquifer storage and is ultimately a function of aquifer hydraulic conductivity, and effective porosity. Because bedrock and granular aquifers tend to have lower hydraulic conductivities and porosities, their ability to attenuate flood peaks is generally small. In karst aquifers, however, extensive cave systems create high hydraulic conductivities and porosities that create low antecedent hydraulic gradients between aquifers and rivers. Cave springs can reverse flow during high discharges in rivers, temporarily storing floodwaters in the aquifer thus reducing the magnitude of flood discharge downstream. To date however, very few studies have quantified the magnitude or controls of transient aquifer storage in karst watersheds. We therefore investigate controls on transient aquifer storage by using 10 years of river and groundwater data from the Suwannee River Basin, which flows over the karstic upper Floridan aquifer in north-central Florida. We use multiple linear regression to compare the effects of three hydrological controls on the magnitude of transient aquifer storage: antecedent stage, recharge and slope of hydrograph rise. We show the dominant control on transient aquifer storage is antecedent stage, whereby lower stages result in greater magnitudes of transient aquifer storage. Our results suggest that measures of groundwater levels prior to an event can be useful in determining whether transient aquifer storage will occur and may provide a useful metric for improving predictions of flood magnitudes.

  2. State Aquifer Recharge Atlas Plates, Geographic NAD83, LDEQ (1999) [aquifer_recharge_potential_LDEQ_1988

    Data.gov (United States)

    Louisiana Geographic Information Center — This is a polygon dataset depicting the boundaries of aquifer systems in the state of Louisiana and adjacent areas of Texas, Arkansas and a portion of Mississippi....

  3. Evolution of magmatism from the uppermost cretaceous to Oligocene, and its relationship to changing tectonic regime, in the Inca de Oro-El Salvador area (Northern Chile)

    International Nuclear Information System (INIS)

    Cornejo, Paula; Matthews, Stephen

    2001-01-01

    We present geochronological and petrological data for extrusive and intrusive rocks in the Inca de Oro and El Salvador sheets (in prep.), and the Potrerillos (Tomlinson et al., 1999) and Salar de Maricunga sheets (Cornejo et al., 1998), III Region, Chile (26 o -27 o S). Most of these data were collected as part of the SERNAGEOMIN regional mapping programme. Additionally, we include published data for El Salvador and Potrerillos districts (Cornejo et al., 1997; Marsh et al., 1997; Gustafson et al., 2001). The dataset includes K/Ar, Ar/Ar and U-Pb mineral ages, which have been carefully selected for quality. The area is underlain by Carboniferous-Permian granitic basement rocks, which are covered by Triassic to Early Upper Cretaceous volcanic and sedimentary successions, including both marine and continental sequences (Cornejo et al., 1993). The period studied in this paper includes extrusive and intrusive rocks of Maastrichtian to Oligocene age, which are of particular interest since they record the 'preparation' of the lithosphere prior to, during, and after the mid-Eocene Incaic deformation and associated porphyry copper event. Shortening in the early-upper Cretaceous (95-85Ma; e.g. Mpodozis and Ramos, 1989; Arevalo and Grocott, 2000) deformed large areas of northen Chile, and marked the transition from the dominance of intra-arc extension to that of shortening punctuated by periods of extension. We recognise seven tectono-magmatic periods from the uppermost Cretaceous to Oligocene, comprising a volcanic sedimentary event contemporaneous with an extensional tectonic regime in the Upper Cretaceous, associated with graben formation, followed by an important compressive event at the beginning of the Tertiary. The middle Paleocene was again dominated by voluminous volcanic activity (collapse calderas) in an extensional regime. During the lowest Eocene the magmatic activity in the area shows a gradual transition from pyroxene-bearing to amphibole-bearing lithologies

  4. Nutrient Removal during Stormwater Aquifer Storage and Recovery in an Anoxic Carbonate Aquifer.

    Science.gov (United States)

    Vanderzalm, Joanne L; Page, Declan W; Dillon, Peter J; Barry, Karen E; Gonzalez, Dennis

    2018-03-01

    Stormwater harvesting coupled to managed aquifer recharge (MAR) provides a means to use the often wasted stormwater resource while also providing protection of the natural and built environment. Aquifers can act as a treatment barrier within a multiple-barrier approach to harvest and use urban stormwater. However, it remains challenging to assess the treatment performance of a MAR scheme due to the heterogeneity of aquifers and MAR operations, which in turn influences water treatment processes. This study uses a probabilistic method to evaluate aquifer treatment performance based on the removal of total organic C (TOC), N, and P during MAR with urban stormwater in an anoxic carbonate aquifer. Total organic C, N, and P are represented as stochastic variables and described by probability density functions (PDFs) for the "injectant" and "recovery"; these injectant and recovery PDFs are used to derive a theoretical MAR removal efficiency PDF. Four long-term MAR sites targeting one of two tertiary carbonate aquifers (T1 and T2) were used to describe the nutrient removal efficiencies. Removal of TOC and total N (TN) was dominated by redox processes, with median removal of TOC between 50 and 60% at all sites and TN from 40 to 50% at three sites with no change at the fourth. Total P removal due to filtration and sorption accounted for median removal of 29 to 53%. Thus, the statistical method was able to characterize the capacity of the anoxic carbonate aquifer treatment barrier for nutrient removal, which highlights that aquifers can be an effective long-term natural treatment option for management of water quality, as well as storage of urban stormwater. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  5. Risk assessment and management of an oil contaminated aquifer

    International Nuclear Information System (INIS)

    Braxein, A.; Daniels, H.; Rouve, G.; Rubin, H.

    1991-01-01

    This paper concerns the provision of the basic information needed for the decision making process regarding the remedial measures leading to reutilization of an oil contaminated aquifer. The study refers to the case history of jet fuel contamination of an aquifer comprising part of the coastal aquifer of Israel. Due to that contamination two major water supply wells were abandoned. This study examines the use of numerical simulations in order to restore the contamination history of the aquifer. Such simulations also provide quantitative information needed for the decision making process regarding the future management of the contaminated aquifer

  6. Remediation of a contaminated thin aquifer by horizontal wells

    Energy Technology Data Exchange (ETDEWEB)

    Breh, W.; Suttheimer, J.; Hoetzl, H. [Univ. of Karlsruhe (Germany); Frank, K. [GEO-Service GmbH, Rheinmuenster (Germany)

    1997-12-31

    At an industrial site in Bruchsal (Germany) a huge trichloroethene contamination was found. After common remedial actions proved to be widely ineffective, new investigations led to a highly contaminated thin aquifer above the main aquifer. The investigation and the beginning of the remediation of the thin aquifer by two horizontal wells is described in this paper. Special attention was given to the dependence between precipitation and the flow direction in the thin aquifer and to hydraulic connections between the thin and the main aquifer. Also a short introduction into a new remedial technique by horizontal wells and first results of the test phase of the horizontal wells are given.

  7. Aquifer transport of Th, U, Ra, and Rn in solution and colloids. 1997 annual progress report

    International Nuclear Information System (INIS)

    Wasserburg, G.J.

    1997-01-01

    'Preparations have been made to collect groundwater samples from the unconfined Pleistocene aquifer on Long Island, N.Y. from wells at Brookhaven National Lab.. Dr. Jan Naidu of the Brookhaven Safety and Environmental Protection Division has been intimately involved with the groundwater monitoring program at the site for many years, and has provided us with detailed information regarding site hydrogeology, groundwater chemistry, and monitor well locations and construction. In consultation with Dr. Naidu, a series of wells have been chosen for sampling that extend over a distance of ∼5000 feet along a single flow path, with estimated water ages of up to ∼20 years. Since the recharge area for these waters has been the source of low levels of tritium (and possibly 90 Sr) contamination, there has been considerable interest in the hydrogeology and chemistry of the area, and all information gathered at the site will be provided to BNL staff. Groundwater sampling is planned for the autumn of 1997. At this time, aquifer materials will also be obtained from the drill core repository of the USGS office in Long Island, where Mr. Henry Ku has indicated that material will be available for the use. As a complement to the studies of U and Th series nuclides, the sampling plan is being extended to include analysis of He isotopes. Concentrations of 4 He are expected to largely reflect the time-integrated recoil production by decay of the U and Th series nuclides, without losses due to adsorption or decay, and will be compared to 222 Rn concentrations, which provide recoil rates over short time periods. The concentrations of 3 He due to decay of contaminant 3 H in these waters will also be measured, and a comparison between the measured concentrations and that produced in the waters since the time of recharge will provide an indication of whether gas losses have occurred. Arrangements have been made to collaborate in this phase of the research with Dr. David Hilton of Scripps

  8. Extraction and development of inset models in support of groundwater age calculations for glacial aquifers

    Science.gov (United States)

    Feinstein, Daniel T.; Kauffman, Leon J.; Haserodt, Megan J.; Clark, Brian R.; Juckem, Paul F.

    2018-06-22

    The U.S. Geological Survey developed a regional model of Lake Michigan Basin (LMB). This report describes the construction of five MODFLOW inset models extracted from the LMB regional model and their application using the particle-tracking code MODPATH to simulate the groundwater age distribution of discharge to wells pumping from glacial deposits. The five study areas of the inset model correspond to 8-digit hydrologic unit code (HUC8) basins. Two of the basins are tributary to Lake Michigan from the east, two are tributary to the lake from the west, and one is just west of the western boundary of the Lake Michigan topographic basin. The inset models inherited many of the inputs to the parent LMB model, including the hydrostratigraphy and layering scheme, the hydraulic conductivity assigned to bedrock layers, recharge distribution, and water use in the form of pumping rates from glacial and bedrock wells. The construction of the inset models entailed modifying some inputs, most notably the grid spacing (reduced from cells 5,000 feet on a side in the parent LMB model to 500 feet on a side in the inset models). The refined grid spacing allowed for more precise location of pumped wells and more detailed simulation of groundwater/surface-water interactions. The glacial hydraulic conductivity values, the top bedrock surface elevation, and the surface-water network input to the inset models also were modified. The inset models are solved using the MODFLOW–NWT code, which allows for more robust handling of conditions in unconfined aquifers than previous versions of MODFLOW. Comparison of the MODFLOW inset models reveals that they incorporate a range of hydrogeologic conditions relative to the glacial part of the flow system, demonstrated by visualization and analysis of model inputs and outputs and reflected in the range of ages generated by MODPATH for existing and hypothetical glacial wells. Certain inputs and outputs are judged to be candidate predictors that, if

  9. Flow regime analysis for fluid injection into a confined aquifer: implications for CO2 sequestration

    Science.gov (United States)

    Guo, B.; Zheng, Z.; Celia, M. A.; Stone, H.

    2015-12-01

    Carbon dioxide injection into a confined saline aquifer may be modeled as an axisymmetric two-phase flow problem. Assuming the two fluids segregate in the vertical direction due to strong buoyancy, and neglecting capillary pressure and miscibility, the lubrication approximation leads to a nonlinear advection-diffusion equation that describes the evolution of the sharp fluid-fluid interface. The flow behaviors in the system are controlled by two dimensionless groups: M, the viscosity ratio of the displaced fluid relative to injected fluid, and Γ , the gravity number, which represents the relative importance of buoyancy and fluid injection. Four different analytical solutions can be derived as the asymptotic approximations, representing specific values of the parameter pairs. The four solutions correspond to: (1) Γ 1; and (4) Γ >> 1, any M values. The first two of these solutions are new, while the third corresponds to the solution of Nordbotten and Celia (2006) for confined injections and the fourth corresponds to the solution of (Lyle et al., 2005) for gravity currents in an unconfined aquifer. Overall, the various axisymmetric flows can be summarized in a Γ-M regime diagram with five distinct dynamic behaviors including the four asymptotic regimes and an intermediate regime (Fig. 1). Data from a number of CO2 injection sites around the world can be used to compute the two dimensionless groups Γ and M associated with each injection. When plotted on the regime diagram, these values show the flow behavior for each injection and how the values vary from site to site. For all the CO2 injections, M is always larger than 1, while Γ can range from 0.01 up to 100. The pairs of (Γ, M) with lower Γ values correspond to solution (3), while the ones with higher Γ values can move up to the intermediate regime and the flow regime for solution (4). The higher values of Γ correspond to pilot-scale injections with low injection rates; most industrial-scale injection

  10. Lava tubes and aquifer vulnerability in the upper Actopan River basin, Veracruz, México

    Science.gov (United States)

    Espinasa-Pereña, R.; Delgado Granados, H.

    2011-12-01

    Rapid infiltration leads to very dry conditions on the surface of some volcanic terrains, with large allogenic streams sometimes sinking underground upon reaching a lava flow. Aquifers in lava flows tend to be heterogeneous and discontinuous, generally unconfined and fissured, and have high transmissivity. Springs associated with basalts may be very large but are typically restricted to lava-flow margins. Concern has been expressed regarding the potential for lava-tube caves to facilitate groundwater contamination similar to that afflicting some karst aquifers (Kempe et al., 2003; Kiernan et al., 2002; Halliday 2003). The upper Actopan River basin is a series of narrow valleys excavated in Tertiary volcanic brechias. Several extensive Holocene basaltic tube-fed lava flows have partially filled these valleys. The youngest and longest flow originates at El Volcancillo, a 780 ybP monogenetic volcano. It is over 50 km long, and was fed through a major master tube, the remains of which form several lava-tube caves (Gassos and Espinasa-Pereña, 2008). Another tube-fed flow initiates at a vent at the bottom of Barranca Huichila and can be followed for 7 km to where it is covered by the Volcancillo flow. The Huichila River is captured by this system of lava tubes and can be followed through several underground sections. In dry weather the stream disappears at a sump in one of these caves, although during hurricanes it overflows the tube, floods the Tengonapa plain, and finally sinks through a series of skylights into the master tube of the Volcancillo flow. Near villages, the cave entrances are used as trash dumps, which are mobilized during floods. These include household garbage, organic materials associated with agriculture and even medical supplies. This is a relatively recent phenomenon, caused by population growth and the building of houses above the lava flows. The water resurges at El Descabezadero, gushing from fractures in the lava above the underlying brechias

  11. Biogeochemical aspects of aquifer thermal energy storage

    NARCIS (Netherlands)

    Brons, H.J.

    1992-01-01

    During the process of aquifer thermal energy storage the in situ temperature of the groundwater- sediment system may fluctuate significantly. As a result the groundwater characteristics can be considerably affected by a variety of chemical, biogeochemical and microbiological

  12. Hydrochemical characterization of groundwater aquifer using ...

    African Journals Online (AJOL)

    Hydrochemical data analysis revealed four sources of solutes. The processes responsible for their enrichment include: chemical weathering, leaching of the overlying sediments, domestic activities, climatic condition and the flow pattern of the aquifer. The factors have contributed to the changes of the groundwater chemistry ...

  13. Transient well flow in vertically heterogeneous aquifers.

    NARCIS (Netherlands)

    Hemker, C.J.

    1999-01-01

    A solution for the general problem of computing well flow in vertically heterogeneous aquifers is found by an integration of both analytical and numerical techniques. The radial component of flow is treated analytically; the drawdown is a continuous function of the distance to the well. The

  14. Aquifer restoration: state of the art

    National Research Council Canada - National Science Library

    Knox, Robert C; Knox, R. C

    1986-01-01

    ... of chemicals or waste materials, improper underground injection of liquid wastes, and placement of septic tank systems in hydrologically and geologically unsuitable locations. Incidents of aquifer pollution from man's waste disposal activities have been discovered with increasing regularity. At the same time, demands for groundwater usage have been inc...

  15. Sedimentological analysis of a contaminated groundwater aquifer

    International Nuclear Information System (INIS)

    Towse, D.

    1991-01-01

    The use of sedimentological reservoir analysis techniques adapted from standard oilfield practice can improve the efficiency and reduce the costs of the evaluation of groundwater aquifers and the design of restoration programs. An evaluation/restoration program at a site in California drilled over 200 test wells in about 750 ac. All wells were logged lithologically and with wireline. The shallow aquifer is a complex braided alluvial floodplain deposit of Late Quaternary age. Analysis demonstrates depositional and erosional responses to periodic hinterland uplifts and to changing climatic conditions. Channel, overbank, lacustrine, and minor deltaic deposits can be recognized. The aquifer architecture has been interpreted to explain the movement of fuel and halogenated hydrocarbon solvents in the sediments and water. Routine engineering geology techniques and hydrologic tests were used to evaluate contamination and to design experimental restoration processes. As demonstrated here, sedimentological techniques show promise in reducing the costs and time required for this type of study. The abundant detailed data will be used in an attempt to develop a microcomputer-based expert system for rapid preliminary analyses of similar aquifers or reservoirs

  16. VULNERABILITY AND RISK OF CONTAMINATION KARSTIC AQUIFERS

    Directory of Open Access Journals (Sweden)

    Yameli Aguilar

    2013-08-01

    Full Text Available Karstic systems occupy nearly 20% of the surface of the earth and are inhabited by numerous human communities. Karstic aquifers are the most exposed to pollution from human activities. Pollution of karstic aquifers is a severe environmental problem worldwide.  In order to face the vulnerability of karstic aquifers to pollution, researchers have created a diversity of study approaches and models, each one having their own strengths and weaknesses depending on the discipline from which they were originated, thus requiring a thorough discussion within the required multidisciplinary character. The objective of this article was to analyze the theoretical and methodological approaches applied to the pollution of karstic aquifers. The European hydrogeological, land evaluation, hydropedological and a geographic approach were analyzed. The relevance of a geomorphological analysis as a cartographic basis for the analysis of vulnerability and risks were emphasized. From the analysis of models, approaches and methodologies discussed the following recommendation is made: to form an interdisciplinary work team, to elaborate a conceptual model according to the site and the working scale and to e, apply and validate the model.

  17. isotopic characteristics of aquifers in sinai

    International Nuclear Information System (INIS)

    Al-Gamal, S.A.

    2004-01-01

    the environmental isotopes data (expressed as δ 2 d and δ 18 O) of different aquifers in sinai were treated using correlation and regression techniques. whereas, rain water isotopic data were treated using empirical orthogonal functions (EOF) techniques. environmental isotopes for different aquifers expressed in terms of O-18 and H-2, were taken to represent the isotopic characteristics. regression equations using the highly correlated variables of δ 2 d and δ 18 O were constructed for each aquifer. the latitudinal variations (of rainwater in sinai and selected climatic stations east mediterranean ) versus rainwater isotopic compositions were analyzed using the normalized variables. it was found that the latitudinal variations of the rainwater isotopic compositions ( δ 2 D, δ 18 O), vapor pressure, and surface temperature occurred in parallel and decreased with latitude. in the east mediterranean, empirical linear relationship between altitude and δ 2 D has indicted that the rate of change of δ 2 D with height is comparable with the dry lapse rate in the atmosphere.The obtained regression equations of environmental isotopes data have impacted on different slopes and different constants expressing the non-homogeneity in the isotopic composition of rainwater recharging the aquifers of sinai , due to the presence of different air masses

  18. SAR interferometry monitoring of subsidence in a detritic basin related to water depletion in the underlying confined carbonate aquifer (Torremolinos, southern Spain).

    Science.gov (United States)

    Ruiz-Constán, A; Ruiz-Armenteros, A M; Martos-Rosillo, S; Galindo-Zaldívar, J; Lazecky, M; García, M; Sousa, J J; Sanz de Galdeano, C; Delgado-Blasco, J M; Jiménez-Gavilán, P; Caro-Cuenca, M; Luque-Espinar, J A

    2018-04-30

    This research underlines the need to improve water management policies for areas linked to confined karstic aquifers subjected to intensive exploitation, and to develop additional efforts towards monitoring their subsidence evolution. We analyze subsidence related to intensive use of groundwater in a confined karstic aquifer, through the use of the InSAR technique, by the southern coast of Spain (Costa del Sol). Carbonates are overlain by an unconfined detritic aquifer with interlayered high transmissivity rocks, in connection with the Mediterranean Sea, where the water level is rather stable. Despite this, an accumulated deformation in the line-of-sight (LOS) direction greater than -100 mm was observed by means of the ERS-1/2 (1992-2000) and Envisat (2003-2009) satellite SAR sensors. During this period, the Costa del Sol experienced a major population increase due to the expansion of the tourism industry, with the consequent increase in groundwater exploitation. The maximum LOS displacement rates recorded during both time spans are respectively -6 mm/yr and -11 mm/yr, respectively. During the entire period, there was an accumulated descent of the confined water level of 140 m, and several fluctuations of more than 80 m correlating with the subsidence trend observed for the whole area. Main sedimentary depocenters (up to 800 m), revealed by gravity prospecting, partly coincide with areas of subsidence maxima; yet ground deformation is also influenced by other factors, the main ones being the fine-grained facies distribution and rapid urbanization due to high touristic pressure. Copyright © 2018 Elsevier B.V. All rights reserved.

  19. Hydrogeology - AQUIFER_SYSTEMS_BEDROCK_IDNR_IN: Bedrock Aquifer Systems of Indiana (Indiana Department of Natural Resources, 1:500,000, Polygon Shapefile)

    Data.gov (United States)

    NSGIC State | GIS Inventory — AQUIFER_SYSTEMS_BEDROCK_IDNR_IN is a polygon shapefile that shows bedrock aquifer systems of the State of Indiana. The source scale of the map depicting the aquifers...

  20. Arsenic release during managed aquifer recharge (MAR)

    Science.gov (United States)

    Pichler, T.; Lazareva, O.; Druschel, G.

    2013-12-01

    The mobilization and addition of geogenic trace metals to groundwater is typically caused by anthropogenic perturbations of the physicochemical conditions in the aquifer. This can add dangerously high levels of toxins to groundwater, thus compromising its use as a source of drinking water. In several regions world-wide, aquifer storage and recovery (ASR), a form of managed aquifer recharge (MAR), faces the problem of arsenic release due to the injection of oxygenated storage water. To better understand this process we coupled geochemical reactive transport modeling to bench-scale leaching experiments to investigate and verify the mobilization of geogenic arsenic (As) under a range of redox conditions from an arsenic-rich pyrite bearing limestone aquifer in Central Florida. Modeling and experimental observations showed similar results and confirmed the following: (1) native groundwater and aquifer matrix, including pyrite, were in chemical equilibrium, thus preventing the release of As due to pyrite dissolution under ambient conditions; (2) mixing of oxygen-rich surface water with oxygen-depleted native groundwater changed the redox conditions and promoted the dissolution of pyrite, and (3) the behavior of As along a flow path was controlled by a complex series of interconnected reactions. This included the oxidative dissolution of pyrite and simultaneous sorption of As onto neo-formed hydrous ferric oxides (HFO), followed by the reductive dissolution of HFO and secondary release of adsorbed As under reducing conditions. Arsenic contamination of drinking water in these systems is thus controlled by the re-equilibration of the system to more reducing conditions rather than a purely oxidative process.

  1. Determination of recharge modes of aquifers by use of chemical and isotopic tracers. Case study of the contact zone between Western High-Atlas Chain and Souss Plain (SW Morocco

    Directory of Open Access Journals (Sweden)

    Tagma, T.

    2008-06-01

    Full Text Available Determination of the origin of recharge of the unconfined aquifer in the right side of the Souss wadi between Agadir and Taroudant (South-western of Morocco was based on the use of hydrochemical and isotopic analysis of groundwater, surface water and springs of the contact zone between the High-Atlas Chain and the Souss plain.The correspondence in the space evolution of the various chemical elements of evaporitic origin (SO42-, Cl-, Sr2+ in groundwater, piedmont springs, and surface water reveals the existence of recharge water from the adjacent High-Atlas Chain.The various recharge modes of the different aquifers (High Atlas and Souss plain determined by isotopic analysis, shows that the source of groundwater for the unconfined Souss aquifer seems to be composite between a direct infiltration on the High-Atlas tributaries and a remote recharge from the bordering High Atlas aquifers.La determinación del origen de los aportes de agua de la capa freática de la ribera derecha del rio Souss entre Agadir y Taroudant (Suroeste de Marruecos se ha basado en la hidroquímica y el análisis isotópico de las aguas subterráneas, aguas superficiales y manantiales de la zona de contacto entre el Alto Atlas y la llanura de Souss.La correspondencia en la evolución espacial de los diferentes elementos químicos de origen evaporítico (SO42-, Cl-, Sr2+ en las aguas subterráneas, manantiales de pie de monte y aguas superficiales, revela la existencia de una recarga de agua procedente de la cadena del Alto Atlas. El análisis de los modos de recarga de los diferentes acuíferos (Alto Atlas y llanura de Souss determinado por análisis isotópico, demuestra que la alimentación de la capa freática de Souss a partir del Alto Atlas parece ser mixta, compuesta por una infiltración directa de los afluentes del Alto Atlas y una alimentación lejana desde los acuiferos que limitan con el borde del Alto Atlas.

  2. Monitoring Aquifer Depletion from Space: Case Studies from the Saharan and Arabian Aquifers

    Science.gov (United States)

    Ahmed, M.; Sultan, M.; Wahr, J. M.; Yan, E.

    2013-12-01

    Access to potable fresh water resources is a human right and a basic requirement for economic development in any society. In arid and semi-arid areas, the characterization and understanding of the geologic and hydrologic settings of, and the controlling factors affecting, these resources is gaining increasing importance due to the challenges posed by increasing population. In these areas, there is immense natural fossil fresh water resources stored in large extensive aquifers, the transboundary aquifers. Yet, natural phenomena (e.g., rainfall patterns and climate change) together with human-related factors (e.g., population growth, unsustainable over-exploitation, and pollution) are threatening the sustainability of these resources. In this study, we are developing and applying an integrated cost-effective approach to investigate the nature (i.e., natural and anthropogenic) and the controlling factors affecting the hydrologic settings of the Saharan (i.e., Nubian Sandstone Aquifer System [NSAS], Northwest Sahara Aquifer System [NWSA]) and Arabian (i.e., Arabian Peninsula Aquifer System [APAS]) aquifer systems. Analysis of the Gravity Recovery and Climate Experiment (GRACE)-derived Terrestrial Water Storage (TWS) inter-annual trends over the NSAS and the APAS revealed two areas of significant TWS depletions; the first correlated with the Dakhla Aquifer System (DAS) in the NSAS and second with the Saq Aquifer System (SAS) in the APAS. Annual depletion rates were estimated at 1.3 × 0.66 × 109 m3/yr and 6.95 × 0.68 × 109 m3/yr for DAS and SAS, respectively. Findings include (1) excessive groundwater extraction, not climatic changes, is responsible for the observed TWS depletions ;(2) the DAS could be consumed in 350 years if extraction rates continue to double every 50 years and the APAS available reserves could be consumed within 60-140 years at present extraction (7.08 × 109 m3/yr) and depletion rates; and (3) observed depletions over DAS and SAS and their

  3. Structural control on the deep hydrogeological and geothermal aquifers related to the fractured Campanian-Miocene reservoirs of north-eastern Tunisia foreland constrained by subsurface data

    Science.gov (United States)

    Khomsi, Sami; Echihi, Oussema; Slimani, Naji

    2012-03-01

    A set of different data including high resolution seismic sections, petroleum wire-logging well data, borehole piezometry, structural cross-sections and outcrop analysis allowed us to characterise the tectonic framework, and its relationships with the deep aquifers seated in Cretaceous-Miocene deep reservoirs. The structural framework, based on major structures, controls the occurrence of deep aquifers and sub-basin aquifer distributions. Five structural domains can be defined, having different morphostructural characteristics. The northernmost domain lying on the north-south axis and Zaghouan thrust system is a domain of recharge by underflow of the different subsurface reservoirs and aquifers from outcrops of highly fractured reservoirs. On the other hand, the morphostructural configuration controls the piezometry of underground flows in the Plio-Quaternary unconfined aquifer. In the subsurface the Late Cretaceous-Miocene reservoirs are widespread with high thicknesses in many places and high porosities and connectivities especially along major fault corridors and on the crestal parts of major anticlines. Among all reservoirs, the Oligo-Miocene, detritic series are widespread and present high cumulative thicknesses. Subsurface and fieldwork outline the occurrence of 10 fractured sandy reservoirs for these series with packages having high hydrodynamic and petrophysical characteristics. These series show low salinities (maximum 5 g/l) in the northern part of the study area and will constitute an important source of drinkable water for the next generations. A regional structural cross-section is presented, compiled from all the different data sets, allowing us to define the major characteristics of the hydrogeological-hydrogeothermal sub-basins. Eight hydrogeological provinces are defined from north-west to south-east. A major thermal anomaly is clearly identified in the south-eastern part of the study area in Sfax-Sidi Il Itayem. This anomaly is possibly related to

  4. San Pedro River Aquifer Binational Report

    Science.gov (United States)

    Callegary, James B.; Minjárez Sosa, Ismael; Tapia Villaseñor, Elia María; dos Santos, Placido; Monreal Saavedra, Rogelio; Grijalva Noriega, Franciso Javier; Huth, A. K.; Gray, Floyd; Scott, C. A.; Megdal, Sharon; Oroz Ramos, L. A.; Rangel Medina, Miguel; Leenhouts, James M.

    2016-01-01

    The United States and Mexico share waters in a number of hydrological basins and aquifers that cross the international boundary. Both countries recognize that, in a region of scarce water resources and expanding populations, a greater scientific understanding of these aquifer systems would be beneficial. In light of this, the Mexican and U.S. Principal Engineers of the International Boundary and Water Commission (IBWC) signed the “Joint Report of the Principal Engineers Regarding the Joint Cooperative Process United States-Mexico for the Transboundary Aquifer Assessment Program" on August 19, 2009 (IBWC-CILA, 2009). This IBWC “Joint Report” serves as the framework for U.S.-Mexico coordination and dialogue to implement transboundary aquifer studies. The document clarifies several details about the program such as background, roles, responsibilities, funding, relevance of the international water treaties, and the use of information collected or compiled as part of the program. In the document, it was agreed by the parties involved, which included the IBWC, the Mexican National Water Commission (CONAGUA), the U.S. Geological Survey (USGS), and the Universities of Arizona and Sonora, to study two priority binational aquifers, one in the San Pedro River basin and the other in the Santa Cruz River basin. This report focuses on the Binational San Pedro Basin (BSPB). Reasons for the focus on and interest in this aquifer include the fact that it is shared by the two countries, that the San Pedro River has an elevated ecological value because of the riparian ecosystem that it sustains, and that water resources are needed to sustain the river, existing communities, and continued development. This study describes the aquifer’s characteristics in its binational context; however, most of the scientific work has been undertaken for many years by each country without full knowledge of the conditions on the other side of the border. The general objective of this study is to

  5. Herbicides and their transformation products in source-water aquifers tapped by public-supply wells in Illinois, 2001-02

    Science.gov (United States)

    Mills, Patrick C.; McMillan, William D.

    2004-01-01

    During 2001-02, ground-water samples were collected from 117 public-supply wells distributed throughout Illinois to evaluate the occurrence of herbicides and their transformation products in the State?s source-water aquifers. Wells were selected using a stratified-random method to ensure representation of the major types of source-water aquifers in the State. Samples were analyzed for 18 herbicides and 18 transformation products, including 3 triazine and 14 chloroacetanilide products. Herbicide compounds (field-applied parent herbicides and their transformation products) were detected in 34 percent of samples. A subset of samples was collected unfiltered to determine if analytical results for herbicides in unfiltered samples are similar to those in paired filtered samples and, thus, can be considered equally representative of herbicide concentrations in ground water supplied to the public. The study by the U.S. Geological Survey was done in cooperation with the Illinois Environmental Protection Agency. Parent herbicides were detected in only 4 percent of all samples. The six most frequently detected herbicide compounds (from 5 to 28 percent of samples) were chloroacetanilide transformation products. The frequent occurrence of transformation products and their higher concentrations relative to those of most parent herbicides confirm the importance of obtaining information on transformation products to understand the mobility and fate of herbicides in ground-water systems. No sample concentrations determined during this study exceeded current (2003) Federal or State drinking-water standards; however, standards are established for only seven parent herbicides. Factors related to the occurrence of herbicide compounds in the State?s source-water aquifers include unconsolidated and unconfined conditions, various hydrogeologic characteristics and well-construction aspects at shallow depths, and proximity to streams. Generally, the closer an aquifer (or well location) is

  6. Sustainable development and management of an aquifer system in western Turkey

    Science.gov (United States)

    Sakiyan, Jale; Yazicigil, Hasan

    This study presents the establishment of sustainable development and management policies for the Küçük Menderes River Basin aquifer system in western Turkey. Geological, hydrogeological, and geophysical data are used conjunctively to define various hydrogeological units and their geometry. Distributions of hydraulic-parameter values and recharge are estimated by geostatistical methods and hydrologic simulations, respectively. A finite-difference groundwater flow model is used to represent the unconfined flow in the aquifer system. The model has been calibrated under steady state and transient conditions. The resulting model was used to test seven management scenarios for a planning period of 21 years to determine the so-called safe yield and sustainable yield of the aquifer system and to investigate the potential impacts of four planned surface water reservoirs on groundwater resources in the basin. The results demonstrate that the continuation of the present pumping rates exceeds both the safe yield and the sustainable yield of the aquifer system. Consequently, the growing need for irrigation water should be met by the construction of the planned surface water reservoirs and the implementation of efficient water management policies and plans. Cette étude présente la proposition d'une politique de développement et de gestion durables du système aquifère du bassin du Petit Mendérès dans l'ouest de la Turquie. Des données géologiques, hydrogéologiques et géophysiques ont été utilisées conjointement pour définir les différentes unités hydrogéologiques et leur géométrie. Les distributions des paramètres hydrauliques et de la recharge ont été estimées respectivement par des méthodes géostatistiques et des simulations hydrologiques. Un modèle d'écoulement souterrain aux éléments finis a été utilisé pour représenter l'écoulement non captif dans le système aquifère. Le modèle a été calibré dans des conditions de r

  7. Source, variability, and transformation of nitrate in a regional karst aquifer: Edwards aquifer, central Texas

    Energy Technology Data Exchange (ETDEWEB)

    Musgrove, M., E-mail: mmusgrov@usgs.gov [U.S. Geological Survey, 1505 Ferguson Lane, Austin, TX 78754 (United States); Opsahl, S.P. [U.S. Geological Survey, 5563 DeZavala, Ste. 290, San Antonio, TX 78249 (United States); Mahler, B.J. [U.S. Geological Survey, 1505 Ferguson Lane, Austin, TX 78754 (United States); Herrington, C. [City of Austin Watershed Protection Department, Austin, TX 78704 (United States); Sample, T.L. [U.S. Geological Survey, 19241 David Memorial Dr., Ste. 180, Conroe, TX 77385 (United States); Banta, J.R. [U.S. Geological Survey, 5563 DeZavala, Ste. 290, San Antonio, TX 78249 (United States)

    2016-10-15

    Many karst regions are undergoing rapid population growth and expansion of urban land accompanied by increases in wastewater generation and changing patterns of nitrate (NO{sub 3}{sup −}) loading to surface and groundwater. We investigate variability and sources of NO{sub 3}{sup −} in a regional karst aquifer system, the Edwards aquifer of central Texas. Samples from streams recharging the aquifer, groundwater wells, and springs were collected during 2008–12 from the Barton Springs and San Antonio segments of the Edwards aquifer and analyzed for nitrogen (N) species concentrations and NO{sub 3}{sup −} stable isotopes (δ{sup 15}N and δ{sup 18}O). These data were augmented by historical data collected from 1937 to 2007. NO{sub 3}{sup −} concentrations and discharge data indicate that short-term variability (days to months) in groundwater NO{sub 3}{sup −} concentrations in the Barton Springs segment is controlled by occurrence of individual storms and multi-annual wet-dry cycles, whereas the lack of short-term variability in groundwater in the San Antonio segment indicates the dominance of transport along regional flow paths. In both segments, longer-term increases (years to decades) in NO{sub 3}{sup −} concentrations cannot be attributed to hydrologic conditions; rather, isotopic ratios and land-use change indicate that septic systems and land application of treated wastewater might be the source of increased loading of NO{sub 3}{sup −}. These results highlight the vulnerability of karst aquifers to NO{sub 3}{sup −} contamination from urban wastewater. An analysis of N-species loading in recharge and discharge for the Barton Springs segment during 2008–10 indicates an overall mass balance in total N, but recharge contains higher concentrations of organic N and lower concentrations of NO{sub 3}{sup −} than does discharge, consistent with nitrification of organic N within the aquifer and consumption of dissolved oxygen. This study demonstrates

  8. Source, variability, and transformation of nitrate in a regional karst aquifer: Edwards aquifer, central Texas

    International Nuclear Information System (INIS)

    Musgrove, M.; Opsahl, S.P.; Mahler, B.J.; Herrington, C.; Sample, T.L.; Banta, J.R.

    2016-01-01

    Many karst regions are undergoing rapid population growth and expansion of urban land accompanied by increases in wastewater generation and changing patterns of nitrate (NO 3 − ) loading to surface and groundwater. We investigate variability and sources of NO 3 − in a regional karst aquifer system, the Edwards aquifer of central Texas. Samples from streams recharging the aquifer, groundwater wells, and springs were collected during 2008–12 from the Barton Springs and San Antonio segments of the Edwards aquifer and analyzed for nitrogen (N) species concentrations and NO 3 − stable isotopes (δ 15 N and δ 18 O). These data were augmented by historical data collected from 1937 to 2007. NO 3 − concentrations and discharge data indicate that short-term variability (days to months) in groundwater NO 3 − concentrations in the Barton Springs segment is controlled by occurrence of individual storms and multi-annual wet-dry cycles, whereas the lack of short-term variability in groundwater in the San Antonio segment indicates the dominance of transport along regional flow paths. In both segments, longer-term increases (years to decades) in NO 3 − concentrations cannot be attributed to hydrologic conditions; rather, isotopic ratios and land-use change indicate that septic systems and land application of treated wastewater might be the source of increased loading of NO 3 − . These results highlight the vulnerability of karst aquifers to NO 3 − contamination from urban wastewater. An analysis of N-species loading in recharge and discharge for the Barton Springs segment during 2008–10 indicates an overall mass balance in total N, but recharge contains higher concentrations of organic N and lower concentrations of NO 3 − than does discharge, consistent with nitrification of organic N within the aquifer and consumption of dissolved oxygen. This study demonstrates that subaqueous nitrification of organic N in the aquifer, as opposed to in soils, might be a

  9. Aquifer thermal energy storage in Finland

    Energy Technology Data Exchange (ETDEWEB)

    Iihola, H; Ala-Peijari, T; Seppaenen, H

    1988-01-01

    The rapid changes and crises in the field of energy during the 1970s and 1980s have forced us to examine the use of energy more critically and to look for new ideas. Seasonal aquifer thermal energy storage (T < 100/sup 0/C) on a large scale is one of the grey areas which have not yet been extensively explored. However, projects are currently underway in a dozen countries. In Finland there have been three demonstration projects from 1974 to 1987. International co-operation under the auspices of the International Energy Agency, Annex VI, 'Environmental and Chemical Aspects of Thermal Energy Storage in Aquifers and Research and Development of Water Treatment Methods' started in 1987. The research being undertaken in 8 countries includes several elements fundamental to hydrochemistry and biochemistry.

  10. Study of Aquifer Thermal Energy Storage

    Science.gov (United States)

    Okuyama, Masaaki; Umemiya, Hiromichi; Shibuya, Ikuko; Haga, Eiji

    Yamagata University 'Aquifer Thermal Energy Storage (ATES)' is the experimental system which has been running since 1982. From the results for along terms of experiments, we obtain many important knowledge. This paper presents the accomplishments for 16 years and the characteristics of thermal energy storage in thermal energy storage well. The conclusions show as follows. 1)In recent years, the thermal recovery factor of warm energy storage well becomes almost constant at about 60%. 2) The thermal recovery factor of cool energy storage well increases gradually and becomes at about 15%. 3) Since the ferric colloidal dam is formed in aquifer, thermal recovery factor increase year after year. 4) Back wash can remove clogging for ferric colloidal dam. 5) The apparent thermal diffusivity decrease gradually due to ferric colloidal dam.

  11. Increasing freshwater recovery upon aquifer storage : A field and modelling study of dedicated aquifer storage and recovery configurations in brackish-saline aquifers

    NARCIS (Netherlands)

    Zuurbier, Koen

    2016-01-01

    The subsurface may provide opportunities for robust, effective, sustainable, and cost-efficient freshwater management solutions. For instance, via aquifer storage and recovery (ASR; Pyne, 2005): “the storage of water in a suitable aquifer through a well during times when water is available, and the

  12. Understanding Uranium Behavior in a Reduced Aquifer

    Science.gov (United States)

    Janot, N.; Lezama-Pacheco, J. S.; Williams, K. H.; Bernier-Latmani, R.; Long, P. E.; Davis, J. A.; Fox, P. M.; Yang, L.; Giammar, D.; Cerrato, J. M.; Bargar, J.

    2012-12-01

    Uranium contamination of groundwater is a concern at several US Department of Energy sites, such Old Rifle, CO. Uranium transport in the environment is mainly controlled by its oxidation state, since oxidized U(VI) is relatively mobile, whereas U(IV) is relatively insoluble. Bio-remediation of contaminated aquifers aims at immobilizing uranium in a reduced form. Previous laboratory and field studies have shown that adding electron donor (lactate, acetate, ethanol) to groundwater stimulates the activity of metal- and sulfate-reducing bacteria, which promotes U(VI) reduction in contaminated aquifers. However, obtaining information on chemical and physical forms of U, Fe and S species for sediments biostimulated in the field, as well as kinetic parameters such as U(VI) reduction rate, is challenging due to the low concentration of uranium in the aquifers (typically bio-remediation experiment at the Old Rifle site, CO, from early iron-reducing conditions to the transition to sulfate-reducing conditions. Several in-well chromatographic columns packed with sediment were deployed and were sampled at different days after the start of bio-reduction. X-ray absorption spectroscopy and X-ray microscopy were used to obtain information on Fe, S and U speciation and distribution. Chemical extractions of the reduced sediments have also been performed, to determine the rate of Fe(II) and U(IV) accumulation.

  13. Carbon-14 measurements in aquifers with methane

    International Nuclear Information System (INIS)

    Barker, J.F.; Fritz, P.; Brown, R.M.

    1979-01-01

    A survey of various groundwater systems indicates that methane is a common trace constituent and occasionally a major carbon species in groundwaters. Thermocatalytic methane had delta 13 Csub(CH 4 )>-45 per mille and microbially produced or biogenic methane had delta 13 Csub(CH 4 ) 13 C values for the inorganic carbon. Thermocatalytic methane had no apparent effect on the inorganic carbon. Because methanogenesis seriously affects the carbon isotope geochemistry of groundwaters, the correction of raw 14 C ages of affected groundwaters must consider these effects. Conceptual models are developed which adjust the 14 C activity of the groundwater for the effects of methanogenesis and for the dilution of carbon present during infiltration by simple dissolution of rock carbonate. These preliminary models are applied to groundwaters from the Alliston sand aquifer where methanogenesis has affected most samples. In this system, methanogenic bacteria using organic matter present in the aquifer matrix as substrate have added inorganic carbon to the groundwater which has initiated further carbonate rock dissolution. These processes have diluted the inorganic carbon 14 C activity. The adjusted groundwater ages can be explained in terms of the complex hydrogeology of this aquifer, but also indicate that these conceptual models must be more rigorously tested to evaluate their appropriateness. (author)

  14. Microbiological risks of recycling urban stormwater via aquifers.

    Science.gov (United States)

    Page, D; Gonzalez, D; Dillon, P

    2012-01-01

    With the release of the Australian Guidelines for Water Recycling: Managed Aquifer Recharge (MAR), aquifers are now being included as a treatment barrier when assessing risk of recycled water systems. A MAR research site recharging urban stormwater in a confined aquifer was used in conjunction with a Quantitative Microbial Risk Assessment to assess the microbial pathogen risk in the recovered water for different end uses. The assessment involved undertaking a detailed assessment of the treatment steps and exposure controls, including the aquifer, to achieve the microbial health-based targets.

  15. Preliminary characterization of an alpine karst aquifer in a complex geological setting using the KARSYS approach. Picos de Europa, North Spain

    Science.gov (United States)

    Ballesteros, Daniel; Malard, Arnauld; Jeannin, Pierre-Yves; Jiménez-Sánchez, Montserrat; García-Sansegundo, Joaquín; Meléndez, Mónica; Sendra, Gemma

    2013-04-01

    Research applied to karst aquifers linked to a homogeneous limestone in high mountain areas affected by several tectonic events is a hard task, due to methodological constraints and the uncertainties of the geological data. The KARSYS approach (Jeannin et al. 2012) is based on the combination of existing geological data and basic principles of karst hydraulic, allowing for characterizing the geometry of an aquifer considering a smaller amount of data than other methods. The Picos de Europa (North Spain) is an alpine karst massif with a surface area of 700 km2, peaks up to 2,648 m and fluvial gorges up to 2,000 m deep, including about 270 km of cave passage. The bedrock is mainly composed of Ordovician quartzite covered by massive Carboniferous limestone and is affected by two systems of thrusts and other faults. The most of the geological structures are from Variscan orogeny (Carboniferous in age), some of them could be originated or modified during the Permian-Mesozoic extensional episode, and the others were originated or reactivated during the Alpine Orogeny. Therefore, the Picos de Europa can be considered as a complex geological environment in which usual hydrogeological methods are difficult to use. The aim of this study is to characterize the geometry of the Picos de Europa aquifers applying the KARSYS approach. The approach includes: 1) the identification of aquifer and aquiclude formations; 2) the inventory of the main springs; 3) the establishment of a 3D geological model, focused on the aquifer boundaries; 4) the implementation of the hydraulic features within the 3D model and the delineation of the karst system. The main aquifer of the Picos de Europa is developed within the Carboniferous limestone and displays a complex geometry generally limited and divided into several unconfined groundwater bodies by Ordovician to Carboniferous rocks related to the thrusts. The lowest limit of the aquifer is marked by the N-dipping detachment level of the thrusts

  16. Restoration of Wadi Aquifers by Artificial Recharge with Treated Waste Water

    KAUST Repository

    Missimer, Thomas M.; Drewes, Jö rg E.; Amy, Gary L.; Maliva,, Robert G.; Keller, Stephanie

    2012-01-01

    , such as damage to sensitive nearshore marine environments and creation of high-salinity interior surface water areas. An investigation of the hydrogeology of wadi aquifers in Saudi Arabia revealed that these aquifers can be used to develop aquifer recharge

  17. Hydrogeology and Aquifer Storage and Recovery Performance in the Upper Floridan Aquifer, Southern Florida

    Science.gov (United States)

    Reese, Ronald S.; Alvarez-Zarikian, Carlos A.

    2007-01-01

    Well construction, hydraulic well test, ambient water-quality, and cycle test data were inventoried and compiled for 30 aquifer storage and recovery facilities constructed in the Floridan aquifer system in southern Florida. Most of the facilities are operated by local municipalities or counties in coastal areas, but five sites are currently being evaluated as part of the Comprehensive Everglades Restoration Plan. The relative performance of all sites with adequate cycle test data was determined, and compared with four hydrogeologic and design factors that may affect recovery efficiency. Testing or operational cycles include recharge, storage, and recovery periods that each last days or months. Cycle test data calculations were made including the potable water (chloride concentration of less than 250 milligrams per liter) recovery efficiency per cycle, total recovery efficiency per cycle, and cumulative potable water recovery efficiencies for all of the cycles at each site. The potable water recovery efficiency is the percentage of the total amount of potable water recharged for each cycle that is recovered; potable water recovery efficiency calculations (per cycle and cumulative) were the primary measures used to evaluate site performance in this study. Total recovery efficiency, which is the percent recovery at the end of each cycle, however, can be substantially higher and is the performance measure normally used in the operation of water-treatment plants. The Upper Floridan aquifer of the Floridan aquifer system currently is being used, or planned for use, at 29 of the aquifer storage and recovery sites. The Upper Floridan aquifer is continuous throughout southern Florida, and its overlying confinement is generally good; however, the aquifer contains brackish to saline ground water that can greatly affect freshwater storage and recovery due to dispersive mixing within the aquifer. The hydrogeology of the Upper Floridan varies in southern Florida; confinement

  18. Hydrogeology of the Cambrian-Ordovician aquifer system in the northern Midwest: B in Regional aquifer-system analysis

    Science.gov (United States)

    Young, H.L.; Siegel, D.I.

    1992-01-01

    The Cambrian-Ordovician aquifer system contains the most extensive and continuous aquifers in the northern Midwest of the United States. It is the source of water for many municipalities, industries, and rural water users. Since the beginning of ground-water development from the aquifer system in the late 1800's, hydraulic heads have declined hundreds of feet in the heavily pumped Chicago-Milwaukee area and somewhat less in other metropolitan areas. The U.S. Geological Survey has completed a regional assessment of this aquifer system within a 161,000-square-mile area encompassing northern Illinois, northwestern Indiana, Iowa, southeastern Minnesota, northern Missouri, and Wisconsin.

  19. Assessment of the chemical status of the alluvial aquifer in the Aosta Plain: an example of the implementation of the Water Framework Directive in Italy

    Science.gov (United States)

    Rotiroti, Marco; Fumagalli, Letizia; Stefania, Gennaro A.; Frigerio, Maria C.; Simonetto, Fulvio; Capodaglio, Pietro; Bonomi, Tullia

    2015-04-01

    The Italian Legislative Decree 30/09 (D.Lgs. 30/09) implements the EU Water Framework Directive (WFD) providing some technical guidelines to assess the chemical status of groundwater bodies. This work presents the estimation of the chemical status of the shallow aquifer in the Aosta Plain (Aosta Valley Region, NW Alpine sector, Italy) on the basis of the D.Lgs. 30/09. The study area covers ~40 km2 along the Dora Baltea River basin. The Aosta Plain hosts an alluvial aquifer formed of lacustrine, glacial, fluvio-glacial and fan deposits of Pleistocene and Holocene ages. The unconfined aquifer features a depth of ~80 m in the western part of the plain and ~20 in the eastern part due to the intercalation of a silty lacustrine layer. The aquifer is mainly recharged by precipitation, surface water and ice and snow melt. Previous studies revealed that SO4, Fe, Mn, Ni, Cr(VI) and PCE represent potential threats for groundwater quality in the Aosta Plain. The chemical status was calculated using the data collected during the 2012 by the Regional Environmental Protection Agency of the Aosta Valley Region from its groundwater quality monitoring network that includes 38 points. Each point was sampled up to four times. Since the D.Lgs. 30/09 excludes Fe and Mn from the assessment of the groundwater chemical status, the present work deals with SO4, Ni, Cr(VI) and PCE. Threshold values (TVs) were estimated on the basis of natural background levels (NBLs) for SO4, Ni and Cr(VI) whereas, for PCE, the reference value (REF) reported by the D.Lgs. 30/09 (i.e., 1.1 µg/L) was used as TV. The NBLs were calculated using the two approaches suggested by the EU research project BRIDGE, that are the pre-selection and the component separation. The TVs were evaluated using the following criteria: (a) if NBL pollution in the Aosta Plain in order to achieve the good chemical status as required by the WFD.

  20. Source, variability, and transformation of nitrate in a regional karst aquifer: Edwards aquifer, central Texas.

    Science.gov (United States)

    Musgrove, MaryLynn; Opsahl, Stephen P.; Mahler, Barbara J.; Herrington, Chris; Sample, Thomas; Banta, John

    2016-01-01

    Many karst regions are undergoing rapid population growth and expansion of urban land accompanied by increases in wastewater generation and changing patterns of nitrate (NO3−) loading to surface and groundwater. We investigate variability and sources of NO3− in a regional karst aquifer system, the Edwards aquifer of central Texas. Samples from streams recharging the aquifer, groundwater wells, and springs were collected during 2008–12 from the Barton Springs and San Antonio segments of the Edwards aquifer and analyzed for nitrogen (N) species concentrations and NO3− stable isotopes (δ15N and δ18O). These data were augmented by historical data collected from 1937 to 2007. NO3− concentrations and discharge data indicate that short-term variability (days to months) in groundwater NO3− concentrations in the Barton Springs segment is controlled by occurrence of individual storms and multi-annual wet-dry cycles, whereas the lack of short-term variability in groundwater in the San Antonio segment indicates the dominance of transport along regional flow paths. In both segments, longer-term increases (years to decades) in NO3− concentrations cannot be attributed to hydrologic conditions; rather, isotopic ratios and land-use change indicate that septic systems and land application of treated wastewater might be the source of increased loading of NO3−. These results highlight the vulnerability of karst aquifers to NO3− contamination from urban wastewater. An analysis of N-species loading in recharge and discharge for the Barton Springs segment during 2008–10 indicates an overall mass balance in total N, but recharge contains higher concentrations of organic N and lower concentrations of NO3−than does discharge, consistent with nitrification of organic N within the aquifer and consumption of dissolved oxygen. This study demonstrates that subaqueous nitrification of organic N in the aquifer, as opposed to in soils, might be a previously

  1. Aquifer thermal energy (heat and chill) storage

    Energy Technology Data Exchange (ETDEWEB)

    Jenne, E.A. (ed.)

    1992-11-01

    As part of the 1992 Intersociety Conversion Engineering Conference, held in San Diego, California, August 3--7, 1992, the Seasonal Thermal Energy Storage Program coordinated five sessions dealing specifically with aquifer thermal energy storage technologies (ATES). Researchers from Sweden, The Netherlands, Germany, Switzerland, Denmark, Canada, and the United States presented papers on a variety of ATES related topics. With special permission from the Society of Automotive Engineers, host society for the 1992 IECEC, these papers are being republished here as a standalone summary of ATES technology status. Individual papers are indexed separately.

  2. The detection of boundaries in leaky aquifers

    International Nuclear Information System (INIS)

    Cook, A.J.

    1989-01-01

    Geological faults in sedimentary basins can affect the regional and local groundwater flow patterns by virtue of their enhanced permeability properties. Faults can be regarded as vertical flow boundaries and potentially important routes for radionuclide migration from a theoretical radioactive waste repository. This report investigates the hydraulic testing methods currently available which may be used to locate vertical hydraulic discontinuities (boundaries) within an aquifer. It aims to define the theoretical limitations to boundary detection by a single pumping test, to determine the optimum design of a pumping test for locating boundaries, and to define the practical limitations to boundary detection by a pumping test. (author)

  3. Geopressured-geothermal aquifers. Final contract report

    Energy Technology Data Exchange (ETDEWEB)

    1983-08-01

    Task 1 is to provide petrophysical and reservoir analysis of wells drilled into geopressured-geothermal aquifers containing dissolved methane. The list of Design Wells and Wells of Opportunity analyzed: Fairfax Foster Sutter No. 2 (WOO), Pleasant Bayou No. 2 (Design), Amoco Fee No. 1 (Design), G.M. Koelemay No. 1 (WOO), Gladys McCall No. 1 (Design), P.R. Girouard No. 1 (WOO), and Crown Zellerbach No. 2 (WOO). Petrophysical and reservoir analysis of the above wells were performed based on availability of data. The analysis performed on each well, the assumptions made during simulation, and conclusions reached.

  4. Denitrification in the karstic Floridan Aquifer

    Science.gov (United States)

    Fork, M.; Albertin, A. R.; Heffernan, J. B.; Katz, B. G.; Cohen, M. J.

    2010-12-01

    Nitrate concentrations in the karstic Floridan Aquifer have increased dramatically over the past 50 years, owing to agricultural intensification and urbanization. Due to low concentrations of organic matter and moderately oxic conditions in the Floridan Aquifer, groundwater denitrification has been assumed to be negligible. In this study, we evaluate that assumption using both existing and new data describing dissolved gases (Ne, N2, O2, Ar) and NO3- concentration and isotopic composition (δ18O- and δ15N-NO3) in the aquifer’s artesian springs. For new data, we collected samples from 33 spring vents representing a gradient of both DO and NO3- concentrations in northern Florida and used Membrane Inlet Mass Spectrometry (MIMS) to directly measure dissolved N2 and Ar. We modeled the physical processes (recharge temperature, dissolution of excess air) driving super-saturation of N2 gas using Ne and Ar where data describing Ne were available. Ar concentrations were correlated closely with recharge temperature, which ranged from 15.7 - 22.2°C, while Ne was closely correlated with excess air, which ranged from 1.05 to 2.66 mg L-1 and averaged 1.83 mg L-1. Estimates of physical mechanisms allowed calculation of expected N2 concentrations that were compared to observed N2 concentrations. Where Ne data were unavailable, we assumed excess air equal to the empirical average. Overall, observed N2 exceeded expectations based on physical processes in 33 of 47 cases; average excess N2 was 0.48 mg L-1 across all sites. In addition, excess N2 was negatively correlated with DO (r2 = 0.46); springs with low DO (Aquifer. Low DOC concentrations indicate that alternative electron donors may fuel nitrate reduction. Scaling to regional estimates of N2 production based on springs discharge and DO concentrations indicates that subsurface denitrification may account for some of the imbalance in springshed nutrient budgets. In addition, we conclude that use of δ15N-NO3- to diagnose

  5. SRP baseline hydrogeologic investigation: Aquifer characterization

    Energy Technology Data Exchange (ETDEWEB)

    Strom, R.N.; Kaback, D.S.

    1992-03-31

    An investigation of the mineralogy and chemistry of the principal hydrogeologic units and the geochemistry of the water in the principal aquifers at Savannah River Site (SRS) was undertaken as part of the Baseline Hydrogeologic Investigation. This investigation was conducted to provide background data for future site studies and reports and to provide a site-wide interpretation of the geology and geochemistry of the Coastal Plain Hydrostratigraphic province. Ground water samples were analyzed for major cations and anions, minor and trace elements, gross alpha and beta, tritium, stable isotopes of hydrogen, oxygen, and carbon, and carbon-14. Sediments from the well borings were analyzed for mineralogy and major and minor elements.

  6. The usefulness of multi-well aquifer tests in heterogeneous aquifers

    International Nuclear Information System (INIS)

    Young, S.C.; Benton, D.J.; Herweijer, J.C.; Sims, P.

    1990-01-01

    Three large-scale (100 m) and seven small-scale (3-7 m) multi-well aquifer tests were conducted in a heterogeneous aquifer to determine the transmissivity distribution across a one-hectare test site. Two of the large-scale tests had constant but different rates of discharge; the remaining large-scale test had a discharge that was pulsed at regulated intervals. The small-scale tests were conducted at two well clusters 20 m apart. The program WELTEST was written to analyze the data. By using the methods of non-linear least squares regression analysis and Broyden's method to solve for non-linear extrema, WELTEST automatically determines the best values of transmissivity and the storage coefficient. The test results show that order of magnitude differences in the calculated transmissivities at a well location can be realized by varying the discharge rate at the pumping well, the duration of the aquifer test, and/or the location of the pumping well. The calculated storage coefficients for the tests cover a five-order magnitude range. The data show a definite trend for the storage coefficient to increase with the distance between the pumping and the observation wells. This trend is shown to be related to the orientation of high hydraulic conductivity zones between the pumping and the observation wells. A comparison among single-well aquifer tests, geological investigations and multi-well aquifer tests indicate that the multi-well tests are poorly suited for characterizing a transmissivity field. (Author) (11 refs., 14 figs.)

  7. Bioremediation of a diesel fuel contaminated aquifer: simulation studies in laboratory aquifer columns

    Science.gov (United States)

    Hess, A.; Höhener, P.; Hunkeler, D.; Zeyer, J.

    1996-08-01

    The in situ bioremediation of aquifers contaminated with petroleum hydrocarbons is commonly based on the infiltration of groundwater supplemented with oxidants (e.g., O 2, NO 3-) and nutrients (e.g., NH 4+, PO 43-). These additions stimulate the microbial activity in the aquifer and several field studies describing the resulting processes have been published. However, due to the heterogeneity of the subsurface and due to the limited number of observation wells usually available, these field data do not offer a sufficient spatial and temporal resolution. In this study, flow-through columns of 47-cm length equipped with 17 sampling ports were filled with homogeneously contaminated aquifer material from a diesel fuel contaminated in situ bioremediation site. The columns were operated over 96 days at 12°C with artificial groundwater supplemented with O 2, NO 3- and PO 43-. Concentration profiles of O 2, NO 3-, NO 2-, dissolved inorganic and organic carbon (DIC and DOC, respectively), protein, microbial cells and total residual hydrocarbons were measured. Within the first 12 cm, corresponding to a mean groundwater residence time of < 3.6 h, a steep O 2 decrease from 4.6 to < 0.3 mg l -1, denitrification, a production of DIC and DOC, high microbial cell numbers and a high removal of hydrocarbons were observed. Within a distance of 24 to 40.5 cm from the infiltration, O 2 was below 0.1 mg l -1 and a denitrifying activity was found. In the presence and in the absence of O 2, n-alkanes were preferentially degraded compared to branched alkanes. The results demonstrate that: (1) infiltration of aerobic groundwater into columns filled with aquifer material contaminated with hydrocarbons leads to a rapid depletion of O 2; (2) O 2 and NO 3- can serve as oxidants for the mineralization of hydrocarbons; and (3) the modelling of redox processes in aquifers has to consider denitrifying activity in presence of O 2.

  8. Aquifers in coastal reclaimed lands - real world assessments

    Science.gov (United States)

    Saha, A.; Bironne, A.; Vonhögen-Peeters, L.; Lee, W. K.; Babovic, V. M.; Vermeulen, P.; van Baaren, E.; Karaoulis, M.; Blanchais, F.; Nguyen, M.; Pauw, P.; Doornenbal, P.

    2017-12-01

    Climate change and population growth are significant concerns in coastal regions around the world, where more than 30% of the world's population reside. The numbers continue to rise as coastal areas are increasingly urbanized. Urbanization creates land shortages along the coasts, which has spurred coastal reclamation activities as a viable solution. In this study, we focus on these reclamation areas; reclaimed areas in Singapore, and in the Netherlands, and investigate the potential of these reclaimed bodies as artificial aquifers that could attenuate water shortage problems in addition to their original purpose. We compare how the reclamation methods determine the hydrogeological characteristics of these manmade aquifers. We highlight similarities in freshwater lens development in the artificial shallow aquifers under natural recharge under diverse conditions, i.e. tropical and temperate zones, using numerical models. The characteristics and responses of these aquifers with dynamic freshwater-saltwater interface are contrasted against naturally occurring coastal aquifers where equilibrium was disturbed by anthropogenic activities. Finally, we assess the risks associated with subsidence and saltwater intrusion, combining measurements and numerical models, in case these aquifers are planned for Aquifer Storage and Recovery (ASR) or Managed Aquifer Recharge (MAR) strategies. Relative performances of some ASR schemes are simulated and compared in the reclaimed lands.

  9. Aquifer recharging in South Carolina: radiocarbon in environmental hydrogeology

    International Nuclear Information System (INIS)

    Stone, P.A.; Knox, R.L.; Mathews, T.D.

    1985-01-01

    Radiocarbon activities of dissolved inorganic carbon (and tritium activities where infiltration rates are rapid and aquifers shallow) provide relatively unambiguous and inexpensive evidence for identification of significant recharge areas. Such evidence is for the actual occurrence of modern recharge in the aquifer and thus is less inferential than stratigraphic or potentiometric evidence. These underutilized isotopic techniques are neither arcane nor complex and have been more-or-less standardized by earlier researchers. In South Carolina, isotopic evidence has been used from both calcareous and siliceous sedimentary aquifers and fractured crystalline rock aquifers. The Tertiary limestone aquifer is shown not to be principally recharged in its subcrop area, unlike conditions assumed for many other sedimentary aquifers in southeastern United States, and instead receives considerable lateral recharge from interfingering updip Tertiary sand aquifers in the middle coastal plain. Induced recharging at Hilton Head Island is mixing ancient relict water and modern recharge water. Recharging to deeper portions of the Cretaceous Middendorf basal sand aquifer occurs at least as far coastward as the middle coastal plain, near sampling sites that stratigraphically appear to be confined. Pronounced mineralization of water in fractured rocks cannot be considered as evidence of ancient or relict ground water that is isolated from modern contaminants, some of these waters contain considerable radiocarbon and hydrogen-bomb tritium

  10. Hydraulic properties from pumping tests data of aquifers in Azare ...

    African Journals Online (AJOL)

    Pumping test data from twelve boreholes in Azare area were analysed to determine the hydraulic properties of the aquifers, and the availability of water to meet the conjugate demands of the increasing population. The values of the aquifer constants obtained from the Cooper-Jacob's non-equilibrium graphical method were ...

  11. Estimating aquifer transmissivity from geo-electrical sounding ...

    African Journals Online (AJOL)

    Aquifer resistivity range from 4.26 ohm-m to 755.3 ohm-m with maximum thickness of 52.25m. A maximum 55.52m depth- tobasement was obtained in the study area. Based on the model obtained, aquifer Transmissivity was calculated and was used to delineate the study area into prospective low and high groundwater ...

  12. Hydrologic and isotopic study of the Quito aquifer

    International Nuclear Information System (INIS)

    Villalba, Fabio; Benalcazar, Julio; Garcia, Marco; Altamirano, Cesar; Altamirano, Homero; Sarasti, Santiago; Mancero, Maria; Leiva, Eduardo; Pino, Jose; Alulema, Rafael; Cedeno, Alberto; Burbano, Napoleon; Paquel, Efren; Becerra, Simon; Andrade, Graciela

    2000-10-01

    The dynamics of the Quito basin and surrounding area aquifers were determined through the use of stable and radioactive isotopes, and the monitoring of the freatic levels and of the bacteriological and physico-chemical quality of the water. A conceptual hydrodynamic model of the Quito aquifer was also proposed in order to establish in the future a sustainable management system

  13. Determining shallow aquifer vulnerability by the DRASTIC model ...

    Indian Academy of Sciences (India)

    Shallow aquifer vulnerability has been assessed using GIS-based DRASTIC model by incorporating the major geological and hydrogeological factors that affect and control the groundwater contamination in a granitic terrain. It provides a relative indication of aquifer vulnerability to the contamination. Further, it has been ...

  14. Aquifer overexploitation: what does it mean?

    Science.gov (United States)

    Custodio, Emilio

    2002-02-01

    Groundwater overexploitation and aquifer overexploitation are terms that are becoming common in water-resources management. Hydrologists, managers and journalists use them when talking about stressed aquifers or some groundwater conflict. Overexploitation may be defined as the situation in which, for some years, average aquifer ion rate is greater than, or close to the average recharge rate. But rate and extent of recharge areas are often very uncertain. Besides, they may be modified by human activities and aquifer development. In practice, however, an aquifer is often considered as overexploited when some persistent negative results of aquifer development are felt or perceived, such as a continuous water-level drawdown, progressive water-quality deterioration, increase of ion cost, or ecological damage. But negative results do not necessarily imply that ion is greater than recharge. They may be simply due to well interferences and the long transient period that follow changes in the aquifer water balance. Groundwater storage is depleted to some extent during the transient period after ion is increased. Its duration depends on aquifer size, specific storage and permeability. Which level of "aquifer overexploitation" is advisable or bearable, depends on the detailed and updated consideration of aquifer-development effects and the measures implemented for correction. This should not be the result of applying general rules based on some indirect data. Monitoring, sound aquifer knowledge, and calculation or modelling of behaviour are needed in the framework of a set of objectives and policies. They should be established by a management institution, with the involvement of groundwater stakeholders, and take into account the environmental and social constraints. Aquifer overexploitation, which often is perceived to be associated with something ethically bad, is not necessarily detrimental if it is not permanent. It may be a step towards sustainable development. Actually

  15. Simple method for quick estimation of aquifer hydrogeological parameters

    Science.gov (United States)

    Ma, C.; Li, Y. Y.

    2017-08-01

    Development of simple and accurate methods to determine the aquifer hydrogeological parameters was of importance for groundwater resources assessment and management. Aiming at the present issue of estimating aquifer parameters based on some data of the unsteady pumping test, a fitting function of Theis well function was proposed using fitting optimization method and then a unitary linear regression equation was established. The aquifer parameters could be obtained by solving coefficients of the regression equation. The application of the proposed method was illustrated, using two published data sets. By the error statistics and analysis on the pumping drawdown, it showed that the method proposed in this paper yielded quick and accurate estimates of the aquifer parameters. The proposed method could reliably identify the aquifer parameters from long distance observed drawdowns and early drawdowns. It was hoped that the proposed method in this paper would be helpful for practicing hydrogeologists and hydrologists.

  16. Hydrogeology of the Umm Er Radhuma Aquifer (Arabian peninsula)

    Science.gov (United States)

    Dirks, Heiko; Al Ajmi, Hussain; Kienast, Peter; Rausch, Randolf

    2018-03-01

    The aim of this article is to enhance the understanding of the Umm Er Radhuma aquifer's genesis, and its hydraulic and hydrochemical development over time. This is a prerequisite for wise use of the fossil groundwater resources contained within. The Umm Er Radhuma is a karstified limestone aquifer, extending over 1.6 Mio. km2 in the eastern part of the Arabian Peninsula. Both epigene and hypogene karstification contributed to the genesis of what is today the most prolific aquifer in the region. Besides man-made abstractions, even the natural outflows are higher than the small recharge (natural storage depletion). The Umm Er Radhuma shows that large aquifers in arid regions are never in "steady state" (where inflows equal outflows), considering Quaternary climate history. The aquifer's adaption to climate changes (precipitation, sea level) can be traced even after thousands of years, and is slower than the climate changes themselves.

  17. Numerical modelling of groundwater flow to understand the impacts of pumping on arsenic migration in the aquifer of North Bengal Plain

    Science.gov (United States)

    Sikdar, P. K.; Chakraborty, Surajit

    2017-03-01

    In this paper, numerical simulations of regional-scale groundwater flow of North Bengal Plain have been carried out with special emphasis on the arsenic (As)-rich alluvium filled gap between the Rajmahal hills on the west and the Garo hills on the east. The proposed concern of this modelling arose from development that has led to large water table declines in the urban area of English Bazar block, Malda district, West Bengal and possible transport of As in the near future from the adjacent As-polluted aquifer. Groundwater occurs under unconfined condition in a thick zone of saturation within the Quaternary alluvial sediments. Modelling indicates that current pumping has significantly changed the groundwater flowpaths from pre-development condition. At the present pumping rate, the pumping wells of the urban area may remain uncontaminated till the next 25 yrs, considering only pure advection of water but some water from the As-polluted zone may enter wells by 50 yrs. But geochemical and other processes such as adsorption, precipitation, redox reaction and microbial activity may significantly retard the predicted rate by advective transport. In the rural areas, majority of the water pumped from the aquifer is for irrigation, which is continuously re-applied on the surface. The near-vertical nature of the flowpaths indicates that, where As is present or released at shallow depths, it will continue to occur in pumping wells. Modelling also indicates that placing all the pumping wells at depths below 100 m may not provide As-free water permanently.

  18. Geomorphic Controls on Aquifer Geometry in Northwestern India

    Science.gov (United States)

    van Dijk, W. M.; Densmore, A. L.; Sinha, R.; Gupta, S.; Mason, P. J.; Singh, A.; Joshi, S. K.; Nayak, N.; Kumar, M.; Shekhar, S.

    2014-12-01

    The Indo-Gangetic foreland basin suffers from one of the highest rates of groundwater extraction in the world, especially in the Indian states of Punjab, Haryana and Rajasthan. To understand the effects of this extraction on ground water levels, we must first understand the geometry and sedimentary architecture of the aquifer system, which in turn depend upon its geomorphic setting. We use satellite images and digital elevation models to map the geomorphology of the Sutlej and Yamuna river systems, while aquifer geometry is assessed using ~250 wells that extend to ~300 m depth in Punjab and Haryana. The Sutlej and Yamuna rivers have deposited large sedimentary fans at their outlets. Elongate downslope ridges on the fan surfaces form distributary networks that radiate from the Sutlej and Yamuna fan apices, and we interpret these ridges as paleochannel deposits associated with discrete fan lobes. Paleochannels picked out by soil moisture variations illustrate a complex late Quaternary history of channel avulsion and incision, probably associated with variations in monsoon intensity. Aquifer bodies on the Sutlej and Yamuna fans have a median thickness of 7 and 6 m, respectively, and follow a heavy-tailed distribution, probably because of stacked sand bodies. The percentage of aquifer material in individual lithologs decreases downstream, although the exponent on the thickness distribution remains the same, indicating that aquifer bodies decrease in number down fan but do not thin appreciably. Critically, the interfan area between the Sutlej and Yamuna fans has thinner aquifers and a lower proportion of aquifer material, despite its proximal location. Our data show that the Sutlej and Yamuna fan systems form the major aquifer systems in this area, and that their geomorphic setting therefore provides a first-order control on aquifer distribution and geometry. The large spatial heterogeneity of the system must be considered in any future aquifer management scheme.

  19. Modeling of CO2 storage in aquifers

    International Nuclear Information System (INIS)

    Savioli, Gabriela B; Santos, Juan E

    2011-01-01

    Storage of CO 2 in geological formations is a means of mitigating the greenhouse effect. Saline aquifers are a good alternative as storage sites due to their large volume and their common occurrence in nature. The first commercial CO 2 injection project is that of the Sleipner field in the Utsira Sand aquifer (North Sea). Nevertheless, very little was known about the effectiveness of CO 2 sequestration over very long periods of time. In this way, numerical modeling of CO 2 injection and seismic monitoring is an important tool to understand the behavior of CO 2 after injection and to make long term predictions in order to prevent CO 2 leaks from the storage into the atmosphere. The description of CO 2 injection into subsurface formations requires an accurate fluid-flow model. To simulate the simultaneous flow of brine and CO 2 we apply the Black-Oil formulation for two phase flow in porous media, which uses the PVT data as a simplified thermodynamic model. Seismic monitoring is modeled using Biot's equations of motion describing wave propagation in fluid-saturated poroviscoelastic solids. Numerical examples of CO 2 injection and time-lapse seismics using data of the Utsira formation show the capability of this methodology to monitor the migration and dispersal of CO 2 after injection.

  20. 14C measurements in aquifers with methane

    International Nuclear Information System (INIS)

    Barker, J.F.; Fritz, P.; Brown, R.M.

    1978-01-01

    A survey of various groundwater systems indicates that methane is a common trace constituent and occasionally a major carbon species in groundwaters. Thermocatalytic methane had delta 13 CCH 4 > -45% 0 and microbially-produced or biogenic methane had delta 13 CCH 4 0 . Groundwaters containing significant biogenic methane had abnormally heavy delta 13 C values for the inorganic carbon. Thermocatalytic methane had no apparent effect on the inorganic carbon. Because methanogenesis seriously affects the carbon isotope geochemistry of groundwaters, the correction of raw 14 C ages of affected groundwaters must consider these effects. Conceptual models are developed which adjust the 14 C activity of the groundwater for the effects of methanogenesis and for the dilution of carbon present during infiltration by simple dissolution of rock carbonate. These preliminary models are applied to groundwaters from the Alliston sand aquifer where methanogenesis has affected most samples. In this system, methanogenic bacteria using organic matter present in the aquifer matrix as substrate, have added inorganic carbon to the groundwater which has initiated further carbonate rock dissolution. These processes have diluted the inorganic carbon 14 C activity. (orig.) [de

  1. Conduit enlargement in an eogenetic karst aquifer

    Science.gov (United States)

    Moore, Paul J.; Martin, Jonathan B.; Screaton, Elizabeth J.; Neuhoff, Philip S.

    2010-11-01

    SummaryMost concepts of conduit development have focused on telogenetic karst aquifers, where low matrix permeability focuses flow and dissolution along joints, fractures, and bedding planes. However, conduits also exist in eogenetic karst aquifers, despite high matrix permeability which accounts for a significant component of flow. This study investigates dissolution within a 6-km long conduit system in the eogenetic Upper Floridan aquifer of north-central Florida that begins with a continuous source of allogenic recharge at the Santa Fe River Sink and discharges from a first-magnitude spring at the Santa Fe River Rise. Three sources of water to the conduit include the allogenic recharge, diffuse recharge through epikarst, and mineralized water upwelling from depth. Results of sampling and inverse modeling using PHREEQC suggest that dissolution within the conduit is episodic, occurring only during 30% of 16 sampling times between March 2003 and April 2007. During low flow conditions, carbonate saturated water flows from the matrix to the conduit, restricting contact between undersaturated allogenic water with the conduit wall. When gradients reverse during high flow conditions, undersaturated allogenic recharge enters the matrix. During these limited periods, estimates of dissolution within the conduit suggest wall retreat averages about 4 × 10 -6 m/day, in agreement with upper estimates of maximum wall retreat for telogenetic karst. Because dissolution is episodic, time-averaged dissolution rates in the sink-rise system results in a wall retreat rate of about 7 × 10 -7 m/day, which is at the lower end of wall retreat for telogenetic karst. Because of the high permeability matrix, conduits in eogenetic karst thus enlarge not just at the walls of fractures or pre-existing conduits such as those in telogenetic karst, but also may produce a friable halo surrounding the conduits that may be removed by additional mechanical processes. These observations stress the

  2. CO2/Brine transport into shallow aquifers along fault zones.

    Science.gov (United States)

    Keating, Elizabeth H; Newell, Dennis L; Viswanathan, Hari; Carey, J W; Zyvoloski, G; Pawar, Rajesh

    2013-01-02

    Unintended release of CO(2) from carbon sequestration reservoirs poses a well-recognized risk to groundwater quality. Research has largely focused on in situ CO(2)-induced pH depression and subsequent trace metal mobilization. In this paper we focus on a second mechanism: upward intrusion of displaced brine or brackish-water into a shallow aquifer as a result of CO(2) injection. Studies of two natural analog sites provide insights into physical and chemical mechanisms controlling both brackish water and CO(2) intrusion into shallow aquifers along fault zones. At the Chimayó, New Mexico site, shallow groundwater near the fault is enriched in CO(2) and, in some places, salinity is significantly elevated. In contrast, at the Springerville, Arizona site CO(2) is leaking upward through brine aquifers but does not appear to be increasing salinity in the shallow aquifer. Using multiphase transport simulations we show conditions under which significant CO(2) can be transported through deep brine aquifers into shallow layers. Only a subset of these conditions favor entrainment of salinity into the shallow aquifer: high aspect-ratio leakage pathways and viscous coupling between the fluid phases. Recognition of the conditions under which salinity is favored to be cotransported with CO(2) into shallow aquifers will be important in environmental risk assessments.

  3. Sequence stratigraphy, seismic stratigraphy, and seismic structures of the lower intermediate confining unit and most of the Floridan aquifer system, Broward County, Florida

    Science.gov (United States)

    Cunningham, Kevin J.; Kluesner, Jared W.; Westcott, Richard L.; Robinson, Edward; Walker, Cameron; Khan, Shakira A.

    2017-12-08

    sequence stratigraphic cycles that compose the Eocene to Miocene Oldsmar, Avon Park, and Arcadia Formations. The mapping of these seismic-reflection and well data has produced a refined Cenozoic sequence stratigraphic, seismic stratigraphic, and hydrogeologic framework of southeastern Florida. The upward transition from the Oldsmar Formation to the Avon Park Formation and the Arcadia Formation embodies the evolution from (1) a tropical to subtropical, shallow-marine, carbonate platform, represented by the Oldsmar and Avon Park Formations, to (2) a broad, temperate, mixed carbonate-siliciclastic shallow marine shelf, represented by the lower part of the Arcadia Formation, and to (3) a temperate, distally steepened carbonate ramp represented by the upper part of the Arcadia Formation.In the study area, the depositional sequences and seismic sequences have a direct correlation with hydrogeologic units. The approximate upper boundary of four principal permeable units of the Floridan aquifer system (Upper Floridan aquifer, Avon Park permeable zone, uppermost major permeable zone of the Lower Floridan aquifer, and Boulder Zone) have sequence stratigraphic and seismic-reflection signatures that were identified on cross sections, mapped, or both, and therefore the sequence stratigraphy and seismic stratigraphy were used to guide the development of a refined spatial representation of these hydrogeologic units. In all cases, the permeability of the four permeable units is related to stratiform megaporosity generated by ancient dissolution of carbonate rock associated with subaerial exposure and unconformities at the upper surfaces of carbonate depositional cycles of several hierarchical scales ranging from high-frequency cycles to depositional sequences. Additionally, interparticle porosity also contributes substantially to the stratiform permeability in much of the Upper Floridan aquifer. Information from seismic stratigraphy allowed 3D geomodeling of hydrogeologic units

  4. Groundwater level responses to precipitation variability in Mediterranean insular aquifers

    Science.gov (United States)

    Lorenzo-Lacruz, Jorge; Garcia, Celso; Morán-Tejeda, Enrique

    2017-09-01

    Groundwater is one of the largest and most important sources of fresh water on many regions under Mediterranean climate conditions, which are exposed to large precipitation variability that includes frequent meteorological drought episodes, and present high evapotranspiration rates and water demand during the dry season. The dependence on groundwater increases in those areas with predominant permeable lithologies, contributing to aquifer recharge and the abundance of ephemeral streams. The increasing pressure of tourism on water resources in many Mediterranean coastal areas, and uncertainty related to future precipitation and water availability, make it urgent to understand the spatio-temporal response of groundwater bodies to precipitation variability, if sustainable use of the resource is to be achieved. We present an assessment of the response of aquifers to precipitation variability based on correlations between the Standardized Precipitation Index (SPI) at various time scales and the Standardized Groundwater Index (SGI) across a Mediterranean island. We detected three main responses of aquifers to accumulated precipitation anomalies: (i) at short time scales of the SPI (24 months). The differing responses were mainly explained by differences in lithology and the percentage of highly permeable rock strata in the aquifer recharge areas. We also identified differences in the months and seasons when aquifer storages are more dependent on precipitation; these were related to climate seasonality and the degree of aquifer exploitation or underground water extraction. The recharge of some aquifers, especially in mountainous areas, is related to precipitation variability within a limited spatial extent, whereas for aquifers located in the plains, precipitation variability influence much larger areas; the topography and geological structure of the island explain these differences. Results indicate large spatial variability in the response of aquifers to precipitation in

  5. Managed aquifer recharge: rediscovering nature as a leading edge technology.

    Science.gov (United States)

    Dillon, P; Toze, S; Page, D; Vanderzalm, J; Bekele, E; Sidhu, J; Rinck-Pfeiffer, S

    2010-01-01

    Use of Managed Aquifer Recharge (MAR) has rapidly increased in Australia, USA, and Europe in recent years as an efficient means of recycling stormwater or treated sewage effluent for non-potable and indirect potable reuse in urban and rural areas. Yet aquifers have been relied on knowingly for water storage and unwittingly for water treatment for millennia. Hence if 'leading edge' is defined as 'the foremost part of a trend; a vanguard', it would be misleading to claim managed aquifer recharge as a leading edge technology. However it has taken a significant investment in scientific research in recent years to demonstrate the effectiveness of aquifers as sustainable treatment systems to enable managed aquifer recharge to be recognised along side engineered treatment systems in water recycling. It is a 'cross-over' technology that is applicable to water and wastewater treatment and makes use of passive low energy processes to spectacularly reduce the energy requirements for water supply. It is robust within limits, has low cost, is suitable from village to city scale supplies, and offers as yet almost untapped opportunities for producing safe drinking water supplies where they do not yet exist. It will have an increasingly valued role in securing water supplies to sustain cities affected by climate change and population growth. However it is not a universal panacea and relies on the presence of suitable aquifers and sources of water together with effective governance to ensure human health and environment protection and water resources planning and management. This paper describes managed aquifer recharge, illustrates its use in Australia, outlining economics, guidelines and policies, and presents some of the knowledge about aquifer treatment processes that are revealing the latent value of aquifers as urban water infrastructure and provide a driver to improving our understanding of urban hydrogeology.

  6. Functioning of the Primary Aquifer Relating to the Maider Basin, Morocco: Case of the Ordovician aquifer.

    Science.gov (United States)

    Ben-said, E.; Boukdir, A.; Mahboub, A.; Younsi, A.; Zitouni, A.; Alili, L.; Ikhmerdi, H.

    2018-05-01

    The basin of Maider is limited northly by the vast ensemble Oriental Saghro-Ougnate, from the east by the Tafilalet plain, from the west by the oriental Jbel Bani, finally from the south and south-east by the Cretaceous Hamada of Kern-Kem. During last decades, groundwater in the basin of Maider, is confronting degradation in both cases: Quantitative and qualitative, as a result of the drought, the overexploitation and the salinization. The aim of this action research is to understand the current state of water resources in the area of stady. At the end of this work, we can get the following conclusions: the general flow of the ordovician aquifer is always directed from the north to the south-east of the basin by following the principal axes of the wadis:Taghbalt, Hssiya and Fezzou. The recharge of the aquifer is primarily done, either by the underground flow, or by the surface runoff of torrential waters from the upstream of Jbel Saghro. The piezometric anomaly noticed at the level of Ait Saàdane, explained by overexploitation linked to the needs of irrigation water. The physicochemical approach for the Maider basin identifies two essential factors of the salinisation of groundwater: the dissolution of the aquifer which is rich in minerals with high temperature on the one hand, and the decrease of the piezometric surface due to the overexploitation and drought on the other hand.

  7. Hydrologic time and sustainability of shallow aquifers

    Science.gov (United States)

    Back, William; ,

    1994-01-01

    Measurement of water and short intervals of time are coeval events that began about 6000 BC in Mesopotamia. Even though time and hydrology have been intimately entwined, with time terms in the denominator of many hydrologic parameters, hydrology's a priori claim to time has not been consummated. Moreover, time takes on a greater importance now than in the past as the focus shifts to small site-scale aquifers whose sustainability can be physically and chemically threatened. One of the challenges for research in hydrogeology is to establish time scales for hydrologic phenomena such as infiltration rates, groundwater flow rates, rates of organic and inorganic reactions, and rates of groundwater withdrawal over the short term, and the long term and to understand the consequences of these various time scales. Credible monitoring programs must consider not only the spatial scale, but also the time scale of the phenomena being monitored.

  8. Optimal Aquifer Pumping Policy to Reduce Contaminant Concentration

    Directory of Open Access Journals (Sweden)

    Ali Abaei

    2012-01-01

    Full Text Available Different sources of ground water contamination lead to non-uniform distribution of contaminant concentration in the aquifer. If elimination or containment of pollution sources was not possible, the distribution of contaminant concentrations could be modified in order to eliminate peak concentrations using optimal water pumping discharge plan. In the present investigation Visual MODFLOW model was used to simulate the flow and transport in a hypothetic aquifer. Genetic Algorithm (GA also was applied to optimize the location and pumping flow rate of wells in order to reduce contaminants peak concentrations in aquifer.

  9. New methodology for aquifer influx status classification for single wells in a gas reservoir with aquifer support

    Directory of Open Access Journals (Sweden)

    Yong Li

    2016-10-01

    Full Text Available For gas reservoirs with strong bottom or edge aquifer support, the most important thing is avoiding aquifer breakthrough in a gas well. Water production in gas wells does not only result in processing problems in surface facilities, but it also explicitly reduces well productivity and reservoir recovery. There are a lot of studies on the prediction of water breakthrough time, but they are not completely practicable due to reservoir heterogeneity. This paper provides a new method together with three diagnostic curves to identify aquifer influx status for single gas wells; the aforementioned curves are based on well production and pressure data. The whole production period of a gas well can be classified into three periods based on the diagnostic curves: no aquifer influx period, early aquifer influx period, and middle-late aquifer influx period. This new method has been used for actual gas well analysis to accurately identify gas well aquifer influx status and the water breakthrough sequence of all wells in the same gas field. Additionally, the evaluation results are significantly beneficial for well production rate optimization and development of an effective gas field.

  10. Isotopic study of the Continental Intercalaire aquifer and its relationship with other aquifers of the northern Sahara

    International Nuclear Information System (INIS)

    Gonfiantini, R.; Sauzay, G.; Payne, B.R.; Conrad, G.; Fontes, J.Ch.

    1974-01-01

    The Northern Sahara contains several aquifers, the largest of which is that of the Continental Intercalaire formations. In its eastern part the aquifer is confined and presents a very homogeneous isotopic composition. The 14 C activity is low or zero except in the outcrop zones of the north (Saharan Atlas), the east (Dahar) and the south (Tinrhert), all of which are recharge zones. In these areas the isotopic composition does not differ appreciably from that of the old water in the confined part of the aquifer. In the western part, where the reservoir outcrops widely, the 14 C activities show the extent of the local recharge. The heavy isotope content indicates the overflow of the surface aquifer of the western Grand Erg into the Continental Intercalaire over the whole Gourara front. The mixtures thus formed pass under the Tademait and drain towards the Touat. In the resurgence zone of the Gulf of G abes in Tunisia the heavy-isotope content confirms the recharging of the aquifer of the Complex terminal by drainage of water from the Continental Intercalaire through the El-Hamma fault system. The water then runs eastwards, mixing with local contributions. The marine Miocene confined aquifer of Zarzis-Djerba in the Gulf of Gabes receives no contribution from the Continental Intercalaire. The water in the aquifer of the western Grand Erg indicates an evaporation mechanism, probably peculiar to the dune systems, which gives rise to heavy-isotope enrichment compared with the recharge of other types of formations. (author) [fr

  11. Hydrogeology and water quality of the Floridan aquifer system and effect of Lower Floridan aquifer withdrawals on the Upper Floridan aquifer at Barbour Pointe Community, Chatham County, Georgia, 2013

    Science.gov (United States)

    Gonthier, Gerard; Clarke, John S.

    2016-06-02

    Two test wells were completed at the Barbour Pointe community in western Chatham County, near Savannah, Georgia, in 2013 to investigate the potential of using the Lower Floridan aquifer as a source of municipal water supply. One well was completed in the Lower Floridan aquifer at a depth of 1,080 feet (ft) below land surface; the other well was completed in the Upper Floridan aquifer at a depth of 440 ft below land surface. At the Barbour Pointe test site, the U.S. Geological Survey completed electromagnetic (EM) flowmeter surveys, collected and analyzed water samples from discrete depths, and completed a 72-hour aquifer test of the Floridan aquifer system withdrawing from the Lower Floridan aquifer.Based on drill cuttings, geophysical logs, and borehole EM flowmeter surveys collected at the Barbour Pointe test site, the Upper Floridan aquifer extends 369 to 567 ft below land surface, the middle semiconfining unit, separating the two aquifers, extends 567 to 714 ft below land surface, and the Lower Floridan aquifer extends 714 to 1,056 ft below land surface.A borehole EM flowmeter survey indicates that the Upper Floridan and Lower Floridan aquifers each contain four water-bearing zones. The EM flowmeter logs of the test hole open to the entire Floridan aquifer system indicated that the Upper Floridan aquifer contributed 91 percent of the total flow rate of 1,000 gallons per minute; the Lower Floridan aquifer contributed about 8 percent. Based on the transmissivity of the middle semiconfining unit and the Floridan aquifer system, the middle semiconfining unit probably contributed on the order of 1 percent of the total flow.Hydraulic properties of the Upper Floridan and Lower Floridan aquifers were estimated based on results of the EM flowmeter survey and a 72-hour aquifer test completed in Lower Floridan aquifer well 36Q398. The EM flowmeter data were analyzed using an AnalyzeHOLE-generated model to simulate upward borehole flow and determine the transmissivity of

  12. Factors Affecting Public-Supply Well Vulnerability in Two Karst Aquifers

    OpenAIRE

    Musgrove, MaryLynn; Katz, Brian G; Fahlquist, Lynne S; Crandall, Christy A; Lindgren, Richard J

    2014-01-01

    Karst aquifers occur in a range of climatic and geologic settings. Nonetheless, they are commonly characterized by their vulnerability to water-quality impairment. Two karst aquifers, the Edwards aquifer in south-central Texas and the Upper Floridan aquifer in western Florida, were investigated to assess factors that control the movement of contaminants to public-supply wells (PSWs). The geochemistry of samples from a selected PSW or wellfield in each aquifer was compared with that from nearb...

  13. Hydrogeologic investigation and simulation of ground-water flow in the Upper Floridan Aquifer of north-central Florida and southwestern Georgia and delineation of contributing areas for selected city of Tallahassee, Florida, water-supply wells

    Science.gov (United States)

    Davis, J. Hal

    1996-01-01

    A 4-year investigation of the Upper Floridan aquifer and ground-water flow system in Leon County, Florida, and surrounding counties of north-central Florida and southwestern Georgia began in 1990. The purpose of the investigation was to describe the ground-water flow system and to delineate the contributing areas to selected City of Tallahassee, Florida, water-supply wells. The investigation was prompted by the detection of low levels of tetrachloroethylene in ground-water samples collected from several of the city's water-supply wells. Hydrologic data and previous studies indicate that; ground-water flow within the Upper Floridan aquifer can be considered steady-state; the Upper Floridan aquifer is a single water-bearing unit; recharge is from precipitation; and that discharge occurs as spring flow, leakage to rivers, leakage to the Gulf of Mexico, and pumpage. Measured transmissivities of the aquifer ranged from 1,300 ft2/d (feet squared per day) to 1,300,000 ft2/