WorldWideScience

Sample records for model simulated soil

  1. Simple Numerical Model to Simulate Penetration Testing in Unsaturated Soils

    Directory of Open Access Journals (Sweden)

    Jarast S. Pegah

    2016-01-01

    Full Text Available Cone penetration test in unsaturated sand is modelled numerically using Finite Element Method. Simple elastic-perfectly plastic Mohr-Coulomb constitutive model is modified with an apparent cohesion to incorporate the effect of suction on cone resistance. The Arbitrary Lagrangian-Eulerian (ALE remeshing algorithm is also implemented to avoid mesh distortion problem due to the large deformation in the soil around the cone tip. The simulated models indicate that the cone resistance was increased consistently under higher suction or lower degree of saturation. Sensitivity analysis investigating the effect of input soil parameters on the cone tip resistance shows that unsaturated soil condition can be adequately modelled by incorporating the apparent cohesion concept. However, updating the soil stiffness by including a suction-dependent effective stress formula in Mohr-Coulomb material model does not influence the cone resistance significantly.

  2. A discrete element model for simulating saturated granular soil

    Institute of Scientific and Technical Information of China (English)

    Mahan Lamei; Ali Asghar Mirghasemi

    2011-01-01

    A numerical model is developed to simulate saturated granular soil,based on the discrete element method.Soil particles are represented by Lagrangian discrete elements,and pore fluid,by appropriate discrete elements which represent alternately Lagrangian mass of water and Eulerian volume of space.Macroscale behavior of the model is verified by simulating undrained biaxial compression tests.Micro-scale behavior is compared to previous literature through pore pressure pattern visualization during shear tests,it is demonstrated that dynamic pore pressure patterns are generated by superposed stress waves.These pore-pressure patterns travel much faster than average drainage rate of the pore fluid and may initiate soil fabric change,ultimately leading to liquefaction in loose sands.Thus,this work demonstrates a tool to roughly link dynamic stress wave patterns to initiation of liquefaction phenomena.

  3. Fully undrained cyclic loading simulation on unsaturated soils using an elastoplastic model for unsaturated soils

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    Komolvilas Veerayut

    2016-01-01

    Full Text Available Several researchers have reported that Bishop’s mean effective stress decreases in unsaturated soils under fully undrained cyclic loading conditions, and unsaturated soils are finally liquefied in a similar manner as saturated soils. This paper presents a series of simulations of such fully undrained cyclic loading on unsaturated soils using an elastoplastic model of the unsaturated soil. This model is formulated using the Bishop’s effective stress tensor incorporating the following concepts: the volumetric movement of the state boundary surface containing the normal consolidation line and the critical state line due to the variation in the degree of saturation, a soil water characteristic curve model considering the effect of specific volume and hysteresis, the subloading surface model, and Boyle’s law. Comparisons between the simulation results and the experimental ones show that the model agreed well with the unsaturated soil behavior under cyclic loading. Finally, the typical cyclic behavior of unsaturated soils under fully undrained conditions, such as the mechanism of liquefaction of unsaturated soils, the compression behavior, and an increase in the degree of saturation, are described through the proposed simulation results.

  4. Evaluation of soil flushing of complex contaminated soil: An experimental and modeling simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Sung Mi; Kang, Christina S. [Department of Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 143-701 (Korea, Republic of); Kim, Jonghwa [Department of Industrial Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 143-701 (Korea, Republic of); Kim, Han S., E-mail: hankim@konkuk.ac.kr [Department of Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 143-701 (Korea, Republic of)

    2015-04-28

    Highlights: • Remediation of complex contaminated soil achieved by sequential soil flushing. • Removal of Zn, Pb, and heavy petroleum oils using 0.05 M citric acid and 2% SDS. • Unified desorption distribution coefficients modeled and experimentally determined. • Nonequilibrium models for the transport behavior of complex contaminants in soils. - Abstract: The removal of heavy metals (Zn and Pb) and heavy petroleum oils (HPOs) from a soil with complex contamination was examined by soil flushing. Desorption and transport behaviors of the complex contaminants were assessed by batch and continuous flow reactor experiments and through modeling simulations. Flushing a one-dimensional flow column packed with complex contaminated soil sequentially with citric acid then a surfactant resulted in the removal of 85.6% of Zn, 62% of Pb, and 31.6% of HPO. The desorption distribution coefficients, K{sub Ubatch} and K{sub Lbatch}, converged to constant values as C{sub e} increased. An equilibrium model (ADR) and nonequilibrium models (TSNE and TRNE) were used to predict the desorption and transport of complex contaminants. The nonequilibrium models demonstrated better fits with the experimental values obtained from the column test than the equilibrium model. The ranges of K{sub Ubatch} and K{sub Lbatch} were very close to those of K{sub Ufit} and K{sub Lfit} determined from model simulations. The parameters (R, β, ω, α, and f) determined from model simulations were useful for characterizing the transport of contaminants within the soil matrix. The results of this study provide useful information for the operational parameters of the flushing process for soils with complex contamination.

  5. Evaluation of soil flushing of complex contaminated soil: an experimental and modeling simulation study.

    Science.gov (United States)

    Yun, Sung Mi; Kang, Christina S; Kim, Jonghwa; Kim, Han S

    2015-04-28

    The removal of heavy metals (Zn and Pb) and heavy petroleum oils (HPOs) from a soil with complex contamination was examined by soil flushing. Desorption and transport behaviors of the complex contaminants were assessed by batch and continuous flow reactor experiments and through modeling simulations. Flushing a one-dimensional flow column packed with complex contaminated soil sequentially with citric acid then a surfactant resulted in the removal of 85.6% of Zn, 62% of Pb, and 31.6% of HPO. The desorption distribution coefficients, KUbatch and KLbatch, converged to constant values as Ce increased. An equilibrium model (ADR) and nonequilibrium models (TSNE and TRNE) were used to predict the desorption and transport of complex contaminants. The nonequilibrium models demonstrated better fits with the experimental values obtained from the column test than the equilibrium model. The ranges of KUbatch and KLbatch were very close to those of KUfit and KLfit determined from model simulations. The parameters (R, β, ω, α, and f) determined from model simulations were useful for characterizing the transport of contaminants within the soil matrix. The results of this study provide useful information for the operational parameters of the flushing process for soils with complex contamination.

  6. Model Establishment for Simulating Soil Organic Carbon Dynamics

    Institute of Scientific and Technical Information of China (English)

    HUANG Yao; LIU Shi-liang; SHEN Qi-rong; ZONG Liang-gang

    2002-01-01

    Assuming that decomposition of organic matter in soils follows the first-order kinetics reaction,a computer model was developed to simulate soil organic matter dynamics. Organic matter in soils is divided up into two parts that include incorporated organic carbon from crop residues or other organic fertilizer and soil intrinsic carbon. The incorporated organic carbon was assumed to consist of two components, labile-C and resistant-C. The model was represented by a differential equation of dCi/dt = Ki× fT × fw × fs × Ci ( i = l,r, S ) and an integral equation of Cit = Cio × EXP ( Ki X fT X fw X fs X t ). Effect of soil parameters of temperature, moisture and texture on the decomposition was functioned by the fT, fw and fs, respectively.Data from laboratory incubation experiments were used to determine the first-order decay rate Ki and the fraction of labile-C of crop residues by employing a nonlinear method. The values of K for the components of labile-C and resistant-C and the soil intrinsic carbon were evaluated to be 0. 025,0. 080 × 10-2 and 0. 065 ×10-3d-1, respectively. The labile-C fraction of wheat straw, wheat roots, rice straw and rice roots were0.50, 0.25, 0.40 and 0.20, respectively. These values are related to the initial residue carbon-to-nitrogen ratio ( C/N) and lignin content.

  7. Impacts of snow and organic soils parameterization on northern Eurasian soil temperature profiles simulated by the ISBA land surface model

    Science.gov (United States)

    Decharme, Bertrand; Brun, Eric; Boone, Aaron; Delire, Christine; Le Moigne, Patrick; Morin, Samuel

    2016-04-01

    In this study we analyzed how an improved representation of snowpack processes and soil properties in the multilayer snow and soil schemes of the Interaction Soil-Biosphere-Atmosphere (ISBA) land surface model impacts the simulation of soil temperature profiles over northern Eurasian regions. For this purpose, we refine ISBA's snow layering algorithm and propose a parameterization of snow albedo and snow compaction/densification adapted from the detailed Crocus snowpack model. We also include a dependency on soil organic carbon content for ISBA's hydraulic and thermal soil properties. First, changes in the snowpack parameterization are evaluated against snow depth, snow water equivalent, surface albedo, and soil temperature at a 10 cm depth observed at the Col de Porte field site in the French Alps. Next, the new model version including all of the changes is used over northern Eurasia to evaluate the model's ability to simulate the snow depth, the soil temperature profile, and the permafrost characteristics. The results confirm that an adequate simulation of snow layering and snow compaction/densification significantly impacts the snowpack characteristics and the soil temperature profile during winter, while the impact of the more accurate snow albedo computation is dominant during the spring. In summer, the accounting for the effect of soil organic carbon on hydraulic and thermal soil properties improves the simulation of the soil temperature profile. Finally, the results confirm that this last process strongly influences the simulation of the permafrost active layer thickness and its spatial distribution.

  8. EVALUATION OF A SIMULATOR MODEL FOR PREDICTING SOIL-WATER CHARACTERISTICS OF SELECTED AGMCULTURAL FIELDS

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    H. E. Igbadun

    2011-06-01

    Full Text Available The ability of the Soil Water Characteribtics-Hydraulic Calculator (SWC-HPC model in predicting soi-water agricultural fields in Zaria, Nigeria, was tested and reprted in this study. The goal was to establish the predictability and reliability of the nodel, and hence, its use in determining water characteristics of soils in the stud/ area. Forty soil samples collected from four irrigation sites were used in the valuation. The soils particle size distribution (specifically, percent clay and sand and organic matter contents were inputted into the model to simulate soil moistur; status at saturation, field capacity and wilting point, soil bulk density and saturated hydraulic conductivity. The model outputs were statistically compared with observed parameters from laboratory tests using root mean square error (RMSE, c< ^efficient of variation (CV, modeling efficiency (EF and coefficient of residual mass (CRM. The model accurately simulated the observed bulk densities of the soil tested, satisfactorily simulated soil moisture content at field capacity, and mot lerately simulated moisture content at saturation and wilting point. The model lowever, poorly simulated saturated hydraulic conductivity of the soils tested. The SWC-HPC may therefore be used only to simulate soil bulk densities and moistui e status at saturation, field capacity and wilting point in the study locations.

  9. Regional soil moisture simulation for Shaanxi Province using SWAT model validation and trend analysis

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The soil moisture in Shaanxi Province,a region with complex topography,is simulated using the distributed hydrological model Soil Water Assessment Tool(SWAT).Comparison and contrast of modeled and observed soil moisture show that the SWAT model can reasonably simulate the long-term trend in soil moisture and the spatiotemporal variability of soil moisture in the region.Comparisons to NCEP/NCAR and ERA40 reanalysis of soil moisture show that the trend of variability in soil moisture simulated by SWAT is more consistent with the observed.SWAT model results suggested that high soil moisture in surface soil layers appears in the southern Shaanxi with high vegetation cover,and the Qinling mountainous region with frequent orographic precipitation.In deeper soil layers,high soil moisture appears in the river basins and plains.The regional soil moisture showed a generally decreasing trend on all soil layers from 1951 to 2004,with a stronger and significant decreasing trend in deeper soil layers,especially in the northern parts of the province.

  10. Evapotranspiration simulated by CRITERIA and AquaCrop models in stony soils

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    Pasquale Campi

    2015-06-01

    Full Text Available The performance of a water balance model is also based on the ability to correctly perform simulations in heterogeneous soils. The objective of this paper is to test CRITERIA and AquaCrop models in order to evaluate their suitability in estimating evapotranspiration at the field scale in two types of soil in the Mediterranean region: non-stony and stony soil. The first step of the work was to calibrate both models under the non-stony conditions. The models were calibrated by using observations on wheat crop (leaf area index or canopy cover, and phenological stages as a function of degree days and pedo-climatic measurements. The second step consisted in the analysing the impact of the soil type on the models performances by comparing simulated and measured values. The outputs retained in the analysis were soil water content (at the daily scale and crop evapotranspiration (at two time scales: daily and crop season. The model performances were evaluated through four statistical tests: normalised difference (D% at the seasonal time scale; and relative root mean square error (RRMSE, efficiency index (EF, coefficient of determination (r2 at the daily scale. At the seasonal scale, values of D% were less than 15% in stony and on-stony soils, indicating a good performance attained by both models. At the daily scale, the RRMSE values (<30% indicate that the evapotranspiration simulated by CRITERIA is acceptable in both soil types. In the stony soil conditions, 3 out 4 statistical tests (RRMSE, EF, r2 indicate the inadequacy of AquaCrop to simulate correctly daily evapotranspiration. The higher performance of CRITERIA model to simulate daily evapotranspiration in stony soils, is due to the soil submodel, which requires the percentage skeleton as an input, while AquaCrop model takes into account the presence of skeleton by reducing the soil volume.

  11. S-World: A high resolution global soil database for simulation modelling (Invited)

    Science.gov (United States)

    Stoorvogel, J. J.

    2013-12-01

    There is an increasing call for high resolution soil information at the global level. A good example for such a call is the Global Gridded Crop Model Intercomparison carried out within AgMIP. While local studies can make use of surveying techniques to collect additional techniques this is practically impossible at the global level. It is therefore important to rely on legacy data like the Harmonized World Soil Database. Several efforts do exist that aim at the development of global gridded soil property databases. These estimates of the variation of soil properties can be used to assess e.g., global soil carbon stocks. However, they do not allow for simulation runs with e.g., crop growth simulation models as these models require a description of the entire pedon rather than a few soil properties. This study provides the required quantitative description of pedons at a 1 km resolution for simulation modelling. It uses the Harmonized World Soil Database (HWSD) for the spatial distribution of soil types, the ISRIC-WISE soil profile database to derive information on soil properties per soil type, and a range of co-variables on topography, climate, and land cover to further disaggregate the available data. The methodology aims to take stock of these available data. The soil database is developed in five main steps. Step 1: All 148 soil types are ordered on the basis of their expected topographic position using e.g., drainage, salinization, and pedogenesis. Using the topographic ordering and combining the HWSD with a digital elevation model allows for the spatial disaggregation of the composite soil units. This results in a new soil map with homogeneous soil units. Step 2: The ranges of major soil properties for the topsoil and subsoil of each of the 148 soil types are derived from the ISRIC-WISE soil profile database. Step 3: A model of soil formation is developed that focuses on the basic conceptual question where we are within the range of a particular soil property

  12. Water and heat transport in hilly red soil of southern China: Ⅱ. Modeling and simulation

    Institute of Scientific and Technical Information of China (English)

    LU Jun; HUANG Zhi-zhen; HAN Xiao-fei

    2005-01-01

    Simulation models of heat and water transport have not been rigorously tested for the red soils of southern China.Based on the theory of nonisothermal water-heat coupled transfer, a simulation model, programmed in Visual Basic 6.0, was developed to predict the coupled transfer of water and heat in hilly red soil. A series of soil column experiments for soil water and heat transfer, including soil columns with closed and evaporating top ends, were used to test the simulation model. Results showed that in the closed columns, the temporal and spatial distribution of moisture and heat could be very well predicted by the model,while in the evaporating columns, the simulated soil water contents were somewhat different from the observed ones. In the heat flow equation by Taylor and Lary (1964), the effect of soil water evaporation on the heat flow is not involved, which may be the main reason for the differences between simulated and observed results. The predicted temperatures were not in agreement with the observed one with thermal conductivities calculated by de Vries and Wierenga equations, so that it is suggested that Kh, soil heat conductivity, be multiplied by 8.0 for the first 6.5 h and by 1.2 later on. Sensitivity analysis of soil water and heat coefficients showed that the saturated hydraulic conductivity, Ks, and the water diffusivity, D(θ), had great effects on soil water transport; the variation of soil porosity led to the difference of soil thermal properties, and accordingly changed temperature redistribution,which would affect water redistribution.

  13. Real-time model for simulating a tracked vehicle on deformable soils

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    Martin Meywerk

    2016-05-01

    Full Text Available Simulation is one possibility to gain insight into the behaviour of tracked vehicles on deformable soils. A lot of publications are known on this topic, but most of the simulations described there cannot be run in real-time. The ability to run a simulation in real-time is necessary for driving simulators. This article describes an approach for real-time simulation of a tracked vehicle on deformable soils. The components of the real-time model are as follows: a conventional wheeled vehicle simulated in the Multi Body System software TRUCKSim, a geometric description of landscape, a track model and an interaction model between track and deformable soils based on Bekker theory and Janosi–Hanamoto, on one hand, and between track and vehicle wheels, on the other hand. Landscape, track model, soil model and the interaction are implemented in MATLAB/Simulink. The details of the real-time model are described in this article, and a detailed description of the Multi Body System part is omitted. Simulations with the real-time model are compared to measurements and to a detailed Multi Body System–finite element method model of a tracked vehicle. An application of the real-time model in a driving simulator is presented, in which 13 drivers assess the comfort of a passive and an active suspension of a tracked vehicle.

  14. Decomposition by ectomycorrhizal fungi alters soil carbon storage in a simulation model

    DEFF Research Database (Denmark)

    Moore, J. A. M.; Jiang, J.; Post, W. M.

    2015-01-01

    that ectomycorrhizal fungi can also be active decomposers when plant carbon allocation to fungi is low. Here, we reviewed the literature on ectomycorrhizal decomposition and we developed a simulation model of the plant-mycorrhizae interaction where a reduction in plant productivity stimulates ectomycorrhizal fungi...... to decompose soil organic matter. Our review highlights evidence demonstrating the potential for ectomycorrhizal fungi to decompose soil organic matter. Our model output suggests that ectomycorrhizal activity accounts for a portion of carbon decomposed in soil, but this portion varied with plant productivity...... and the mycorrhizal carbon uptake strategy simulated. Lower organic matter inputs to soil were largely responsible for reduced soil carbon storage. Using mathematical theory, we demonstrated that biotic interactions affect predictions of ecosystem functions. Specifically, we developed a simple function to model...

  15. An open source simulation model for soil and sediment bioturbation.

    Science.gov (United States)

    Schiffers, Katja; Teal, Lorna Rachel; Travis, Justin Mark John; Solan, Martin

    2011-01-01

    Bioturbation is one of the most widespread forms of ecological engineering and has significant implications for the structure and functioning of ecosystems, yet our understanding of the processes involved in biotic mixing remains incomplete. One reason is that, despite their value and utility, most mathematical models currently applied to bioturbation data tend to neglect aspects of the natural complexity of bioturbation in favour of mathematical simplicity. At the same time, the abstract nature of these approaches limits the application of such models to a limited range of users. Here, we contend that a movement towards process-based modelling can improve both the representation of the mechanistic basis of bioturbation and the intuitiveness of modelling approaches. In support of this initiative, we present an open source modelling framework that explicitly simulates particle displacement and a worked example to facilitate application and further development. The framework combines the advantages of rule-based lattice models with the application of parameterisable probability density functions to generate mixing on the lattice. Model parameters can be fitted by experimental data and describe particle displacement at the spatial and temporal scales at which bioturbation data is routinely collected. By using the same model structure across species, but generating species-specific parameters, a generic understanding of species-specific bioturbation behaviour can be achieved. An application to a case study and comparison with a commonly used model attest the predictive power of the approach.

  16. Simulation Models of Leaf Area Index and Yield for Cotton Grown with Different Soil Conditioners.

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    Lijun Su

    Full Text Available Simulation models of leaf area index (LAI and yield for cotton can provide a theoretical foundation for predicting future variations in yield. This paper analyses the increase in LAI and the relationships between LAI, dry matter, and yield for cotton under three soil conditioners near Korla, Xinjiang, China. Dynamic changes in cotton LAI were evaluated using modified logistic, Gaussian, modified Gaussian, log normal, and cubic polynomial models. Universal models for simulating the relative leaf area index (RLAI were established in which the application rate of soil conditioner was used to estimate the maximum LAI (LAIm. In addition, the relationships between LAIm and dry matter mass, yield, and the harvest index were investigated, and a simulation model for yield is proposed. A feasibility analysis of the models indicated that the cubic polynomial and Gaussian models were less accurate than the other three models for simulating increases in RLAI. Despite significant differences in LAIs under the type and amount of soil conditioner applied, LAIm could be described by aboveground dry matter using Michaelis-Menten kinetics. Moreover, the simulation model for cotton yield based on LAIm and the harvest index presented in this work provided important theoretical insights for improving water use efficiency in cotton cultivation and for identifying optimal application rates of soil conditioners.

  17. TRANSOL, a dynamic simulation model for transport and transformation of solutes in soils

    NARCIS (Netherlands)

    Kroes, J.G.; Rijtema, P.E.

    1996-01-01

    The dynamic simulation model TRANSOL has been developed to fulfil the need for a tool to analyse leaching of solutes from the soil surface to groundwater and surface waters. A description is given of the modelled processes: conversion, formation, cropuptake, precipitation, equilibrium and non-equili

  18. Simulation of Tillage Systems Impact on Soil Biophysical Properties Using the SALUS Model

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    Luigi Sartori

    2011-02-01

    Full Text Available A sustainable land management has been defined as the management system that allows for production, while minimizing risk, maintaining quality of soil and water. Tillage systems can significantly decrease soil carbon storage and influence the soil environment of a crop. Crop growth models can be useful tools in evaluating the impact of different tillage systems on soil biophysical properties and on the growth and final yield of the crops. The objectives of this paper were i to illustrate the SALUS model and its tillage component; ii to evaluate the effects of different tillage systems on water infiltration and time to ponding, iii to simulate the effect of tillage systems on some soil biophysical properties. The SALUS (System Approach to Land Use Sustainability model is designed to simulate continuous crop, soil, water and nutrient conditions under different tillage and crop residues management strategies for multiple years. Predictions of changes in surface residue, bulk density, runoff, drainage and evaporation were consistent with expected behaviours of these parameters as described in the literature. The experiment to estimate the time to ponding curve under different tillage system confirmed the theory and showed the beneficial effects of the residue on soil surface with respect to water infiltration. It also showed that the no-tillage system is a more appropriate system to adopt in areas characterized by high intensity rainfall.

  19. Simulation of water movement and isoproturon behaviour in a heavy clay soil using the MACRO model

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    T. J. Besien

    1997-01-01

    Full Text Available In this paper, the dual-porosity MACRO model has been used to investigate methods of reducing leaching of isoproturon from a structured heavy clay soil. The MACRO model was applied to a pesticide leaching data-set generated from a plot scale experiment on a heavy clay soil at the Oxford University Farm, Wytham, England. The field drain was found to be the most important outflow from the plot in terms of pesticide removal. Therefore, this modelling exercise concentrated on simulating field drain flow. With calibration of field-saturated and micropore saturated hydraulic conductivity, the drain flow hydrographs were simulated during extended periods of above average rainfall, with both the hydrograph shape and peak flows agreeing well. Over the whole field season, the observed drain flow water budget was well simulated. However, the first and second drain flow events after pesticide application were not simulated satisfactorily. This is believed to be due to a poor simulation of evapotranspiration during a period of low rainfall around the pesticide application day. Apart from an initial rapid drop in the observed isoproturon soil residue, the model simulated isoproturon residues during the 100 days after pesticide application reasonably well. Finally, the calibrated model was used to show that changes in agricultural practice (deep ploughing, creating fine consolidated seed beds and organic matter applications could potentially reduce pesticide leaching to surface waters by up to 60%.

  20. Modification of the RothC model to simulate soil C mineralization of exogenous organic matter

    Science.gov (United States)

    Mondini, Claudio; Cayuela, Maria Luz; Sinicco, Tania; Fornasier, Flavio; Galvez, Antonia; Sánchez-Monedero, Miguel Angel

    2017-07-01

    The development of soil organic C (SOC) models capable of producing accurate predictions for the long-term decomposition of exogenous organic matter (EOM) in soils is important for the effective management of organic amendments. However, reliable C modeling in amended soils requires specific optimization of current C models to take into account the high variability in EOM origin and properties. The aim of this work was to improve the prediction of C mineralization rates in amended soils by modifying the RothC model to encompass a better description of EOM quality. The standard RothC model, involving C input to the soil only as decomposable (DPM) or resistant (RPM) organic material, was modified by introducing additional pools of decomposable (DEOM), resistant (REOM) and humified (HEOM) EOM. The partitioning factors and decomposition rates of the additional EOM pools were estimated by model fitting to the respiratory curves of amended soils. For this task, 30 EOMs from 8 contrasting groups (compost, anaerobic digestates, sewage sludge, agro-industrial waste, crop residues, bioenergy by-products, animal residues and meat and bone meals) were added to 10 soils and incubated under different conditions. The modified RothC model was fitted to C mineralization curves in amended soils with great accuracy (mean correlation coefficient 0.995). In contrast to the standard model, the EOM-optimized RothC was able to better accommodate the large variability in EOM source and composition, as indicated by the decrease in the root mean square error of the simulations for different EOMs (from 29.9 to 3.7 % and 20.0 to 2.5 % for soils amended with bioethanol residue and household waste compost, respectively). The average decomposition rates for DEOM and REOM pools were 89 and 0.4 yr-1, higher than the standard model coefficients for DPM (10 yr-1) and RPM (0.3 yr-1). The results indicate that the explicit treatment of EOM heterogeneity enhances the model ability to describe amendment

  1. Simulation of nitrous oxide effluxes, crop yields and soil physical properties using the LandscapeDNDC model in managed ecosystem

    Science.gov (United States)

    Nyckowiak, Jedrzej; Lesny, Jacek; Haas, Edwin; Juszczak, Radoslaw; Kiese, Ralf; Butterbach-Bahl, Klaus; Olejnik, Janusz

    2014-05-01

    Modeling of nitrous oxide emissions from soil is very complex. Many different biological and chemical processes take place in soils which determine the amount of emitted nitrous oxide. Additionaly, biogeochemical models contain many detailed factors which may determine fluxes and other simulated variables. We used the LandscapeDNDC model in order to simulate N2O emissions, crop yields and soil physical properties from mineral cultivated soils in Poland. Nitrous oxide emissions from soils were modeled for fields with winter wheat, winter rye, spring barley, triticale, potatoes and alfalfa crops. Simulations were carried out for the plots of the Brody arable experimental station of Poznan University of Life Science in western Poland and covered the period 2003 - 2012. The model accuracy and its efficiency was determined by comparing simulations result with measurements of nitrous oxide emissions (measured with static chambers) from about 40 field campaigns. N2O emissions are strongly dependent on temperature and soil water content, hence we compared also simulated soil temperature at 10cm depth and soil water content at the same depth with the daily measured values of these driving variables. We compared also simulated yield quantities for each individual experimental plots with yield quantities which were measured in the period 2003-2012. We conclude that the LandscapeDNDC model is capable to simulate soil N2O emissions, crop yields and physical properties of soil with satisfactorily good accuracy and efficiency.

  2. Modelling cadmium contamination in paddy soils under long-term remediation measures: Model development and stochastic simulations.

    Science.gov (United States)

    Peng, Chi; Wang, Meie; Chen, Weiping

    2016-09-01

    A pollutant accumulation model (PAM) based on the mass balance theory was developed to simulate long-term changes of heavy metal concentrations in soil. When combined with Monte Carlo simulation, the model can predict the probability distributions of heavy metals in a soil-water-plant system with fluctuating environmental parameters and inputs from multiple pathways. The model was used for evaluating different remediation measures to deal with Cd contamination of paddy soils in Youxian county (Hunan province), China, under five scenarios, namely the default scenario (A), not returning paddy straw to the soil (B), reducing the deposition of Cd (C), liming (D), and integrating several remediation measures (E). The model predicted that the Cd contents of soil can lowered significantly by (B) and those of the plants by (D). However, in the long run, (D) will increase soil Cd. The concentrations of Cd in both soils and rice grains can be effectively reduced by (E), although it will take decades of effort. The history of Cd pollution and the major causes of Cd accumulation in soil were studied by means of sensitivity analysis and retrospective simulation.

  3. Simulation of the Vapor Intrusion Process for Non-Homogeneous Soils Using a Three-Dimensional Numerical Model

    OpenAIRE

    Bozkurt, Ozgur; Pennell, Kelly G.; Suuberg, Eric M.

    2009-01-01

    This paper presents model simulation results of vapor intrusion into structures built atop sites contaminated with volatile or semi-volatile chemicals of concern. A three-dimensional finite element model was used to investigate the importance of factors that could influence vapor intrusion when the site is characterized by non-homogeneous soils. Model simulations were performed to examine how soil layers of differing properties alter soil gas concentration profiles and vapor intrusion rates i...

  4. Mathematical Modelling and Simulation of Mobility of Heavy Metals in Soil Contaminated With Sewage Sludge

    Directory of Open Access Journals (Sweden)

    Jimoh ABDULFATAI

    2007-01-01

    Full Text Available This paper is aimed at developing a model equation that can predict the mobility of heavy metal in the soil contaminated with sewage sludge. The model equation was developed and represented by the expression below... The developed equation was then simulated using MathCAD 2000 professional software. The experimental and model results obtained from the simulation of the developed equation were compared numerically and graphically. It was observed that there are reasonable levels of agreement between the two results. The model revealed close fitting when compared with the experimental results. This is further substantiated through the result of the correlation coefficient analysis that was found to be unity for the experiment. Thus, the model developed can be considered as a good representation of the phenomenon of mobility of heavy metals in the soil.

  5. Using synthetic models to simulate aging of Cu contamination in soils.

    Science.gov (United States)

    Proffit, S; Marin, B; Cances, B; Ponthieu, M; Sayen, S; Guillon, E

    2015-05-01

    The Bureau Commun de Référence (BCR) sequential extraction scheme and micro-synchrotron-based X-ray fluorescence (μ-SXRF) analysis were used to determine the Cu fractionation in a calcareous vineyard soil and a synthetic soil (mixture of seven constituents: calcite, birnessite, ferrihydrite, goethite, lignocellulosic residue, kaolinite, and quartz) at different Cu contamination rates (190, 1270, and 6350 mg kg(-1) of Cu) and aging times (1, 30, 92, and 181 days). The Cu distribution in the spiked vineyard and synthetic soils was different from the original vineyard one and was influenced by the loading level. The newly added Cu was preferentially present in the acid soluble fraction. Aging of the contaminated vineyard and synthetic soils during 6 months led to the redistribution of Cu from the weakly bound acid soluble fraction to the strongly bound reducible one. The evolution with time could satisfactorily be simulated by the Elovich diffusion model for the synthetic soils. It was less significant as less marked in the contaminated vineyard soil than in the synthetic one, even though the trends observed in both were similar. This study supported the hypothesis that "simple" synthetic models could be used to approach the Cu fractionation and its evolution with time in vineyard soils.

  6. Seasonally Frozen Soil Monitoring Using Passive Microwave Satellite Data and Simulation Modeling

    Science.gov (United States)

    Toll, D. L.; Owe, M.; Levine, E.

    1998-01-01

    Satellite data and simulation modeling were used to assess seasonally frozen soils in the central US - Canada borders area (46-53 degrees N and 96-108 degrees). We used Scanning Multichannel Microwave Radiometer (SMMR) satellite data to delineate the top layer of frozen soils. SMMR is a passive microwave sensor having five channels (6.6, 10, 18, 21 and 37 GHz) with a horizontal and vertical polarization. SMRR data are available between 1978-1987 with noon and midnight overpass and footprint sizes between 25 km and 150 km. SMMR data were processed from resampled 1/4 degree grid cells during fall freeze-up and spring thaw (fall 1985 - spring 1987). The dielectric properties of a target may directly affect the satellite signal. The dielectric value is an order of magnitude smaller for frozen soil water. There are other significant changes to the emitted microwave signal from changes to the surface physical temperature, attenuation of the soil signal from plant water and soil moisture. We further characterized the temporal and spatial dynamic of frozen soils using the FroST (Frozen Soil Temperature) simulation model. The FroST model was used to further predict soil water and ice content, and soil temperature. SMMR results were compared versus 5-cm soil temperature data from available weather stations (14 in Canada and 11 for available months in the US). SMMR data were analyzed as a function of frequency, polarization, polarization difference, and "frequency gradient". In addition, vegetation density, physical temperature and snow depth were also considered. Preliminary analysis of SMMR derived frozen soil/thaw classification using a simple threshold classification indicates a mean overall classification accuracy by season of 85 percent. A sensitivity analysis for different soils with varying amounts of snow was conducted with FroST, which showed that the amount of snow, and the time of snow fall and melt affected the ice and water content, and depth of thaw. These

  7. A Constitutive Model for Simulating Soil-Concrete Interfaces

    Science.gov (United States)

    1986-07-01

    nclude A.,a Code) Or. T. J. Ross (505) 844-9087 NTESA II DD FORM 1473, 83 APR EDITION OF 1 JAN 73 IS ORSOLETE. UNCLASSIFIED SECURITY CLASSIFICATION...concerning strain softening. Bazant , et al., (Ref. 12), incorporated strain softening into a consitutive model by using a nonlocal continuum theory...Concrete," Mechanics of Materials Vol. 3, 1984, pp. 271-294. 12. Bazant , Z. P., Belytschko, T. B., and Chang, T., "Continuum Theory for Strain

  8. Methods, Computational Platform, Verification, and Application of Earthquake-Soil-Structure-Interaction Modeling and Simulation

    Science.gov (United States)

    Tafazzoli, Nima

    Seismic response of soil-structure systems has attracted significant attention for a long time. This is quite understandable with the size and the complexity of soil-structure systems. The focus of three important aspects of ESSI modeling could be on consistent following of input seismic energy and a number of energy dissipation mechanisms within the system, numerical techniques used to simulate dynamics of ESSI, and influence of uncertainty of ESSI simulations. This dissertation is a contribution to development of one such tool called ESSI Simulator. The work is being done on extensive verified and validated suite for ESSI Simulator. Verification and validation are important for high fidelity numerical predictions of behavior of complex systems. This simulator uses finite element method as a numerical tool to obtain solutions for large class of engineering problems such as liquefaction, earthquake-soil-structure-interaction, site effect, piles, pile group, probabilistic plasticity, stochastic elastic-plastic FEM, and detailed large scale parallel models. Response of full three-dimensional soil-structure-interaction simulation of complex structures is evaluated under the 3D wave propagation. Domain-Reduction-Method is used for applying the forces as a two-step procedure for dynamic analysis with the goal of reducing the large size computational domain. The issue of damping of the waves at the boundary of the finite element models is studied using different damping patterns. This is used at the layer of elements outside of the Domain-Reduction-Method zone in order to absorb the residual waves coming out of the boundary layer due to structural excitation. Extensive parametric study is done on dynamic soil-structure-interaction of a complex system and results of different cases in terms of soil strength and foundation embedment are compared. High efficiency set of constitutive models in terms of computational time are developed and implemented in ESSI Simulator

  9. Numerical simulation of landslide-generated waves using a soil-water coupling smoothed particle hydrodynamics model

    Science.gov (United States)

    Shi, Chuanqi; An, Yi; Wu, Qiang; Liu, Qingquan; Cao, Zhixian

    2016-06-01

    We simulate the generation of a landslide-induced impulse wave with a newly-developed soil-water coupling model in the smoothed particle hydrodynamics (SPH) framework. The model includes an elasto-plastic constitutive model for soil, a Navier-Stokes equation based model for water, and a bilateral coupling model at the interface. The model is tested with simulated waves induced by a slow and a fast landslide. Good agreement is obtained between simulation results and experimental data. The generated wave and the deformation of the landslide body can both be resolved satisfactorily. All parameters in our model have their physical meaning in soil mechanics and can be obtained from conventional soil mechanics experiments directly. The influence of the dilatancy angle of soil shows that the non-associated flow rule must be selected, and the value of the dilatancy angle should not be chosen arbitrarily, if it is not determined with relative experiments.

  10. A constitutive model of frozen soil with damage and numerical simulation for the coupled problem

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Based on the microcosmic mechanics of composite materials, an elastic constitutive model for frozen soil with damage is presented. For frozen sandy soil with a range of ice contents and under a range of temperature conditions, quantitative results determined by this constitutive model agree with practically measured stress-strain curves. After numerically simulating the coupled water, temperature and stress fields of channel frozen and frozen roadbed using a self-developed finite-element routine, more accurate and practical calculation results for the temperature field coupled with stress, displacement and strain fields are obtained; the results match predictions and tests undertaken by earlier researchers. Our results support the reliability of our routine for calculating interdependent physical quantities of frozen soil and for describing the relationships between them. Our program can offer necessary constraints for engineering design and construction in permafrost regions.

  11. Mathematical simulation of soil vapor extraction systems: Model development and numerical examples

    Science.gov (United States)

    Rathfelder, Klaus; Yeh, William W.-G.; Mackay, Douglas

    1991-12-01

    This paper describes the development of a numerical model for prediction of soil vapor extraction processes. The major emphasis is placed on field-scale predictions with the objective to advance development of planning tools for design and operation of venting systems. The numerical model solves two-dimensional flow and transport equations for general n-component contaminant mixtures. Flow is limited to the gas phase and local equilibrium partitioning is assumed in tracking contaminants in the immiscible fluid, water, gas, and solid phase. Model predictions compared favorably with analytical solutions and multicomponent column venting experiments. Sensitivity analysis indicates equilibrium phase partitioning is a good assumption in modeling organic liquid volatilization occurring in field venting operations. Mass transfer rates in volatilization from the water phase and contaminant desorption are potentially rate limiting. Simulations of hypothetical field-scale problems show efficiency of venting operations is most sensitive to vapor pressure and the magnitude and distribution of soil permeability.

  12. SMASS - a simulation model of physical and chemical processes in acid sulphate soils; Version 2.1

    NARCIS (Netherlands)

    Bosch, van den H.; Bronswijk, J.J.B.; Groenenberg, J.E.; Ritsema, C.J.

    1998-01-01

    The Simulation Model for Acid Sulphate Soils (SMASS) has been developed to predict the effects of water management strategies on acidification and de-acidification in areas with acid sulphate soils. It has submodels for solute transport, chemistry, oxygen transport and pyrite oxidation. The model mu

  13. Simulation of fan topography and soil profile using a coupled soilscape-landscape evolution model

    Science.gov (United States)

    Welivitiya, Dimuth; Willgoose, Garry; Hancock, Greg

    2017-04-01

    In this study the evolution of a fluvial fan, its topography and soil profile grading under erosion and deposition and soil profile weathering was simulated using SSPAM coupled soil-landscape evolution model. A constant rainfall was simulated on a synthetic landform and a fluvial fan depositional structure was allowed to form at the latter part of the landform. At each time step the geomorphological and particle size distribution information of the fan was recorded. Using this recorded information, the evolutionary characteristics of the fan as well as the surface and subsurface sediment characteristics was examined and compared with experimental and field observation data. Different fan profile sections were also derived from the recorded data and analysed. The simulation produced a fluvial fan semicircular in shape, with concave up long profiles and convex up cross profiles. The surface sediment sizes of the simulated fan were coarsest near the fan apex and fines toward the fan toe with coarse grained sediment filaments extending radially from the fan apex. These geomorphological features and surface sediment distribution agrees well with field observations of natural fans. The results of the simulation also show that the fan develops as a result of the channel bringing sediments in to the fan and periodically changing its path due to steepening of channel gradient by sediment deposition. The position of the channel is fixed at the fan apex and the channel path constantly changes along any radial direction form the fan apex. This process is remarkably similar to the process of "Fan head trenching" described in literature which is the dominant process in fluvial fan development in the field. Finally, the analysis of fan cross-sections revealed complex sediment layering patterns in the fan profile. The simulation results of the SSSPAM coupled soilscape-landscape evolution model provide qualitatively correct geomorphological and sedimentary characterization of the

  14. Comparison of simulated forest soil response to acid deposition reduction with two models of differing complexity

    Directory of Open Access Journals (Sweden)

    J. P. Mol-Dijkstra

    1998-01-01

    Full Text Available Great effort has been dedicated to developing soil acidification models for use on different scales. This paper focuses on the changes in model performance of a site scale soil acidification model (NUCSAM and a national to European scale soil acidification model (SMART 2. This was done to gain insight into the effects of model simplification. Because these models aim to predict the response to reduction in acid deposition, these models must be tested under such circumstances. A straightforward calibration and validation of the regional model, however, is hampered by lack of observations over a sufficient time period. Consequently, NUCSAM was calibrated and validated to a manipulation experiment involving reduced acid deposition in the Speuld forest, the Netherlands. SMART 2 was then used with calibrated input data from NUCSAM. The acid deposition was excluded by a roof beneath the canopy. The roofed area consists of a plot receiving pristine deposition levels of nitrogen (N and sulphur (S and a control plot receiving ambient deposition. NUCSAM was calibrated on the ambient plot, followed by a validation of both models on the pristine plot. Both models predicted soil solution concentrations within the 95% confidence interval of the observed responses for both the ambient plot and the pristine plot at 90 cm depth. Despite the large seasonal and vertical (spatial variation in soil solution chemistry, the trends in annual flux- weighted soil solution chemistry, as predicted by SMART 2 and NUCSAM, corresponded well.The annual leaching fluxes below the root zone were also similar although differences exist for the topsoil. For the topsoil, NUCSAM simulated the nutrients and acid related constituents better than SMART 2. Both models overestimated the ammonium (NH4 concentration at 10 cm depth. SMART 2 underestimated calcium and magnesium (BC2+ concentration at 10 depth, whereas NUCSAM overestimated BC2+ concentration at 90 cm depth. NUCSAM predicted

  15. Simulation of estrogen transport and behavior in laboratory soil columns using a cellular automata model

    Science.gov (United States)

    Chen, Qingcai; Shi, Jianghong; Liu, Xiaowei; Wu, Wei; Liu, Bo; Zhang, Hui

    2013-03-01

    A cellular automata model (CA model) was used to simulate the soil column leaching process of estrogens during the processes of migration and transformation. The results of the simulated leaching experiment showed that the first-order degradation rates of 17α-ethynylestradiol (EE2), 17β-estradiol (E2) and estrone (E1) were 0.131 h- 1 for E2, 0.099 h- 1 for E1 and 0.064 h- 1 for EE2 in the EE2 and E2 leaching process, and the first-order sorption rates were 5.94 h- 1 for E2, 5.63 h- 1 for EE2, 3.125 h- 1 for E1. Their sorption rates were positively correlated with the n-octanol/water partition coefficients. When the diffusion rate was low, its impact on the simulation results was insignificant. The increase in sorption and degradation rates caused the decrease in the total estrogens that leached. In addition, increasing the sorption rate could delay the emerging time of the maximum concentration of estrogen that leached, whereas increasing the degradation rate could shorten the emerging time of the maximum concentration of estrogen that leached. The comparison made between the experimental data and the simulation results of the CA model and the HYDRUS-1D software showed that the establishment of one-component and multi-component CA models could simulate EE2 and E2 soil column leaching processes, and the CA models achieve an intuitive, dynamic, and visual simulation.

  16. Coupled stochastic soil moisture simulation-optimization model of deficit irrigation

    Science.gov (United States)

    Alizadeh, Hosein; Mousavi, S. Jamshid

    2013-07-01

    This study presents an explicit stochastic optimization-simulation model of short-term deficit irrigation management for large-scale irrigation districts. The model which is a nonlinear nonconvex program with an economic objective function is built on an agrohydrological simulation component. The simulation component integrates (1) an explicit stochastic model of soil moisture dynamics of the crop-root zone considering interaction of stochastic rainfall and irrigation with shallow water table effects, (2) a conceptual root zone salt balance model, and 3) the FAO crop yield model. Particle Swarm Optimization algorithm, linked to the simulation component, solves the resulting nonconvex program with a significantly better computational performance compared to a Monte Carlo-based implicit stochastic optimization model. The model has been tested first by applying it in single-crop irrigation problems through which the effects of the severity of water deficit on the objective function (net benefit), root-zone water balance, and irrigation water needs have been assessed. Then, the model has been applied in Dasht-e-Abbas and Ein-khosh Fakkeh Irrigation Districts (DAID and EFID) of the Karkheh Basin in southwest of Iran. While the maximum net benefit has been obtained for a stress-avoidance (SA) irrigation policy, the highest water profitability has been resulted when only about 60% of the water used in the SA policy is applied. The DAID with respectively 33% of total cultivated area and 37% of total applied water has produced only 14% of the total net benefit due to low-valued crops and adverse soil and shallow water table conditions.

  17. Modeling of soil water infiltration with rainfall simulator in different agricultural systems

    Directory of Open Access Journals (Sweden)

    Thais E. M. dos Santos

    2016-06-01

    Full Text Available ABSTRACT This study aimed to compare models for predicting soil water infiltration rate and erosive rates using a rainfall simulator in different systems of common bean (Phaseolus vulgaris L. cultivation. The evaluated mathematical models were: Kostiakov, Kostiakov-Lewis, Green-Ampt and Horton. Infiltration tests were carried out considering six treatments: bean cultivated on contour with rock barriers spaced at 0.5 m between crop rows (BC1; bean cultivated on contour with rock barriers spaced at 1.0 m between crop rows (BC2; bean cultivated downslope (BDS; bean cultivated on contour with mulch (BCM; bare soil (BS and soil under natural cover (NC. Four replicates were considered, totaling 24 field tests. Kostiakov-Lewis's equation showed the lowest values of standard error. Soil water infiltration rate was equal to 53.3 mm h-1 in the natural vegetation treatment and to 9.49 mm h-1 in the downslope treatment. Surface roughness and the time of beginning of surface runoff were significantly higher for the conditions with mulch cover.

  18. Evaluating the Potential Use of Remotely-Sensed and Model-Simulated Soil Moisture for Agricultural Drought Risk Monitoring

    Science.gov (United States)

    Yan, Hongxiang; Moradkhani, Hamid

    2016-04-01

    Current two datasets provide spatial and temporal resolution of soil moisture at large-scale: the remotely-sensed soil moisture retrievals and the model-simulated soil moisture products. Drought monitoring using remotely-sensed soil moisture is emerging, and the soil moisture simulated using land surface models (LSMs) have been used operationally to monitor agriculture drought in United States. Although these two datasets yield important drought information, their drought monitoring skill still needs further quantification. This study provides a comprehensive assessment of the potential of remotely-sensed and model-simulated soil moisture data in monitoring agricultural drought over the Columbia River Basin (CRB), Pacific Northwest. Two satellite soil moisture datasets were evaluated, the LPRM-AMSR-E (unscaled, 2002-2011) and ESA-CCI (scaled, 1979-2013). The USGS Precipitation Runoff Modeling System (PRMS) is used to simulate the soil moisture from 1979-2011. The drought monitoring skill is quantified with two indices: drought area coverage (the ability of drought detection) and drought severity (according to USDM categories). The effects of satellite sensors (active, passive), multi-satellite combined, length of climatology, climate change effect, and statistical methods are also examined in this study.

  19. Integrating models to simulate emergent behaviour: effects of organic matter on soil hydraulics in the ICZ-1D soil-vegetation model

    Science.gov (United States)

    Valstar, Johan; Rowe, Ed; Konstantina, Moirogiorgou; Giannakis, Giorgos; Nikolaidis, Nikolaos

    2014-05-01

    explore the complex interactions involved in soil development and change. We were unable to identify appropriately-detailed existing models for plant productivity and for the dynamics of soil aggregation and porosity, and so developed the PROSUM and CAST models, respectively, to simulate these subsystems. Moreover, we applied the BRNS generator to obtain a chemical equilibrium model. These were combined with HYDRUS-1D (water and solute transport), a weathering model (derived from the SAFE model) and a simple bioturbation model. The model includes several feedbacks, such as the effect of soil organic matter on water retention and hydraulic conductivity. We encountered several important challenges when building the integrated model. First, a mechanism was developed that initiates the execution of a single time step for an individual sub-model and accounts for the relevant mass transfers between sub-models. This allows for different and sometimes variable time step duration in the submodels. Secondly, we removed duplicated processes and identified and included relevant solute production terms that had been neglected. The model is being tested against datasets obtained from several Soil Critical Zone Observatories in Europe. This contribution focuses on the design strategy for the model.

  20. Simulating soil C stability with mechanistic systems models: a multisite comparison of measured fractions and modelled pools

    Science.gov (United States)

    Robertson, Andy; Schipanski, Meagan; Sherrod, Lucretia; Ma, Liwang; Ahuja, Lajpat; McNamara, Niall; Smith, Pete; Davies, Christian

    2016-04-01

    Agriculture, covering more than 30% of global land area, has an exciting opportunity to help combat climate change by effectively managing its soil to promote increased C sequestration. Further, newly sequestered soil carbon (C) through agriculture needs to be stored in more stable forms in order to have a lasting impact on reducing atmospheric CO2 concentrations. While land uses in different climates and soils require different management strategies, the fundamental mechanisms that regulate C sequestration and stabilisation remain the same. These mechanisms are used by a number of different systems models to simulate C dynamics, and thus assess the impacts of change in management or climate. To evaluate the accuracy of these model simulations, our research uses a multidirectional approach to compare C stocks of physicochemical soil fractions collected at two long-term agricultural sites. Carbon stocks for a number of soil fractions were measured at two sites (Lincoln, UK; Colorado, USA) over 8 and 12 years, respectively. Both sites represent managed agricultural land but have notably different climates and levels of disturbance. The measured soil fractions act as proxies for varying degrees of stability, with C contained within these fractions relatable to the C simulated within the soil pools of mechanistic systems models1. Using stable isotope techniques at the UK site, specific turnover times of C within the different fractions were determined and compared with those simulated in the pools of 3 different models of varying complexity (RothC, DayCent and RZWQM2). Further, C dynamics and N-mineralisation rates of the measured fractions at the US site were assessed and compared to results of the same three models. The UK site saw a significant increase in C stocks within the most stable fractions, with topsoil (0-30cm) sequestration rates of just over 0.3 tC ha-1 yr-1 after only 8 years. Further, the sum of all fractions reported C sequestration rates of nearly 1

  1. Evaluation of a simple, point-scale hydrologic model in simulating soil moisture using the Delaware environmental observing system

    Science.gov (United States)

    Legates, David R.; Junghenn, Katherine T.

    2017-02-01

    Many local weather station networks that measure a number of meteorological variables (i.e., mesonetworks) have recently been established, with soil moisture occasionally being part of the suite of measured variables. These mesonetworks provide data from which detailed estimates of various hydrological parameters, such as precipitation and reference evapotranspiration, can be made which, when coupled with simple surface characteristics available from soil surveys, can be used to obtain estimates of soil moisture. The question is Can meteorological data be used with a simple hydrologic model to estimate accurately daily soil moisture at a mesonetwork site? Using a state-of-the-art mesonetwork that also includes soil moisture measurements across the US State of Delaware, the efficacy of a simple, modified Thornthwaite/Mather-based daily water balance model based on these mesonetwork observations to estimate site-specific soil moisture is determined. Results suggest that the model works reasonably well for most well-drained sites and provides good qualitative estimates of measured soil moisture, often near the accuracy of the soil moisture instrumentation. The model exhibits particular trouble in that it cannot properly simulate the slow drainage that occurs in poorly drained soils after heavy rains and interception loss, resulting from grass not being short cropped as expected also adversely affects the simulation. However, the model could be tuned to accommodate some non-standard siting characteristics.

  2. Evaluation of land surface model simulations of evapotranspiration over a 12 year crop succession: impact of the soil hydraulic properties

    Directory of Open Access Journals (Sweden)

    S. Garrigues

    2014-10-01

    Full Text Available Evapotranspiration has been recognized as one of the most uncertain term in the surface water balance simulated by land surface models. In this study, the SURFEX/ISBA-A-gs simulations of evapotranspiration are assessed at local scale over a 12 year Mediterranean crop succession. The model is evaluated in its standard implementation which relies on the use of the ISBA pedotransfer estimates of the soil properties. The originality of this work consists in explicitly representing the succession of crop cycles and inter-crop bare soil periods in the simulations and assessing its impact on the dynamic of simulated and measured evapotranspiration over a long period of time. The analysis focuses on key soil parameters which drive the simulation of evapotranspiration, namely the rooting depth, the soil moisture at saturation, the soil moisture at field capacity and the soil moisture at wilting point. The simulations achieved with the standard values of these parameters are compared to those achieved with the in situ values. The portability of the ISBA pedotransfer functions is evaluated over a typical Mediterranean crop site. Various in situ estimates of the soil parameters are considered and distinct parametrization strategies are tested to represent the evapotranspiration dynamic over the crop succession. This work shows that evapotranspiration mainly results from the soil evaporation when it is continuously simulated over a Mediterranean crop succession. The evapotranspiration simulated with the standard surface and soil parameters of the model is largely underestimated. The deficit in cumulative evapotranspiration amounts to 24% over 12 years. The bias in daily daytime evapotranspiration is −0.24 mm day−1. The ISBA pedotransfer estimates of the soil moisture at saturation and at wilting point are overestimated which explains most of the evapotranspiration underestimation. The overestimation of the soil moisture at wilting point causes the

  3. Evaluation of land surface model simulations of evapotranspiration over a 12 year crop succession: impact of the soil hydraulic properties

    Science.gov (United States)

    Garrigues, S.; Olioso, A.; Calvet, J.-C.; Martin, E.; Lafont, S.; Moulin, S.; Chanzy, A.; Marloie, O.; Desfonds, V.; Bertrand, N.; Renard, D.

    2014-10-01

    Evapotranspiration has been recognized as one of the most uncertain term in the surface water balance simulated by land surface models. In this study, the SURFEX/ISBA-A-gs simulations of evapotranspiration are assessed at local scale over a 12 year Mediterranean crop succession. The model is evaluated in its standard implementation which relies on the use of the ISBA pedotransfer estimates of the soil properties. The originality of this work consists in explicitly representing the succession of crop cycles and inter-crop bare soil periods in the simulations and assessing its impact on the dynamic of simulated and measured evapotranspiration over a long period of time. The analysis focuses on key soil parameters which drive the simulation of evapotranspiration, namely the rooting depth, the soil moisture at saturation, the soil moisture at field capacity and the soil moisture at wilting point. The simulations achieved with the standard values of these parameters are compared to those achieved with the in situ values. The portability of the ISBA pedotransfer functions is evaluated over a typical Mediterranean crop site. Various in situ estimates of the soil parameters are considered and distinct parametrization strategies are tested to represent the evapotranspiration dynamic over the crop succession. This work shows that evapotranspiration mainly results from the soil evaporation when it is continuously simulated over a Mediterranean crop succession. The evapotranspiration simulated with the standard surface and soil parameters of the model is largely underestimated. The deficit in cumulative evapotranspiration amounts to 24% over 12 years. The bias in daily daytime evapotranspiration is -0.24 mm day-1. The ISBA pedotransfer estimates of the soil moisture at saturation and at wilting point are overestimated which explains most of the evapotranspiration underestimation. The overestimation of the soil moisture at wilting point causes the underestimation of

  4. Simulation of the Vapor Intrusion Process for Non-Homogeneous Soils Using a Three-Dimensional Numerical Model.

    Science.gov (United States)

    Bozkurt, Ozgur; Pennell, Kelly G; Suuberg, Eric M

    2009-01-01

    This paper presents model simulation results of vapor intrusion into structures built atop sites contaminated with volatile or semi-volatile chemicals of concern. A three-dimensional finite element model was used to investigate the importance of factors that could influence vapor intrusion when the site is characterized by non-homogeneous soils. Model simulations were performed to examine how soil layers of differing properties alter soil gas concentration profiles and vapor intrusion rates into structures. The results illustrate difference in soil gas concentration profiles and vapor intrusion rates between homogeneous and layered soils. The findings support the need for site conceptual models to adequately represent the site's geology when conducting site characterizations, interpreting field data and assessing the risk of vapor intrusion at a given site. For instance, in layered geologies, a lower permeability and diffusivity soil layer between the source and building often limits vapor intrusion rates, even if a higher permeability layer near the foundation permits increased soil gas flow rates into the building. In addition, the presence of water-saturated clay layers can considerably influence soil gas concentration profiles. Therefore, interpreting field data without accounting for clay layers in the site conceptual model could result in inaccurate risk calculations. Important considerations for developing more accurate conceptual site models are discussed in light of the findings.

  5. Causes of variation in soil carbon simulations from CMIP5 Earth system models and comparison with observations

    Directory of Open Access Journals (Sweden)

    K. E. O. Todd-Brown

    2013-03-01

    Full Text Available Stocks of soil organic carbon represent a large component of the carbon cycle that may participate in climate change feedbacks, particularly on decadal and centennial timescales. For Earth system models (ESMs, the ability to accurately represent the global distribution of existing soil carbon stocks is a prerequisite for accurately predicting future carbon–climate feedbacks. We compared soil carbon simulations from 11 model centers to empirical data from the Harmonized World Soil Database (HWSD and the Northern Circumpolar Soil Carbon Database (NCSCD. Model estimates of global soil carbon stocks ranged from 510 to 3040 Pg C, compared to an estimate of 1260 Pg C (with a 95% confidence interval of 890–1660 Pg C from the HWSD. Model simulations for the high northern latitudes fell between 60 and 820 Pg C, compared to 500 Pg C (with a 95% confidence interval of 380–620 Pg C for the NCSCD and 290 Pg C for the HWSD. Global soil carbon varied 5.9 fold across models in response to a 2.6-fold variation in global net primary productivity (NPP and a 3.6-fold variation in global soil carbon turnover times. Model–data agreement was moderate at the biome level (R2 values ranged from 0.38 to 0.97 with a mean of 0.75; however, the spatial distribution of soil carbon simulated by the ESMs at the 1° scale was not well correlated with the HWSD (Pearson correlation coefficients less than 0.4 and root mean square errors from 9.4 to 20.8 kg C m−2. In northern latitudes where the two data sets overlapped, agreement between the HWSD and the NCSCD was poor (Pearson correlation coefficient 0.33, indicating uncertainty in empirical estimates of soil carbon. We found that a reduced complexity model dependent on NPP and soil temperature explained much of the 1° spatial variation in soil carbon within most ESMs (R2 values between 0.62 and 0.93 for 9 of 11 model centers. However, the same reduced complexity model only explained 10% of the spatial variation in HWSD

  6. Parallel 3-d simulations for porous media models in soil mechanics

    Science.gov (United States)

    Wieners, C.; Ammann, M.; Diebels, S.; Ehlers, W.

    Numerical simulations in 3-d for porous media models in soil mechanics are a difficult task for the engineering modelling as well as for the numerical realization. Here, we present a general numerical scheme for the simulation of two-phase models in combination with an material model via the stress response with a specialized parallel saddle point solver. Therefore, we give a brief introduction into the theoretical background of the Theory of Porous Media and constitute a two-phase model consisting of a porous solid skeleton saturated by a viscous pore-fluid. The material behaviour of the skeleton is assumed to be elasto-viscoplastic. The governing equations are transfered to a weak formulation suitable for the application of the finite element method. Introducing an formulation in terms of the stress response, we define a clear interface between the assembling process and the parallel solver modules. We demonstrate the efficiency of this approach by challenging numerical experiments realized on the Linux Cluster in Chemnitz.

  7. Simulating the mobility of meteoric 10Be in the landscape through a coupled soil-hillslope model (Be2D)

    Science.gov (United States)

    Campforts, Benjamin; Vanacker, Veerle; Vanderborght, Jan; Baken, Stijn; Smolders, Erik; Govers, Gerard

    2016-04-01

    Meteoric 10Be allows for the quantification of vertical and lateral soil fluxes over long time scales (103-105 yr). However, the mobility of meteoric 10Be in the soil system makes a translation of meteoric 10Be inventories into erosion and deposition rates complex. Here, we present a spatially explicit 2D model simulating the behaviour of meteoric 10Be on a hillslope. The model consists of two parts. The first component deals with advective and diffusive mobility of meteoric 10Be within the soil profile, and the second component describes lateral soil and meteoric 10Be fluxes over the hillslope. Soil depth is calculated dynamically, accounting for soil production through weathering as well as downslope fluxes of soil due to creep, water and tillage erosion. Synthetic model simulations show that meteoric 10Be inventories can be related to erosion and deposition across a wide range of geomorphological and pedological settings. Our results also show that meteoric 10Be can be used as a tracer to detect human impact on soil fluxes for soils with a high affinity for meteoric 10Be. However, the quantification of vertical mobility is essential for a correct interpretation of the observed variations in meteoric 10Be profiles and inventories. Application of the Be2D model to natural conditions using data sets from the Southern Piedmont (Bacon et al., 2012) and Appalachian Mountains (Jungers et al., 2009; West et al., 2013) allows to reliably constrain parameter values. Good agreement between simulated and observed meteoric 10Be concentrations and inventories is obtained with realistic parameter values. Furthermore, our results provide detailed insights into the processes redistributing meteoric 10Be at the soil-hillslope scale.

  8. Regional Simulation of Soil Organic Carbon Dynamics for Dry Farmland in East China by Coupling a 1:500 000 Soil Database with the Century Model

    Institute of Scientific and Technical Information of China (English)

    WANG Shi-Hang; SHI Xue-Zheng; ZHAO Yong-Cun; D.C.WEINDORF; YU Dong-Sheng; XU Sheng-Xiang; TAN Man-Zhi; SUN Wei-Xia

    2011-01-01

    Changes in soil organic carbon (SOC) in agricultural soils influence soil quality and greenhouse gas concentrations in the atmosphere. Dry farmland covers more than 70% of the whole cropland area in China and plays an important role in mitigating carbon dioxide (CO2) emissions. In this study, 4 109 dry farmland soil polygons were extracted using spatial overlay analysis of the soil layer (1:500 000) and the land use layer (1:500 000) to support Century model simulations of SOC dynamics for dry farmland in Anhui Province, East China from 1980 to 2008. Considering two field-validation sites,the Century model performed relatively well in modeling SOC dynamics for dry farmland in the province. The simulated results showed that the area-weighted mean soil organic carbon density (SOCD) of dry farmland increased from 18.77 Mg C ha-1 in 1980 to 23.99 Mg C ha-1 in 2008 with an average sequestration rate of 0.18 Mg C ha-1 year-1. Approximately 94.9% of the total dry farmland area sequestered carbon while 5.1% had carbon lost. Over the past 29 years, the net SOC gain in dry farmland soils of the province was 19.37 Tg, with an average sequestration rate of 0.67 Tg C year-1 Augmentation of SOC was primarily due to increased consumption of nitrogen fertilizer and farmyard manure. Moreover,SOC dynamics were highly differentiated among dry farmland soil groups. The integration of the Century model with a fine-scale soil database approach could be conveniently utilized as a tool for the accurate simulation of SOC dynamics at the regional scale.

  9. Simulation and Prediction of Soil Organic Carbon Dynamics in Jiangsu Province Based on Model and GIS Techniques

    Institute of Scientific and Technical Information of China (English)

    SHEN Yu; HUANG Yao; ZONG Liang-gang; ZHANG Wen; XU Mao; LIU Lin-wang

    2003-01-01

    Based on the databases of soils, meteorology, crop production, and agricultural management, changes in the soil organic carbon (SOC) of agro-ecosystems in Jiangsu Province were simulated by using a soil organic carbon model with a linkage of GIS. Four data sets of soil organic carbon measured from various field experiments in Jiangsu Province were used to validate the model. It was demonstrated that the model simulation in general agreed with the field measurements. Model simulation indicated that the SOC content in approximately 77% of the agricultural soils in Jiangsu Province has increased since the Second National Soil Survey completed in the early 1980s. Compared with the values in 1985, the SOC content in 2000 was estimated to increase by 1.0-3.0 g kg-1 for the north and the coastal areas of the province, and by 3.5-5.0 g kg-1 for the region of Tai Lake in the south. A slight decrease (about 0.5-1.5 g kg-1 ) was estimated for the central region of Jiangsu Province and the Nanjing-Zhenjiang hilly area. Model prediction for 2010 A.D. under two scena-rios, i.e., with 30 and 50% of the harvested crop straw incorporation, suggested that the SOC in Jiangsu Province would increase, and thus that the agricultural soils would have potential as organic carbon storage. The incorporation of crop straw into soils is of great benefit to increase soil carbon storage, consequently to benefit the control of the rise of atmospheric CO2 concentration and to maintain the sustainable development of agriculture.

  10. Evaluation of air-soil temperature relationships simulated by land surface models during winter across the permafrost region

    Science.gov (United States)

    Wang, Wenli; Rinke, Annette; Moore, John C.; Ji, Duoying; Cui, Xuefeng; Peng, Shushi; Lawrence, David M.; McGuire, A. David; Burke, Eleanor J.; Chen, Xiaodong; Delire, Christine; Koven, Charles; MacDougall, Andrew; Saito, Kazuyuki; Zhang, Wenxin; Alkama, Ramdane; Bohn, Theodore J.; Ciais, Philippe; Decharme, Bertrand; Gouttevin, Isabelle; Hajima, Tomohiro; Krinner, Gerhard; Lettenmaier, Dennis P.; Miller, Paul A.; Smith, Benjamin; Sueyoshi, Tetsuo

    2016-01-01

     A realistic simulation of snow cover and its thermal properties are important for accurate modelling of permafrost. We analyze simulated relationships between air and near-surface (20 cm) soil temperatures in the Northern Hemisphere permafrost region during winter, with a particular focus on snow insulation effects in nine land surface models and compare them with observations from 268 Russian stations. There are large across-model differences as expressed by simulated differences between near-surface soil and air temperatures, (ΔT), of 3 to 14 K, in the gradients between soil and air temperatures (0.13 to 0.96°C/°C), and in the relationship between ΔT and snow depth. The observed relationship between ΔT and snow depth can be used as a metric to evaluate the effects of each model's representation of snow insulation, and hence guide improvements to the model’s conceptual structure and process parameterizations. Models with better performance apply multi-layer snow schemes and consider complex snow processes. Some models show poor performance in representing snow insulation due to underestimation of snow depth and/or overestimation of snow conductivity. Generally, models identified as most acceptable with respect to snow insulation simulate reasonable areas of near-surface permafrost (12–16 million km2). However, there is not a simple relationship between the quality of the snow insulation in the acceptable models and the simulated area of Northern Hemisphere near-surface permafrost, likely because several other factors such as differences in the treatment of soil organic matter, soil hydrology, surface energy calculations, and vegetation also provide important controls on simulated permafrost distribution.

  11. A Bézier-Spline-based Model for the Simulation of Hysteresis in Variably Saturated Soil

    Science.gov (United States)

    Cremer, Clemens; Peche, Aaron; Thiele, Luisa-Bianca; Graf, Thomas; Neuweiler, Insa

    2017-04-01

    Most transient variably saturated flow models neglect hysteresis in the p_c-S-relationship (Beven, 2012). Such models tend to inadequately represent matrix potential and saturation distribution. Thereby, when simulating flow and transport processes, fluid and solute fluxes might be overestimated (Russo et al., 1989). In this study, we present a simple, computationally efficient and easily applicable model that enables to adequately describe hysteresis in the p_c-S-relationship for variably saturated flow. This model can be seen as an extension to the existing play-type model (Beliaev and Hassanizadeh, 2001), where scanning curves are simplified as vertical lines between main imbibition and main drainage curve. In our model, we use continuous linear and Bézier-Spline-based functions. We show the successful validation of the model by numerically reproducing a physical experiment by Gillham, Klute and Heermann (1976) describing primary drainage and imbibition in a vertical soil column. With a deviation of 3%, the simple Bézier-Spline-based model performs significantly better that the play-type approach, which deviates by 30% from the experimental results. Finally, we discuss the realization of physical experiments in order to extend the model to secondary scanning curves and in order to determine scanning curve steepness. {Literature} Beven, K.J. (2012). Rainfall-Runoff-Modelling: The Primer. John Wiley and Sons. Russo, D., Jury, W. A., & Butters, G. L. (1989). Numerical analysis of solute transport during transient irrigation: 1. The effect of hysteresis and profile heterogeneity. Water Resources Research, 25(10), 2109-2118. https://doi.org/10.1029/WR025i010p02109. Beliaev, A.Y. & Hassanizadeh, S.M. (2001). A Theoretical Model of Hysteresis and Dynamic Effects in the Capillary Relation for Two-phase Flow in Porous Media. Transport in Porous Media 43: 487. doi:10.1023/A:1010736108256. Gillham, R., Klute, A., & Heermann, D. (1976). Hydraulic properties of a porous

  12. Representing the effects of alpine grassland vegetation cover on the simulation of soil thermal dynamics by ecosystem models applied to the Qinghai-Tibetan Plateau

    Science.gov (United States)

    Yi, S.; Li, N.; Xiang, B.; Wang, X.; Ye, B.; McGuire, A.D.

    2013-01-01

    Soil surface temperature is a critical boundary condition for the simulation of soil temperature by environmental models. It is influenced by atmospheric and soil conditions and by vegetation cover. In sophisticated land surface models, it is simulated iteratively by solving surface energy budget equations. In ecosystem, permafrost, and hydrology models, the consideration of soil surface temperature is generally simple. In this study, we developed a methodology for representing the effects of vegetation cover and atmospheric factors on the estimation of soil surface temperature for alpine grassland ecosystems on the Qinghai-Tibetan Plateau. Our approach integrated measurements from meteorological stations with simulations from a sophisticated land surface model to develop an equation set for estimating soil surface temperature. After implementing this equation set into an ecosystem model and evaluating the performance of the ecosystem model in simulating soil temperature at different depths in the soil profile, we applied the model to simulate interactions among vegetation cover, freeze-thaw cycles, and soil erosion to demonstrate potential applications made possible through the implementation of the methodology developed in this study. Results showed that (1) to properly estimate daily soil surface temperature, algorithms should use air temperature, downward solar radiation, and vegetation cover as independent variables; (2) the equation set developed in this study performed better than soil surface temperature algorithms used in other models; and (3) the ecosystem model performed well in simulating soil temperature throughout the soil profile using the equation set developed in this study. Our application of the model indicates that the representation in ecosystem models of the effects of vegetation cover on the simulation of soil thermal dynamics has the potential to substantially improve our understanding of the vulnerability of alpine grassland ecosystems to

  13. Soil erosion under climate change in Great Britain: long-term simulations using high-resolution regional models

    Science.gov (United States)

    Ciampalini, Rossano; Kendon, Elizabeth; Constantine, José Antonio; Schindewolf, Marcus; Hall, Ian

    2016-04-01

    Twenty-first century climate change simulations for Great Britain reveal an increase in heavy precipitation that may lead to widespread soil loss and reduced soil carbon stores by increasing the likelihood of surface runoff. We find the quality and resolution of the simulated rainfall used to drive soil loss variation can widely influence the results. Hourly high definition rainfall simulations from a 1.5km resolution regional climate model are used to examine the soil erosion response in two UK catchments. The catchments have different sensitivity to soil erosion. "Rother" in West Sussex, England, reports some of the most erosive events that have been observed during the last 50 years in the UK. "Conwy" in North Wales, is resilient to soil erosion because of the abundant natural vegetation cover and very limited agricultural practises. We modelled with Erosion3D to check variations in soil erosion as influenced by climate variations for the periods 1996-2009 and 2086-2099. Our results indicate the Rother catchment is the most erosive, while the Conwy catchment is confirmed as the more resilient to soil erosion. The values of the reference-base period are consistent with the values of those locally observed in the previous decades. A soil erosion comparison for the two periods shows an increasing of sediment production (off-site erosion) for the end of the century at about 27% in the Rother catchment and about 50% for the Conwy catchment. The results, thanks to high-definition rainfall predictions, throw some light on the effect of climatic change effects in Great Britain.

  14. Sensitivity of meteorological input and soil properties in simulating aerosols (dust, PM10, and BC) using CHIMERE chemistry transport model

    Indian Academy of Sciences (India)

    Nishi Srivastava; S K Satheesh; Nadège Blond

    2014-08-01

    The objective of this study is to evaluate the ability of a European chemistry transport model, ‘CHIMERE’ driven by the US meteorological model MM5, in simulating aerosol concentrations [dust, PM10 and black carbon (BC)] over the Indian region. An evaluation of a meteorological event (dust storm); impact of change in soil-related parameters and meteorological input grid resolution on these aerosol concentrations has been performed. Dust storm simulation over Indo-Gangetic basin indicates ability of the model to capture dust storm events. Measured (AERONET data) and simulated parameters such as aerosol optical depth (AOD) and Angstrom exponent are used to evaluate the performance of the model to capture the dust storm event. A sensitivity study is performed to investigate the impact of change in soil characteristics (thickness of the soil layer in contact with air, volumetric water, and air content of the soil) and meteorological input grid resolution on the aerosol (dust, PM10, BC) distribution. Results show that soil parameters and meteorological input grid resolution have an important impact on spatial distribution of aerosol (dust, PM10, BC) concentrations.

  15. Land Surface Model and Particle Swarm Optimization Algorithm Based on the Model-Optimization Method for Improving Soil Moisture Simulation in a Semi-Arid Region.

    Directory of Open Access Journals (Sweden)

    Qidong Yang

    Full Text Available Improving the capability of land-surface process models to simulate soil moisture assists in better understanding the atmosphere-land interaction. In semi-arid regions, due to limited near-surface observational data and large errors in large-scale parameters obtained by the remote sensing method, there exist uncertainties in land surface parameters, which can cause large offsets between the simulated results of land-surface process models and the observational data for the soil moisture. In this study, observational data from the Semi-Arid Climate Observatory and Laboratory (SACOL station in the semi-arid loess plateau of China were divided into three datasets: summer, autumn, and summer-autumn. By combing the particle swarm optimization (PSO algorithm and the land-surface process model SHAW (Simultaneous Heat and Water, the soil and vegetation parameters that are related to the soil moisture but difficult to obtain by observations are optimized using three datasets. On this basis, the SHAW model was run with the optimized parameters to simulate the characteristics of the land-surface process in the semi-arid loess plateau. Simultaneously, the default SHAW model was run with the same atmospheric forcing as a comparison test. Simulation results revealed the following: parameters optimized by the particle swarm optimization algorithm in all simulation tests improved simulations of the soil moisture and latent heat flux; differences between simulated results and observational data are clearly reduced, but simulation tests involving the adoption of optimized parameters cannot simultaneously improve the simulation results for the net radiation, sensible heat flux, and soil temperature. Optimized soil and vegetation parameters based on different datasets have the same order of magnitude but are not identical; soil parameters only vary to a small degree, but the variation range of vegetation parameters is large.

  16. Quantifying Responses of Winter Wheat Physiological Processes to Soil Water Stress for Use in Growth Simulation Modeling

    Institute of Scientific and Technical Information of China (English)

    HU Ji-Chao; CAO Wei-Xing; ZHANG Jia-Bao; JIANG Dong; FENG Jie

    2004-01-01

    A deep understanding of crop-water eco-physiological relations is the basis for quantifying plant physiological responses to soil water stress. Pot experiments were conducted to investigate the winter wheat crop-water relations under both drought and waterlogging conditions in two sequential growing seasons from 2000 to 2002, and then the data were used to develop and validate models simulating the responses of winter wheat growth to drought and waterlogging stress. The experiment consisted of four treatments, waterlogging (keep 1 to 2 cm water layer depth above soil surface), control (70%-80% field capacity), light drought (40%-50% field capacity) and severe drought (30%-40% field capacity) with six replicates at five stages in the 2000-2001 growth season. Three soil water content treatments (waterlogging, control and drought) with two replicates were designed in the 2001-2002 growth season. Waterlogging and control treatments are the same as in the 2000-2001 growth season. For the drought treatment, no water was supplied and the soil moisture decreased from field capacity to wilting point. Leaf net photosynthetic rate, transpiration rate, predawn leaf water potential, soil water potential, soil water content and dry matter weight of individual organs were measured. Based on crop-water eco-physiological relations, drought and waterlogging stress factors for winter wheat growth simulation model were put forward. Drought stress factors integrated soil water availability, the sensitivity of different development stages and the difference between physiological processes (such as photosynthesis, transpiration and partitioning). The quantification of waterlogging stress factor considered different crop species, soil water status, waterlogging days and sensitivity at different growth stages. Data sets from the pot experiments revealed favorable performance reliability for the simulation sub-models with the drought and waterlogging stress factors.

  17. Simulating soybean productivity under rainfed conditions for major soil types using APEX model in East Central Mississippi

    Science.gov (United States)

    Bangbang Zhang; Gary Feng; John J. Read; Xiangbin Kong; Ying Ouyang; Ardeshir Adeli; Johnie N. Jenkins

    2016-01-01

    Knowledge of soybean yield constraints under rainfed conditions on major soil types in East CentralMississippi would assist growers in the region to effectively utilize the benefits of water/irrigation man-agement. The objectives of this study were to use the Agricultural Policy/Environmental eXtender (APEX)agro-ecosystem model to simulate rainfed soybean grain yield (...

  18. Evapotranspiration simulated by CRITERIA and AquaCrop models in stony soils

    National Research Council Canada - National Science Library

    Pasquale Campi; Francesca Modugno; Alejandra Navarro; Fausto Tomei; Giulia Villani; Marcello Mastrorilli

    2015-01-01

    .... The objective of this paper is to test CRITERIA and AquaCrop models in order to evaluate their suitability in estimating evapotranspiration at the field scale in two types of soil in the Mediterranean region...

  19. Infiltration-soil moisture redistribution under natural conditions: experimental evidence as a guideline for realizing simulation models

    Directory of Open Access Journals (Sweden)

    R. Morbidelli

    2011-06-01

    Full Text Available The evolution in time, t, of the experimental soil moisture vertical profile under natural conditions is investigated in order to address the corresponding simulation modelling. The measurements were conducted in a plot with a bare silty loam soil. The soil water content, θ, was continuously monitored at different depths, z, using a Time Domain Reflectometry (TDR system. For each profile four buriable three-rod waveguides were inserted horizontally at different depths (5, 15, 25 and 35 cm. In addition, we used sensors of air temperature and relative humidity, wind speed, solar radiation, evaporation and rain as supports for the application of selected simulation models, as well as for the detection of elements leading to their improvement. The results indicate that, under natural conditions, very different trends of the θ(z,t function can be observed in the given fine-textured soil, where the formation of a sealing layer over the parent soil requires an adjustment of the simulation modelling commonly used for hydrological applications. In particular, because of the considerable variations in the shape of the moisture content vertical profile as a function of time, a generalization of the existing models should incorporate a representation of the variability in time of the saturated hydraulic conductivity of the uppermost soil. This conclusion is supported by the fact that the observed shape of θ(z can be appropriately reproduced by adopting this approach, however the observed rainfall rate and the occurrence of freeze-thaw cycles with high soil moisture contents have to be explicitly incorporated.

  20. Infiltration-soil moisture redistribution under natural conditions: experimental evidence as a guideline for realizing simulation models

    Directory of Open Access Journals (Sweden)

    R. Morbidelli

    2011-09-01

    Full Text Available The evolution in time, t, of the experimental soil moisture vertical profile under natural conditions is investigated in order to address the corresponding simulation modelling. The measurements were conducted in a plot with a bare silty loam soil. The soil water content, θ, was continuously monitored at different depths, z, using a Time Domain Reflectometry (TDR system. Four buriable three-rod waveguides were inserted horizontally at different depths (5, 15, 25 and 35 cm. In addition, we used sensors of air temperature and relative humidity, wind speed, solar radiation, evaporation and rain as supports for the application of selected simulation models, as well as for the detection of elements leading to their improvement. The results indicate that, under natural conditions, very different trends of the θ(z, t function can be observed in the given fine-textured soil, where the formation of a sealing layer over the parent soil requires an adjustment of the simulation modelling commonly used for hydrological applications. In particular, because of the considerable variations in the shape of the moisture content vertical profile as a function of time, a generalization of the existing models should incorporate a first approximation of the variability in time of the saturated hydraulic conductivity, K1s, of the uppermost soil. This conclusion is supported by the fact that the observed shape of θ(z, t can be appropriately reproduced by adopting the proposed approach with K1s kept constant during each rainfall event but considered variable from event to event, however the observed rainfall rate and the occurrence of freeze-thaw cycles with high soil moisture contents have to be explicitly incorporated in a functional form for K1s(t.

  1. Validation and application of a two-dimensional model to simulate soil salt transport under mulched drip irrigation

    Science.gov (United States)

    Jiao, Huiqing; Zhao, Chengyi; Sheng, Yu; Chen, Yan; Shi, Jianchu; Li, Baoguo

    2017-04-01

    Water shortage and soil salinization increasingly become the main constraints for sustainable development of agriculture in Southern Xinjiang, China. Mulched drip irrigation, as a high-efficient water-saving irrigation method, has been widely applied in Southern Xinjiang for cotton production. In order to analyze the reasonability of describing the three-dimensional soil water and salt transport processes under mulched drip irrigation with a relatively simple two-dimensional model, a field experiment was conducted from 2007 to 2015 at Aksu of Southern Xinjiang, and soil water and salt transport processes were simulated through the three-dimensional and two-dimensional models based on COMSOL. Obvious differences were found between three-dimensional and two-dimensional simulations for soil water flow within the early 12 h of irrigation event and for soil salt transport in the area within 15 cm away from drip tubes during the whole irrigation event. The soil water and salt contents simulated by the two-dimensional model, however, agreed well with the mean values between two adjacent emitters simulated by the three-dimensional model, and also coincided with the measurements as corresponding RMSE less than 0.037 cm3 cm-3 and 1.80 g kg-1, indicating that the two-dimensional model was reliable for field irrigation management. Subsequently, the two-dimensional model was applied to simulate the dynamics of soil salinity for five numerical situations and for a widely adopted irrigation pattern in Southern Xinjiang (about 350 mm through mulched drip irrigation during growing season of cotton and total 400 mm through flooding irrigations before sowing and after harvesting). The simulation results indicated that the contribution of transpiration to salt accumulation in root layer was about 75% under mulched drip irrigation. Moreover, flooding irrigations before sowing and after harvesting were of great importance for salt leaching of arable layer, especially in bare strip where

  2. Simulation of Salinity Distribution in Soil Under Drip Irrigation Tape with Saline Water Using SWAP Model

    Directory of Open Access Journals (Sweden)

    M. Tabei

    2016-02-01

    Full Text Available Introduction: The to be limited available water amount from one side and to be increased needs of world population from the other side have caused increase of cultivation for products. For this reason, employing new irrigation ways and using new water resources like using the uncommon water (salty water, water drainage are two main strategies for regulating water shortage conditions. On the other side, accumulation of salts on the soil surface in dry regions having low rainfall and much evaporation, i.e. an avoidable case. As doing experiment for determining moisture distribution form demands needs a lot of time and conducting desert experiments are costly, stimulator models are suitable alternatives in answering the problem concerning moving and saltiness distribution. Materials and Methods: In this research, simulation of soil saltiness under drip irrigation was done by the SWAP model and potency of the above model was done in comparison with evaluated relevant results. SWAP model was performed based on measured data in a corn field equipped with drip irrigation system in the farming year 1391-92 in the number one research field in the engineering faculty of water science, ShahidChamran university of Ahvaz and hydraulic parameters of soil obtained from RETC . Statistical model in the form of a random full base plan with four attendants for irrigating water saltiness including salinity S1 (Karoon River water with salinity 3 ds/m as a control treatment, S2 (S1 +0/5, S3 (S1 +1 and S4 (S1 +1/5 dS/m, in 3 repetition and in 3 intervals of 10 cm emitter, 20 cm emitters on the stack, at a depth of 0-90 cm (instead of each 30 cm from soil surface and intervals of 30, 60 and 90 days after modeling cultiviation was done. The cultivation way was done handheld in plots including four rows of 3 m in distance of 75 cm rows and with denseness of 80 bushes in a hectar. Drip irrigation system was of type strip with space of 20 cm pores. Results and Discussion

  3. Calibration of soil moisture flow simulation models aided by the active heated fiber optic distributed temperature sensing AHFO

    Science.gov (United States)

    Rodriguez-Sinobas, Leonor; Zubelzu, Sergio; Sobrino, Fernando Fernando; Sánchez, Raúl

    2017-04-01

    Most of the studies dealing with the development of water flow simulation models in soils, are calibrated using experimental data measured by soil probe sensors or tensiometers which locate at specific points in the study area. However since the beginning of the XXI century, the use of Distributed Fiber Optic Temperature Measurement for estimating temperature variation along a cable of fiber optic has been assessed in multiple environmental applications. Recently, its application combined with an active heating pulses technique (AHFO) has been reported as a sensor to estimate soil moisture. This method applies a known amount of heat to the soil and monitors the temperature evolution, which mainly depends on the soil moisture content. Thus, it allows estimations of soil water content every 12.5 cm along the fiber optic cable, as long as 1500 m , with 2 % accuracy , every second. This study presents the calibration of a soil water flow model (developed in Hydrus 2D) with the AHFO technique. The model predicts the distribution of soil water content of a green area irrigated by sprinkler irrigation. Several irrigation events have been evaluated in a green area located at the ETSI Agronómica, Agroalimentaria y Biosistemas in Madrid where an installation of 147 m of fiber optic cable at 15 cm depth is deployed. The Distribute Temperature Sensing unit was a SILIXA ULTIMA SR (Silixa Ltd, UK) and has spatial and temporal resolution of 0.29 m. Data logged in the DTS unit before, during and after the irrigation event were used to calibrate the estimations in the Hydrus 2D model during the infiltration and redistribution of soil water content within the irrigation interval. References: Karandish, F., & Šimůnek, J. (2016). A field-modeling study for assessing temporal variations of soil-water-crop interactions under water-saving irrigation strategies. Agricultural Water Management, 178, 291-303. Li, Y., Šimůnek, J., Jing, L., Zhang, Z., & Ni, L. (2014). Evaluation of

  4. Implementation of the Barcelona Basic Model into TOUGH-FLAC for simulations of the geomechanical behavior of unsaturated soils

    Energy Technology Data Exchange (ETDEWEB)

    Rutqvist, J.; Ijiri, Y.; Yamamoto, H.

    2010-06-01

    This paper presents the implementation of the Barcelona Basic Model (BBM) into the TOUGH-FLAC simulator analyzing the geomechanical behavior of unsaturated soils. We implemented the BBM into TOUGH-FLAC by (1) extending an existing FLAC{sup 3D} module for the Modified Cam-Clay (MCC) model in FLAC{sup 3D} and (2) adding computational routines for suction-dependent strain and net stress (i.e., total stress minus gas pressure) for unsaturated soils. We implemented a thermo-elasto-plastic version of the BBM, wherein the soil strength depends on both suction and temperature. The implementation of the BBM into TOUGH-FLAC was verified and tested against several published numerical model simulations and laboratory experiments involving the coupled thermal-hydrological-mechanical (THM) behavior of unsaturated soils. The simulation tests included modeling the mechanical behavior of bentonite-sand mixtures, which are being considered as back-fill and buffer materials for geological disposal of spent nuclear fuel. We also tested and demonstrated the use of the BBM and TOUGH-FLAC for a problem involving the coupled THM processes within a bentonite-backfilled nuclear waste emplacement tunnel. The simulation results indicated complex geomechanical behavior of the bentonite backfill, including a nonuniform distribution of buffer porosity and density that could not be captured in an alternative, simplified, linear-elastic swelling model. As a result of the work presented in this paper, TOUGH-FLAC with BBM is now fully operational and ready to be applied to problems associated with nuclear waste disposal in bentonite-backfilled tunnels, as well as other scientific and engineering problems related to the mechanical behavior of unsaturated soils.

  5. Simulation of pesticide leaching in a cracking clay soil with the PEARL model

    NARCIS (Netherlands)

    Scorza, R.P.; Boesten, J.J.T.I.

    2005-01-01

    Testing of pesticide leaching models is important to increase confidence in their use in pesticide registration procedures world-wide. The chromatographic PEARL model was tested against the results of a field leaching study on a cracking clay soil with a tracer (bromide), a mobile pesticide (bentazo

  6. New opportunities for integrating mechanisms into soil carbon models for global simulations (Invited)

    Science.gov (United States)

    Torn, M. S.; Riley, W. J.; Contributions From: The Lake Constance Think Tank On Global Change; Feedback From Organic Carbon Dynamics-An Esf Workshop

    2010-12-01

    Numerical models of soil carbon cycling are being used to attribute carbon sinks, predict climate-ecosystem feedbacks, and evaluate climate mitigation strategies such as biofuels and sequestration. Current conceptions of SOC cycling and its expression in mathematical models rest heavily on the concept of recalcitrance - that some organic structures are intrinsically inert. However, recent research enabled by isotopic, spectroscopic, and molecular marker tools finds little evidence that recalcitrance, for example through selective preservation of plant derived material or resynthesis products, determines the long residence time of some OC in soils in a generalizable way. More likely, rates of carbon cycling are determined by the interaction of the organic matter and the soil environment including microorganisms, mineralogy, and climate. This does not mean compound chemistry is not important, rather that it does not act in isolation of other factors. Without the foundational principle that chemical composition defines the rate of decomposition, many tenets of old models are not supported, for example regarding decomposition response to change in temperature or plant species composition. Much progress could be made in the near term to improve soil carbon models by, for example, improving representations of oxygen diffusion and limitation, root carbon inputs, isotopic tracers, and making depth- or transport-related processes explicit. In other areas, new research is needed to translate recent findings into new parameters, for example, to replace texture with parameters for reactive mineral surface area to represent organo-mineral interaction. For the next generation of land model in the Community Earth System Model (was Community Climate System Model), we are developing new representations of many of these processes based on new data and understandings, to enable more accurate assessment of the vulnerability of soil organic carbon to predicted global climate change.

  7. A new, catchment-scale model for simulating methyl and total mercury in soils and surface waters

    Science.gov (United States)

    Futter, M. N.; Poste, A. E.; Whitehead, P. G.; Dillon, P. J.

    2012-04-01

    Mercury (Hg) is a potent and persistent neurotoxin. It is subject to long-range atmospheric transport, accumulates in catchment soils, and can pose health risks to humans and animals both at the point of use as well as in remote locations. Elevated concentrations of methyl mercury (MeHg) in fish are related to atmospheric Hg deposition and have resulted in fish consumption advisories in many parts of North America and Fennoscandia. After more than 150 years of elevated Hg deposition in Europe and North America, there remains a large inventory of Hg in the terrestrial catchments of lakes, which continues to be exported to receiving waters despite decreasing atmospheric inputs. While a substantial Hg pool exists in boreal catchment soils, fluxes of Hg from catchments via stream runoff tend to be much lower than atmospheric Hg inputs. Terrestrial catchments receiving similar atmospheric Hg inputs can have markedly different patterns of Hg output in stream water. Considering the importance of catchment processes in determining Hg flux to lakes and subsequent MeHg concentrations in fish, there is a need to characterize Hg cycling and transport in boreal and temperate forest-covered catchments. We present a new, catchment-scale, process-based dynamic model for simulating Hg in soils and surface waters. The Integrated Catchments Model for Mercury (INCA-Hg) simulates transport of gaseous, dissolved and solid Hg and transformations between elemental (Hg0), ionic (Hg(II)) and MeHg in natural and semi-natural landscapes. The mathematical description represents the model as a series of linked, first-order differential equations describing chemical and hydrological processes in catchment soils and waters which control surface water Hg dynamics and subsequent fluxes to lakes and other receiving waters. The model simulates daily time series between one and one hundred years long and can be applied to catchments ranging in size from Canada where we were able to reproduce observed

  8. Some Sensitivity Studies of Chemical Transport Simulated in Models of the Soil-Plant-Litter System

    Energy Technology Data Exchange (ETDEWEB)

    Begovich, C.L.

    2002-10-28

    Fifteen parameters in a set of five coupled models describing carbon, water, and chemical dynamics in the soil-plant-litter system were varied in a sensitivity analysis of model response. Results are presented for chemical distribution in the components of soil, plants, and litter along with selected responses of biomass, internal chemical transport (xylem and phloem pathways), and chemical uptake. Response and sensitivity coefficients are presented for up to 102 model outputs in an appendix. Two soil properties (chemical distribution coefficient and chemical solubility) and three plant properties (leaf chemical permeability, cuticle thickness, and root chemical conductivity) had the greatest influence on chemical transport in the soil-plant-litter system under the conditions examined. Pollutant gas uptake (SO{sub 2}) increased with change in plant properties that increased plant growth. Heavy metal dynamics in litter responded to plant properties (phloem resistance, respiration characteristics) which induced changes in the chemical cycling to the litter system. Some of the SO{sub 2} and heavy metal responses were not expected but became apparent through the modeling analysis.

  9. Some sensitivity studies of chemical transport simulated in models of the soil-plant-litter system

    Energy Technology Data Exchange (ETDEWEB)

    Begovich, C.L.; Luxmoore, R.J.

    1979-09-01

    Fifteen parameters in a set of five coupled models describing carbon, water, and chemical dynamics in the soil-plant-litter system were varied in a sensitivity analysis of model response. Results are presented for chemical distribution in the components of soil, plants, and litter along with selected responses of biomass, internal chemical transport (xylem and phloem pathways), and chemical uptake. Response and sensitivity coefficients are presented for up to 102 model outputs in an appendix. Two soil properties (chemical distribution coefficient and chemical solubility) and three plant properties (leaf chemical permeability, cuticle thickness, and root chemical conductivity) had the greatest influence on chemical transport in the soil-plant-litter system under the conditions examined. Pollutant gas uptake (SO/sub 2/) increased with change in plant properties that increased plant growth. Heavy metal dynamics in litter responded to plant properties (phloem resistance, respiration characteristics) which induced changes in the chemical cycling to the litter system. Some of the SO/sub 2/ and heavy metal responses were not expected but became apparent through the modeling analysis.

  10. Long-term manure carbon sequestration in soil simulated with the Daisy model on the basis of short-term incubation study

    DEFF Research Database (Denmark)

    Karki, Yubaraj Kumar; Børgesen, Christen Duus; Thomsen, Ingrid Kaag

    2013-01-01

    This study focused on simulating the long-term soil carbon sequestration after application of anaerobically digested and non-digested cattle manure using the Daisy model. The model was parameterized and calibrated for soil carbon (C) release during a 247 days incubation study including a coarse s...

  11. Long-term manure carbon sequestration in soil simulated with the Daisy model on the basis of short-term incubation study

    DEFF Research Database (Denmark)

    Karki, Yubaraj Kumar; Børgesen, Christen Duus; Thomsen, Ingrid Kaag

    2013-01-01

    This study focused on simulating the long-term soil carbon sequestration after application of anaerobically digested and non-digested cattle manure using the Daisy model. The model was parameterized and calibrated for soil carbon (C) release during a 247 days incubation study including a coarse s...

  12. Critical state soil constitutive model for methane hydrate soil

    National Research Council Canada - National Science Library

    S. Uchida; K. Soga; K. Yamamoto

    2012-01-01

      This paper presents a new constitutive model that simulates the mechanical behavior of methane hydrate-bearing soil based on the concept of critical state soil mechanics, referred to as the Methane...

  13. Estimation of the ICBM/2 Organic Matter Simulation Model parameters for biogas digestate mineralisaion in soil using Near Infrared Data.

    Science.gov (United States)

    Cabassi, Giovanni; Cavalli, Daniele; Borrelli, Lamberto; Degano, Luigi; Marino Gallina, Pietro

    2014-05-01

    The use of simulation models to study the turnover of soil organic matter (SOM) can support experimental data interpretation and the optimization of manure management. Icbm/2 (Katter, 2001) is a SOM simulation model that describes the turnover of SOM with three pools : one for old humified SOM (CO) and two for added manure, CL ( labile "young" C) and CS (stable "young" C). C outflows from CL and CR to be humified (h) and lost as CO2-C (1-h). All pools decay with firs-order kinetics with parameter kYL, kYR and kO (fig. 1).With this model of SOM turnover, during manure decomposition into the soil, only the evolved CO2 can be easily measured. Near infrared spectroscopy has been proved to be a useful technique for soil C evaluation. Since different soil C pools are expected to have different chemical composition, it was proven that NIR can be used as a cheap technique to develop calibration models to estimate the amount of C belonging to different pools). The aim of this work was compare the calibration of ICBM/2 using C respiration data or optimal NIR prediction of CO and CL pools. A total of six laboratory treatments were established using the same soil corresponding to the application of five fertilisers and a control treatment: 1) control without N fertilisation; 2) ammonium sulphate; 3) anaerobically digested dairy cow slurry (Digested slurry); 4-5) the liquid (Liquid fraction) and solid (Solid fraction) fractions after mechanical separation of Digested slurry; and 6) anaerobically stored dairy cow slurry (Stored slurry). The "nursery" method was used with 12 sampling dates. NIR analysis were performed on the air dried grounded soils. Spectra were collected using an FT-NIR Spectrometer. Parameters calibration was done separately for each soil using the downhill simplex method. For each manure, a C partitioning factor (Fi) was optimised. In each optimization step respiration measured data or NIR estimates CL and CO were used as imput for minimisation objective

  14. Simulating the carbon, water, energy budgets and greenhouse gas emissions of arctic soils with the ISBA land surface model

    Science.gov (United States)

    Morel, Xavier; Decharme, Bertrand; Delire, Christine

    2017-04-01

    Permafrost soils and boreal wetlands represent an important challenge for future climate simulations. Our aim is to be able to correctly represent the most important thermal, hydrologic and carbon cycle related processes in boreal areas with our land surface model ISBA (Masson et al, 2013). This is particularly important since ISBA is part of the CNRM-CM Climate Model (Voldoire et al, 2012), that is used for projections of future climate changes. To achieve this goal, we replaced the one layer original soil carbon module based on the CENTURY model (Parton et al, 1987) by a multi-layer soil carbon module that represents C pools and fluxes (CO2 and CH4), organic matter decomposition, gas diffusion (Khvorostyanov et al., 2008), CH4 ebullition and plant-mediated transport, and cryoturbation (Koven et al., 2009). The carbon budget of the new model is closed. The soil carbon module is tightly coupled to the ISBA energy and water budget module that solves the one-dimensional Fourier law and the mixed-form of the Richards equation explicitly to calculate the time evolution of the soil energy and water budgets (Boone et al., 2000; Decharme et al. 2011). The carbon, energy and water modules are solved using the same vertical discretization. Snowpack processes are represented by a multi-layer snow model (Decharme et al, 2016). We test this new model on a pair of monitoring sites in Greenland, one in a permafrost area (Zackenberg Ecological Research Operations, Jensen et al, 2014) and the other in a region without permafrost (Nuuk Ecological Research Operations, Jensen et al, 2013); both sites are established within the GeoBasis part of the Greenland Ecosystem Monitoring (GEM) program. The site of Chokurdakh, in a permafrost area of Siberia is is our third studied site. We test the model's ability to represent the physical variables (soil temperature and water profiles, snow height), the energy and water fluxes as well as the carbon dioxyde and methane fluxes. We also test the

  15. Evaluation of land surface model simulations of evapotranspiration over a 12-year crop succession: impact of soil hydraulic and vegetation properties

    Science.gov (United States)

    Garrigues, S.; Olioso, A.; Calvet, J. C.; Martin, E.; Lafont, S.; Moulin, S.; Chanzy, A.; Marloie, O.; Buis, S.; Desfonds, V.; Bertrand, N.; Renard, D.

    2015-07-01

    Evapotranspiration has been recognized as one of the most uncertain terms in the surface water balance simulated by land surface models. In this study, the SURFEX/ISBA-A-gs (Interaction Sol-Biosphere-Atmosphere) simulations of evapotranspiration are assessed at the field scale over a 12-year Mediterranean crop succession. The model is evaluated in its standard implementation which relies on the use of the ISBA pedotransfer estimates of the soil properties. The originality of this work consists in explicitly representing the succession of crop cycles and inter-crop bare soil periods in the simulations and assessing its impact on the dynamics of simulated and measured evapotranspiration over a long period of time. The analysis focuses on key parameters which drive the simulation of ET, namely the rooting depth, the soil moisture at saturation, the soil moisture at field capacity and the soil moisture at wilting point. A sensitivity analysis is first conducted to quantify the relative contribution of each parameter on ET simulation over 12 years. The impact of the estimation method used to retrieve the soil parameters (pedotransfer function, laboratory and field methods) on ET is then analysed. The benefit of representing the variations in time of the rooting depth and wilting point is evaluated. Finally, the propagation of uncertainties in the soil parameters on ET simulations is quantified through a Monte Carlo analysis and compared with the uncertainties triggered by the mesophyll conductance which is a key above-ground driver of the stomatal conductance. This work shows that evapotranspiration mainly results from the soil evaporation when it is continuously simulated over a Mediterranean crop succession. This results in a high sensitivity of simulated evapotranspiration to uncertainties in the soil moisture at field capacity and the soil moisture at saturation, both of which drive the simulation of soil evaporation. Field capacity was proved to be the most

  16. Exploring diversity of crop and soil management within smallholder African farms: A dynamic model for simulation of N balances and use efficiencies at field scale

    NARCIS (Netherlands)

    Tittonell, P.A.; Leffelaar, P.A.; Vanlauwe, B.; Wijk, van M.T.; Giller, K.E.

    2006-01-01

    Adding a dynamic, temporal dimension to the calculation of nitrogen balances is proposed as an alternative approach to assessing the impact of crop and soil management decisions on the establishment of farmer-induced soil fertility gradients within smallholder African farms. A simulation model that

  17. Modifying the Soil and Water Assessment Tool to simulate cropland carbon flux: model development and initial evaluation.

    Science.gov (United States)

    Zhang, Xuesong; Izaurralde, R César; Arnold, Jeffrey G; Williams, Jimmy R; Srinivasan, Raghavan

    2013-10-01

    Climate change is one of the most compelling modern issues and has important implications for almost every aspect of natural and human systems. The Soil and Water Assessment Tool (SWAT) model has been applied worldwide to support sustainable land and water management in a changing climate. However, the inadequacies of the existing carbon algorithm in SWAT limit its application in assessing impacts of human activities on CO2 emission, one important source of greenhouse gasses (GHGs) that traps heat in the earth system and results in global warming. In this research, we incorporate a revised version of the CENTURY carbon model into SWAT to describe dynamics of soil organic matter (SOM)-residue and simulate land-atmosphere carbon exchange. We test this new SWAT-C model with daily eddy covariance (EC) observations of net ecosystem exchange (NEE) and evapotranspiration (ET) and annual crop yield at six sites across the U.S. Midwest. Results show that SWAT-C simulates well multi-year average NEE and ET across the spatially distributed sites and capture the majority of temporal variation of these two variables at a daily time scale at each site. Our analyses also reveal that performance of SWAT-C is influenced by multiple factors, such as crop management practices (irrigated vs. rainfed), completeness and accuracy of input data, crop species, and initialization of state variables. Overall, the new SWAT-C demonstrates favorable performance for simulating land-atmosphere carbon exchange across agricultural sites with different soils, climate, and management practices. SWAT-C is expected to serve as a useful tool for including carbon flux into consideration in sustainable watershed management under a changing climate. We also note that extensive assessment of SWAT-C with field observations is required for further improving the model and understanding potential uncertainties of applying it across large regions with complex landscapes.

  18. A Dynamic Model for Simulating Atmospheric, Surface and Soil Water Interactions in Hillslope of Loess Area Under Natural Conditions and Its Application

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The mechanism of atmospheric, surface and soil water interactions (water transformation) in hillslope under natural conditions was analyzed, and a dynamic model was developed to simulate infiltration, overland flow and soil water movement during natural rainfall in hillslope, by bringing forward concepts such as rainfall intensity on slope and a correction coefficient of saturated soil water content for soil surface seal. Some factors, including slope angle, slope orientation and raindrop inclination, which affect the rainfall amount on slope, were taken into account while developing the dynamic model. The effect of surface seal on infiltration and water balance under a boundary condition of the second kind was also considered. Application of the model in a field experiment showed that the model simulated precisely the infiltration, overland flow and soil water movement in hillslope under natural rainfall conditions.

  19. Simulating the dynamics of polycyclic aromatic hydrocarbon (PAH) in contaminated soil through composting by COP-Compost model.

    Science.gov (United States)

    Zhang, Yuan; Guan, Yidong; Shi, Qi

    2015-02-01

    Organic pollutants (OPs) are potentially present in composts, and the assessment of their content and bioaccessibility in these composts is of paramount importance to minimize the risk of soil contamination and improve soil fertility. In this work, integration of the dynamics of organic carbon (OC) and OPs in an overall experimental framework is first proposed and adopted to validate the applicability of the COP-Compost model and to calibrate the model parameters on the basis of what has been achieved with the COP-Compost model. The COP-Compost model was evaluated via composting experiments containing 16 US Environmental Protection Agency (USEPA) polycyclic aromatic hydrocarbons (PAHs) and the sorption coefficient (Kd) values of two types of OP: fluorenthene (FLT) and pyrene (PHE). In our study, these compounds are used to characterize the sequential extraction and are quantified as soluble, sorbed, and non-extractable fractions. The model was calibrated, and coupling the OC and OP modules improved the simulation of the OP behavior and bioaccessibility during composting. The results show good agreement between the simulated and experimental results describing the evolution of different organic pollutants using the OP module, as well as the coupling module. However, no clear relationship is found between the Kd and the property of organic fractions. Further estimation of parameters is still necessary to modify the insufficiency of this present research.

  20. From near-surface to root-zone soil moisture using an exponential filter: an assessment of the method based on in-situ observations and model simulations

    Directory of Open Access Journals (Sweden)

    C. Albergel

    2008-12-01

    Full Text Available A long term data acquisition effort of profile soil moisture is under way in southwestern France at 13 automated weather stations. This ground network was developed in order to validate remote sensing and model soil moisture estimates. In this paper, both those in situ observations and a synthetic data set covering continental France are used to test a simple method to retrieve root zone soil moisture from a time series of surface soil moisture information. A recursive exponential filter equation using a time constant, T, is used to compute a soil water index. The Nash and Sutcliff coefficient is used as a criterion to optimise the T parameter for each ground station and for each model pixel of the synthetic data set. In general, the soil water indices derived from the surface soil moisture observations and simulations agree well with the reference root-zone soil moisture. Overall, the results show the potential of the exponential filter equation and of its recursive formulation to derive a soil water index from surface soil moisture estimates. This paper further investigates the correlation of the time scale parameter T with soil properties and climate conditions. While no significant relationship could be determined between T and the main soil properties (clay and sand fractions, bulk density and organic matter content, the modelled spatial variability and the observed inter-annual variability of T suggest that a weak climate effect may exist.

  1. Evaluating the performance of coupled snow-soil models in SURFEXv8 to simulate the permafrost thermal regime at a high Arctic site

    Science.gov (United States)

    Barrere, Mathieu; Domine, Florent; Decharme, Bertrand; Morin, Samuel; Vionnet, Vincent; Lafaysse, Matthieu

    2017-09-01

    Climate change projections still suffer from a limited representation of the permafrost-carbon feedback. Predicting the response of permafrost temperature to climate change requires accurate simulations of Arctic snow and soil properties. This study assesses the capacity of the coupled land surface and snow models ISBA-Crocus and ISBA-ES to simulate snow and soil properties at Bylot Island, a high Arctic site. Field measurements complemented with ERA-Interim reanalyses were used to drive the models and to evaluate simulation outputs. Snow height, density, temperature, thermal conductivity and thermal insulance are examined to determine the critical variables involved in the soil and snow thermal regime. Simulated soil properties are compared to measurements of thermal conductivity, temperature and water content. The simulated snow density profiles are unrealistic, which is most likely caused by the lack of representation in snow models of the upward water vapor fluxes generated by the strong temperature gradients within the snowpack. The resulting vertical profiles of thermal conductivity are inverted compared to observations, with high simulated values at the bottom of the snowpack. Still, ISBA-Crocus manages to successfully simulate the soil temperature in winter. Results are satisfactory in summer, but the temperature of the top soil could be better reproduced by adequately representing surface organic layers, i.e., mosses and litter, and in particular their water retention capacity. Transition periods (soil freezing and thawing) are the least well reproduced because the high basal snow thermal conductivity induces an excessively rapid heat transfer between the soil and the snow in simulations. Hence, global climate models should carefully consider Arctic snow thermal properties, and especially the thermal conductivity of the basal snow layer, to perform accurate predictions of the permafrost evolution under climate change.

  2. A Dynamic Model for Simulating Atmospheric,Surface and Soil Water Interactions in Hillslope of Loess Area Under Natural Conditions and Its Application

    Institute of Scientific and Technical Information of China (English)

    ZHANGSHUHAN; NIEGUANGYONG; 等

    2001-01-01

    The mechanism of atmospheric,surface and soil water interactions( water transformation) in hillslope under natural conditions was analyzed,and a dynamic model was developed to simulate infiltration,overland flow and soil water movement during natural rainfall in hillslope,by bringing froward concepts such as rainfall intensity on slope and a correction coefficient of saturated soil water content for soil surface seal.Some factors,including slope angle,slope orientation and raindrop inclination,which affect the rainfall amount on slope, were taken into account while developing the dynamic model.The effect of surface seal on infiltration and water balance under a boundary condition of the second kind was aslo considered. Application of the model in a field experiment showed that the model simulated precisely the infiltration,overland flow and sol water monvement in hillsope under natural rainfall conditions.

  3. Simulation of soil erosion and deposition in a changing land use: A modelling approach to implement the support practice factor

    Science.gov (United States)

    Pelacani, Samanta; Märker, Michael; Rodolfi, Giuliano

    2008-07-01

    Using the USPED (Unit Stream Power Erosion Deposition) model, three land use scenarios were analysed for an Italian small catchment (15 km 2) of high landscape value. The upper Orme stream catchment, located in the Chianti area, 30 km south of Florence, has a long historical agriculture record. Information on land use and soil conservation practices date back to 1821, hence offering an opportunity to model impacts of land use change on erosion and deposition. For this study, a procedure that takes into account soil conservation practices and potential sediment storage is proposed. The approach was to calculate and model the flow accumulation considering rural and logging roads, location of urban areas, drainage ditches, streams, gullies and permanent sediment sinks. This calculation attempts to assess the spatial variability, especially the impact of support practices ( P factor). Weather data from 1980-2003 were taken into account to calculate the R factor. However, to consider the intense pluviometric conditions in terms of the erosivity factor, the 0.75th quantile was used, while the lowest erosivity was modelled using the 0.25th quantile. Results of the USPED model simulation show that in 1821 the mean annual net erosion for the watershed was 2.8 Mg ha - 1 y - 1 ; in 1954 it was 4.2 Mg ha - 1 y - 1 ; and in 2004 it was 5.3 Mg ha - 1 y - 1 . Conservation practices can reduce erosion processes by ≥ 20 Mg ha - 1 y - 1 when the 1821 practices are introduced in the present management. On the other hand, if the support practices are not considered in the model, soil erosion risk is overestimated. Field observation for the present-day simulation confirmed that erosion and associated sediment deposition predicted by the model depend, as expected, on geomorphology and land use. The model shows limitations that are mainly due to the input data. A high resolution DEM is essential for the delineation of reliable topographic potential to predict erosion and deposition

  4. Quantifying the impact of realistic soil and lake distributions in an Atmosphere-Ocean General Circulation Model simulation of the late Pliocene.

    Science.gov (United States)

    Tindall, Julia; Pound, Matthew; Haywood, Alan; Salzmann, Ulrich

    2013-04-01

    Model simulations of past climates, such as the late Pliocene, are driven by the boundary conditions that were appropriate at the time - if such data is available. The Pliocene Research, Interpretation and Synoptic Mapping dataset, PRISM3, provides boundary conditions for model simulations of the late Pliocene (~3.2ma) and has been used in the Pliocene Palaeoclimate Modelling Intercomparison Project (PlioMIP). In the absence of observational constraints, the PlioMIP simulations assumed that Pliocene lake locations and soil parameters were the same as modern - however in reality there are notable differences between Pliocene and modern lakes and soils. Here we present new global datasets of Pliocene lakes and soils, which can be used to provide more accurate forcing data for climate models. The new datasets are used to drive a 350 year simulation with the Hadley Centre atmosphere-ocean General Circulation Model (GCM), HadCM3. It is shown that using the Pliocene lakes and soils datasets have an impact on the modelled temperature and precipitation, although these effects are spatially localised and are often limited to certain seasons. Changes in Pliocene vegetation patterns that can be attributed to using realistic lakes and soils is also discussed.

  5. Assessing the ability of mechanistic volatilization models to simulate soil surface conditions: a study with the Volt'Air model.

    Science.gov (United States)

    Garcia, L; Bedos, C; Génermont, S; Braud, I; Cellier, P

    2011-09-01

    Ammonia and pesticide volatilization in the field is a surface phenomenon involving physical and chemical processes that depend on the soil surface temperature and water content. The water transfer, heat transfer and energy budget sub models of volatilization models are adapted from the most commonly accepted formalisms and parameterizations. They are less detailed than the dedicated models describing water and heat transfers and surface status. The aim of this work was to assess the ability of one of the available mechanistic volatilization models, Volt'Air, to accurately describe the pedo-climatic conditions of a soil surface at the required time and space resolution. The assessment involves: (i) a sensitivity analysis, (ii) an evaluation of Volt'Air outputs in the light of outputs from a reference Soil-Vegetation-Atmosphere Transfer model (SiSPAT) and three experimental datasets, and (iii) the study of three tests based on modifications of SiSPAT to establish the potential impact of the simplifying assumptions used in Volt'Air. The analysis confirmed that a 5 mm surface layer was well suited, and that Volt'Air surface temperature correlated well with the experimental measurements as well as with SiSPAT outputs. In terms of liquid water transfers, Volt'Air was overall consistent with SiSPAT, with discrepancies only during major rainfall events and dry weather conditions. The tests enabled us to identify the main source of the discrepancies between Volt'Air and SiSPAT: the lack of gaseous water transfer description in Volt'Air. They also helped to explain why neither Volt'Air nor SiSPAT was able to represent lower values of surface water content: current classical water retention and hydraulic conductivity models are not yet adapted to cases of very dry conditions. Given the outcomes of this study, we discuss to what extent the volatilization models can be improved and the questions they pose for current research in water transfer modeling and parameterization.

  6. Long-term effects of fertilization on soil organic carbon changes in continuous corn of northeast China: RothC model simulations.

    Science.gov (United States)

    Yang, X M; Zhang, X P; Fang, H J; Zhu, P; Ren, J; Wang, L C

    2003-10-01

    Soil organic C (SOC) content can increase by managing land use practices in which the rates of organic C input exceed those of organic C mineralization. Understanding the changes in SOC content of Black soils (mainly Typic Halpudoll) in northeast China is necessary for sustainable using of soil resources there. We used the RothC model to estimate SOC levels of Black soils under monoculture cropping corn in a long-term fertilization trial at Gongzhuling, Jilin Province, China. The model outputs for the changes in SOC were compared with measured data in this long-term fertilization/manure trial. The sound performance of model in simulating SOC changes suggests that RothC is feasible with Black soils in the temperate climatic region of northeast China. The modeled and measured results indicated that the treatment without fertilizer/farmyard manure (FYM) addition led to a continuous decline in SOC during the study period and N and NPK fertilization were inadequate to maintain the SOC levels in the plow layer (upper 20 cm) unless FYM was added under the current conventional management associated with no above-ground crop residues returning into the soil. Soil organic carbon could follow the same path of decline if the same management practices are maintained. Model results indicate that returning above-ground crop residues to the soil from 2002 to 2022 would increase SOC by 26% for the treatment without fertilization addition, 40% for N treatment, 45% for NPK treatment, and 38% and 46% for N and NPK treatments with FYM addition, compared to the levels in the corresponding treatments in 2002. The simulation results suggest that the RothC model is a feasible tool to assess SOC trend under different management practices, and returning above-ground crop residues into the soil would lead to a remarkable increase in SOC of Black soils in the region.

  7. Simulation with models of increasing complexity of CO2 emissions and nitrogen mineralisation, after soil application of labelled pig slurry and maize stalks

    Science.gov (United States)

    Bechini, Luca; Marino Gallina, Pietro; Geromel, Gabriele; Corti, Martina; Cavalli, Daniele

    2015-04-01

    High amounts of nitrogen are available per unit area in regions with intensive livestock operations. In swine farms, pig slurries are frequently incorporated in the soil together with maize stalks. Simulation models may help to understand nitrogen dynamics associated with animal manure and crop residue decomposition in the soil, and to support the definition of best management practices. The objective of this work was to test the ability of different models to simulate CO2 emissions and nitrogen mineralisation during a laboratory incubation (under optimal soil water content and constant temperature) of maize stalks (ST) and pig slurry (PS). A loam soil was amended with labelled (15N) or unlabelled maize stalks and pig slurries, in the presence of ammonium sulphate (AS). These treatments were established: unfertilised soil; ST15 + AS + PS; ST + AS15 + PS; and ST + AS + PS15. During 180 days, we measured CO2 emissions; microbial biomass C, N, and 15N; and soil mineral N (SMN and SM-15N). Three models of increasing complexity were calibrated using measured data. The models were two modifications of ICBM 2B/N (Kätterer and Andrén, 2001) and CN-SIM (Petersen et al., 2005). The three models simulated rather accurately the emissions of CO2 throughout the incubation period (Relative Root Mean Squared Error, RRMSE = 8-25). The simplest model (with one pool for ST and one for PS) strongly overestimated SMN immobilisation from day 3 to day 21, both in the treatments with AS15 and PS15 (RRMSE = 27-30%). The other two models represented rather well the dynamics of SMN in the soil (RRMSE = 21-25%), simulating a fast increase of nitrate concentration in the first days, and slower rates of nitrification thereafter. Worse performances were obtained with all models for the simulation of SM-15N in the treatment with ST15 (RRMSE = 64-104%): experimental data showed positive mineralization of stalk-derived N from the beginning of the incubation, while models strongly underestimated

  8. WEPP and ANN models for simulating soil loss and runoff in a semi-arid Mediterranean region.

    Science.gov (United States)

    Albaradeyia, Issa; Hani, Azzedine; Shahrour, Isam

    2011-09-01

    This paper presents the use of both the Water Erosion Prediction Project (WEPP) and the artificial neural network (ANN) for the prediction of runoff and soil loss in the central highland mountainous of the Palestinian territories. Analyses show that the soil erosion is highly dependent on both the rainfall depth and the rainfall event duration rather than on the rainfall intensity as mostly mentioned in the literature. The results obtained from the WEPP model for the soil loss and runoff disagree with the field data. The WEPP underestimates both the runoff and soil loss. Analyses conducted with the ANN agree well with the observation. In addition, the global network models developed using the data of all the land use type show a relatively unbiased estimation for both runoff and soil loss. The study showed that the ANN model could be used as a management tool for predicting runoff and soil loss.

  9. Seasonal variations of soil erosion in UK under climate change: simulations with the use of high-resolution regional climatic models

    Science.gov (United States)

    Ciampalini, Rossano; Kendon, Elizabeth; Constantine, José Antonio; Schindewolf, Marcus; Hall, Ian

    2017-04-01

    Climate change is expected to have a significant impact on the hydrological cycle, twenty-first century climate change simulations for Great Britain forecast an increase of surface runoff and flooding frequency. Once quality and resolution of the simulated rainfall deeply influence the results, we adopted rainfall simulations issued of a high-resolution climate model recently carried out for extended periods (13 years for present-day and future periods 2100) at 1.5 km grid scale over the south of the United Kingdom (simulations, which for the future period use the Intergovernmental Panel on Climate Change RCP 8.5 scenario, Kendon et al., 2014). We simulated soil erosion with 3D soil erosion model Schmidt (1990) on two catchments of Great Britain: the Rother catchment (350 km2) in West Sussex, England, because it has reported some of the most erosive events observed during the last 50 years in the UK, and the Conwy catchment (628 Km2) in North Wales, which is extremely resilient to soil erosion because of the abundant natural vegetation. Estimation of changes in soil moisture, saturation deficit as well as vegetation cover at daily time step have been done with the Joint UK Land Environment Simulator (JULES) (Best et al, 2011). Our results confirm the Rother catchment is the most erosive, while the Conwy catchment is the more resilient to soil erosion. Sediment production is perceived increase in both cases for the end of the century (27% and 50%, respectively). Seasonal disaggregation of the results revels that, while the most part of soil erosion is produced in winter months (DJF), the higher soil erosion variability for future periods is observed in summer (JJA). This behaviour is supported by the rainfall simulation analyse which highlighted this dual behaviour in precipitations.

  10. Soil loss prediction in Guaraíra river experimental basin, Paraíba, Brazil based on two erosion simulation models

    Directory of Open Access Journals (Sweden)

    Jorge Flávio Cazé B. da Costa Silva

    2007-12-01

    Full Text Available In this study, two hydrological models to estimate soil losses and sediment yield due to sheet and channel erosion, at the basin outlet, are applied to Guaraíra River Experimental Basin, located in Paraíba State, northeastern Brazil. The soil erosion models are (a the classical Universal Soil Loss Equation (USLE, which is used to simulate annual and monthly soil losses; and (b Kineros model, which is used to simulate the sediment yield within the basin. Kineros model is a physically-based distributed model that uses a cascade of planes and channels to represent the basin and to describe the processes of interception, infiltration, surface runoff and erosion within the basin. The USLE is computed using land use, soil erodibility, topographic digital maps, as well as observed rainfall data. It was found that Guaraíra river experimental basin has a low potential for soil losses; however, specific areas which are susceptible to the erosion process in the basin could be detected by the modeling techniques coupled to a GIS (Geographic Information System.

  11. Inter-comparison of hydrological model simulations with dense time series of SAR-derived soil moisture maps

    Science.gov (United States)

    Iacobellis, V.; Gioia, A.; Milella, P.; Satalino, G.; Balenzano, A.; Mattia, F.

    2012-04-01

    Over the last years, a vast number of experimental and theoretical studies has widely demonstrated the sensitivity of SAR data to soil moisture content, however, operational services integrating SAR measurements into land process models are not yet available. Important progresses in this field are expected, on the one hand, from SAR missions characterized by a short revisiting time, such as the COSMO-SkyMed or the forthcoming Sentinel-1 and ALOS-2 missions, on the other hand, from a strong effort in implementing hydrological models able to reproduce the dynamic of soil moisture content of the top layer (5 cm depth) of soil. With this latter purpose, we used the DREAM model [Manfreda et al., 2005], realized in a GIS-based approach, that explicitly takes into account the spatial heterogeneity of hydrological processes. The DREAM model carries out continuous hydrological simulations using the daily and the hourly scales. The distinctive feature of the model, which consists of evaluating the lateral flow through a water content redistribution weighted by the topographic index, was preserved. The latter provided the basis for the nested implementation of the Richard equation which has been used for evaluating vertical flows in the top soil layer (5cm).The Richard routine exploits the numerical solution proposed by Simunek et al. [2009] and runs, for each cell of the river basin, in a sub-module of 60 minutes with a vertical (i.e. depth) and temporal resolution of 1 cm and 1 s, respectively. The model was applied to the portion of the Celone at Foggia San Severo river basin downstream the San Giusto Dam, which is a tributary of the Candelaro river, in Puglia region (Southern Italy). Over this area quasi-dense time series of ALOS/PALSAR ScanSAR WB1 and COSMO-SkyMedStripMap images were acquired in 2007 and 2010, respectively. The SAR data have been used to derive time-series of soil moisture maps by means of the SMOSAR software developed for Sentinel-1 data [Balenzano et

  12. Simulation of Quinoa (Chenopodium Quinoa Willd.) response to soil salinity using the saltmed model

    DEFF Research Database (Denmark)

    Razzaghi, Fatemeh; Plauborg, Finn; Ahmadi, Seyed Hamid

    Quinoa (Chenopodium quinoa Willd.) is a crop with high tolerance to salinity and drought and its response to varying soil moisture and salinity levels was studied in a field lysimeter experiment. Quinoa (cv. Titicaca) was irrigated with different concentrations of saline water (0, 10, 20, 30 and 40...

  13. A numerical model (MISER) for the simulation of coupled physical, chemical and biological processes in soil vapor extraction and bioventing systems

    Science.gov (United States)

    Rathfelder, Klaus M.; Lang, John R.; Abriola, Linda M.

    2000-05-01

    The efficiency and effectiveness of soil vapor extraction (SVE) and bioventing (BV) systems for remediation of unsaturated zone soils is controlled by a complex combination of physical, chemical and biological factors. The Michigan soil vapor extraction remediation (MISER) model, a two-dimensional numerical simulator, is developed to advance our ability to investigate the performance of field scale SVE and BV systems by integrating processes of multiphase flow, multicomponent compositional transport with nonequilibrium interphase mass transfer, and aerobic biodegradation. Subsequent to the model presentation, example simulations of single well SVE and BV systems are used to illustrate the interplay between physical, chemical and biological processes and their potential influence on remediation efficiency and the pathways of contaminant removal. Simulations of SVE reveal that removal efficiency is controlled primarily by the ability to engineer gas flow through regions of organic liquid contaminated soil and by interphase mass transfer limitations. Biodegradation is found to play a minor role in mass removal for the examined SVE scenarios. Simulations of BV systems suggest that the effective supply of oxygen may not be the sole criterion for efficient BV performance. The efficiency and contaminant removal pathways in these systems can be significantly influenced by interdependent dynamics involving biological growth factors, interphase mass transfer rates, and air injection rates. Simulation results emphasize the need for the continued refinement and validation of predictive interphase mass transfer models applicable under a variety of conditions and for the continued elucidation and quantification of microbial processes under unsaturated field conditions.

  14. Using the DeNitrification-DeComposition Framework to Simulate Global Soil Nitrous Oxide Emissions in the Community Land Model with Coupled Carbon and Nitrogen

    Science.gov (United States)

    Seok, B.; Saikawa, E.

    2015-12-01

    Soils are among the largest emission sources of nitrous oxide (N2O), which is a strong greenhouse gas and is the leading stratospheric ozone depleting substance. Thus, there is a rising concern for mitigating N2O emissions from soils. And yet, our understanding of the global magnitude and the impacts of soil N2O emissions on the climate and the stratospheric ozone layer is still limited, and our ability to mitigate N2O emissions thus remains a challenge. One approach to assess the global magnitude and impacts of N2O emissions is to use global biogeochemical models. Currently, most of these models use a simple or a conceptual framework to simulate soil N2O emissions. However, if we are to reduce the uncertainty in determining the N2O budget, a better representation of the soil N2O emissions process is essential. In our attempts to fulfill this objective, we have further improved the parameterization of soil N2O emissions in the Community Land Model with coupled Carbon and Nitrogen (CLM-CN) by implementing the DeNitrification-DeComposition (DNDC) model and validated our model results to existing measurements. We saw a general improvement in simulated N2O emissions with the updated parameterization and further improvements for specific sites when the model was nudged with measured soil temperature and moisture data of the respective site. We present the latest updates and changes made to CLM-CN with one-way coupled DNDC model (CLMCN-N2O) and compare the results between model versions and against other global biogeochemical models.

  15. COLIWAVE a simulation model for survival of E. coli O157 : H7 in dairy manure and manure-amended soil

    NARCIS (Netherlands)

    Semenov, Alexander V.; Franz, Eelco; van Bruggen, Ariena H. C.

    2010-01-01

    A simulation model was developed to investigate the relative effects of temperature, oxygen concentration, substrate content and competition by autochthonous microbial community on the oscillatory behaviour and survival of Escherichia coli O157:H7 in manure and manure-amended soil. The overall decli

  16. COLIWAVE a simulation model for survival of E. coli O157 : H7 in dairy manure and manure-amended soil

    NARCIS (Netherlands)

    Semenov, Alexander V.; Franz, Eelco; van Bruggen, Ariena H. C.

    2010-01-01

    A simulation model was developed to investigate the relative effects of temperature, oxygen concentration, substrate content and competition by autochthonous microbial community on the oscillatory behaviour and survival of Escherichia coli O157:H7 in manure and manure-amended soil. The overall decli

  17. Coliwave a simulation model for survival of E.coli 0157:H7 in dairy manure and manure-amended soil

    NARCIS (Netherlands)

    Semenov, A.V.; Franz, E.; Bruggen, van A.H.C.

    2010-01-01

    A simulation model was developed to investigate the relative effects of temperature, oxygen concentration, substrate content and competition by autochthonous microbial community on the oscillatory behaviour and survival of Escherichia coli O157:H7 in manure and manure-amended soil. The overall decli

  18. Simulation of changes in heavy metal contamination in farmland soils of a typical manufacturing center through logistic-based cellular automata modeling.

    Science.gov (United States)

    Qiu, Menglong; Wang, Qi; Li, Fangbai; Chen, Junjian; Yang, Guoyi; Liu, Liming

    2016-01-01

    A customized logistic-based cellular automata (CA) model was developed to simulate changes in heavy metal contamination (HMC) in farmland soils of Dongguan, a manufacturing center in Southern China, and to discover the relationship between HMC and related explanatory variables (continuous and categorical). The model was calibrated through the simulation and validation of HMC in 2012. Thereafter, the model was implemented for the scenario simulation of development alternatives for HMC in 2022. The HMC in 2002 and 2012 was determined through soil tests and cokriging. Continuous variables were divided into two groups by odds ratios. Positive variables (odds ratios >1) included the Nemerow synthetic pollution index in 2002, linear drainage density, distance from the city center, distance from the railway, slope, and secondary industrial output per unit of land. Negative variables (odds ratios soil pH, and distance from bodies of water. Categorical variables, including soil type, parent material type, organic content grade, and land use type, also significantly influenced HMC according to Wald statistics. The relative operating characteristic and kappa coefficients were 0.91 and 0.64, respectively, which proved the validity and accuracy of the model. The scenario simulation shows that the government should not only implement stricter environmental regulation but also strengthen the remediation of the current polluted area to effectively mitigate HMC.

  19. COLIWAVE a simulation model for survival of E. coli O157 : H7 in dairy manure and manure-amended soil

    NARCIS (Netherlands)

    Semenov, Alexander V.; Franz, Eelco; van Bruggen, Ariena H. C.

    2010-01-01

    A simulation model was developed to investigate the relative effects of temperature, oxygen concentration, substrate content and competition by autochthonous microbial community on the oscillatory behaviour and survival of Escherichia coli O157:H7 in manure and manure-amended soil. The overall

  20. Three-dimensional micro-scale flow simulation and colloid transport modeling in saturated soil porous media

    Science.gov (United States)

    Qiu, Charmaine; Gao, Hui; Fan, Dimin; Jin, Yan; Wang, Lian-Ping

    2008-11-01

    Adequate understanding of the mechanism of colloid retention by soil porous media is essential to the prediction and monitoring of the transport of contaminants by groundwater in the subsurface environment. Preliminary studies reveal that pore-scale processes are governed by colloid-grain and colloid-colloid interactions. In this talk, we focus on the assessment of their effects using a computational approach. First, micro-scale viscous flow in a model porous medium, i.e., a square channel filled with spherical grains, is simulated by simultaneously applying a mesoscopic lattice Boltzmann equation and a Navier-Stokes based hybrid approach, for rigorous cross-validation of the simulated flow. Lagrangian tacking of individual colloids is then conducted by solving colloids equation of motion including local hydrodynamic effects and physicochemical forces. Analysis of colloid transport will encompass effects of flow straining, depth-dependent spatial distribution, and retention of colloids under different solution ionic strengths, flow speeds, and packing configurations. Comparison with parallel experimental results using confocal microscopy will be briefly discussed.

  1. Soil Moisture Data Assimilation in Soil Water Flow Modeling

    Science.gov (United States)

    Pachepsky, Y. A.; Guber, A.; Jacques, D.; Pan, F.; van Genuchten, M.; Cady, R. E.; Nicholson, T. J.

    2010-12-01

    Soil water flow modeling has multiple applications. This modeling is based on simplifications stemming from both conceptual uncertainty and lack of detailed knowledge about parameters. Modern soil moisture sensors can provide detailed information about changes in soil water content in time and with depth. This information can be used for data assimilation in soil water flow modeling. The ensemble Kalman filter appears to be an appropriate method for that. Earlier we demonstrated ensemble simulations of soil water flow by using sets of pedotransfer functions (empirical relationships between soil hydraulic properties and soil basic properties, such as particle size distribution, bulk density, organic carbon content, etc.). The objective of this work was to apply the data assimilation with the ensemble Kalman filter to soil water flow modeling, using soil water content monitoring with TDR probes and an ensemble of soil water flow models parameterized with different pedotransfer functions. Experiments were carried out at the Bekkevoort site, Belgium. Sixty time domain reflectometry (TDR) probes with two rods) were installed along the trench in loamy soil at 12 locations with 50-cm horizontal spacing at five depths (15, 35, 55, 75, and 95 cm). Water content and weather parameters were monitored for one year with 15 min frequency. Soil water flow was simulated using the HYDRUS6 software. Mean daily means of water contents at the observation depths were the measurements used in data assimilation. Eighteen pedotransfer functions for water retention and one for hydraulic conductivity were applied to generate ensembles to evaluate the uncertainty in simulation results, whereas the replicated measurements at each of measurement depths were used to characterize the uncertainty in data. Data assimilation appeared to be very efficient. Even assimilating measurements at a single depth provided substantial improvement in simulations at other observation depths. Results on

  2. Modeling soil moisture memory in savanna ecosystems

    Science.gov (United States)

    Gou, S.; Miller, G. R.

    2011-12-01

    Antecedent soil conditions create an ecosystem's "memory" of past rainfall events. Such soil moisture memory effects may be observed over a range of timescales, from daily to yearly, and lead to feedbacks between hydrological and ecosystem processes. In this study, we modeled the soil moisture memory effect on savanna ecosystems in California, Arizona, and Africa, using a system dynamics model created to simulate the ecohydrological processes at the plot-scale. The model was carefully calibrated using soil moisture and evapotranspiration data collected at three study sites. The model was then used to simulate scenarios with various initial soil moisture conditions and antecedent precipitation regimes, in order to study the soil moisture memory effects on the evapotranspiration of understory and overstory species. Based on the model results, soil texture and antecedent precipitation regime impact the redistribution of water within soil layers, potentially causing deeper soil layers to influence the ecosystem for a longer time. Of all the study areas modeled, soil moisture memory of California savanna ecosystem site is replenished and dries out most rapidly. Thus soil moisture memory could not maintain the high rate evapotranspiration for more than a few days without incoming rainfall event. On the contrary, soil moisture memory of Arizona savanna ecosystem site lasts the longest time. The plants with different root depths respond to different memory effects; shallow-rooted species mainly respond to the soil moisture memory in the shallow soil. The growing season of grass is largely depended on the soil moisture memory of the top 25cm soil layer. Grass transpiration is sensitive to the antecedent precipitation events within daily to weekly timescale. Deep-rooted plants have different responses since these species can access to the deeper soil moisture memory with longer time duration Soil moisture memory does not have obvious impacts on the phenology of woody plants

  3. Numerical Simulation of Preferential Flow of Contaminants in Soil

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A simple modeling approach was suggested to simulate preferential transport of water and contaminants in soil.After saturated hydraulic conductivity was interpolated by means of Krige interpolation method or scaling method, and then zoned,the locations where saturated hydraulic conductivity was larger represented regions where preferential flow occurred,because heterogeneity of soil,one of the mechanisms resulting in preferential flow,could be reflected through the difference in saturated hydraulic conductivity.The modeling approach was validated through numerical simulation of contaminant transport in a two-dimensional hypothetical soil profile.The results of the numerical simulation showed that the approach suggested in this study was feasible.

  4. Numerical simulation of soil creep with a visco-hypoplastic constitutive model

    Science.gov (United States)

    Wang, Shun; Wu, Wei

    2016-04-01

    Slow-moving landslides make up a great part of geohazards in the Three Gorges reservoir (TGR) in China. Most of them move at speed of several centimeters per year (or even less) and show evidence of creep behaviour. It has been suggested that motion of creep landslides is mainly governed by the viscous properties of sheared materials forming the rupture zone, as these zones are where most of the slope deformation localizes. Understanding of creep behaviour of slipping material calls for laboratory tests as well as advanced constitutive models. For this purpose, a high order visco-hypoplastic constitutive model has been introduced. Unlike some of the visco-hypoplasric models, which consider the total strain rate as a combination of reversible strain rate and viscous strain rate respectively, such as dot{bm{e}}=dot{bm{e}}^e+dot{bm{e}}vis (where dot{bm{e}}, dot{bm{e}}e and dot{bm{e}}vis are the total strain rate ,reversible strain rate and viscous strain rate respectively), the proposed visco-hypolastic constitutive model decompose the Cauchy stress into a statical part and a dynamical part, bm{s}=hat{bm{s}}+\\check{bm{s}} (where bm{s},hat{bm{s}} and \\check{bm{s}} are total stress ,statical stress and dynamical stress respectively), whereas the strain rate has been considered as a whole. Within in this framework, stress change induced by strain acceleration can be taken into account. Moreover, compared with some special creep models, which may only valid for one or two stages of the three-state creep, i.e. primary creep, secondary creep and tertiary creep, this novel scheme is able to describe creep test with the whole three stages. This model has been also implemented into FEM code to evaluate some boundary-value problems. An explicit adaptive Rung-Kutta-Fehlberg algorithm is applied for stress-point integration. For verification of this model, numerical triaxial tests compared with laboratory tests have been conducted. Then a homogenous slope has been taken as an

  5. Liquid Water and Vapor Flow in Arid Soil: Comparison of Weighing Lysimeter Data with Simulations from a Process-Based Model

    Science.gov (United States)

    Berli, M.; Dijkema, J.; Koonce, J.; Ghezzehei, T. A.; van der Ploeg, M. J.; Van Genuchten, M.

    2015-12-01

    Desert soils account for about a third of the Earth's land surface and are believed to be important players in terrestrial energy balance. However, the mechanisms that govern energy and mass fluxes across the land-atmosphere interface of hot deserts remain poorly understood. This knowledge gap also spills over to our insufficient understanding of the ecology and hydrology of deserts. A recently constructed weighing lysimeter (3 m deep and 2.26 m in diameter) located in Boulder City, NV, provides data of water and energy fluxes across the soil-atmosphere boundary of the Mojave Desert. The lysimeter has been filled with homogenized desert soil from nearby Eldorado Valley, instrumented with a suite of more than 150 sensors at multiple depth between 2.5 and 250 cm and under continuous operation since July 2008. In this study, we report on water content, water potential, and temperature data from one hydrologic year at high spatial and temporal resolutions. The data was used to develop, calibrate and validate a coupled, process-based water flow and storage model using Hydrus-1D. The model simulates liquid water flow, heat flow, and non-isothermal vapor flow along the soil profile. Detailed soil bulk density and porosity profiles are known based on soil mass and volume determined during lysimeter soil installation. Water retention property was determined from concurrent volumetric water content and matric potential measurements. A density-dependent scaling relation was developed to adjust water retention properties to the different soil bulk densities in the profile. The water flux across the soil-atmosphere boundary was determined from high-resolution lysimeter scale data. The saturated hydraulic conductivity was estimated via inverse modeling, using a subset of the soil moisture data. The calibrated model was validated using the remainder of the data set. The model accurately captures the soil temperature dynamics through the year and across the profile. The water

  6. The impact of different soil texture datasets on soil moisture and evapotranspiration simulated by CLM4

    Science.gov (United States)

    Yan, B.; Dickinson, R. E.

    2012-12-01

    Evapotranspiration (ET) is both a moisture flux and an energy flux. It has a substantial impact on climate. Community Land Model Version 4 (CLM4) is a widely used land surface model that simulates moisture, energy and momentum exchange between land and atmosphere. However, ET from CLM4 suffers from relatively low accuracy, especially for ground evaporation. In the parameterization of CLM4, soil texture, by determining soil hydraulic properties, affects the evolution of soil moisture and consequently ET. The three components of ET in climate models can more readily be improved after an evaluation of soil texture dataset's impact on ET simulations. Besides the IGBP-DIS (International Geosphere-Biosphere Programme Data and Information System) dataset used in CLM4, another two US multi-layer soil particle content datasets, Soil Database for the Conterminous United States (CONUS-SOIL) and Global Soil Texture and Derived Water-Holding Capacities (Webb2000), are also used. The latter two show a consistent substantial reduction of both sand and clay contents in Mississippi River Basin. CLM4 is run off line over the US with the three different soil texture datasets (Control Run, CONUS SOIL and Webb2000). Comparisons of simulated soil moisture with NCEP (National Centers for Environmental Prediction) reanalysis data show a higher agreement between CONUS SOIL and NCEP over Mississippi River Basin. Compared with Control Run, soil moisture from the other two runs increases in Western US and decreases in Eastern US, which produces a stronger west-east soil moisture gradient. The response of ET to soil moisture change differs in different climate regimes. In Mississippi River Basin, the change of ET is negligible even if soil moisture increases substantially. On the other hand, in eastern US and US Central Great Plains, ET is very sensitive to soil moisture during the warm seasons, with the change of up to 10 W/m2.

  7. Sensitivity and uncertainty analysis of estimated soil hydraulic parameters for simulating soil water content

    Science.gov (United States)

    Gupta, Manika; Garg, Naveen Kumar; Srivastava, Prashant K.

    2014-05-01

    The sensitivity and uncertainty analysis has been carried out for the scalar parameters (soil hydraulic parameters (SHPs)), which govern the simulation of soil water content in the unsaturated soil zone. The study involves field experiments, which were conducted in real field conditions for wheat crop in Roorkee, India under irrigated conditions. Soil samples were taken for the soil profile of 60 cm depth at an interval of 15 cm in the experimental field to determine soil water retention curves (SWRCs). These experimentally determined SWRCs were used to estimate the SHPs by least square optimization under constrained conditions. Sensitivity of the SHPs estimated by various pedotransfer functions (PTFs), that relate various easily measurable soil properties like soil texture, bulk density and organic carbon content, is compared with lab derived parameters to simulate respective soil water retention curves. Sensitivity analysis was carried out using the monte carlo simulations and the one factor at a time approach. The different sets of SHPs, along with experimentally determined saturated permeability, are then used as input parameters in physically based, root water uptake model to ascertain the uncertainties in simulating soil water content. The generalised likelihood uncertainty estimation procedure (GLUE) was subsequently used to estimate the uncertainty bounds (UB) on the model predictions. It was found that the experimentally obtained SHPs were able to simulate the soil water contents with efficiencies of 70-80% at all the depths for the three irrigation treatments. The SHPs obtained from the PTFs, performed with varying uncertainties in simulating the soil water contents. Keywords: Sensitivity analysis, Uncertainty estimation, Pedotransfer functions, Soil hydraulic parameters, Hydrological modelling

  8. Hydraulic properties comparison in the calibration of CropSyst, SWAP and MACRO models in simulating soil water content for 3 years

    Science.gov (United States)

    Bonfante, A.; Fragnito, F.; Manna, P.; Orefice, N.; Pastori, M.; Perego, A.

    2009-04-01

    The quantification of the water balance components within soil-crop-climate system is strictly required to derive proper management conditions for plant growth and environmental protection. Numerical models are currently accepted as helpful tools to gain into the processes occurring in the soil-crop-climate system and to extrapolate data. A large number of available models solves, at field scale, the water balance components by the well known Richard's equation. Despite their common basis of the representation of water flow in the unsaturated zone, it is possible that with the same pedological, climatic and agronomic management conditions, apparently similar hydrological models give different answers. Therefore, to test the capability of a model to represent reality, model simulation must be compared with experimental data and with simulations by other models. The objective of the present study was to evaluate and compare the performances of three well known models (SWAP, MACRO and CropSyst based on the solution of the Richard's equation). Main attention was focussed on the effects of the calibration of the three models on the soil hydraulic properties parameterization. The performance of SWAP, MACRO and CropSyst is compared using field data collected from a structured fine soil (Vertic Calciustepts located in Cerese, Mantova, Italy) cropped to maize. The models are tested and compared on the basis of their ability to predict in situ the measured soil water content at different depths during the years 2002-2004. Water contents was measured with a TDR equipment at 5 depth, where possible with daily frequency. All three models produce acceptable predictions, as evidence by an average root mean square error (RMSE) within ± 0.031 and an average coefficient of residual mass (CRM) within ± 0.66. The SWAP and CropSyst models produces the better performance, but in absolute none of the models is consistently more accurate than the others. In any case the different

  9. Health risks from arsenic-contaminated soil in Flin Flon-Creighton, Canada: Integrating geostatistical simulation and dose-response model

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Hua [Environmental Systems Engineering Program, Faculty of Engineering, University of Regina, Regina, Saskatchewan, S4S 0A2 (Canada); Huang Guohe, E-mail: huang@iseis.or [Environmental Systems Engineering Program, Faculty of Engineering, University of Regina, Regina, Saskatchewan, S4S 0A2 (Canada); Zeng Guangming [College of Environmental Science and Engineering, Hunan University, Changsha, Hunan 410082 (China)

    2009-08-15

    Elevated concentrations of arsenic were detected in surface soils adjacent to a smelting complex in northern Canada. We evaluated the cancer risks caused by exposure to arsenic in two communities through combining geostatistical simulation with demographic data and dose-response models in a framework. Distribution of arsenic was first estimated using geostatistical circulant-embedding simulation method. We then evaluated the exposures from inadvertent ingestion, inhalation and dermal contact. Risks of skin caner and three internal cancers were estimated at both grid scale and census-unit scale using parametric dose-response models. Results indicated that local residents could face non-negligible cancer risks (skin cancer and liver cancer mainly). Uncertainties of risk estimates were discussed from the aspects of arsenic concentrations, exposed population and dose-response model. Reducing uncertainties would require additional soil sampling, epidemic records as well as complementary studies on land use, demographic variation, outdoor activities and bioavailability of arsenic. - Cancer risks induced by arsenic in soil were evaluated using geostatistical simulation and dose-response model.

  10. Comparing measured with simulated vertical soil stress under vehicle load

    DEFF Research Database (Denmark)

    Keller, Thomas; Lamandé, Mathieu; Arvidsson, Johan;

    in the soil profile at 0.3, 0.5 and 0.7 m depth was measured during wheeling at field capacity on five soils (13-66% clay). Stress propagation was then simulated with the semi-analytical model, using vertical stress at 0.1 m depth estimated from tyre characteristics as upper boundary condition, and v...

  11. Comparing measured with simulated vertical soil stress under vehicle load

    DEFF Research Database (Denmark)

    Keller, Thomas; Lamandé, Mathieu; Arvidsson, Johan

    in the soil profile at 0.3, 0.5 and 0.7 m depth was measured during wheeling at field capacity on five soils (13-66% clay). Stress propagation was then simulated with the semi-analytical model, using vertical stress at 0.1 m depth estimated from tyre characteristics as upper boundary condition, and v...

  12. Numerical Simulation on Freezing Process of Saturated Granlar Soil

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The relation between ice pressure and load as a criterion of segregated ice initiation is introduced into the rigid ice model to simulate frost heave in saturated and granular soil. The calculated results show that unfrozen water content, thermal conductivity and hydraulic conductivity change greatly in frozen fringe. In numerical simulations, the influence of load, hydraulic conductivity and property of soil containing water on the process of soil freezing are analyzed, and the simulation curves such as cumulative heave,the change of depth of frozen and the distributions of water content are similar to the observations reported elsewhere.

  13. How important is a detailed hydrological representation when modelling soil carbon dynamics in Chinese red soils.

    Science.gov (United States)

    Oyesiku-Blakemore, Joseph; Verrot, Lucile; Geris, Josie; Zhang, Ganlin; Peng, Xinhua; Hallett, Paul; Smith, Jo

    2017-04-01

    Soil carbon and nitrogen processing are strongly influenced by the hydrology of soils. When simulating these processes models represent soil hydrology in some way. The hydrological components of soil carbon and nitrogen models vary greatly in their complexity, as does the burden of simulation time and data requirements. Hydrology specific models, such as Hydrus, have more detailed representations of soil hydrology than those used in some soil carbon and nitrogen models, such as ECOSSE, and can provide a more accurate and precise description of the movement and content of water in soil. Moisture content is one of the key variables controlling the processing of carbon and nitrogen in soil models. A higher soil moisture content results in increased methane production through the anaerobic decomposition of soil carbon pools. It also alters the rate at which aerobic decomposition occurs, with low and high soil moisture contents limiting the decomposition of SOC. An inaccurate estimate of soil moisture will introduce errors in the estimated rates of model SOC transformations, which would result in errors in the simulated SOC. In order to shed light on this uncertainty we use the same input data to simulate soil moisture contents in a Red Soil region of China, using both the ECOSSE model and Hydrus 2D. We compare the simulations of both models with measurements of soil moisture at the site and each other. We highlight where the models differ and identify the conditions under which errors are likely to occur. We then simulate SOC dynamics using the ECOSSE model and its original hydrology with the ECOSSE model simulations using the Hydrus 2D simulations. This shows the importance of including a detailed representation of soil moisture when simulating soil organic matter dynamics.

  14. Scenarios of organic amendment use to increase soil carbon stocks and nitrogen availability in cropped soils at the territory scale: spatial and temporal simulations with the NCSOIL/CERES-EGC crop model

    Science.gov (United States)

    Noirot-Cosson, Paul-Emile; Vaudour, Emmanuelle; Aubry, Christine; Gilliot, Jean-Marc; Gabrielle, Benoît; Houot, Sabine

    2014-05-01

    The application of Exogenous Organic Matter (EOM) on cropped soils is a promising way to increase soil organic carbon and available nitrogen for crops while recycling organic agricultural and urban wastes. In peri-urban territories where the specialization of agriculture limits the resource in organic amendments since livestock farming is scarce, a better management of EOM land application from all origins at the territory scale could be thought to maximize their benefits. The objective was to predict the effect of various EOM types and uses on C and N fluxes and crop production for each homogeneous spatial unit of the territory, first step for the territorial optimization of EOM land application. The study area, located 30km west of Paris, covers 221km² and is mostly characterized by croplands. The effects of repeated EOM applications were studied using a mechanistic crop model: CERES-EGC accounting for soil characteristics, crop production systems, and climate. The whole territory was divided into homogeneous spatial units, each defined by soil and crop production system characteristics. Four different soil types were characterized, mapped and parameterized in the model. Kinetics of C and N mineralization during soil incubations were used to optimize soil organic matter characteristics and parameters in the sub-model NCSOIL of CERES-EGC. Crop production systems were defined and spatially inferred using the French land parcel identification system. Climatic data measured on the territory were used to make a 20 year-meteorological scenario. Based on these initial informations, crop yields and C and N fluxes were simulated for the actual crop productions and soil type combinations of the territory. Then, different scenarios of EOM uses were also simulated based on different EOM types, added quantities and frequencies of application within the crop successions respecting the 170kgN/ha/yr legal limit. All the parameters studied, crop yields, N outputs, carbon storage

  15. Simulation of Soil Water Content Variability in a Heavy Clay Soil under Contrasting Soil Managements

    Science.gov (United States)

    Pedrera, A.; Vanderlinden, K.; Martínez, G.; Espejo, A. J.; Giráldez, J. V.

    2012-04-01

    Soil water content (SWC) is a key variable for numerous physical, chemical and biological processes that take place at or near the soil surface. Understanding the spatial and temporal variability of SWC at the field scale is of prime importance for implementing efficient measurement strategies in applications. The aim of this study was to characterize the spatial and temporal variation of gravimetric SWC in a heavy clay soil, in a wheat-sunflower-legume rotation under conventional (CT) and no-till (NT) using a simple water balance model. An experimental field in SW Spain, where conventional (CT) and no-till (NT) management of a heavy clay soil are being compared since 1983, was sampled for gravimetric SWC on 38 occasions during 2008 and 2009. Topsoil clay content across the six plots was on average 55%, with a standard deviation of 2.7%. The soil profile was sampled at 54 locations, evenly distributed over the three CT and NT plots, at depths of 0-10, 25-35, and 55-65 cm. Topsoil water retention curves (SWRC) were determined in the laboratory on undisturbed soil samples from each of the 54 locations. A weather station recorded daily precipitation and evapotranspiration, as calculated by the Penman-Monteith FAO equation. The water balance was calculated using the Thornthwaite-Mather model with a daily time step. Three parameters, water holding capacity, and water evaporation corrector coefficients for each of the two years, were inversely estimated at the 54 SWC observation points and probability density functions were identified. Spatial variability of SWC was estimated using a Monte Carlo approach, and simulated and observed variability were compared. This Monte Carlo scheme, using a simple water balance model with only three parameters, was found to be useful for evaluating the influence of soil management on the variability of SWC in heavy clay soils.

  16. Modelling large-scale spatial variability of soil properties with sequential stochastic simulation conditioned by universal kriging in a Hungarian study site

    Science.gov (United States)

    Szatmári, Gábor; Barta, Károly; Pásztor, László

    2015-04-01

    Modelling of large-scale spatial variability of soil properties is a promising subject in soil science, as well as in general environmental research, since the resulted model(s) can be applied to solve various problems. In addition to "purely" map an environmental element, the spatial uncertainty of the map product can deduced, specific areas could be identified and/or delineated (contaminated or endangered regions, plots for fertilization, etc.). Geostatistics, which can be regarded as a subset of statistics specialized in analysis and interpretation of geographically referenced data, offer a huge amount of tools to solve these tasks. Numerous spatial modeling methods have been developed in the past decades based on the regionalized variable theory. One of these techniques is sequential stochastic simulation, which can be conditioned with universal kriging (also referred to as regression kriging). As opposed to universal kriging (UK), sequential simulation conditioned with universal kriging (SSUK) provides not just one but several alternative and equally probable "maps", i.e. realizations. The realizations reproduce the global statistics (e.g. sample histogram, variogram), i.e. they reflect/model the reality in a certain global (and not local!) sense. In this paper we present and test SSUK developed in R-code and its utilizations in a water erosion affected study area. Furthermore, we compare the results from UK and SSUK. For this purpose, two soil variables were selected: soil organic matter (SOM) content and rooting depth (RD). SSUK approach is illustrated with a legacy soil dataset from a study area endangered by water erosion in Central Hungary. Legacy soil data was collected in the end of the 1980s in the framework of the National Land Evaluation Programme. Spatially exhaustive covariates were derived from a digital elevation model and from the land-use-map of the study area. SSUK was built upon a UK prediction system for both variables and 200 realizations

  17. USE OF THE “ROTHC” MODEL TO SIMULATE SOIL ORGANIC CARBON DYNAMICS ON A SILTY-LOAM INCEPTISOL IN NORTHERN ITALY UNDER DIFFERENT FERTILIZATION PRACTICES

    Directory of Open Access Journals (Sweden)

    Rosa Francaviglia

    2014-01-01

    Full Text Available We evaluated the efficiency of the RothC model to simulate Soil Organic Carbon (SOC dynamics after 12 years of organic and mineral fertilization practices in a study area located in northern Italy, on a silty-loam Inceptisol with a rotation including tomato, maize and alfalfa. The model performance was assessed by RMSE and EF coefficients. RothC simulated well observed SOC decreases in 71 samples (RMSE=7.42; EF=0.79, while performed with less accuracy when considering all samples (96 samples; RMSE=12.37; EF=0.58, due to the fact that the model failed in case of measured SOC increases (25 samples; RMSE=20.77; EF=-0.038. The model was used to forecast the SOC dynamics over a 50 year period under the same pedoclimatic conditions. Only clay contents >15% allowed to predict increasing levels of SOC respect to the starting values.

  18. The Changing Model of Soil

    Science.gov (United States)

    Richter, D. D.; Yaalon, D.

    2012-12-01

    The contemporary genetic model of soil is changing rapidly in response to advances in soil science and to human and environmental forcings in the 21st century (Richter and Yaalon, 2012). Three ongoing changes in the model of soil include that: (1) lower soil boundaries are much deeper than the solum, historically the O to B horizons, (2) most soils are polygenetic paleosols, products of soil-forming processes that have ranged widely over soils' lifetimes, and (3) soils are globally human-natural bodies, no longer natural bodies. Together, these changes in the model of soil mean that human forcings are a global wave of soil polygenesis altering fluxes of matter and energy and transforming soil thermodynamics as potentially very deep systems. Because soils are non-linear systems resulting from high-order interactions of physics, chemistry, and biology, trajectories of how human forcings alter soils over decades are not readily predictable and require long-term soil observations. There is much to learn about how soils are changing internally as central components of management systems and externally in relation to wider environments. To be critical, research has been remarkably superficial in studies of soil, reductionist in approach, and lacking in time-series observations of responses to soil management. While this criticism may sound negative, it creates significant opportunities for contemporary soil scientists.

  19. Tracey - a simulation model of trace element fluxes in soil-plant system for long-term assessment of a radioactive groundwater contamination

    Energy Technology Data Exchange (ETDEWEB)

    Gaerdenaes, Annemieke (Dept. of Soil and Environment, Swedish Univ. of Agricultural Sciences, Uppsala (Sweden)); Eckersten, Henrik (Dept. of Ecology and Crop Production, Swedish Univ. of Agricultural Sciences, Uppsala (Sweden)); Reinlert, Andre (Dept. of Physical Geography and Ecosystems Analysis, Lund Univ., Lund (Sweden)); Gustafsson, David; Jansson, Per-Erik (Dept. Land and WaterResources, Royal Inst. of Technology, Stockholm (Sweden)); Ekstroem, Per-Anders; Avila, Rodolfo (Facilia AB, Bromma (Sweden)); Greger, Maria (Dept. of Botany, Stockholm Univ., Stockholm (Sweden))

    2009-10-15

    We developed a general trace element model called Tracey to simulate dynamically the possible accumulation of radionuclides as a result of an long-term radioactive contamination of groundwater in terrestrial ecosystems. The overall objectives of the study are to: 1) Develop and evaluate a multi-compartmental model that dynamically simulates the transport and accumulation of a radionuclide in the soil-plant system at a time scale relevant for risk assessment of nuclear fuel waste; and 2) Asses the possible accumulation of radionuclide in terrestrial ecosystems due to an eventual long-term continuous radioactive groundwater contamination. Specific objectives were to assess: - The proportion of the contamination accumulated and where it is stored in the ecosystem. - The importance of the plant uptake approach for accumulation of radionuclides. - The most important radionuclide properties and ecosystem characteristics for accumulation and losses. - The proportion of the contamination lost and how is it lost. - The circumstances which stimulated export of radionuclides to other ecosystems. The model presented here, called Tracey, is a stand-alone version to allow for long simulation periods relevant for the time scale of risk assessment of nuclear waste (i.e. several thousand years) with time steps as short as one day. Tracey is a multi-compartmental model in which fluxes and storage of radionuclide are described for different plant parts and for several soil layers. Each layer includes pools of slowly and quickly decomposing litter, humus, solved and absorbed trace element. The trace element fluxes are assumed to be proportional to either water or carbon fluxes, these fluxes are simulated using the dynamic model CoupModel for fluxes of water, carbon, nitrogen and carbon in terrestrial ecosystems. Two different model approaches were used to describe plant uptake of radionuclides. The one called passive uptake approach is driven by water uptake and the one called active

  20. Simulation of nitrogen leaching in sandy soils in the Netherlands with the ANIMO model and the integrated modelling system STONE

    NARCIS (Netherlands)

    Wolf, J.; Hack-ten Broeke, M.J.D.; Rötter, R.P.

    2005-01-01

    Over the years, modelling approaches have played an increasingly important role in designing agricultural and environmental policies and formulating measures to reduce nutrient emissions in The Netherlands. In recent years, increased emphasis has been put on validation of models used for that purpos

  1. Dynamics models of soil organic carbon

    Institute of Scientific and Technical Information of China (English)

    YANGLi-xia; PANJian-jun

    2003-01-01

    As the largest pool of terrestrial organic carbon, soils interact strongly with atmosphere composition, climate, and land change. Soil organic carbon dynamics in ecosystem plays a great role in global carbon cycle and global change. With development of mathematical models that simulate changes in soil organic carbon, there have been considerable advances in understanding soil organic carbon dynamics. This paper mainly reviewed the composition of soil organic matter and its influenced factors, and recommended some soil organic matter models worldwide. Based on the analyses of the developed results at home and abroad, it is suggested that future soil organic matter models should be developed toward based-process models, and not always empirical ones. The models are able to reveal their interaction between soil carbon systems, climate and land cover by technique and methods of GIS (Geographical Information System) and RS (Remote Sensing). These models should be developed at a global scale, in dynamically describing the spatial and temporal changes of soil organic matter cycle. Meanwhile, the further researches on models should be strengthen for providing theory basis and foundation in making policy of green house gas emission in China.

  2. Experimental and fate and transport model simulation results of Se and B released from FGDG, soil and soil-FGDG mixture.

    Data.gov (United States)

    U.S. Environmental Protection Agency — The leachate concentrations of Se and B released from FGDG, soil and soil-FGDG mixture obtained from EPA-method 1314 is included in the data set. The non-equilibrium...

  3. Analog modeling of transient moisture flow in unsaturated soil

    NARCIS (Netherlands)

    Wind, G.P.

    1979-01-01

    Hydraulic and electronic analog models are developed for the simulation of moisture flow and accumulation in unsaturated soil. The analog models are compared with numerical models and checked with field observations. Application of soil physical knowledge on a soil technological problem by means of

  4. Geostatistical independent simulation of spatially correlated soil variables

    Science.gov (United States)

    Boluwade, Alaba; Madramootoo, Chandra A.

    2015-12-01

    The selection of best management practices to reduce soil and water pollution often requires estimation of soil properties. It is important to find an efficient and robust technique to simulate spatially correlated soils parameters. Co-kriging and co-simulation are techniques that can be used. These methods are limited in terms of computer simulation due to the problem of solving large co-kriging systems and difficulties in fitting a valid model of coregionalization. The order of complexity increases as the number of covariables increases. This paper presents a technique for the conditional simulation of a non-Gaussian vector random field on point support scale. The technique is termed Independent Component Analysis (ICA). The basic principle underlining ICA is the determination of a linear representation of non-Gaussian data so that the components are considered statistically independent. With such representation, it would be easy and more computationally efficient to develop direct variograms for the components. The process is presented in two stages. The first stage involves the ICA decomposition. The second stage involves sequential Gaussian simulation of the generated components (which are derived from the first stage). This technique was applied for spatially correlated extractable cations such as magnesium (Mg) and iron (Fe) in a Canadian watershed. This paper has a strong application in stochastic quantification of uncertainties of soil attributes in soil remediation and soil rehabilitation.

  5. Impact of the soil hydrology scheme on simulated soil moisture memory in a GCM

    Science.gov (United States)

    Hagemann, Stefan; Stacke, Tobias

    2013-04-01

    Soil moisture-atmosphere feedback effects play an important role in several regions of the globe. For some of these regions, soil moisture memory may contribute significantly to the development of the regional climate. Identifying those regions can help to improve predictability in seasonal to decadal climate forecasts. The present study investigates how different setups of the soil hydrology scheme affect soil moisture memory simulated by the global climate model of the Max Planck Institute for Meteorology (MPI-M), ECHAM6/JSBACH. First, the standard setup applied for the CMIP5 exercise is used, in which soil water is represented by a single soil moisture reservoir. Second, a new five soil layer hydrology scheme is utilized where the previous bucket soil moisture now corresponds to the root zone soil moisture. In the standard setup, transpiration may access the whole soil moisture that is exceeding the wilting point over vegetated areas. However, in the five layer scheme, soil water below the root zone cannot be accessed by transpiration directly, but only be transported upwards into the root zone by diffusion following the Richard's equation. Thus, this below the root zone, which is not present in the standard setup, can act as buffer in the transition between wet and dry periods. A second notable difference between the two setups is the formulation of bare soil evaporation. In the standard setup, it may only occur if the whole soil moisture bucket is almost completely saturated, while in the new setup, it depends only on the saturation of the upper most soil layer. As the latter is much thinner than the root zone (bucket), bare soil evaporation can occur more frequently, especially after rainfall events. For the second setup, two further variants are considered: one where the bare soil evaporation was modified and one where a new parameter dataset of soil water holding capacities was used. Soil moisture memory of the different setups will be analysed from global

  6. Tracey - a simulation model of trace element fluxes in soil-plant system for long-term assessment of a radioactive groundwater contamination

    Energy Technology Data Exchange (ETDEWEB)

    Gaerdenaes, Annemieke (Dept. of Soil and Environment, Swedish Univ. of Agricultural Sciences, Uppsala (Sweden)); Eckersten, Henrik (Dept. of Ecology and Crop Production, Swedish Univ. of Agricultural Sciences, Uppsala (Sweden)); Reinlert, Andre (Dept. of Physical Geography and Ecosystems Analysis, Lund Univ., Lund (Sweden)); Gustafsson, David; Jansson, Per-Erik (Dept. Land and WaterResources, Royal Inst. of Technology, Stockholm (Sweden)); Ekstroem, Per-Anders; Avila, Rodolfo (Facilia AB, Bromma (Sweden)); Greger, Maria (Dept. of Botany, Stockholm Univ., Stockholm (Sweden))

    2009-10-15

    We developed a general trace element model called Tracey to simulate dynamically the possible accumulation of radionuclides as a result of an long-term radioactive contamination of groundwater in terrestrial ecosystems. The overall objectives of the study are to: 1) Develop and evaluate a multi-compartmental model that dynamically simulates the transport and accumulation of a radionuclide in the soil-plant system at a time scale relevant for risk assessment of nuclear fuel waste; and 2) Asses the possible accumulation of radionuclide in terrestrial ecosystems due to an eventual long-term continuous radioactive groundwater contamination. Specific objectives were to assess: - The proportion of the contamination accumulated and where it is stored in the ecosystem. - The importance of the plant uptake approach for accumulation of radionuclides. - The most important radionuclide properties and ecosystem characteristics for accumulation and losses. - The proportion of the contamination lost and how is it lost. - The circumstances which stimulated export of radionuclides to other ecosystems. The model presented here, called Tracey, is a stand-alone version to allow for long simulation periods relevant for the time scale of risk assessment of nuclear waste (i.e. several thousand years) with time steps as short as one day. Tracey is a multi-compartmental model in which fluxes and storage of radionuclide are described for different plant parts and for several soil layers. Each layer includes pools of slowly and quickly decomposing litter, humus, solved and absorbed trace element. The trace element fluxes are assumed to be proportional to either water or carbon fluxes, these fluxes are simulated using the dynamic model CoupModel for fluxes of water, carbon, nitrogen and carbon in terrestrial ecosystems. Two different model approaches were used to describe plant uptake of radionuclides. The one called passive uptake approach is driven by water uptake and the one called active

  7. Underestimation of boreal soil carbon stocks by mathematical soil carbon models linked to soil nutrient status

    Science.gov (United States)

    Ťupek, Boris; Ortiz, Carina A.; Hashimoto, Shoji; Stendahl, Johan; Dahlgren, Jonas; Karltun, Erik; Lehtonen, Aleksi

    2016-08-01

    Inaccurate estimate of the largest terrestrial carbon pool, soil organic carbon (SOC) stock, is the major source of uncertainty in simulating feedback of climate warming on ecosystem-atmosphere carbon dioxide exchange by process-based ecosystem and soil carbon models. Although the models need to simplify complex environmental processes of soil carbon sequestration, in a large mosaic of environments a missing key driver could lead to a modeling bias in predictions of SOC stock change.We aimed to evaluate SOC stock estimates of process-based models (Yasso07, Q, and CENTURY soil sub-model v4) against a massive Swedish forest soil inventory data set (3230 samples) organized by a recursive partitioning method into distinct soil groups with underlying SOC stock development linked to physicochemical conditions.For two-thirds of measurements all models predicted accurate SOC stock levels regardless of the detail of input data, e.g., whether they ignored or included soil properties. However, in fertile sites with high N deposition, high cation exchange capacity, or moderately increased soil water content, Yasso07 and Q models underestimated SOC stocks. In comparison to Yasso07 and Q, accounting for the site-specific soil characteristics (e. g. clay content and topsoil mineral N) by CENTURY improved SOC stock estimates for sites with high clay content, but not for sites with high N deposition.Our analysis suggested that the soils with poorly predicted SOC stocks, as characterized by the high nutrient status and well-sorted parent material, indeed have had other predominant drivers of SOC stabilization lacking in the models, presumably the mycorrhizal organic uptake and organo-mineral stabilization processes. Our results imply that the role of soil nutrient status as regulator of organic matter mineralization has to be re-evaluated, since correct SOC stocks are decisive for predicting future SOC change and soil CO2 efflux.

  8. Vertical variations of soil hydraulic properties within two soil profiles and its relevance for soil water simulations

    Science.gov (United States)

    Schwen, Andreas; Zimmermann, Michael; Bodner, Gernot

    2014-08-01

    Numerical simulations of soil water dynamics can be valuable tools for the assessment of different soil and land management practices. For accurate simulations, the soil hydraulic properties (SHP), i.e. the hydraulic conductivity and water retention function have to be properly known. They can be either estimated from physical soil properties by pedotransfer functions (PTF) or measured. In most studies, soil profiles are analyzed and sampled with respect to their pedogenic horizons. While considerable effort has been put on horizontal spatial SHP variations, vertical changes within soil profiles have not been analyzed in detail. Therefore, the objectives of this study were (i) the SHP measurement along vertical transects within two soil profiles, (ii) to evaluate their spatial variation and correlation with physical soil properties, and (iii) to assess the impact of the SHP determination method and its spatial discretization on simulated soil water balance components. Two soils, an agriculturally used silty-loam Chernozem and a forested sandy Cambisol were sampled in 0.05 m increments along vertical transects. The parameters of a dual porosity model were derived using the evaporation method and scaling was applied to derive representative mean SHP parameters and scaling factors as a measure of spatial variability. State-space models described spatial variations of the scaling factors by physical soil properties. Simulations with HYDRUS 1D delivered the soil water balance for different climatic conditions with the SHP being estimated from horizon-wise PTFs, or discretized either sample-wise, according to the pedogenic horizons, or as hydrologically relevant units (hydropedological approach). Considerable SHP variations were found for both soil profiles. In the Chernozem, variations of the hydraulic conductivity were largest within the ploughed Ap-horizon and could be attributed to variations in soil structure (macropores). In the subsoil, soil water retention showed

  9. A coupling ocean-atmosphere climatic modelling study for rainfall and soil moisture simulations on the São Francisco River basin

    Directory of Open Access Journals (Sweden)

    Regla Duthit Somoza

    2011-12-01

    Full Text Available The aim of this study was to obtain a better understanding of the Ocean-Atmosphere Global Circulation Coupling Model (CGCM performance for forecasting the interannual rainfall variability on the São Francisco River Basin, during austral summer (DJF 1997-2007. In addition, the rainfall predictions and calculated potential vapor transpiration were the input variables for the Hydrological Balance Model (HBM experiments to obtain soil moisture estimations. Simulations using CGCM were compared with forecastings based on the Atmosphere Global Circulation Model (AGCM, which has been used previously for this purpose. Even though there were systematic errors of rainfall over estimations for the Basin, the CGCM had better performance than the AGCM at the spatial representation and showed positive correlation coefficients with observation values. These facts corroborate that ocean-atmosphere coupling is an important mechanism to be taken into account for rainfall forecasting at the Brazilian southeast zone. On the other hand, the HBM-AGCM and the HBM-CGCM were quite similar in terms of correlation coefficients (0,6 for soil moisture estimation. This suggests that the corrected estimated precipitation and potential evapotranspiration (ETP resulting from climate modeling and dynamics of the AGCM and CGCM, as input data for water balance models in the seasonal scale, can be used to provide support to the best practices for the management of surface water in the basin of the São Francisco River.

  10. Investigating soil controls on soil moisture spatial variability: Numerical simulations and field observations

    Science.gov (United States)

    Wang, Tiejun; Franz, Trenton E.; Zlotnik, Vitaly A.; You, Jinsheng; Shulski, Martha D.

    2015-05-01

    Due to its complex interactions with various processes and factors, soil moisture exhibits significant spatial variability across different spatial scales. In this study, a modeling approach and field observations were used to examine the soil control on the relationship between mean (θ bar) and standard deviation (σθ) of soil moisture content. For the numerical experiments, a 1-D vadose zone model along with van Genuchten parameters generated by pedotransfer functions was used for simulating soil moisture dynamics under different climate and surface conditions. To force the model, hydrometeorological and physiological data that spanned over three years from five research sites within the continental US were used. The modeling results showed that under bare surface conditions, different forms of the θ bar -σθ relationship as observed in experimental studies were produced. For finer soils, a positive θ bar -σθ relationship gradually changed to an upward convex and a negative one from arid to humid conditions; whereas, a positive relationship existed for coarser soils, regardless of climatic conditions. The maximum σθ for finer soils was larger under semiarid conditions than under arid and humid conditions, while the maximum σθ for coarser soils increased with increasing precipitation. Moreover, vegetation tended to reduce θ bar and σθ, and thus affected the θ bar -σθ relationship. A sensitivity analysis was also conducted to examine the controls of different van Genuchten parameters on the θ bar -σθ relationship under bare surface conditions. It was found that the residual soil moisture content mainly affected σθ under dry conditions, while the saturated soil moisture content and the saturated hydraulic conductivity largely controlled σθ under wet conditions. Importantly, the upward convex θ bar -σθ relationship was mostly caused by the shape factor n that accounts for pore size distribution. Finally, measured soil moisture data from a

  11. Improvement of Soil Respiration Parameterization in a Dynamic Global Vegetation Model and Its Impact on the Simulation of Terrestrial Carbon Fluxes

    OpenAIRE

    Kim, Dongmin; Lee, Myong-In; Seo, Eunkyo

    2017-01-01

    Soil decomposition is one of the critical processes for maintaining a terrestrial ecosystem and the global carbon cycle. The sensitivity of soil respiration (Rs) to temperature, the so-called Q10 value, is required for parameterizing the soil decomposition process and is assumed to be a constant in conventional numerical models, while realistically it is not in cases of spatiotemporal heterogeneity. This study develops a new parameterization method for determining Q10 by considering the soil ...

  12. A protocol for conducting rainfall simulation to study soil runoff.

    Science.gov (United States)

    Kibet, Leonard C; Saporito, Louis S; Allen, Arthur L; May, Eric B; Kleinman, Peter J A; Hashem, Fawzy M; Bryant, Ray B

    2014-04-03

    Rainfall is a driving force for the transport of environmental contaminants from agricultural soils to surficial water bodies via surface runoff. The objective of this study was to characterize the effects of antecedent soil moisture content on the fate and transport of surface applied commercial urea, a common form of nitrogen (N) fertilizer, following a rainfall event that occurs within 24 hr after fertilizer application. Although urea is assumed to be readily hydrolyzed to ammonium and therefore not often available for transport, recent studies suggest that urea can be transported from agricultural soils to coastal waters where it is implicated in harmful algal blooms. A rainfall simulator was used to apply a consistent rate of uniform rainfall across packed soil boxes that had been prewetted to different soil moisture contents. By controlling rainfall and soil physical characteristics, the effects of antecedent soil moisture on urea loss were isolated. Wetter soils exhibited shorter time from rainfall initiation to runoff initiation, greater total volume of runoff, higher urea concentrations in runoff, and greater mass loadings of urea in runoff. These results also demonstrate the importance of controlling for antecedent soil moisture content in studies designed to isolate other variables, such as soil physical or chemical characteristics, slope, soil cover, management, or rainfall characteristics. Because rainfall simulators are designed to deliver raindrops of similar size and velocity as natural rainfall, studies conducted under a standardized protocol can yield valuable data that, in turn, can be used to develop models for predicting the fate and transport of pollutants in runoff.

  13. Inverse modeling of soil characteristics from surface soil moisture observations: potential and limitations

    Directory of Open Access Journals (Sweden)

    A. Loew

    2008-01-01

    Full Text Available Land surface models (LSM are widely used as scientific and operational tools to simulate mass and energy fluxes within the soil vegetation atmosphere continuum for numerous applications in meteorology, hydrology or for geobiochemistry studies. A reliable parameterization of these models is important to improve the simulation skills. Soil moisture is a key variable, linking the water and energy fluxes at the land surface. An appropriate parameterisation of soil hydraulic properties is crucial to obtain reliable simulation of soil water content from a LSM scheme. Parameter inversion techniques have been developed for that purpose to infer model parameters from soil moisture measurements at the local scale. On the other hand, remote sensing methods provide a unique opportunity to estimate surface soil moisture content at different spatial scales and with different temporal frequencies and accuracies. The present paper investigates the potential to use surface soil moisture information to infer soil hydraulic characteristics using uncertain observations. Different approaches to retrieve soil characteristics from surface soil moisture observations is evaluated and the impact on the accuracy of the model predictions is quantified. The results indicate that there is in general potential to improve land surface model parameterisations by assimilating surface soil moisture observations. However, a high accuracy in surface soil moisture estimates is required to obtain reliable estimates of soil characteristics.

  14. Modeling greenhouse gas emissions (CO2, N2O, CH4) from managed arable soils with a fully coupled hydrology-biogeochemical modeling system simulating water and nutrient transport and associated carbon and nitrogen cycling at catchment scale

    Science.gov (United States)

    Klatt, Steffen; Haas, Edwin; Kraus, David; Kiese, Ralf; Butterbach-Bahl, Klaus; Kraft, Philipp; Plesca, Ina; Breuer, Lutz; Zhu, Bo; Zhou, Minghua; Zhang, Wei; Zheng, Xunhua; Wlotzka, Martin; Heuveline, Vincent

    2014-05-01

    The use of mineral nitrogen fertilizer sustains the global food production and therefore the livelihood of human kind. The rise in world population will put pressure on the global agricultural system to increase its productivity leading most likely to an intensification of mineral nitrogen fertilizer use. The fate of excess nitrogen and its distribution within landscapes is manifold. Process knowledge on the site scale has rapidly grown in recent years and models have been developed to simulate carbon and nitrogen cycling in managed ecosystems on the site scale. Despite first regional studies, the carbon and nitrogen cycling on the landscape or catchment scale is not fully understood. In this study we present a newly developed modelling approach by coupling the fully distributed hydrology model CMF (catchment modelling framework) to the process based regional ecosystem model LandscapeDNDC for the investigation of hydrological processes and carbon and nitrogen transport and cycling, with a focus on nutrient displacement and resulting greenhouse gas emissions in a small catchment at the Yanting Agro-ecological Experimental Station of Purple Soil, Sichuan province, China. The catchment hosts cypress forests on the outer regions, arable fields on the sloping croplands cultivated with wheat-maize rotations and paddy rice fields in the lowland. The catchment consists of 300 polygons vertically stratified into 10 soil layers. Ecosystem states (soil water content and nutrients) and fluxes (evapotranspiration) are exchanged between the models at high temporal scales (hourly to daily) forming a 3-dimensional model application. The water flux and nutrients transport in the soil is modelled using a 3D Richards/Darcy approach for subsurface fluxes with a kinematic wave approach for surface water runoff and the evapotranspiration is based on Penman-Monteith. Biogeochemical processes are modelled by LandscapeDNDC, including soil microclimate, plant growth and biomass allocation

  15. A geotechnical characterization of lunar soils and lunar soil simulants

    Science.gov (United States)

    Graf, John Carl

    Many of the essential materials needed for the construction of a lunar base can be produced from the resources found on the lunar surface. Processing natural resources on the moon into useful products will reduce the need, and the cost, to bring everything from earth. The lunar regolith has been intensely studied with respect to understanding the formation of the moon and the earth, but as a construction material, the regolith is poorly characterized and poorly understood. To better understand how to 'work' with the lunar regolith, four loosely related research projects were conducted. Two projects relate to characterizing and understanding the geotechnical properties of regolith, two projects relate to manipulating and processing granular materials in the lunar environment. The shapes of lunar soil grains are characterized using fractals - results directly and quantitatively describe the rugged reentrant nature of the large scale structure and the relatively smooth surface texture of lunar soil grains. The nature of lunar soil cohesion is considered using tensile strength measurements of lunar soil simulant. It is likely that mechanical interlocking of irregular grains is the primary cause of lunar soil cohesion. This mechanism is highly sensitive to grain shape, but relatively insensitive to particle packing density. A series of experiments are conducted to try to understand how granular particles might sort by size in a vacuum. Even in a vacuum, fine particle subjected to shear strain segregate by a mechanism called the random fluctuating sieve The random fluctuating sieve also controls particle motion that determines the structure of wind-blown sand ripples. Hybrid microwave heating was used to sinter large structural bricks from lunar soil stimulant. While heating was prone to thermal runaway, microwave heating holds great promise as a simple, direct method of making sintered structural bricks.

  16. Surface modeling of soil antibiotics.

    Science.gov (United States)

    Shi, Wen-jiao; Yue, Tian-xiang; Du, Zheng-ping; Wang, Zong; Li, Xue-wen

    2016-02-01

    Large numbers of livestock and poultry feces are continuously applied into soils in intensive vegetable cultivation areas, and then some veterinary antibiotics are persistent existed in soils and cause health risk. For the spatial heterogeneity of antibiotic residues, developing a suitable technique to interpolate soil antibiotic residues is still a challenge. In this study, we developed an effective interpolator, high accuracy surface modeling (HASM) combined vegetable types, to predict the spatial patterns of soil antibiotics, using 100 surface soil samples collected from an intensive vegetable cultivation area located in east of China, and the fluoroquinolones (FQs), including ciprofloxacin (CFX), enrofloxacin (EFX) and norfloxacin (NFX), were analyzed as the target antibiotics. The results show that vegetable type is an effective factor to be combined to improve the interpolator performance. HASM achieves less mean absolute errors (MAEs) and root mean square errors (RMSEs) for total FQs (NFX+CFX+EFX), NFX, CFX and EFX than kriging with external drift (KED), stratified kriging (StK), ordinary kriging (OK) and inverse distance weighting (IDW). The MAE of HASM for FQs is 55.1 μg/kg, and the MAEs of KED, StK, OK and IDW are 99.0 μg/kg, 102.8 μg/kg, 106.3 μg/kg and 108.7 μg/kg, respectively. Further, RMSE simulated by HASM for FQs (CFX, EFX and NFX) are 106.2 μg/kg (88.6 μg/kg, 20.4 μg/kg and 39.2 μg/kg), and less 30% (27%, 22% and 36%), 33% (27%, 27% and 43%), 38% (34%, 23% and 41%) and 42% (32%, 35% and 51%) than the ones by KED, StK, OK and IDW, respectively. HASM also provides better maps with more details and more consistent maximum and minimum values of soil antibiotics compared with the measured data. The better performance can be concluded that HASM takes the vegetable type information as global approximate information, and takes local sampling data as its optimum control constraints.

  17. Applying the Artificial Neural Network to Predict the Soil Responses in the DEM Simulation

    Science.gov (United States)

    Li, Z.; Chow, J. K.; Wang, Y. H.

    2017-06-01

    This paper aims to bridge the soil properties and the soil response in the discrete element method (DEM) simulation using the artificial neural network (ANN). The network was designed to output the stress-strain-volumetric response from inputting the soil properties. 31 biaxial shearing tests with varying soil parameters were generated using the DEM simulations. Based on these 31 training samples, a three-layer neural network was established. 2 extra samples were generated to examine the validity of the network, and the predicted curves using the ANN were well matched with those from the DEM simulations. Overall, the ANN was found promising in effectively modelling the soil behaviour.

  18. A quantitative model for integrating landscape evolution and soil formation

    Science.gov (United States)

    Vanwalleghem, T.; Stockmann, U.; Minasny, B.; McBratney, Alex B.

    2013-06-01

    evolution is closely related to soil formation. Quantitative modeling of the dynamics of soils and landscapes should therefore be integrated. This paper presents a model, named Model for Integrated Landscape Evolution and Soil Development (MILESD), which describes the interaction between pedogenetic and geomorphic processes. This mechanistic model includes the most significant soil formation processes, ranging from weathering to clay translocation, and combines these with the lateral redistribution of soil particles through erosion and deposition. The model is spatially explicit and simulates the vertical variation in soil horizon depth as well as basic soil properties such as texture and organic matter content. In addition, sediment export and its properties are recorded. This model is applied to a 6.25 km2 area in the Werrikimbe National Park, Australia, simulating soil development over a period of 60,000 years. Comparison with field observations shows how the model accurately predicts trends in total soil thickness along a catena. Soil texture and bulk density are predicted reasonably well, with errors of the order of 10%, however, field observations show a much higher organic carbon content than predicted. At the landscape scale, different scenarios with varying erosion intensity result only in small changes of landscape-averaged soil thickness, while the response of the total organic carbon stored in the system is higher. Rates of sediment export show a highly nonlinear response to soil development stage and the presence of a threshold, corresponding to the depletion of the soil reservoir, beyond which sediment export drops significantly.

  19. Spatial averaging infiltration model for layered soil

    Institute of Scientific and Technical Information of China (English)

    HU HePing; YANG ZhiYong; TIAN FuQiang

    2009-01-01

    To quantify the influences of soil heterogeneity on infiltration, a spatial averaging infiltration model for layered soil (SAI model) is developed by coupling the spatial averaging approach proposed by Chen et al. and the Generalized Green-Ampt model proposed by Jia et al. In the SAI model, the spatial heterogeneity along the horizontal direction is described by a probability distribution function, while that along the vertical direction is represented by the layered soils. The SAI model is tested on a typical soil using Monte Carlo simulations as the base model. The results show that the SAI model can directly incorporate the influence of spatial heterogeneity on infiltration on the macro scale. It is also found that the homogeneous assumption of soil hydraulic conductivity along the horizontal direction will overestimate the infiltration rate, while that along the vertical direction will underestimate the infiltration rate significantly during rainstorm periods. The SAI model is adopted in the spatial averaging hydrological model developed by the authors, and the results prove that it can be applied in the macro-scale hydrological and land surface process modeling in a promising way.

  20. Spatial averaging infiltration model for layered soil

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    To quantify the influences of soil heterogeneity on infiltration, a spatial averaging infiltration model for layered soil (SAI model) is developed by coupling the spatial averaging approach proposed by Chen et al. and the Generalized Green-Ampt model proposed by Jia et al. In the SAI model, the spatial hetero- geneity along the horizontal direction is described by a probability distribution function, while that along the vertical direction is represented by the layered soils. The SAI model is tested on a typical soil using Monte Carlo simulations as the base model. The results show that the SAI model can directly incorporate the influence of spatial heterogeneity on infiltration on the macro scale. It is also found that the homogeneous assumption of soil hydraulic conductivity along the horizontal direction will overes- timate the infiltration rate, while that along the vertical direction will underestimate the infiltration rate significantly during rainstorm periods. The SAI model is adopted in the spatial averaging hydrological model developed by the authors, and the results prove that it can be applied in the macro-scale hy- drological and land surface process modeling in a promising way.

  1. Water and heat fluxes in desert soils: 2. Numerical simulations

    Science.gov (United States)

    Scanlon, Bridget R.; Milly, P. C. D.

    1994-03-01

    Transient one-dimensional fluxes of soil water (liquid and vapor) and heat in response to 1 year of atmospheric forcing were simulated numerically for a site in the Chihuahuan Desert of Texas. The model was initialized and evaluated using the monitoring data presented in a companion paper (Scanlon, this issue). Soil hydraulic and thermal properties were estimated a priori from a combination of laboratory measurements, models, and other published information. In the first simulation, the main drying curves were used to describe soil water retention, and hysteresis was ignored. Remarkable consistency was found between computed and measured water potentials and temperatures. Attenuation and phase shift of the seasonal cycle of water potentials below the shallow subsurface active zone (0.0- to 0.3-m depth) were similar to those of temperatures, suggesting that water potential fluctuations were driven primarily by temperature changes. Water fluxes in the upper 0.3 m of soil were dominated by downward and upward liquid fluxes that resulted from infiltration of rain and subsequent evaporation from the surface. Upward flux was vapor dominated only in the top several millimeters of the soil during periods of evaporation. Below a depth of 0.3 m, water fluxes varied slowly and were dominated by downward thermal vapor flux that decreased with depth, causing a net accumulation of water. In a second simulation, nonhysteretic water retention was instead described by the estimated main wetting curves; the resulting differences in fluxes were attributed to lower initial water contents (given fixed initial water potential) and unsaturated hydraulic conductivities that were lower than they were in the first simulation. Below a depth of 0.3 m, the thermal vapor fluxes dominated and were similar to those in the first simulation. Two other simulations were performed, differing from the first only in the prescription of different (wetter) initial water potentials. These three simulations

  2. Lunar Soil Constitutive Model and Finite Element Modeling for Landing Impact Simulation%着陆冲击仿真月壤本构模型及有限元建模

    Institute of Scientific and Technical Information of China (English)

    梁东平; 柴洪友

    2012-01-01

    为建立合理的月壤有限元模型用于着陆器着陆冲击动力学仿真分析,在对已知月壤的相关力学特性参数和试验数据进行分析推理的基础上,推断出月壤屈服面在低围压条件下可能会呈现出剪切膨胀特性,而在高围压条件下则可能会呈现出塑性压缩和应变硬化特性,因此定性地选择帽盖德鲁克-普拉格(Cap Drucker-Prager,CDP)模型作为月壤本构模型。模型的参数通过月壤或模拟月壤的试验数据定量地标定。对着陆器地面着陆冲击试验进行有限元建模和仿真分析,仿真结果表明:模型参数的标定方法是合理可行的;CDP模型可以准确模拟月壤在着陆冲击载荷下的动力学响应,可用于着陆冲击动力学仿真月壤有限元建模。对月壤模型参数进行了参数分析,并评估了月壤模型参数对着陆器着陆冲击性能的影响。%The purpose of this study is to construct finite element model of lunar soil for landing impact simulation of lunar lander.Based on the analysis of the known mechanical properties and tri-axial test data of lunar soil sample,it is found that lunar soil may exhibit shear-induced dilation at low confining pressure and plastic compression and strain hardening at high confining pressure.Cap Drucker-Prager(CDP) model is selected as the constitutive model of lunar soil according to the previous qualitative analysis,and the model parameters are calibrated quantitatively by test data of lunar soil or lunar soil stimulants.Finite element modeling and simulation analysis of lunar lander landing impact tests are conducted,the results indicate that calibration methods of model parameters are practical and reasonable.Dynamic response behaviors of lunar soil under landing impact condition can be accurately simulated by CDP model,and the model can be used for lunar soil finite element modeling.Parameters analysis of lunar soil model is conducted,and effects of parameters of lunar

  3. Evaluation of water management strategies for acid sulphate soils using a simulation model: a case study in Indonesia

    NARCIS (Netherlands)

    Bronswijk, J.J.B.; Groenenberg, J.E.; Ritsema, C.J.; Wijk, van A.L.M.; Nugroho, K.

    1995-01-01

    Reclamation and drainage of potential acid sulphate soils results in acidification and release of toxic elements, hampering their use for agriculture. Ecologically valuable habitats located downstream of reclamation areas may be disrupted. Proper water management is essential to a sustainable reclam

  4. [Simulation of cropland soil moisture based on an ensemble Kalman filter].

    Science.gov (United States)

    Liu, Zhao; Zhou, Yan-Lian; Ju, Wei-Min; Gao, Ping

    2011-11-01

    By using an ensemble Kalman filter (EnKF) to assimilate the observed soil moisture data, the modified boreal ecosystem productivity simulator (BEPS) model was adopted to simulate the dynamics of soil moisture in winter wheat root zones at Xuzhou Agro-meteorological Station, Jiangsu Province of China during the growth seasons in 2000-2004. After the assimilation of observed data, the determination coefficient, root mean square error, and average absolute error of simulated soil moisture were in the ranges of 0.626-0.943, 0.018-0.042, and 0.021-0.041, respectively, with the simulation precision improved significantly, as compared with that before assimilation, indicating the applicability of data assimilation in improving the simulation of soil moisture. The experimental results at single point showed that the errors in the forcing data and observations and the frequency and soil depth of the assimilation of observed data all had obvious effects on the simulated soil moisture.

  5. Advances in the Coupled Soil Water and Groundwater Models

    Institute of Scientific and Technical Information of China (English)

    杨玉峥; 王志敏

    2014-01-01

    Models simulating the reciprocal transformation between the soil water and groundwater are of great practical importance to the development and utilization of water resources and prevention and remedy of water pollution. In this paper, popular coupled models of soil water and groundwater will be analyzed. Besides, advantages and disadvantages of different models will be summarized as a reference for the numerical model of soil water and groundwater.

  6. Numerical Simulation of Moisture Movement in Unsaturated Expansive Soil Slope Suffering Permeation

    Institute of Scientific and Technical Information of China (English)

    Chen Shanxiong; Yu Song; Liu Zhiguo; Xu Haibin

    2005-01-01

    This study develops a way of analyzing moisture movement in unsaturated expansive soil slope. The basic equations and the integrated finite difference method for moisture movement in unsaturated soils are briefly described, and the calculation code MFUS2 has been developed. The moisture movements in unsaturated expansive soil slopes suffering precipitation were simulated numerically. The simulation results show that expansion or contraction must be taken into account in an analysis model. A simplified equivalent model for calculating rainwater infiltration into expansive soil slopes has been developed. The simplified equivalent model divides the soil slope into two layers according to the extent of weathering of the soil mass at depth. Layer Ⅰ is intensively weathered and moisture can be fully evaporated or rapidly absorbed. The moisture movement parameters take into account the greater soil permeability caused by fissures. Layer Ⅱ is unweathered and the soil is basically undisturbed. The moisture movement parameters of homogeneous soils are applicable. The moisture movements in unsaturated expansive soil slopes suffering precipitation were simulated numerically using the simplified equivalent model. The simulation results show that the moisture movement in the expansive soil slope under rainfall permeation mainly takes place in the extensively weathered layer Ⅰ, which closely simulates the real situation.

  7. Effects of uncertainty in major input variables on simulated functional soil behaviour

    NARCIS (Netherlands)

    Finke, P.A.; Wösten, J.H.M.; Jansen, M.J.W.

    1997-01-01

    Uncertainties in major input variables in water and solute models were quantified and their effects on simulated functional aspects of soil behaviour were studied using basic soil properties from an important soil map unit in the Netherlands. Two sources of uncertainty were studied: spatial

  8. Effects of uncertainty in major input variables on simulated functional soil behaviour

    NARCIS (Netherlands)

    Finke, P.A.; Wösten, J.H.M.; Jansen, M.J.W.

    1996-01-01

    Uncertainties in major input variables in water and solute models were quantified and their effects on simulated functional aspects of soil behaviour were studied using basic soil properties from an important soil map unit in the Netherlands. Two sources of uncertainty were studied: spatial

  9. Soft Soil Impact Testing and Simulation of Aerospace Structures

    Science.gov (United States)

    Fasanella, Edwin L.; Jackson, Karen E.; Kellas, Sotiris

    2008-01-01

    In June 2007, a 38-ft/s vertical drop test of a 5-ft-diameter, 5-ft-long composite fuselage section that was retrofitted with a novel composite honeycomb Deployable Energy Absorber (DEA) was conducted onto unpacked sand. This test was one of a series of tests to evaluate the multi-terrain capabilities of the DEA and to generate test data for model validation. During the test, the DEA crushed approximately 6-in. and left craters in the sand of depths ranging from 7.5- to 9-in. A finite element model of the fuselage section with DEA was developed for execution in LS-DYNA, a commercial nonlinear explicit transient dynamic code. Pre-test predictions were generated in which the sand was represented initially as a crushable foam material MAT_CRUSHABLE_FOAM (Mat 63). Following the drop test, a series of hemispherical penetrometer tests were conducted to assist in soil characterization. The penetrometer weighed 20-lb and was instrumented with a tri-axial accelerometer. Drop tests were performed at 16-ft/s and crater depths were measured. The penetrometer drop tests were simulated as a means for developing a more representative soil model based on a soil and foam material definition MAT_SOIL_AND FOAM (Mat 5) in LS-DYNA. The model of the fuselage with DEA was reexecuted using the updated soil model and test-analysis correlations are presented.

  10. Integration of soil microbial processes in a reactive transport model for simulating effects of root-controlled water flow on carbon and nutrient cycling

    Science.gov (United States)

    Espeleta, J. F.; Cardon, Z. G.; Mayer, K. U.; Rastetter, E. B.; Neumann, R. B.

    2013-12-01

    The rhizosphere is a hotbed of microbial activity in terrestrial ecosystems, and numerous models of rhizosphere dynamics have been focused in two main arenas: (1) water flow and nutrient transport around roots, and (2) carbon and nutrient exchanges between roots and microbes. However, coupling of microbial processes with physical flow (water and nutrients) in soils around plant roots is key to understanding how water, carbon and nutrient cycles interact at different scales. In order to explore how spatial distribution and timing of water flow directed by plant roots shapes rhizosphere biogeochemical function, we have developed a mechanistic model that combines a microbial food web with dynamic water flow and associated solute transport (advection, diffusion and cation exchange). We used the flexibility of a previously developed code, MIN3P (a multicomponent reactive transport model developed for variably saturated porous media) and incorporated microbial processes of carbon and nitrogen uptake, assimilation and secretion; microbial growth and death; exo-enzyme production; protozoal grazing, and soil organic matter decomposition within a soil matrix. We focused our attention at the mm-spatial scale, exploring the interaction of temporal oscillations in the magnitude and direction of water flow with soil C and N gradients. In this first modeling step, we prescribed dynamic soil water content representative of the transpiration stream (soil water loss) and hydraulic redistribution (soil water gain), as well as the flux of carbon into the soil. Although we are still in the process of building explicit root and plant behavior into the model, our preliminary results suggest that the diel pulsing of water out/into the soil can potentially change patterns of microbial C/N limitation and soil N availability. We are currently expanding our model to include the effect of plant root processes (uptake and exudation) and investigating the mechanisms explaining the interplay

  11. Simulation of large-scale soil water systems using groundwater data and satellite based soil moisture

    Science.gov (United States)

    Kreye, Phillip; Meon, Günter

    2016-04-01

    Complex concepts for the physically correct depiction of dominant processes in the hydrosphere are increasingly at the forefront of hydrological modelling. Many scientific issues in hydrological modelling demand for additional system variables besides a simulation of runoff only, such as groundwater recharge or soil moisture conditions. Models that include soil water simulations are either very simplified or require a high number of parameters. Against this backdrop there is a heightened demand of observations to be used to calibrate the model. A reasonable integration of groundwater data or remote sensing data in calibration procedures as well as the identifiability of physically plausible sets of parameters is subject to research in the field of hydrology. Since this data is often combined with conceptual models, the given interfaces are not suitable for such demands. Furthermore, the application of automated optimisation procedures is generally associated with conceptual models, whose (fast) computing times allow many iterations of the optimisation in an acceptable time frame. One of the main aims of this study is to reduce the discrepancy between scientific and practical applications in the field of hydrological modelling. Therefore, the soil model DYVESOM (DYnamic VEgetation SOil Model) was developed as one of the primary components of the hydrological modelling system PANTA RHEI. DYVESOMs structure provides the required interfaces for the calibrations made at runoff, satellite based soil moisture and groundwater level. The model considers spatial and temporal differentiated feedback of the development of the vegetation on the soil system. In addition, small scale heterogeneities of soil properties (subgrid-variability) are parameterized by variation of van Genuchten parameters depending on distribution functions. Different sets of parameters are operated simultaneously while interacting with each other. The developed soil model is innovative regarding concept

  12. Towards an improved modeling of chemical weathering in the SoilGen soil evolution model

    Science.gov (United States)

    Opolot, Emmanuel; Finke, Peter

    2014-05-01

    As the need for soil information particularly in the fields of agriculture, land evaluation, hydrology, biogeochemistry and climate change keeps increasing, models for soil evolution are increasingly becoming valuable tools to provide such soil information. Although still limited, such models are progressively being developed. The SoilGen model is one of such models with capabilities to provide soil information such as soil texture, pH, base saturation, organic carbon, CEC, etc over multi-millennia time scale. SoilGen is a mechanistic water flow driven pedogenetic model describing soil forming processes such as carbon cycling, clay migration, decalcification, bioturbation, physical weathering and chemical weathering. The model has been calibrated and confronted with field measurements in a number of case studies, giving plausible results. Discrepancies between measured and simulated soil properties as concluded from case studies have been mainly attributed to (i) the simple chemical weathering system (ii) poor estimates of initial data inputs such as bulk density and element fluxes, and (iii) incorrect values of variables that describe boundary conditions such as precipitation and potential evapotranspiration. This study focuses on extending the chemical weathering system, such that it can deal with a more heterogeneous composition of primary minerals and includes more elements such as Fe and Si. We propose and discuss here an extended description of chemical weathering in the model that is based on more primary minerals, taking into account the role of the specific area of these minerals, and the effect of physical weathering on these specific areas over time. In the initial stage, the proposed chemical weathering mechanism is also implemented in PHREEQC (a widely applied geochemical code with capabilities to simulate equilibrium reactions involving water and minerals, surface complexes and ion exchangers, etc.) to facilitate comparison with the model results

  13. Explicitly representing soil microbial processes in Earth system models: Soil microbes in earth system models

    Energy Technology Data Exchange (ETDEWEB)

    Wieder, William R. [Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder Colorado USA; Allison, Steven D. [Department of Ecology and Evolutionary Biology, University of California, Irvine California USA; Department of Earth System Science, University of California, Irvine California USA; Davidson, Eric A. [Appalachian Laboratory, University of Maryland Center for Environmental Science, Frostburg Maryland USA; Georgiou, Katerina [Department of Chemical and Biomolecular Engineering, University of California, Berkeley California USA; Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley California USA; Hararuk, Oleksandra [Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria British Columbia Canada; He, Yujie [Department of Earth System Science, University of California, Irvine California USA; Department of Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette Indiana USA; Hopkins, Francesca [Department of Earth System Science, University of California, Irvine California USA; Jet Propulsion Laboratory, California Institute of Technology, Pasadena California USA; Luo, Yiqi [Department of Microbiology & Plant Biology, University of Oklahoma, Norman Oklahoma USA; Smith, Matthew J. [Computational Science Laboratory, Microsoft Research, Cambridge UK; Sulman, Benjamin [Department of Biology, Indiana University, Bloomington Indiana USA; Todd-Brown, Katherine [Department of Microbiology & Plant Biology, University of Oklahoma, Norman Oklahoma USA; Pacific Northwest National Laboratory, Richland Washington USA; Wang, Ying-Ping [CSIRO Ocean and Atmosphere Flagship, Aspendale Victoria Australia; Xia, Jianyang [Department of Microbiology & Plant Biology, University of Oklahoma, Norman Oklahoma USA; Tiantong National Forest Ecosystem Observation and Research Station, School of Ecological and Environmental Sciences, East China Normal University, Shanghai China; Xu, Xiaofeng [Department of Biological Sciences, University of Texas at El Paso, Texas USA

    2015-10-01

    Microbes influence soil organic matter (SOM) decomposition and the long-term stabilization of carbon (C) in soils. We contend that by revising the representation of microbial processes and their interactions with the physicochemical soil environment, Earth system models (ESMs) may make more realistic global C cycle projections. Explicit representation of microbial processes presents considerable challenges due to the scale at which these processes occur. Thus, applying microbial theory in ESMs requires a framework to link micro-scale process-level understanding and measurements to macro-scale models used to make decadal- to century-long projections. Here, we review the diversity, advantages, and pitfalls of simulating soil biogeochemical cycles using microbial-explicit modeling approaches. We present a roadmap for how to begin building, applying, and evaluating reliable microbial-explicit model formulations that can be applied in ESMs. Drawing from experience with traditional decomposition models we suggest: (1) guidelines for common model parameters and output that can facilitate future model intercomparisons; (2) development of benchmarking and model-data integration frameworks that can be used to effectively guide, inform, and evaluate model parameterizations with data from well-curated repositories; and (3) the application of scaling methods to integrate microbial-explicit soil biogeochemistry modules within ESMs. With contributions across scientific disciplines, we feel this roadmap can advance our fundamental understanding of soil biogeochemical dynamics and more realistically project likely soil C response to environmental change at global scales.

  14. Stochastic Modeling of Soil Salinity

    CERN Document Server

    Suweis, S; Van der Zee, S E A T M; Daly, E; Maritan, A; Porporato, A; 10.1029/2010GL042495

    2012-01-01

    A minimalist stochastic model of primary soil salinity is proposed, in which the rate of soil salinization is determined by the balance between dry and wet salt deposition and the intermittent leaching events caused by rainfall events. The long term probability density functions of salt mass and concentration are found by reducing the coupled soil moisture and salt mass balance equation to a single stochastic differential equation driven by multiplicative Poisson noise. The novel analytical solutions provide insight on the interplay of the main soil, plant and climate parameters responsible for long-term soil salinization. In particular, they show the existence of two distinct regimes, one where the mean salt mass remains nearly constant (or decreases) with increasing rainfall frequency, and another where mean salt content increases markedly with increasing rainfall frequency. As a result, relatively small reductions of rainfall in drier climates may entail dramatic shifts in long-term soil salinization trend...

  15. A model based on soil structural aspects describing the fate of genetically modified bacteria in soil

    NARCIS (Netherlands)

    Hoeven, van der N.; Elsas, van J.D.; Heijnen, C.E.

    1996-01-01

    A computer simulation model was developed which describes growth and competition of bacteria in the soil environment. In the model, soil was assumed to contain millions of pores of a few different size classes. An introduced bacterial strain, e.g. a genetically modified micro-organism (GEMMO), was a

  16. A model based on soil structural aspects describing the fate of genetically modified bacteria in soil

    NARCIS (Netherlands)

    Hoeven, van der N.; Elsas, van J.D.; Heijnen, C.E.

    1996-01-01

    A computer simulation model was developed which describes growth and competition of bacteria in the soil environment. In the model, soil was assumed to contain millions of pores of a few different size classes. An introduced bacterial strain, e.g. a genetically modified micro-organism (GEMMO), was a

  17. Soil hydrologic characterization for modeling large scale soil remediation protocols

    Science.gov (United States)

    Romano, Nunzio; Palladino, Mario; Di Fiore, Paola; Sica, Benedetto; Speranza, Giuseppe

    2014-05-01

    In Campania Region (Italy), the Ministry of Environment identified a National Interest Priority Sites (NIPS) with a surface of about 200,000 ha, characterized by different levels and sources of pollution. This area, called Litorale Domitio-Agro Aversano includes some polluted agricultural land, belonging to more than 61 municipalities in the Naples and Caserta provinces. In this area, a high level spotted soil contamination is moreover due to the legal and outlaw industrial and municipal wastes dumping, with hazardous consequences also on the quality of the water table. The EU-Life+ project ECOREMED (Implementation of eco-compatible protocols for agricultural soil remediation in Litorale Domizio-Agro Aversano NIPS) has the major aim of defining an operating protocol for agriculture-based bioremediation of contaminated agricultural soils, also including the use of crops extracting pollutants to be used as biomasses for renewable energy production. In the framework of this project, soil hydrologic characterization plays a key role and modeling water flow and solute transport has two main challenging points on which we focus on. A first question is related to the fate of contaminants infiltrated from stormwater runoff and the potential for groundwater contamination. Another question is the quantification of fluxes and spatial extent of root water uptake by the plant species employed to extract pollutants in the uppermost soil horizons. Given the high variability of spatial distribution of pollutants, we use soil characterization at different scales, from field scale when facing root water uptake process, to regional scale when simulating interaction between soil hydrology and groundwater fluxes.

  18. Simulation modeling and arena

    CERN Document Server

    Rossetti, Manuel D

    2015-01-01

    Emphasizes a hands-on approach to learning statistical analysis and model building through the use of comprehensive examples, problems sets, and software applications With a unique blend of theory and applications, Simulation Modeling and Arena®, Second Edition integrates coverage of statistical analysis and model building to emphasize the importance of both topics in simulation. Featuring introductory coverage on how simulation works and why it matters, the Second Edition expands coverage on static simulation and the applications of spreadsheets to perform simulation. The new edition als

  19. Soil Carbon and Nitrogen Cycle Modeling

    Science.gov (United States)

    Woo, D.; Chaoka, S.; Kumar, P.; Quijano, J. C.

    2012-12-01

    Second generation bioenergy crops, such as miscanthus (Miscantus × giganteus) and switchgrass (Panicum virgatum), are regarded as clean energy sources, and are an attractive option to mitigate the human-induced climate change. However, the global climate change and the expansion of perennial grass bioenergy crops have the power to alter the biogeochemical cycles in soil, especially, soil carbon storages, over long time scales. In order to develop a predictive understanding, this study develops a coupled hydrological-soil nutrient model to simulate soil carbon responses under different climate scenarios such as: (i) current weather condition, (ii) decreased precipitation by -15%, and (iii) increased temperature up to +3C for four different crops, namely miscanthus, switchgrass, maize, and natural prairie. We use Precision Agricultural Landscape Modeling System (PALMS), version 5.4.0, to capture biophysical and hydrological components coupled with a multilayer carbon and ¬nitrogen cycle model. We apply the model at daily time scale to the Energy Biosciences Institute study site, located in the University of Illinois Research Farms, in Urbana, Illinois. The atmospheric forcing used to run the model was generated stochastically from parameters obtained using available data recorded in Bondville Ameriflux Site. The model simulations are validated with observations of drainage and nitrate and ammonium concentrations recorded in drain tiles during 2011. The results of this study show (1) total soil carbon storage of miscanthus accumulates most noticeably due to the significant amount of aboveground plant carbon, and a relatively high carbon to nitrogen ratio and lignin content, which reduce the litter decomposition rate. Also, (2) the decreased precipitation contributes to the enhancement of total soil carbon storage and soil nitrogen concentration because of the reduced microbial biomass pool. However, (3) an opposite effect on the cycle is introduced by the increased

  20. Selected soil thermal conductivity models

    Directory of Open Access Journals (Sweden)

    Rerak Monika

    2017-01-01

    Full Text Available The paper presents collected from the literature models of soil thermal conductivity. This is a very important parameter, which allows one to assess how much heat can be transferred from the underground power cables through the soil. The models are presented in table form, thus when the properties of the soil are given, it is possible to select the most accurate method of calculating its thermal conductivity. Precise determination of this parameter results in designing the cable line in such a way that it does not occur the process of cable overheating.

  1. Modelling erosion and its interaction with soil organic carbon.

    Science.gov (United States)

    Oyesiku-Blakemore, Joseph; Verrot, Lucile; Geris, Josie; Zhang, Ganlin; Peng, Xinhua; Hallett, Paul; Smith, Jo

    2017-04-01

    Water driven soil erosion removes and relocates a significant quantity of soil organic carbon. In China the quantity of carbon removed from the soil through water erosion has been reported to be 180+/-80 Mt y-1 (Yue et al., 2011). Being able to effectively model the movement of such a large quantity of carbon is important for the assessment of soil quality and carbon storage in the region and further afield. A large selection of erosion models are available and much work has been done on evaluating the performance of these in developed countries (Merritt et al., 2006). Fewer studies have evaluated the application of these models on soils in developing countries. Here we evaluate and compare the performance of two of these models, WEPP (Laflen et al., 1997) and RUSLE (Renard et al., 1991), for simulations of soil erosion and deposition at the slope scale on a Chinese Red Soil under cultivation using measurements taken at the site. We also describe work to dynamically couple the movement of carbon presented in WEPP to a model of soil organic matter and nutrient turnover, ECOSSE (Smith et al., 2010). This aims to improve simulations of both erosion and carbon cycling by using the simulated rates of erosion to alter the distribution of soil carbon, the depth of soil and the clay content across the slopes, changing the simulated rate of carbon turnover. This, in turn, affects the soil carbon available to be eroded in the next timestep, so improving estimates of carbon erosion. We compare the simulations of this coupled modelling approach with those of the unaltered ECOSSE and WEPP models to determine the importance of coupling erosion and turnover models on the simulation of carbon losses at catchment scale.

  2. Feasibility of High-Resolution Soil Erosion Measurements by Means of Rainfall Simulations and SfM Photogrammetry

    Directory of Open Access Journals (Sweden)

    Phoebe Hänsel

    2016-11-01

    Full Text Available The silty soils of the intensively used agricultural landscape of the Saxon loess province, eastern Germany, are very prone to soil erosion, mainly caused by water erosion. Rainfall simulations, and also increasingly structure-from-motion (SfM photogrammetry, are used as methods in soil erosion research not only to assess soil erosion by water, but also to quantify soil loss. This study aims to validate SfM photogrammetry determined soil loss estimations with rainfall simulations measurements. Rainfall simulations were performed at three agricultural sites in central Saxony. Besides the measured data runoff and soil loss by sampling (in mm, terrestrial images were taken from the plots with digital cameras before and after the rainfall simulation. Subsequently, SfM photogrammetry was used to reconstruct soil surface changes due to soil erosion in terms of high resolution digital elevation models (DEMs for the pre- and post-event (resolution 1 × 1 mm. By multi-temporal change detection, the digital elevation model of difference (DoD and an averaged soil loss (in mm is received, which was compared to the soil loss by sampling. Soil loss by DoD was higher than soil loss by sampling. The method of SfM photogrammetry-determined soil loss estimations also include a comparison of three different ground control point (GCP approaches, revealing that the most complex one delivers the most reliable soil loss by DoD. Additionally, soil bulk density changes and splash erosion beyond the plot were measured during the rainfall simulation experiments in order to separate these processes and associated surface changes from the soil loss by DoD. Furthermore, splash was negligibly small, whereas higher soil densities after the rainfall simulations indicated soil compaction. By means of calculated soil surface changes due to soil compaction, the soil loss by DoD achieved approximately the same value as the soil loss by rainfall simulation.

  3. Spatial Variation of Soil Type and Soil Moisture in the Regional Atmospheric Modeling System

    Energy Technology Data Exchange (ETDEWEB)

    Buckley, R.

    2001-06-27

    Soil characteristics (texture and moisture) are typically assumed to be initially constant when performing simulations with the Regional Atmospheric Modeling System (RAMS). Soil texture is spatially homogeneous and time-independent, while soil moisture is often spatially homogeneous initially, but time-dependent. This report discusses the conversion of a global data set of Food and Agriculture Organization (FAO) soil types to RAMS soil texture and the subsequent modifications required in RAMS to ingest this information. Spatial variations in initial soil moisture obtained from the National Center for Environmental Predictions (NCEP) large-scale models are also introduced. Comparisons involving simulations over the southeastern United States for two different time periods, one during warmer, more humid summer conditions, and one during cooler, dryer winter conditions, reveals differences in surface conditions related to increases or decreases in near-surface atmospheric moisture con tent as a result of different soil properties. Three separate simulation types were considered. The base case assumed spatially homogeneous soil texture and initial soil moisture. The second case assumed variable soil texture and constant initial soil moisture, while the third case allowed for both variable soil texture and initial soil moisture. The simulation domain was further divided into four geographically distinct regions. It is concluded there is a more dramatic impact on thermodynamic variables (surface temperature and dewpoint) than on surface winds, and a more pronounced variability in results during the summer period. While no obvious trends in surface winds or dewpoint temperature were found relative to observations covering all regions and times, improvement in surface temperatures in most regions and time periods was generally seen with the incorporation of variable soil texture and initial soil moisture.

  4. Multifractal Model of Soil Water Erosion

    Science.gov (United States)

    Oleshko, Klaudia

    2017-04-01

    Breaking of solid surface symmetry during the interaction between the rainfall of high erosivity index and internally unstable volcanic soil/vegetation systems, results in roughness increasing as well as fertile horizon loosing. In these areas, the sustainability of management practices depends on the ability to select and implement the precise indicators of soil erodibility and vegetation capacity to protect the system against the extreme damaging precipitation events. Notwithstanding, the complex, non-linear and scaling nature of the phenomena involved in the interaction among the soil, vegetation and precipitation is still not taken into account by the numerous commonly used empirical, mathematical and computer simulation models: for instance, by the universal soil loss equation (USLE). The soil erodibility factor (K-factor) is still measuring by a set of empirical, dimensionless parameters and indexes, without taking into account the scaling (frequently multifractal) origin of a broad range of heterogeneous, anisotropic and dynamical phenomena involved in hydric erosion. Their mapping is not representative of this complex system spatial variability. In our research, we propose to use the toolbox of fractals and multifractals techniques in vista of its ability to measure the scale invariance and type/degree of soil, vegetation and precipitation symmetry breaking. The hydraulic units are chosen as the precise measure of soil/vegetation stability. These units are measured and modeled for soils with contrasting architecture, based on their porosity/permeability (Poroperm) as well as retention capacity relations. The simple Catalog of the most common Poroperm relations is proposed and the main power law relations among the elements of studied system are established and compared for some representative agricultural and natural Biogeosystems of Mexico. All resulted are related with the Mandelbrot' Baby Theorem in order to construct the universal Phase Diagram which

  5. Monitoring and modeling the soil hydraulic behavior in stony soils

    Science.gov (United States)

    Dragonetti, Giovanna; Lamaddalena, Nicola; Comegna, Alessandro; Coppola, Antonio

    2014-05-01

    Describing the soil hydrological behavior at applicative scales remains a complex task, mainly because of the spatial heterogeneity of the vadose zone. Addressing the impact of the unsaturated zone heterogeneity involves measuring and/or modeling water content evolution with fine spatial and temporal resolution. The presence of stones introduces difficulties for both the measurement of the water content and the soil hydraulic properties. In this context, the main objective of this study was to assess the role of stones on TDR-based water content measurements, as well as on the pattern of variability of simulated water contents at field-scale during water infiltration, drainage and evaporation processes. Also, the role of stones was evaluated as one possible explanation of the differences frequently observed between the measured hydraulic behavior and that estimated by using pedotransfer functions.

  6. Impact of Spatial Soil and Climate Input Data Aggregation on Regional Yield Simulations.

    Directory of Open Access Journals (Sweden)

    Holger Hoffmann

    Full Text Available We show the error in water-limited yields simulated by crop models which is associated with spatially aggregated soil and climate input data. Crop simulations at large scales (regional, national, continental frequently use input data of low resolution. Therefore, climate and soil data are often generated via averaging and sampling by area majority. This may bias simulated yields at large scales, varying largely across models. Thus, we evaluated the error associated with spatially aggregated soil and climate data for 14 crop models. Yields of winter wheat and silage maize were simulated under water-limited production conditions. We calculated this error from crop yields simulated at spatial resolutions from 1 to 100 km for the state of North Rhine-Westphalia, Germany. Most models showed yields biased by <15% when aggregating only soil data. The relative mean absolute error (rMAE of most models using aggregated soil data was in the range or larger than the inter-annual or inter-model variability in yields. This error increased further when both climate and soil data were aggregated. Distinct error patterns indicate that the rMAE may be estimated from few soil variables. Illustrating the range of these aggregation effects across models, this study is a first step towards an ex-ante assessment of aggregation errors in large-scale simulations.

  7. Global patterns and controls of soil organic carbon dynamics as simulated by multiple terrestrial biosphere models: Current status and future directions.

    Science.gov (United States)

    Tian, Hanqin; Lu, Chaoqun; Yang, Jia; Banger, Kamaljit; Huntzinger, Deborah N; Schwalm, Christopher R; Michalak, Anna M; Cook, Robert; Ciais, Philippe; Hayes, Daniel; Huang, Maoyi; Ito, Akihiko; Jain, Atul K; Lei, Huimin; Mao, Jiafu; Pan, Shufen; Post, Wilfred M; Peng, Shushi; Poulter, Benjamin; Ren, Wei; Ricciuto, Daniel; Schaefer, Kevin; Shi, Xiaoying; Tao, Bo; Wang, Weile; Wei, Yaxing; Yang, Qichun; Zhang, Bowen; Zeng, Ning

    2015-06-01

    Soil is the largest organic carbon (C) pool of terrestrial ecosystems, and C loss from soil accounts for a large proportion of land-atmosphere C exchange. Therefore, a small change in soil organic C (SOC) can affect atmospheric carbon dioxide (CO2) concentration and climate change. In the past decades, a wide variety of studies have been conducted to quantify global SOC stocks and soil C exchange with the atmosphere through site measurements, inventories, and empirical/process-based modeling. However, these estimates are highly uncertain, and identifying major driving forces controlling soil C dynamics remains a key research challenge. This study has compiled century-long (1901-2010) estimates of SOC storage and heterotrophic respiration (Rh) from 10 terrestrial biosphere models (TBMs) in the Multi-scale Synthesis and Terrestrial Model Intercomparison Project and two observation-based data sets. The 10 TBM ensemble shows that global SOC estimate ranges from 425 to 2111 Pg C (1 Pg = 10(15) g) with a median value of 1158 Pg C in 2010. The models estimate a broad range of Rh from 35 to 69 Pg C yr(-1) with a median value of 51 Pg C yr(-1) during 2001-2010. The largest uncertainty in SOC stocks exists in the 40-65°N latitude whereas the largest cross-model divergence in Rh are in the tropics. The modeled SOC change during 1901-2010 ranges from -70 Pg C to 86 Pg C, but in some models the SOC change has a different sign from the change of total C stock, implying very different contribution of vegetation and soil pools in determining the terrestrial C budget among models. The model ensemble-estimated mean residence time of SOC shows a reduction of 3.4 years over the past century, which accelerate C cycling through the land biosphere. All the models agreed that climate and land use changes decreased SOC stocks, while elevated atmospheric CO2 and nitrogen deposition over intact ecosystems increased SOC stocks-even though the responses varied

  8. Multiaxial probabilistic elastic-plastic constitutive simulations of soils

    Science.gov (United States)

    Sadrinezhad, Arezoo

    Fokker-Planck-Kolmogorov (FPK) equation approach has recently been developed to simulate elastic-plastic constitutive behaviors of materials with uncertain material properties. The FPK equation approach transforms the stochastic constitutive rate equation, which is a stochastic, nonlinear, ordinary differential equation (ODE) in the stress-pseudo time space into a second-order accurate, deterministic, linear FPK partial differential equation (PDE) in the probability density of stress-pseudo time space. This approach does not suffer from the drawbacks of the traditional approaches such as the Monte Carlo approach and the perturbation approach for solving nonlinear ODEs with random coefficients. In this study, the existing one dimensional FPK framework for probabilistic constitutive modeling of soils is extended to multi--dimension. However, the multivariate FPK PDEs cannot be solved using the traditional mathematical techniques such as finite difference techniques due to their high computational cost. Therefore, computationally efficient algorithms based on the Fourier spectral approach are developed for solving a class of FPK PDEs that arises in probabilistic elasto-plasticity. This class includes linear FPK PDEs in (stress) space and (pseudo) time - having space-independent but time-dependent, and both space- and time-dependent coefficients - with impulse initial conditions and reflecting boundary conditions. The solution algorithms, rely on first mapping the stress space of the governing PDE between 0 and 2pi using the change of coordinates rule, followed by approximating the solution of the PDE in the 2pi-periodic domain by a finite Fourier series in the stress space and unknown time-dependent solution coefficients. Finally, the time-dependent solution coefficients are obtained from the initial condition. The accuracy and efficiency of the developed algorithms are tested. The developed algorithms are used to simulate uniaxial and multiaxial, monotonic and cyclic

  9. A Study of the Behavior and Micromechanical Modelling of Granular Soil. Volume 3. A Numerical Investigation of the Behavior of Granular Media Using Nonlinear Discrete Element Simulation

    Science.gov (United States)

    1991-05-22

    Eisenberg 1987). Among other formulations, the existing models are based on the theories of elasticity, hypoelasticity , plasticity and viscoplasticity...AD-A238 158 AFOSR4R. 91 069.1 A STUDY OF THE BEHAVIOR AND MICROMECHANICAL MODELLING OF GRANULAR SOIL DTIC VOLUME mI ELECTIE A NUMERICAL INVESTIGATION...Final 1/6/ 9-5/15/91 4. nU AN SUS"Ll5. FUNDING NUMBERS A Study of the Behavior and Micromechanical Modelling of Grant AFOSR-89-0350 Granular Soil PR

  10. Coupled soil-leaf-canopy and atmosphere radiative transfer modeling to simulate hyperspectral multi-angular surface reflectance and TOA radiance data

    NARCIS (Netherlands)

    Verhoef, W.; Bach, H.

    2007-01-01

    Coupling radiative transfer models for the soil background and vegetation canopy layers is facilitated by means of the four-stream flux interaction concept and use of the adding method. Also the coupling to a state-of-the-art atmospheric radiative transfer model like MODTRAN4 can be established in t

  11. Toward more realistic projections of soil carbon dynamics by Earth system models: SOIL CARBON MODELING

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Yiqi; Ahlstrom, Anders; Allison, Steven D.; Batjes, Niels H.; Brovkin, Victor; Carvalhais, N.; Chappell, Adrian; Ciais, Philippe; Davidson, Eric A.; Finzi, Adien; Georgiou, Katerina; Guenet, Bertrand; Hararuk, Oleksandra; Harden, Jennifer W.; He, Yujie; Hopkins, Francesca; Jiang, Lifen; Koven, C.; Jackson, Robert B.; Jones, Chris D.; Lara, Mark J.; Liang, Junyi; McGuire, A. David; Parton, William J.; Peng, Changhui; Randerson, J.; Salazar, Alejandro; Sierra , Carlos A.; Smith, Matthew J.; Tian, Hanqin; Todd-Brown, Katherine EO; Torn, Margaret S.; van Groenigen, Kees Jan; Wang, Ying Ping; West, Tristram O.; Wei, Yaxing; Wieder, William R.; Xia, Jianyang; Xu, Xia; Xu, Xiaofeng; Zhou, Tao

    2016-01-21

    Soil carbon (C) is a critical component of Earth system models (ESMs) and its diverse representations are a major source of the large spread across models in the terrestrial C sink from the 3rd to 5th assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Improving soil C projections is of a high priority for Earth system modeling in the future IPCC and other assessments. To achieve this goal, we suggest that (1) model structures should reflect real-world processes, (2) parameters should be calibrated to match model outputs with observations, and (3) external forcing variables should accurately prescribe the environmental conditions that soils experience. Firstly, most soil C cycle models simulate C input from litter production and C release through decomposition. The latter process has traditionally been represented by 1st-order decay functions, regulated primarily by temperature, moisture, litter quality, and soil texture. While this formulation well captures macroscopic SOC dynamics, better understanding is needed of their underlying mechanisms as related to microbial processes, depth-dependent environmental controls, and other processes that strongly affect soil C dynamics. Secondly, incomplete use of observations in model parameterization is a major cause of bias in soil C projections from ESMs. Optimal parameter calibration with both pool- and flux-based datasets through data assimilation is among the highest priorities for near-term research to reduce biases among ESMs. Thirdly, external variables are represented inconsistently among ESMs, leading to differences in modeled soil C dynamics. We recommend the implementation of traceability analyses to identify how external variables and model parameterizations influence SOC dynamics in different ESMs. Overall, projections of the terrestrial C sink can be substantially improved when reliable datasets are available to select the most representative model structure, constrain parameters, and

  12. Deacidification effect of the litter layer on forest soil during snowmelt runoff--laboratory experiment and its basic formularization for simulation modeling.

    Science.gov (United States)

    Kikuchi, Ryunosuke

    2004-02-01

    The forest soil ecosystem can buffer and neutralize acidic airborne pollutants to some extent, but extensive acidification degrades the soil ecosystem. Several investigations have shown that surface flows often show particularly low pH values in rivers and lakes during snowmelt and that this acidification phenomenon takes place in a short time frame. Acid water from snowmelt first makes contact with the litter layer in the soil ecosystem. Therefore, a laboratory experiment was performed to study the impact of forest litter on the chemical composition of the water solution. The experiment presented in this paper confirmed that deacidification with a little leachate of organic matter is caused by cation exchange not only in upper mineral soil but also in the litter layer and that leachate of labile Al is restrained in the presence of litter. An attempt was made to incorporate these factors into the biogeochemical module of the model (ILWAS) to accurately estimate damage by acidification.

  13. Runoff simulation sensitivity to remotely sensed initial soil water content

    Science.gov (United States)

    Goodrich, D. C.; Schmugge, T. J.; Jackson, T. J.; Unkrich, C. L.; Keefer, T. O.; Parry, R.; Bach, L. B.; Amer, S. A.

    1994-05-01

    A variety of aircraft remotely sensed and conventional ground-based measurements of volumetric soil water content (SW) were made over two subwatersheds (4.4 and 631 ha) of the U.S. Department of Agriculture's Agricultural Research Service Walnut Gulch experimental watershed during the 1990 monsoon season. Spatially distributed soil water contents estimated remotely from the NASA push broom microwave radiometer (PBMR), an Institute of Radioengineering and Electronics (IRE) multifrequency radiometer, and three ground-based point methods were used to define prestorm initial SW for a distributed rainfall-runoff model (KINEROS; Woolhiser et al., 1990) at a small catchment scale (4.4 ha). At a medium catchment scale (631 ha or 6.31 km2) spatially distributed PBMR SW data were aggregated via stream order reduction. The impacts of the various spatial averages of SW on runoff simulations are discussed and are compared to runoff simulations using SW estimates derived from a simple daily water balance model. It was found that at the small catchment scale the SW data obtained from any of the measurement methods could be used to obtain reasonable runoff predictions. At the medium catchment scale, a basin-wide remotely sensed average of initial water content was sufficient for runoff simulations. This has important implications for the possible use of satellite-based microwave soil moisture data to define prestorm SW because the low spatial resolutions of such sensors may not seriously impact runoff simulations under the conditions examined. However, at both the small and medium basin scale, adequate resources must be devoted to proper definition of the input rainfall to achieve reasonable runoff simulations.

  14. Assimilating soil moisture into an Earth System Model

    Science.gov (United States)

    Stacke, Tobias; Hagemann, Stefan

    2017-04-01

    Several modelling studies reported potential impacts of soil moisture anomalies on regional climate. In particular for short prediction periods, perturbations of the soil moisture state may result in significant alteration of surface temperature in the following season. However, it is not clear yet whether or not soil moisture anomalies affect climate also on larger temporal and spatial scales. In an earlier study, we showed that soil moisture anomalies can persist for several seasons in the deeper soil layers of a land surface model. Additionally, those anomalies can influence root zone moisture, in particular during explicitly dry or wet periods. Thus, one prerequisite for predictability, namely the existence of long term memory, is evident for simulated soil moisture and might be exploited to improve climate predictions. The second prerequisite is the sensitivity of the climate system to soil moisture. In order to investigate this sensitivity for decadal simulations, we implemented a soil moisture assimilation scheme into the Max-Planck Institute for Meteorology's Earth System Model (MPI-ESM). The assimilation scheme is based on a simple nudging algorithm and updates the surface soil moisture state once per day. In our experiments, the MPI-ESM is used which includes model components for the interactive simulation of atmosphere, land and ocean. Artificial assimilation data is created from a control simulation to nudge the MPI-ESM towards predominantly dry and wet states. First analyses are focused on the impact of the assimilation on land surface variables and reveal distinct differences in the long-term mean values between wet and dry state simulations. Precipitation, evapotranspiration and runoff are larger in the wet state compared to the dry state, resulting in an increased moisture transport from the land to atmosphere and ocean. Consequently, surface temperatures are lower in the wet state simulations by more than one Kelvin. In terms of spatial pattern

  15. Soil texture reclassification by an ensemble model

    Science.gov (United States)

    Cisty, Milan; Hlavcova, Kamila

    2015-04-01

    Many environmental problems in which soil data serves as an inputs to simulation models are not restricted to national boundaries and therefore require international cooperation if solutions are to be found. The classification of soils according to their texture is one of the basic methods used for soil description. The term "soil texture" indicates the distribution of soil particles in the soil according to their size (diameter). The most preferred representation of texture classification is a grading curve. Because not all countries use the same classification system, databases from these countries cannot provide us with uniform data, which can serve as the inputs for various computations or models. This study deals with a description of a texture system reclassification to USDA classification system by the proposed model on a data set from Slovakia originally labeled by Slovakian national classification system. However, the authors of the paper suppose that the methodology proposed could be used more generally and that the information provided is also applicable when dealing with other existing soil texture classification systems. Some researchers have already proposed to fit the measured PSDs by various continuous parametric grading curves. When gaining such a relationship, it is possible to obtain a granular fraction's percentage ratio in the sample under consideration for any size of the particle diameter, which means that it is possible to get the values necessary for accomplishing a translation from one texture classification system to another. Several authors have conducted comparative studies on various PSD models in order to determine the best model for the soil groups selected for their studies (Nemes et al., 1999; Hwang, 2004; Botula et al., 2013). The reported findings of the abovementioned works somewhat differ from each other, and there is no generally suitable PSD model available. Because the transformation of a soil texture system is usually only

  16. Simulating climate change impact on soil erosion using RUSLE model − A case study in a watershed of mid-Himalayan landscape

    Indian Academy of Sciences (India)

    Surya Gupta; Suresh Kumar

    2017-04-01

    Climate change, particularly due to the changed precipitation trend, can have a severe impact on soil erosion. The effect is more pronounced on the higher slopes of the Himalayan region. The goal of this study was to estimate the impact of climate change on soil erosion in a watershed of the Himalayan region using RUSLE model. The GCM (general circulation model) derived emission scenarios (HadCM3 A2a and B2a SRES) were used for climate projection. The statistical downscaling model (SDSM) was used to downscale the precipitation for three future periods, 2011–2040, 2041–2070, and 2071–2099, at large scale. Rainfall erosivity (R) was calculated for future periods using the SDSM downscaled precipitation data. ASTER digital elevation model (DEM) and Indian Remote Sensing data – IRS LISS IV satellite data were used to generate the spatial input parameters required by RUSLE model. A digital soil-landscape map was prepared to generate spatially distributed soil erodibility (K) factor map of the watershed. Topographic factors, slope length (L) and steepness (S) were derived from DEM. Normalised difference vegetation index (NDVI) derived from the satellite data was used to represent spatial variation vegetation density and condition under various land use/land cover. This variation was used to represent spatial vegetation cover factor. Analysis revealed that the average annual soil loss may increase by 28.38, 25.64 and 20.33% in the 2020s, 2050s and 2080s, respectively under A2 scenario, while under B2 scenario, it may increase by 27.06, 25.31 and 23.38% in the 2020s, 2050s and 2080s, respectively, from the base period (1985–2013). The study provides a comprehensive understanding of the possible future scenario of soil erosion in the mid-Himalaya for scientists and policy makers.

  17. Simulating climate change impact on soil erosion using RUSLE model - A case study in a watershed of mid-Himalayan landscape

    Science.gov (United States)

    Gupta, Surya; Kumar, Suresh

    2017-06-01

    Climate change, particularly due to the changed precipitation trend, can have a severe impact on soil erosion. The effect is more pronounced on the higher slopes of the Himalayan region. The goal of this study was to estimate the impact of climate change on soil erosion in a watershed of the Himalayan region using RUSLE model. The GCM (general circulation model) derived emission scenarios (HadCM3 A2a and B2a SRES) were used for climate projection. The statistical downscaling model (SDSM) was used to downscale the precipitation for three future periods, 2011-2040, 2041-2070, and 2071-2099, at large scale. Rainfall erosivity ( R) was calculated for future periods using the SDSM downscaled precipitation data. ASTER digital elevation model (DEM) and Indian Remote Sensing data - IRS LISS IV satellite data were used to generate the spatial input parameters required by RUSLE model. A digital soil-landscape map was prepared to generate spatially distributed soil erodibility ( K) factor map of the watershed. Topographic factors, slope length ( L) and steepness ( S) were derived from DEM. Normalised difference vegetation index (NDVI) derived from the satellite data was used to represent spatial variation vegetation density and condition under various land use/land cover. This variation was used to represent spatial vegetation cover factor. Analysis revealed that the average annual soil loss may increase by 28.38, 25.64 and 20.33% in the 2020s, 2050s and 2080s, respectively under A2 scenario, while under B2 scenario, it may increase by 27.06, 25.31 and 23.38% in the 2020s, 2050s and 2080s, respectively, from the base period (1985-2013). The study provides a comprehensive understanding of the possible future scenario of soil erosion in the mid-Himalaya for scientists and policy makers.

  18. Toward hyper-resolution land-surface modeling: The effects of fine-scale topography and soil texture on CLM4.0 simulations over the Southwestern U.S.

    Science.gov (United States)

    Singh, R. S.; Reager, J. T.; Miller, N. L.; Famiglietti, J. S.

    2015-04-01

    Increasing computational efficiency and the need for improved accuracy are currently driving the development of "hyper-resolution" land-surface models that can be implemented at continental scales with resolutions of 1 km or finer. Here we report research incorporating fine-scale grid resolutions into the NCAR Community Land Model (CLM v4.0) for simulations at 1, 25, and 100 km resolution using 1 km soil and topographic information. Multiyear model runs were performed over the Southwestern U.S., including the entire state of California and the Colorado River basin. The results show changes in the total amount of CLM-modeled water storage, and changes in the spatial and temporal distributions of water in snow and soil reservoirs, as well as changes in surface fluxes and the energy balance. To inform future model progress and continued development needs and weaknesses, we compare simulation outputs to station and gridded observations of model fields. Although the higher grid-resolution model is not driven by high-resolution forcing, grid resolution changes alone yield significant improvement (reduction in error) between model outputs and observations, where the RMSE decreases by more than 35%, 36%, 34%, and 12% for soil moisture, terrestrial water storage anomaly, sensible heat, and snow water equivalent, respectively. As an additional exercise, we performed a 100 m resolution simulation over a spatial subdomain. Those results indicate that parameters such as drainage, runoff, and infiltration are significantly impacted when hillslope scales of ˜100 m or finer are considered, and we show the ways in which limitations of the current model physics, including no lateral flow between grid cells, may affect model simulation accuracy.

  19. Understanding the Impacts of Soil, Climate, and Farming Practices on Soil Organic Carbon Sequestration: A Simulation Study in Australia.

    Science.gov (United States)

    Godde, Cécile M; Thorburn, Peter J; Biggs, Jody S; Meier, Elizabeth A

    2016-01-01

    Carbon sequestration in agricultural soils has the capacity to mitigate greenhouse gas emissions, as well as to improve soil biological, physical, and chemical properties. The review of literature pertaining to soil organic carbon (SOC) dynamics within Australian grain farming systems does not enable us to conclude on the best farming practices to increase or maintain SOC for a specific combination of soil and climate. This study aimed to further explore the complex interactions of soil, climate, and farming practices on SOC. We undertook a modeling study with the Agricultural Production Systems sIMulator modeling framework, by combining contrasting Australian soils, climates, and farming practices (crop rotations, and management within rotations, such as fertilization, tillage, and residue management) in a factorial design. This design resulted in the transposition of contrasting soils and climates in our simulations, giving soil-climate combinations that do not occur in the study area to help provide insights into the importance of the climate constraints on SOC. We statistically analyzed the model's outputs to determinate the relative contributions of soil parameters, climate, and farming practices on SOC. The initial SOC content had the largest impact on the value of SOC, followed by the climate and the fertilization practices. These factors explained 66, 18, and 15% of SOC variations, respectively, after 80 years of constant farming practices in the simulation. Tillage and stubble management had the lowest impacts on SOC. This study highlighted the possible negative impact on SOC of a chickpea phase in a wheat-chickpea rotation and the potential positive impact of a cover crop in a sub-tropical climate (QLD, Australia) on SOC. It also showed the complexities in managing to achieve increased SOC, while simultaneously aiming to minimize nitrous oxide (N2O) emissions and nitrate leaching in farming systems. The transposition of contrasting soils and climates in

  20. Tropospheric vertical column densities of NO2 over managed dryland ecosystems (Xinjiang, China): MAX-DOAS measurements vs. 3-D dispersion model simulations based on laboratory-derived NO emission from soil samples

    Science.gov (United States)

    Mamtimin, B.; Behrendt, T.; Badawy, M. M.; Wagner, T.; Qi, Y.; Wu, Z.; Meixner, F. X.

    2015-01-01

    We report on MAX-DOAS observations of NO2 over an oasis-ecotone-desert ecosystem in NW China. There, local ambient NO2 concentrations originate from enhanced biogenic NO emission of intensively managed soils. Our target oasis "Milan" is located at the southern edge of the Taklimakan desert, very remote and well isolated from other potential anthropogenic and biogenic NOx sources. Four observation sites for MAX-DOAS measurements were selected, at the oasis centre, downwind and upwind of the oasis, and in the desert. Biogenic NO emissions in terms of (i) soil moisture and (ii) soil temperature of Milan oasis (iii) different land-cover type sub-units (cotton, Jujube trees, cotton/Jujube mixture, desert) were quantified by laboratory incubation of corresponding soil samples. Net potential NO fluxes were up-scaled to oasis scale by areal distribution and classification of land-cover types derived from satellite images using GIS techniques. A Lagrangian dispersion model (LASAT, Lagrangian Simulation of Aerosol Transport) was used to calculate the dispersion of soil emitted NO into the atmospheric boundary layer over Milan oasis. Three-dimensional (3-D) NO concentrations (30 m horizontal resolution) have been converted to 3-D NO2 concentrations, assuming photostationary state conditions. NO2 column densities were simulated by suitable vertical integration of modelled 3-D NO2 concentrations at those downwind and upwind locations, where the MAX-DOAS measurements were performed. Downwind-upwind differences (a direct measure of Milan oasis' contribution to the areal increase of ambient NO2 concentration) of measured and simulated slant (as well as vertical) NO2 column densities show excellent agreement. This agreement is considered as the first successful attempt to prove the validity of the chosen approach to up-scale laboratory-derived biogenic NO fluxes to ecosystem field conditions, i.e. from the spatial scale of a soil sample (cm2) to the size of an entire agricultural

  1. Tropospheric vertical column densities of NO2 over managed dryland ecosystems (Xinjiang, China): MAX-DOAS measurements vs. 3-D dispersion model simulations based on laboratory derived NO emission from soil samples

    Science.gov (United States)

    Mamtimin, B.; Behrendt, T.; Badawy, M. M.; Wagner, T.; Qi, Y.; Wu, Z.; Meixner, F. X.

    2014-07-01

    We report on MAX-DOAS observations of NO2 over an oasis-ecotone-desert ecosystem in NW-China. There, local ambient NO2 concentrations originate from enhanced biogenic NO emission of intensively managed soils. Our target oasis "Milan" is located at the southern edge of the Taklimakan desert, very remote and well isolated from other potential anthropogenic and biogenic NOx sources. Four observation sites for MAX-DOAS measurements were selected, at the oasis center, downwind and upwind of the oasis, and in the desert. Biogenic NO emissions in terms of (i) soil moisture and (ii) soil temperature of Milan oasis' (iii) different land-cover type sub-units (cotton, Jujube trees, cotton/Jujube mixture, desert) were quantified by laboratory incubation of corresponding soil samples. Net potential NO fluxes were up-scaled to oasis scale by areal distribution and classification of land-cover types derived from satellite images using GIS techniques. A Lagrangian dispersion model (LASAT, Lagrangian Simulation of Aerosol-Transport) was used to calculate the dispersion of soil emitted NO into the atmospheric boundary layer over Milan oasis. Three dimensional NO concentrations (30 m horizontal resolution) have been converted to 3-D NO2 concentrations, assuming photostationary state conditions. NO2 column densities were simulated by suitable vertical integration of modeled 3-D NO2 concentrations at those downwind and upwind locations, where the MAX-DOAS measurements were performed. Downwind-upwind differences (a direct measure of Milan oasis' contribution to the areal increase of ambient NO2 concentration) of measured and simulated slant (as well as vertical) NO2 column densities show excellent agreement. This agreement is considered as the first successful attempt to prove the validity of the chosen approach to up-scale laboratory derived biogenic NO fluxes to ecosystem field conditions, i.e. from the spatial scale of a soil sample (cm2) to the size of an entire agricultural

  2. Tropospheric vertical column densities of NO2 over managed dryland ecosystems (Xinjiang, China: MAX-DOAS measurements vs. 3-D dispersion model simulations based on laboratory derived NO emission from soil samples

    Directory of Open Access Journals (Sweden)

    B. Mamtimin

    2014-07-01

    Full Text Available We report on MAX-DOAS observations of NO2 over an oasis-ecotone-desert ecosystem in NW-China. There, local ambient NO2 concentrations originate from enhanced biogenic NO emission of intensively managed soils. Our target oasis "Milan" is located at the southern edge of the Taklimakan desert, very remote and well isolated from other potential anthropogenic and biogenic NOx sources. Four observation sites for MAX-DOAS measurements were selected, at the oasis center, downwind and upwind of the oasis, and in the desert. Biogenic NO emissions in terms of (i soil moisture and (ii soil temperature of Milan oasis' (iii different land-cover type sub-units (cotton, Jujube trees, cotton/Jujube mixture, desert were quantified by laboratory incubation of corresponding soil samples. Net potential NO fluxes were up-scaled to oasis scale by areal distribution and classification of land-cover types derived from satellite images using GIS techniques. A Lagrangian dispersion model (LASAT, Lagrangian Simulation of Aerosol-Transport was used to calculate the dispersion of soil emitted NO into the atmospheric boundary layer over Milan oasis. Three dimensional NO concentrations (30 m horizontal resolution have been converted to 3-D NO2 concentrations, assuming photostationary state conditions. NO2 column densities were simulated by suitable vertical integration of modeled 3-D NO2 concentrations at those downwind and upwind locations, where the MAX-DOAS measurements were performed. Downwind-upwind differences (a direct measure of Milan oasis' contribution to the areal increase of ambient NO2 concentration of measured and simulated slant (as well as vertical NO2 column densities show excellent agreement. This agreement is considered as the first successful attempt to prove the validity of the chosen approach to up-scale laboratory derived biogenic NO fluxes to ecosystem field conditions, i.e. from the spatial scale of a soil sample (cm2 to the size of an entire

  3. Computer Modeling and Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Pronskikh, V. S. [Fermilab

    2014-05-09

    Verification and validation of computer codes and models used in simulation are two aspects of the scientific practice of high importance and have recently been discussed by philosophers of science. While verification is predominantly associated with the correctness of the way a model is represented by a computer code or algorithm, validation more often refers to model’s relation to the real world and its intended use. It has been argued that because complex simulations are generally not transparent to a practitioner, the Duhem problem can arise for verification and validation due to their entanglement; such an entanglement makes it impossible to distinguish whether a coding error or model’s general inadequacy to its target should be blamed in the case of the model failure. I argue that in order to disentangle verification and validation, a clear distinction between computer modeling (construction of mathematical computer models of elementary processes) and simulation (construction of models of composite objects and processes by means of numerical experimenting with them) needs to be made. Holding on to that distinction, I propose to relate verification (based on theoretical strategies such as inferences) to modeling and validation, which shares the common epistemology with experimentation, to simulation. To explain reasons of their intermittent entanglement I propose a weberian ideal-typical model of modeling and simulation as roles in practice. I suggest an approach to alleviate the Duhem problem for verification and validation generally applicable in practice and based on differences in epistemic strategies and scopes

  4. Theory Modeling and Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Shlachter, Jack [Los Alamos National Laboratory

    2012-08-23

    Los Alamos has a long history in theory, modeling and simulation. We focus on multidisciplinary teams that tackle complex problems. Theory, modeling and simulation are tools to solve problems just like an NMR spectrometer, a gas chromatograph or an electron microscope. Problems should be used to define the theoretical tools needed and not the other way around. Best results occur when theory and experiments are working together in a team.

  5. Global patterns and controls of soil organic carbon dynamics as simulated by multiple terrestrial biosphere models. Current status and future directions

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Hanqin [Auburn Univ., AL (United States); Lu, Chaoqun [Auburn Univ., AL (United States); Yang, Jia [Auburn Univ., AL (United States); Banger, Kamaljit [Auburn Univ., AL (United States); Huntzinger, Deborah N. [Northern Arizona Univ., Flagstaff, AZ (United States); Schwalm, Christopher R. [Northern Arizona Univ., Flagstaff, AZ (United States); Michalak, A. M. [Carnegie Inst. for Science, Stanford, CA (United States); Cook, Robert B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Ciais, Philippe [Climate and Environment Sciences Lab. (LSCE) (France); Hayes, Daniel J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Huang, Maoyi [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Ito, Akihiko [National Inst. for Environmental Studies, Tsukuba (Japan); Jain, Atul K. [Univ. of Illinois, Urbana-Champaign, IL (United States); Lei, Huimin [Tsinghua Univ., Beijing (China); Mao, Jiafu [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pan, Shufen [Auburn Univ., AL (United States); Post, W. M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Peng, Shushi [Climate and Environment Sciences Lab. (LSCE) (France); Poulter, Benjamin [Montana State Univ., Bozeman, MT (United States); Ren, Wei [Auburn Univ., AL (United States); Ricciuto, Daniel M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Schaefer, Kevin [National Snow and Ice Data Center, Boulder, CO (United States); Shi, Xiaoying [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tao, Bo [Auburn Univ., AL (United States); Wang, Weile [National Aeronautics and Space Administration, Mountain View, CA (United States); Wei, Yaxing [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Yang, Qichun [Auburn Univ., AL (United States); Zhang, Bowen [Auburn Univ., AL (United States); Zeng, Ning [Univ. of Maryland, College Park, MD (United States)

    2015-06-05

    Soil is the largest organic carbon (C) pool of terrestrial ecosystems, and loss from soil accounts for a large pro portion of land-atmosphere C exchange. Due to large pool size and variable residence time from years to millennia, even small changes in soil organic C(SOC) have substantial effects on the terrestrial C budget, thereby affecting atmospheric carbon dioxide (CO2)concentration and climate change. In the past decades, a wide variety of studies have been conducted to quantify global SOC stocks and soil exchange with the atmosphere through site measurements, inventories, and empirical/process-based modeling. However, these estimates are highly uncertain and identifying major driving forces controlling soil C storage and fluxes remains a key research challenge his study has compiled century-long (1901-2010)estimates of SOC storage and heterotrophic respiration (Rh) from ten terrestrial biosphere models (TBMs) in the Multi-scale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP) and two observation based datasets. The ten-TBM ensemble shows that global SOC estimate range from 4 to 2111 Pg C (1 Pg = 1015g) with a median value of 1158 Pg C33 in 2010. Modeling approach estimates a broad range of Rh from 35 to 69 Pg C yr-1 with a median value of 51Pg C yr-1 during 200–2010. The largest uncertainty in SOC stocks exists in the 40–65°N latitude band while Rh differences are the largest in the tropics. All the models agreed that climate and land use changes have decreased SOC stocks while elevated CO2 and atmospheric nitrogen deposition have increased SOC stocks though the response varied significantly among models. Model representations of temperature and moisture sensitivity,nutrient limitation and land use partially explain the divergent estimates of global SOC stocks and soil fluxes in this study. In addition, major sources of uncertainty from model estimation include exclusion of SOC storage in

  6. Oscillating dynamics of bacterial populations and their predators in response to fresh organic matter added to soil: The simulation model 'BACWAVE-WEB'

    NARCIS (Netherlands)

    Zelenev, V.V.; Bruggen, van A.H.C.; Leffelaar, P.A.; Bloem, J.; Semenov, A.M.

    2006-01-01

    Recently, regular oscillations in bacterial populations and growth rates of bacterial feeding nematodes (BFN) were shown to occur after addition of fresh organic matter to soil. This paper presents a model developed to investigate potential mechanisms of those oscillations, and whether they were ini

  7. Oscillating dynamics of bacterial populations and their predators in response to fresh organic matter added to soil: The simulation model 'BACWAVE-WEB'

    NARCIS (Netherlands)

    Zelenev, V.V.; Bruggen, van A.H.C.; Leffelaar, P.A.; Bloem, J.; Semenov, A.M.

    2006-01-01

    Recently, regular oscillations in bacterial populations and growth rates of bacterial feeding nematodes (BFN) were shown to occur after addition of fresh organic matter to soil. This paper presents a model developed to investigate potential mechanisms of those oscillations, and whether they were

  8. Simulation modeling of carcinogenesis.

    Science.gov (United States)

    Ellwein, L B; Cohen, S M

    1992-03-01

    A discrete-time simulation model of carcinogenesis is described mathematically using recursive relationships between time-varying model variables. The dynamics of cellular behavior is represented within a biological framework that encompasses two irreversible and heritable genetic changes. Empirical data and biological supposition dealing with both control and experimental animal groups are used together to establish values for model input variables. The estimation of these variables is integral to the simulation process as described in step-by-step detail. Hepatocarcinogenesis in male F344 rats provides the basis for seven modeling scenarios which illustrate the complexity of relationships among cell proliferation, genotoxicity, and tumor risk.

  9. The uncertainty of modeled soil carbon stock change for Finland

    Science.gov (United States)

    Lehtonen, Aleksi; Heikkinen, Juha

    2013-04-01

    Countries should report soil carbon stock changes of forests for Kyoto Protocol. Under Kyoto Protocol one can omit reporting of a carbon pool by verifying that the pool is not a source of carbon, which is especially tempting for the soil pool. However, verifying that soils of a nation are not a source of carbon in given year seems to be nearly impossible. The Yasso07 model was parametrized against various decomposition data using MCMC method. Soil carbon change in Finland between 1972 and 2011 were simulated with Yasso07 model using litter input data derived from the National Forest Inventory (NFI) and fellings time series. The uncertainties of biomass models, litter turnoverrates, NFI sampling and Yasso07 model were propagated with Monte Carlo simulations. Due to biomass estimation methods, uncertainties of various litter input sources (e.g. living trees, natural mortality and fellings) correlate strongly between each other. We show how original covariance matrices can be analytically combined and the amount of simulated components reduce greatly. While doing simulations we found that proper handling correlations may be even more essential than accurate estimates of standard errors. As a preliminary results, from the analysis we found that both Southern- and Northern Finland were soil carbon sinks, coefficient of variations (CV) varying 10%-25% when model was driven with long term constant weather data. When we applied annual weather data, soils were both sinks and sources of carbon and CVs varied from 10%-90%. This implies that the success of soil carbon sink verification depends on the weather data applied with models. Due to this fact IPCC should provide clear guidance for the weather data applied with soil carbon models and also for soil carbon sink verification. In the UNFCCC reporting carbon sinks of forest biomass have been typically averaged for five years - similar period for soil model weather data would be logical.

  10. FEM modelling of soil behaviour under compressive loads

    Science.gov (United States)

    Ungureanu, N.; Vlăduţ, V.; Biriş, S. Şt

    2017-01-01

    Artificial compaction is one of the most dangerous forms of degradation of agricultural soil. Recognized as a phenomenon with multiple negative effects in terms of environment and agricultural production, soil compaction is strongly influenced by the size of external load, soil moisture, size and shape of footprint area, soil type and number of passes. Knowledge of soil behavior under compressive loads is important in order to prevent or minimize soil compaction. In this paper were developed, by means of the Finite Element Method, various models of soil behavior during the artificial compaction produced by the wheel of an agricultural trailer. Simulations were performed on two types of soil (cohesive and non-cohesive) with known characteristics. By applying two loads (4.5 kN and 21 kN) in footprints of different sizes, were obtained the models of the distributions of stresses occuring in the two types of soil. Simulation results showed that soil stresses increase with increasing wheel load and vary with soil type.

  11. Understanding the Impacts of Soil, Climate and Farming Practices on Soil Organic Carbon Sequestration: a Simulation Study in Australia

    Directory of Open Access Journals (Sweden)

    Cecile Marie Godde

    2016-05-01

    Full Text Available Carbon sequestration in agricultural soils has the capacity to mitigate greenhouse gas emissions, as well as to improve soil biological, physical and chemical properties. The review of literature pertaining to soil organic carbon (SOC dynamics within Australian grain farming systems does not enable us to conclude on the best farming practices to increase or maintain SOC for a specific combination of soil and climate. This study aimed to further explore the complex interactions of soil, climate and farming practices on SOC. We undertook a modeling study with the APSIM (Agricultural Production Systems sIMulator modeling framework, by combining contrasting Australian soils, climates and farming practices (crop rotations, and management within rotations, such as fertilization, tillage and residue management in a factorial design. This design resulted in the transposition of contrasting soils and climates in our simulations, giving soil-climate combinations that do not occur in the study area to help provide insights into the importance of the climate constraints on SOC. We statistically analyzed the model’s outputs to determinate the relative contributions of soil parameters, climate and farming practices on SOC. The initial SOC content had the largest impact on the value of SOC, followed by the climate and the fertilization practices. These factors explained 66%, 18% and 15% of SOC variations, respectively, after 80 years of constant farming practices in the simulation. Tillage and stubble management had the lowest impacts on SOC. This study highlighted the possible negative impact on SOC of a chickpea phase in a wheat-chickpea rotation and the potential positive impact of a cover crop in a sub-tropical climate (Queensland on SOC. It also showed the complexities in managing to achieve increased SOC, while simultaneously aiming to minimize nitrous oxide (N2O emissions and nitrate leaching in farming systems. The transposition of contrasting soils

  12. Water table effects on measured and simulated fluxes in weighing lysimeters for differently-textured soils

    Directory of Open Access Journals (Sweden)

    Wegehenkel Martin

    2015-03-01

    Full Text Available Weighing lysimeters can be used for studying the soil water balance and to analyse evapotranspiration (ET. However, not clear was the impact of the bottom boundary condition on lysimeter results and soil water movement. The objective was to analyse bottom boundary effects on the soil water balance. This analysis was carried out for lysimeters filled with fine- and coarse-textured soil monoliths by comparing simulated and measured data for lysimeters with a higher and a lower water table. The eight weighable lysimeters had a 1 m2 grass-covered surface and a depth of 1.5 m. The lysimeters contained four intact monoliths extracted from a sandy soil and four from a soil with a silty-clay texture. For two lysimeters of each soil, constant water tables were imposed at 135 cm and 210 cm depths. Evapotranspiration, change in soil water storage, and groundwater recharge were simulated for a 3-year period (1996 to 1998 using the Hydrus-1D software. Input data consisted of measured weather data and crop model-based simulated evaporation and transpiration. Snow cover and heat transport were simulated based on measured soil temperatures. Soil hydraulic parameter sets were estimated (i from soil core data and (ii based on texture data using ROSETTA pedotransfer approach. Simulated and measured outflow rates from the sandy soil matched for both parameter sets. For the sand lysimeters with the higher water table, only fast peak flow events observed on May 4, 1996 were not simulated adequately mainly because of differences between simulated and measured soil water storage caused by ET-induced soil water storage depletion. For the silty-clay soil, the simulations using the soil hydraulic parameters from retention data (i were matching the lysimeter data except for the observed peak flows on May, 4, 1996, which here probably resulted from preferential flow. The higher water table at the lysimeter bottom resulted in higher drainage in comparison with the lysimeters

  13. Simulation of a soil loosening process by means of the modified distinct element method

    NARCIS (Netherlands)

    Momuzu, M.; Oida, A.; Yamazaki, M.; Koolen, A.J.

    2002-01-01

    We apply the Distinct Element Method (DEM) to analyze the dynamic behavior of soil. However, the conventional DEM model for calculation of contact forces between elements has some problems; for example, the movement of elements is too discrete to simulate real soil particle movement. Therefore, we m

  14. Linkage of the Soil and Water Assessment Tool and the Texas Water Availability Model to simulate the effects of brush management on monthly storage of Canyon Lake, south-central Texas, 1995-2010

    Science.gov (United States)

    Asquith, William H.; Bumgarner, Johnathan R.

    2014-01-01

    The U.S. Geological Survey (USGS), in cooperation with the Texas State Soil and Water Conservation Board, developed and applied an approach to create a linkage between the published upper Guadalupe River Soil Water Assessment Tool (SWAT) brush-management (ashe juniper [Juniperus ashei]) model and the full authorization version Guadalupe River Water Availability Model (WAM). The SWAT model was published by the USGS, and the Guadalupe River WAM is available from the Texas Commission on Environmental Quality. The upper Guadalupe River watershed is a substantial component of the Guadalupe River WAM. This report serves in part as documentation of a proof of concept on the feasibility of linking these two water-resources planning models for the purpose of simulating possible increases in water storage in Canyon Lake as a result of different brush-management scenarios.

  15. Effects of soil moisture on the diurnal pattern of pesticide emission: Comparison of simulations with field measurements

    Science.gov (United States)

    Reichman, Rivka; Yates, Scott R.; Skaggs, Todd H.; Rolston, Dennis E.

    2013-02-01

    Pesticide volatilization from agricultural soils is one of the main pathways in which pesticides are dispersed in the environment and affects ecosystems including human welfare. Thus, it is necessary to have accurate knowledge of the various physical and chemical mechanisms that affect volatilization rates from field soils. A verification of the influence of soil moisture modeling on the simulated volatilization rate, soil temperature and soil-water content is presented. Model simulations are compared with data collected in a field study that measured the effect of soil moisture on diazinon volatilization. These data included diurnal changes in volatilization rate, soil-water content, and soil temperature measured at two depths. The simulations were performed using a comprehensive non-isothermal model, two water retention functions, and two soil surface resistance functions, resulting in four tested models. Results show that the degree of similarity between volatilization curves simulated using the four models depended on the initial water content. Under fairly wet conditions, the simulated curves mainly differ in the magnitude of their deviation from the measured values. However, under intermediate and low moisture conditions, the simulated curves also differed in their pattern (shape). The model prediction accuracy depended on soil moisture. Under normal practices, where initial soil moisture is about field capacity or higher, a combination of Brooks and Corey water retention and the van de Grind and Owe soil surface resistance functions led to the most accurate predictions. However, under extremely dry conditions, when soil-water content in the top 1 cm is below the volumetric threshold value, the use of a full-range water retention function increased prediction accuracy. The different models did not affect the soil temperature predictions, and had a minor effect on the predicted soil-water content of Yolo silty clay soil.

  16. Soil phosphorus landscape models for precision soil conservation.

    Science.gov (United States)

    Hong, Jinseok; Grunwald, Sabine; Vasques, Gustavo M

    2015-05-01

    Phosphorus (P) enrichment in soils has been documented in the Santa Fe River watershed (SFRW, 3585 km) in north-central Florida. Yet the environmental factors that control P distribution in soils across the landscape, with potential contribution to water quality impairment, are not well understood. The main goal of this study was to develop soil-landscape P models to support a "precision soil conservation" approach combining fine-scale (i.e., site-specific) and coarse-scale (i.e., watershed-extent) assessment of soil P. The specific objectives were to: (i) identify those environmental properties that impart the most control on the spatial distribution of soil Mehlich-1 extracted P (MP) in the SFRW; (ii) model the spatial patterns of soil MP using geostatistical methods; and (iii) assess model quality using independent validation samples. Soil MP data at 137 sites were fused with spatially explicit environmental covariates to develop soil MP prediction models using univariate (lognormal kriging, LNK) and multivariate methods (regression kriging, RK, and cokriging, CK). Incorporation of exhaustive environmental data into multivariate models (RK and CK) improved the prediction of soil MP in the SFRW compared with the univariate model (LNK), which relies solely on soil measurements. Among all tested environmental covariates, land use and vegetation related properties (topsoil) and geologic data (subsoil) showed the largest predictive power to build inferential models for soil MP. Findings from this study contribute to a better understanding of spatially explicit interactions between soil P and other environmental variables, facilitating improved land resource management while minimizing adverse risks to the environment.

  17. Simulating soil-water movement through loess-veneered landscapes using nonconsilient saturated hydraulic conductivity measurements

    Science.gov (United States)

    Williamson, Tanja N.; Lee, Brad D.; Schoeneberger, Philip J.; McCauley, W. M.; Indorante, Samuel J.; Owens, Phillip R.

    2014-01-01

    Soil Survey Geographic Database (SSURGO) data are available for the entire United States, so are incorporated in many regional and national models of hydrology and environmental management. However, SSURGO does not provide an understanding of spatial variability and only includes saturated hydraulic conductivity (Ksat) values estimated from particle size analysis (PSA). This study showed model sensitivity to the substitution of SSURGO data with locally described soil properties or alternate methods of measuring Ksat. Incorporation of these different soil data sets significantly changed the results of hydrologic modeling as a consequence of the amount of space available to store soil water and how this soil water is moved downslope. Locally described soil profiles indicated a difference in Ksat when measured in the field vs. being estimated from PSA. This, in turn, caused a difference in which soil layers were incorporated in the hydrologic simulations using TOPMODEL, ultimately affecting how soil water storage was simulated. Simulations of free-flowing soil water, the amount of water traveling through pores too large to retain water against gravity, were compared with field observations of water in wells at five slope positions along a catena. Comparison of the simulated data with the observed data showed that the ability to model the range of conditions observed in the field varied as a function of three soil data sets (SSURGO and local field descriptions using PSA-derived Ksat or field-measured Ksat) and that comparison of absolute values of soil water storage are not valid if different characterizations of soil properties are used.

  18. Functional behaviour of pedotransfer functions in soil water flow simulation

    NARCIS (Netherlands)

    Soet, M.; Stricker, J.N.M.

    2003-01-01

    Soil hydraulic parameter values for large-scale modelling cannot be obtained by direct methods. Pedotransfer functions (PTFs) that relate soil hydraulic properties (SHPs) to generally available soil texture data may provide an alternative. A considerable number of PTF models has been developed, the

  19. Coupling Modified Linear Spectral Mixture Analysis and Soil Conservation Service Curve Number (SCS-CN Models to Simulate Surface Runoff: Application to the Main Urban Area of Guangzhou, China

    Directory of Open Access Journals (Sweden)

    Jianhui Xu

    2016-11-01

    Full Text Available Land surface characteristics, including soil type, terrain slope, and antecedent soil moisture, have significant impacts on surface runoff during heavy precipitation in highly urbanized areas. In this study, a Linear Spectral Mixture Analysis (LSMA method is modified to extract high-precision impervious surface, vegetation, and soil fractions. In the modified LSMA method, the representative endmembers are first selected by combining a high-resolution image from Google Earth; the unmixing results of the LSMA are then post-processed to reduce errors of misclassification with Normalized Difference Built-up Index (NDBI and Normalized Difference Vegetation Index (NDVI. The modified LSMA is applied to the Landsat 8 Operational Land Imager (OLI image from 18 October 2015 of the main urban area of Guangzhou city. The experimental result indicates that the modified LSMA shows improved extraction performance compared with the conventional LSMA, as it can significantly reduce the bias and root-mean-square error (RMSE. The improved impervious surface, vegetation, and soil fractions are used to calculate the composite curve number (CN for each pixel according to the Soil Conservation Service curve number (SCS-CN model. The composite CN is then adjusted with regional data of the terrain slope and total 5-day antecedent precipitation. Finally, the surface runoff is simulated with the SCS-CN model by combining the adjusted CN and real precipitation data at 1 p.m., 4 May 2015.

  20. Modelling and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Casetti, E.; Vogt, W.G.; Mickle, M.H.

    1984-01-01

    This conference includes papers on the uses of supercomputers, multiprocessors, artificial intelligence and expert systems in various energy applications. Topics considered include knowledge-based expert systems for power engineering, a solar air conditioning laboratory computer system, multivariable control systems, the impact of power system disturbances on computer systems, simulating shared-memory parallel computers, real-time image processing with multiprocessors, and network modeling and simulation of greenhouse solar systems.

  1. Analysis of Variation Characters and Prediction Model of Soil Temperature in Solar Greenhouse

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    [Objective] The aim was to study the soil temperature changes and its forecast model in greenhouse by solar heat. [Method] Annual and daily variation characters of soil temperature were analyzed in this paper by using the observation data of air temperature out of solar greenhouse and different layers soil temperature in it. The soil temperature (daily maximum, daily minimum and daily mean) forecasting models were also studied. Simulation and test were conducted to the forecast model of soil temperature in ...

  2. Is received dose from ingested soil independent of soil PAH concentrations?-Animal model results.

    Science.gov (United States)

    Peters, Rachel E; James, Kyle; Cave, Mark; Wickstrom, Mark; Siciliano, Steven D

    2016-09-01

    Polycyclic aromatic hydrocarbon (PAH) bioavailability from ingested soils will vary between soils; however, the nature of this variation is not well characterized. A juvenile swine model was used to link external exposure to internal benzo[a]pyrene (BaP) and anthracene exposure following oral PAH ingestion of 27 different impacted site soils, soots, or spiked artificial soils. Internal exposure of BaP and anthracene, represented by area under the plasma-time curve, did not relate to soil concentration in impacted site soils, but did relate in spiked artificial soil. Point of departure modeling identified soil PAH concentrations greater than 1900 mg kg(-1) as the point where area under the curve becomes proportional to external dose. A BaP internal exposure below 1900 mg kg(-1) had an upper 95% confidence interval estimate of 33% of external exposure. Weak relationships between soil:simulated gastrointestinal fluid PAH partitioning and area under the curve values suggest that differences in internal PAH exposure between soils may not be dominated by differences in PAH partitioning. The data seem to best support exposure assessment assuming constant internal PAH exposure below soil concentrations of 1900 mg kg(-1) . However, because constant internal exposure would challenge several existing paradigms, a bioavailability estimate of 33% of the external exposure is suggested as a likely workable solution. Environ Toxicol Chem 2016;35:2261-2269. © 2016 SETAC.

  3. Validation of simulation models

    DEFF Research Database (Denmark)

    Rehman, Muniza; Pedersen, Stig Andur

    2012-01-01

    In philosophy of science, the interest for computational models and simulations has increased heavily during the past decades. Different positions regarding the validity of models have emerged but the views have not succeeded in capturing the diversity of validation methods. The wide variety...... of models has been somewhat narrow-minded reducing the notion of validation to establishment of truth. This article puts forward the diversity in applications of simulation models that demands a corresponding diversity in the notion of validation....... of models with regards to their purpose, character, field of application and time dimension inherently calls for a similar diversity in validation approaches. A classification of models in terms of the mentioned elements is presented and used to shed light on possible types of validation leading...

  4. Misrepresentation and amendment of soil moisture in conceptual hydrological modelling

    Science.gov (United States)

    Zhuo, Lu; Han, Dawei

    2016-04-01

    Although many conceptual models are very effective in simulating river runoff, their soil moisture schemes are generally not realistic in comparison with the reality (i.e., getting the right answers for the wrong reasons). This study reveals two significant misrepresentations in those models through a case study using the Xinanjiang model which is representative of many well-known conceptual hydrological models. The first is the setting of the upper limit of its soil moisture at the field capacity, due to the 'holding excess runoff' concept (i.e., runoff begins on repletion of its storage to the field capacity). The second is neglect of capillary rise of water movement. A new scheme is therefore proposed to overcome those two issues. The amended model is as effective as its original form in flow modelling, but represents more logically realistic soil water processes. The purpose of the study is to enable the hydrological model to get the right answers for the right reasons. Therefore, the new model structure has a better capability in potentially assimilating soil moisture observations to enhance its real-time flood forecasting accuracy. The new scheme is evaluated in the Pontiac catchment of the USA through a comparison with satellite observed soil moisture. The correlation between the XAJ and the observed soil moisture is enhanced significantly from 0.64 to 0.70. In addition, a new soil moisture term called SMDS (Soil Moisture Deficit to Saturation) is proposed to complement the conventional SMD (Soil Moisture Deficit).

  5. A simple model of carbon in the soil profile for agricultural soils in Northwestern Europe

    Science.gov (United States)

    Taghizadeh-Toosi, Arezoo; Hutchings, Nicholas J.; Vejlin, Jonas; Christensen, Bent T.; Olesen, Jørgen E.

    2014-05-01

    World soil carbon (C) stocks are second to those in the ocean, and represent three times as much C as currently present in the atmosphere. The amount of C in soil may play a significant role in carbon exchanges between the atmosphere and the terrestrial environment. The C-TOOL model is a three-pool linked soil organic carbon (SOC) model in well-drained mineral soils under agricultural land management to allow generalized parameterization for estimating effects of management measures at medium to long time scales for the entire soil profile (0-100 cm). C-TOOL has been developed to enable simulations of SOC turnover in soil using temperature dependent first order kinetics for describing decomposition. Compared with many other SOC models, C-TOOL applies a less complicated structure, which facilitates easier calibration, and it requires only few inputs (i.e., average monthly air temperature, soil clay content,soil carbon-to-nitrogen ratio, and C inputs to the soil from plants and other sources). C-TOOL was parameterized using SOC and radiocarbon data from selected long-term field treatments in United Kingdom, Sweden and Denmark. However, less data were available for evaluation of subsoil C (25-100 cm) from the long-term experiments applied. In Denmark a national 7×7 km grid net was established in 1986 for soil C monitoring down to 100 cm depth. The results of SOC showed a significant decline from 1997 to 2009 in the 0-50 cm soil layer. This was mainly attributed to changes in the 25-50 cm layer, where a decline in SOC was found for all soil texture types. Across the period 1986 to 2009 there was clear tendency for increasing SOC on the sandy soils and reductions on the loamy soils. This effect is linked to land use, since grasslands and dairy farms are more abundant in the western parts of Denmark, where most of the sandy soils are located. The results and the data from soil monitoring have been used to validate the C-TOOL modelling approach used for accounting of

  6. Defining and modeling the soil geochemical background of heavy metals from the Hengshi River watershed (southern China): integrating EDA, stochastic simulation and magnetic parameters.

    Science.gov (United States)

    Zhou, Xu; Xia, Beicheng

    2010-08-15

    It is crucial to separate the soil geochemical background concentrations from anthropogenic anomalies and to provide a realistic environmental geochemical map honoring the fluctuations in original data. This study was carried out in the Hengshi River watershed, north of Guangdong, China and the method proposed combined exploratory data analysis (EDA), sequential indicator co-simulation (SIcS) and the ratio of isothermal remnant magnetization (S(100)=-IRM(-100 mT)/SIRM). The results showed that this is robust procedure for defining and mapping soil geochemical background concentrations in mineralized regions. The rock magnetic parameter helps to improve the mapping process by distinguishing anthropogenic influences. In this study, the geochemical backgrounds for four potentially toxic heavy metals (copper 200mg/kg; zinc 23 0mg/kg; lead 190 mg/kg and cadmium 1.85 mg/kg) Cu, Zn and Cd exceeded the soil Grade II limits (for pHgeochemical background level for Cd exceeds standard six times. Results suggest that local public health is at high-risk along the riparian region of the Hengshi River, although the watershed ecosystem has not been severely disturbed.

  7. Simulation of Zinc Release Affected by Microbial Inoculation and Salinity Levels in a non-sterile Calcareous Soil Using kinetic Models

    Directory of Open Access Journals (Sweden)

    hamidreza boostani

    2017-02-01

    Full Text Available Introduction: Zinc (Zn is an important nutrient element for humans and plants that controls many biochemical and physiological functions of living organisms. Zinc deficiency is common in high pH, low organic matter, carbonatic, saline and sodic soils. Salinity is a major abiotic environmental stresses that limits growth and production in arid and semi-arid regions of the world. Bioavailability of Zn is low in calcareous and saline soils having high levels of pH and calcium. Desorption of Zinc (Zn from soil as influenced by biological activities is one of the important factors that control Zn bioavailability. Few reports on the effects of salinity on the availability and desorption kinetics of Zn are available. Rupa et al. (2000 reported that increasing the salt concentration led to increase Zn desorption from soil due to ion competition on soil exchangeable sites. Different kinetic equations have been used to describe the release kinetics of nutrients. Reyhanitabar and Gilkes (2010 found that the power function model was the best equation to describe the release of Zn from some calcareous soil of Iran, whereas Baranimotlagh and Gholami (2013 stated that the best model for describing Zn desorption from 15 calcareous soils of Iran was the first-order equation.less attention has been paid to kinetics of Zn release by DTPA extractant over time by inoculation of plant growth promoting rhizobacteria and mycorrhizae fungi in comination with soil salinity.The objective of this study was to evaluate the effect of plant growth promoting rhizobacteria (PGPR and mycorrhizae fungi (MF inoculation on release kinetic of Zn in a calcareous soil at different salinity levels after in cornplantation Materials and Methods: A composite sample of bulk soil from the surface horizon (0-30 cm of a calcareous soil from southern part of Iran was collected, air dried, passed through 2 mm sieve, and thoroughly mixed. Routine soil analysis was performed to determine some

  8. Soil water content and water balance simulation of Caragana korshinskii Kom. in the semiarid Chinese Loess Plateau

    Directory of Open Access Journals (Sweden)

    Jian Shengqi

    2014-06-01

    Full Text Available In this paper, to evaluate the hydrological effects of Caragana korshinskii Kom., measured data were combined with model-simulated data to assess the C. korshinskii soil water content based on water balance equation. With measured and simulated canopy interception, plant transpiration and soil evaporation, soil water content was modeled with the water balance equation. The monthly variations in the modeled soil water content by measured and simulated components (canopy interception, plant transpiration, soil evaporation were then compared with in situ measured soil water content. Our results shows that the modeled monthly water loss (canopy interception + soil evaporation + plant transpiration by measured and simulated components ranges from 43.78 mm to 113.95 mm and from 47.76 mm to 125.63 mm, respectively, while the monthly input of water (precipitation ranges from 27.30 mm to 108.30 mm. The relative error between soil water content modeled by measured and simulated components was 6.41%. To sum up, the net change in soil water (ΔSW is negative in every month of the growing season. The soil moisture is approaching to wilting coefficient at the end of the growth season, and the soil moisture recovered during the following season.

  9. Simulation of soil moisture and evapotranspiration in a soil profile during the 1999 MAP-Riviera Campaign

    Directory of Open Access Journals (Sweden)

    M. Zappa

    2003-01-01

    Full Text Available Detailed plot-scale observations of basic hydrometeorological variables represent valuable data for assessing the quality of the soil moisture module and evapotranspiration scheme in hydrological models. This study presents the validation of soil moisture and evapotranspiration (ET simulation during the special observing period (R-SOP of the Riviera Project (July–November 1999, a sub-project of the Mesoscale Alpine Programme (MAP. The location investigated was a sandy soil plot at the edge of a corn field. The hydrological model PREVAH was driven using three meteorological data sets: hourly data from an experimental tower in the Riviera Valley (southern Switzerland, hourly data interpolated for the Riviera site during the R-SOP period from permanent automatic stations (MeteoSwiss network and interpolated daily data (1980–2000. The quality of the interpolated meteorological data was evaluated with respect to data collected at an experimental tower. The interpolated data proved fairly representative for the location under investigation. The hydrological simulations were compared with recorded observations of soil moisture and latent heat flux (LE. The simulation of soil moisture was accurate in case of all three meteorological data sets. The results of ET simulations with three simple parameterisations showed high correlation to LE derived using the Bowen ratio and measured through eddy correlation. The quantitative agreement between observed and simulated LE was poorer because of the presence of a fully developed wind valley system during periods of good weather. This wind system claims part of the available energy and therefore reduces the amount of energy available for LE. The 21-year simulation at daily time step shows that the R-SOP period in 1999 was warm and wet compared to the last 21 years. Keywords: MAP-Riviera Project, soil moisture, evapotranspiration, hydrological modelling, model evaluation

  10. Modelling the soil carbon cycle of pine ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Nakane, K. [Hiroshima, Univ., Dept. of Environ. Studies, Fac. of Integrated Arts and Sciences, Higashi Hiroshima (Japan)

    1994-12-31

    Soil carbon cycling rates and carbon budgets were calculated for stands of four pine species. Pinus sylvestris (at Jaedraaas, Sweden), P. densiflora (Hiroshima, Japan), P. elliottii (Florida, USA) and P. radiata (Canberra, Australia), using a simulation model driven by daily observations of mean air temperature and precipitation. Inputs to soil carbon through litterfall differ considerably among the four pine forests, but the accumulation of the A{sub 0} layer and humus in mineral soil is less variable. Decomposition of the A{sub 0} layer and humus is fastest for P. densiflora and slowest for P. sylvestris stands with P. radiata and P. elliottii intermediate. The decomposition rate is lower for the P. elliottii stand than for P. densiflora in spite of its higher temperatures and slightly higher precipitation. Seasonal changes in simulated soil carbon are observed only for the A{sub 0} layer at the P. densiflora site. Simulated soil respiration rates vary seasonally in three stands (P. sylvestris, P. densiflora and P. radiata). In simulations for pine trees planted on bare soil, all soil organic matter fractions except the humus in mineral soil recover to half their asymptotic values within 30 to 40 years of planting for P. sylvestris and P. densiflora, compared with 10 to 20 years for P. radiata and P. elliottii. The simulated recovery of soil carbon following clear-cutting is fastest for the P. elliottii stand and slowest for P. sylvestris. Management of P. elliottii and P. radiata stands on 40-years rotations is sustainable because carbon removed through harvest is restored in the interval between successive clear-cuts. However p. densiflora and P. sylvestris stands may be unable to maintain soil carbon under such a short rotation. High growth rates of P. elliottii and p. radiata stands in spite of relatively poor soil conditions and slow carbon cycling may be related to the physiological responses of species to environmental conditions. (Abstract Truncated)

  11. Modelling of Cadmium Transport in Soil-Crop System

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A model for simulating cadmium transport in a soil-plant system was built using a commercial simu lating program named Powersim on the basis of input-output processes happening in the soil-plant system.Convective and dispersive transport processes of cadmium in soil profile are embedded. Simulations on a daily base have been done up to a total simulating time of 250 years. Results show that applications of sewage sludge and fertilizer at the simulated rates would only cause slight cadmium accumulations in each layer of the soil, and cadmium accumulation would be levelling off, reaching an equilibrium concentrations layer by layer downward after certain time. The time scale to reach an equilibrium concentration varies from 10 years for the top three layers to over 250 years for the bottom layers. Plant cadmium uptake would increase from 52 ug m-2 under initial soil cadmium concentrations to 65 μg m-2 under equilibrium soil cadmium concentrations, which would not exceed the maximum allowable cadmium concentration in wheat grains. Main parameters which influence cadmium accumulation and transport in soil are total cadmium input, rainfall, evaporation, plant uptake and soil properties.

  12. Hillslope soil erosion and runoff model for natural rainfall events

    Institute of Scientific and Technical Information of China (English)

    Zhanyu Zhang; Guohua Zhang; Changqing Zuo; Xiaoyu Pi

    2008-01-01

    By using the momentum theorem and water balance principle, basic equations of slope runoff were derived, soil erosion by raindrop splash and runoff were discussed and a model was established for decribing hillslope soil erosion processes. The numerical solution of the model was obtained by adopting the Preissmann format and considering the common solution-determining conditions, from which not only the runoff and soil erosion but also their processes can be described. The model was validated by ten groups of observation data of Soil Conservation Ecological Science and Technology Demonstration Park of Jiangxi Province. Comparisons show that the maximum relative error between simulation and experimental data is about 10.98% for total runoff and 15% for total erosion, 5.2% for runoff process and 6.1% for erosion process, indicating that the model is conceptually realistic and reliable and offers a feasible approach for further studies on the soil erosion process.

  13. 基于土壤分层的木薯块根拔起系统动力学仿真模型%Dynamics Simulation Model o f Cassava Tuber Lifting System Based on Soil Layering

    Institute of Scientific and Technical Information of China (English)

    杨望; 张硕; 陈科余; 杨坚

    2016-01-01

    针对土壤采用整体建模方法建模,木薯块根拔起过程动力学仿真精度受限及耕作层表土材料建模参数测定困难的问题,采用物理试验、FEM 和光滑粒子流体动力学方法 ( Smoothed particle hydrodynamics , SPH )的耦合方法,建立土壤硬度测试系统动力学仿真模型,对木薯种植地耕作层土壤建模材料参数弹性模量进行了反求.同时,建立了基于土壤分层的木薯块根拔起系统动力学仿真模型,且和采用整体建模方法建立的木薯块根拔起系统动力学仿真模型进行了精度比较. 结果表明:建模材料参数弹性模量的反求方法有效,基于土壤分层的木薯块根拔起系统动力学仿真模型精度高.%According to establish soil model using integral modeling method , the precision of dynamics simulation of cas-sava tuber lifting process was limited .And topsoil ' s material parameter on plough layer was difficult to determine .Dy-namics simulation model of soil hardness testing system was established .Physical test and coupling method of FEM and SPH were used in the model .Elastic modulus of soil on cassava planting field ' s plough layer was reversed .Dynamics simulation model of cassava tuber lifting system based on soil layering and integral modeling were built , respectively .And the precision between the two methods was compared .The results show that the reverse method is effective .The model based on soil layering has high precision .

  14. Soil Erosion Study through Simulation: An Educational Tool.

    Science.gov (United States)

    Huber, Thomas P.; Falkenmayer, Karen

    1987-01-01

    Discusses the need for education about soil erosion and advocates the use of the Universal Soil Loss Equation (USLE) to show the impacts of human and natural action on the land. Describes the use of a computer simulated version of the USLE in several environmental and farming situations. (TW)

  15. Coupling Landform Evolution and Soil Pedogenesis - Initial Results From the SSSPAM5D Model

    Science.gov (United States)

    Willgoose, G. R.; Welivitiya, W. D. D. P.; Hancock, G. R.; Cohen, S.

    2015-12-01

    Evolution of soil on a dynamic landform is a crucial next step in landscape evolution modelling. Some attempts have been taken such as MILESD by Vanwalleghem et al. to develop a first model which is capable of simultaneously evolving both the soil profile and the landform. In previous work we have presented physically based models for soil pedogenesis, mARM and SSSPAM. In this study we present the results of coupling a landform evolution model with our SSSPAM5D soil pedogenesis model. In previous work the SSSPAM5D soil evolution model was used to identify trends of the soil profile evolution on a static landform. Two pedogenetic processes, namely (1) armouring due to erosion, and (2) physical and chemical weathering were used in those simulations to evolve the soil profile. By incorporating elevation changes (due to erosion and deposition) we have advanced the SSSPAM5D modelling framework into the realm of landscape evolution. Simulations have been run using elevation and soil grading data of the engineered landform (spoil heap) at the Ranger Uranium Mine, Northern Territory, Australia. The results obtained for the coupled landform-soil evolution simulations predict the erosion of high slope areas, development of rudimentary channel networks in the landform and deposition of sediments in lowland areas, and qualitatively consistent with landform evolution models on their own. Examination of the soil profile characteristics revealed that hill crests are weathering dominated and tend to develop a thick soil layer. The steeper hillslopes at the edge of the landform are erosion dominated with shallow soils while the foot slopes are deposition dominated with thick soil layers. The simulation results of our coupled landform and soil evolution model provide qualitatively correct and timely characterization of the soil evolution on a dynamic landscape. Finally we will compare the characteristics of erosion and deposition predicted by the coupled landform-soil SSSPAM

  16. Sensitivity analysis and calibration of a soil carbon model (SoilGen2 in two contrasting loess forest soils

    Directory of Open Access Journals (Sweden)

    Y. Y. Yu

    2013-01-01

    Full Text Available To accurately estimate past terrestrial carbon pools is the key to understanding the global carbon cycle and its relationship with the climate system. SoilGen2 is a useful tool to obtain aspects of soil properties (including carbon content by simulating soil formation processes; thus it offers an opportunity for both past soil carbon pool reconstruction and future carbon pool prediction. In order to apply it to various environmental conditions, parameters related to carbon cycle process in SoilGen2 are calibrated based on six soil pedons from two typical loess deposition regions (Belgium and China. Sensitivity analysis using the Morris method shows that decomposition rate of humus (kHUM, fraction of incoming plant material as leaf litter (frecto and decomposition rate of resistant plant material (kRPM are the three most sensitive parameters that would cause the greatest uncertainty in simulated change of soil organic carbon in both regions. According to the principle of minimizing the difference between simulated and measured organic carbon by comparing quality indices, the suited values of kHUM, (frecto and kRPM in the model are deduced step by step and validated for independent soil pedons. The difference of calibrated parameters between Belgium and China may be attributed to their different vegetation types and climate conditions. This calibrated model allows more accurate simulation of carbon change in the whole pedon and has potential for future modeling of carbon cycle over long timescales.

  17. Temporal and spatial variability of soil hydraulic properties with implications on soil moisture simulations and irrigation scheduling

    Science.gov (United States)

    Feki, Mouna; Ravazzani, Giovanni; Mancini, Marco

    2017-04-01

    The increase in consumption of water resources, combined with climate change impacts, calls for new sources of water supply and/or different managements of available resources in agriculture. One way to increase the quality and quantity of agricultural production is using modern technology to make farms more "intelligent", the so-called "precision agriculture" also known as 'smart farming'. To this aim hydrological models play crucial role for their ability to simulate water movement from soil surface to groundwater and to predict onset of stress condition. However, optimal use of mathematical models requires intensive, time consuming and expensive collection of soil related parameters. Typically, soils to be characterized, exhibit large variations in space and time as well during the cropping cycle, due to biological processes and agricultural management practices: tillage, irrigation, fertilization and harvest. Soil properties are subjected to diverse physical and chemical changes that lead to a non-stability in terms of water and chemical movements within the soil and to the groundwater as well. The aim of this study is to assess the variability of soil hydraulic properties over a cropping cycle. The study site is a surface irrigated Maize field located in Secugnago (45◦13'31.70" N, 9 ◦36'26.82 E), in Northern Italy-Lombardy region. The field belongs to the Consortium Muzza Bassa Lodigiana, within which meteorological data together with soil moisture were monitored during the cropping season of 2015. To investigate soil properties variations, both measurements in the field and laboratory tests on both undisturbed and disturbed collected samples were performed. Soil samples were taken from different locations within the study area and at different depths (surface, 20cm and 40cm) at the beginning and in the middle of the cropping cycle and after the harvest. During three measuring campaigns, for each soil samples several parameters were monitored (Organic

  18. Water Yield and Sediment Yield Simulations for Teba Catchment in Spain Using SWRRB Model: Ⅰ. Model Input and Simulation Experiment

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Water yield and sediment yield in the Teba catchment, Spain, were simulated using SWRRB (Simulator for Water Resources in Rural Basins) model. The model is composed of 198 mathematical equations. About 120 items (variables) were input for the simulation, including meteorological and climatic factors, hydrologic factors, topographic factors, parent materials, soils, vegetation, human activities, etc. The simulated results involved surface runoff, subsurface runoff, sediment, peak flow, evapotranspiration, soil water, total biomass,etc. Careful and thorough input data preparation and repeated simulation experiments are the key to get the accurate results. In this work the simulation accuracy for annual water yield prediction reached to 83.68%.``

  19. Numerical Simulation on Explosion in Double-Layer Medium of Concrete and Soil

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The numerical simulation on explosion in concrete and soil is performed by using the three-dimension finite element code LS-DYNA, into which a continuum damage model which can well describe the fracture of concrete is implemented. As a consequence, wave propagation and attenuation in concrete and on soil-concrete interface are obtained respectively. Moreover, the damage regions of concrete at different thicknesses of soil (TOS) and depths of charge (DOC) are procured. The existent soil reduces damage region of concrete. Numerical results provide reference for design of warhead and protective structure and blasting.

  20. The mathematical simulation of the temperature fields of building envelopes under permanent frozen soil conditions

    Science.gov (United States)

    Anisimov, M. V.; Babuta, M. N.; Kuznetsova, U. N.; Safonova, E. V.; Minaeva, O. M.

    2016-04-01

    The physical-mathematical model of the thermal state of the aired technical underground taking into account the air exchange and design features of construction under permanent frozen soil conditions has been suggested. The computational scheme of the temperature fields prediction of building envelopes of projected buildings and soil under and nearby buildings has been developed. The numerical simulation of the temperature fields of building envelopes changes was conducted during a year. The results of the numerical simulation showed that the heat coming from the technical undergrounds and through the walls does not influence the temperature field of the soil neither under a building nor at a distance from it.

  1. Discrete and continuum modelling of soil cutting

    Science.gov (United States)

    Coetzee, C. J.

    2014-12-01

    Both continuum and discrete methods are used to investigate the soil cutting process. The Discrete Element Method ( dem) is used for the discrete modelling and the Material-Point Method ( mpm) is used for continuum modelling. M pmis a so-called particle method or meshless finite element method. Standard finite element methods have difficulty in modelling the entire cutting process due to large displacements and deformation of the mesh. The use of meshless methods overcomes this problem. M pm can model large deformations, frictional contact at the soil-tool interface, and dynamic effects (inertia forces). In granular materials the discreteness of the system is often important and rotational degrees of freedom are active, which might require enhanced theoretical approaches like polar continua. In polar continuum theories, the material points are considered to possess orientations. A material point has three degrees-of-freedom for rigid rotations, in addition to the three classic translational degrees-of-freedom. The Cosserat continuum is the most transparent and straightforward extension of the nonpolar (classic) continuum. Two-dimensional dem and mpm (polar and nonpolar) simulations of the cutting problem are compared to experiments. The drag force and flow patterns are compared using cohesionless corn grains as material. The corn macro (continuum) and micro ( dem) properties were obtained from shear and oedometer tests. Results show that the dilatancy angle plays a significant role in the flow of material but has less of an influence on the draft force. Nonpolar mpm is the most accurate in predicting blade forces, blade-soil interface stresses and the position and orientation of shear bands. Polar mpm fails in predicting the orientation of the shear band, but is less sensitive to mesh size and mesh orientation compared to nonpolar mpm. dem simulations show less material dilation than observed during experiments.

  2. Effects of soil-type datasets on regional terrestrial water cycle simulations under different climatic regimes

    Science.gov (United States)

    Zheng, H.; Yang, Z.-L.

    2016-12-01

    Hydrological simulations play an important role in estimating terrestrial water budgets and monitoring extreme events such as floods. This study investigates how these simulations are affected by soil-type datasets and characterizes how these effects vary with climate. We study the differences between two ensemble simulations in China with the Noah-MP land surface model using two soil datasets from the Food and Agriculture Organization and Beijing Normal University. The differences in ensemble means are analyzed over a 10 year period from 2003 to 2012 with respect to estimated soil moisture, the partition of precipitation between evapotranspiration and runoff, and a flood magnitude index. Results show that the hydrological simulations using sandier soil types result in lower soil moisture, lower evapotranspiration, and higher subsurface runoff. Each of these effects varies uniquely with aridity. The changes in soil moisture decrease with increasing aridity, while the changes in water balance components (evapotranspiration and runoff) peak in the transitional zone between humid and arid regions. The flood magnitude, expressed as the maximum daily flow normalized by annual flow, is also substantially influenced by the input soil type. Soil types with more clay and less sand content yield significantly bigger floods, especially in arid regions.

  3. Mechanical properties of lunar regolith and lunar soil simulant

    Science.gov (United States)

    Perkins, Steven W.

    1989-01-01

    Through the Surveyor 3 and 7, and Apollo 11-17 missions a knowledge of the mechanical properties of Lunar regolith were gained. These properties, including material cohesion, friction, in-situ density, grain-size distribution and shape, and porosity, were determined by indirect means of trenching, penetration, and vane shear testing. Several of these properties were shown to be significantly different from those of terrestrial soils, such as an interlocking cohesion and tensile strength formed in the absence of moisture and particle cementation. To characterize the strength and deformation properties of Lunar regolith experiments have been conducted on a lunar soil simulant at various initial densities, fabric arrangements, and composition. These experiments included conventional triaxial compression and extension, direct tension, and combined tension-shear. Experiments have been conducted at low levels of effective confining stress. External conditions such as membrane induced confining stresses, end platten friction and material self weight have been shown to have a dramatic effect on the strength properties at low levels of confining stress. The solution has been to treat these external conditions and the specimen as a full-fledged boundary value problem rather than the idealized elemental cube of mechanics. Centrifuge modeling allows for the study of Lunar soil-structure interaction problems. In recent years centrifuge modeling has become an important tool for modeling processes that are dominated by gravity and for verifying analysis procedures and studying deformation and failure modes. Centrifuge modeling is well established for terrestrial enginering and applies equally as well to Lunar engineering. A brief review of the experiments is presented in graphic and outline form.

  4. Microbial mediation of biogeochemical cycles revealed by simulation of global changes with soil transplant and cropping.

    Science.gov (United States)

    Zhao, Mengxin; Xue, Kai; Wang, Feng; Liu, Shanshan; Bai, Shijie; Sun, Bo; Zhou, Jizhong; Yang, Yunfeng

    2014-10-01

    Despite microbes' key roles in driving biogeochemical cycles, the mechanism of microbe-mediated feedbacks to global changes remains elusive. Recently, soil transplant has been successfully established as a proxy to simulate climate changes, as the current trend of global warming coherently causes range shifts toward higher latitudes. Four years after southward soil transplant over large transects in China, we found that microbial functional diversity was increased, in addition to concurrent changes in microbial biomass, soil nutrient content and functional processes involved in the nitrogen cycle. However, soil transplant effects could be overridden by maize cropping, which was attributed to a negative interaction. Strikingly, abundances of nitrogen and carbon cycle genes were increased by these field experiments simulating global change, coinciding with higher soil nitrification potential and carbon dioxide (CO2) efflux. Further investigation revealed strong correlations between carbon cycle genes and CO2 efflux in bare soil but not cropped soil, and between nitrogen cycle genes and nitrification. These findings suggest that changes of soil carbon and nitrogen cycles by soil transplant and cropping were predictable by measuring microbial functional potentials, contributing to a better mechanistic understanding of these soil functional processes and suggesting a potential to incorporate microbial communities in greenhouse gas emission modeling.

  5. Radon transport in fractured soil. Laboratory experiments and modelling

    Energy Technology Data Exchange (ETDEWEB)

    Hoff, A.

    1997-10-01

    Radon (Rn-222) transport in fractured soil has been investigated by laboratory experiments and by modelling. Radon transport experiments have been performed with two sand columns (homogeneous and inhomogeneous) and one undisturbed clayey till column containing a net of preferential flow paths (root holes). A numerical model (the finite-element model FRACTRAN) and an analytic model (a pinhole model) have been applied in simulations if soil gas and radon transport in fractured soil. Experiments and model calculations are included in a discussion of radon entry rates into houses placed on fractured soil. The main conclusion is, that fractures does not in general alter transport of internally generated radon out of soil, when the pressure and flow conditions in the soil is comparable to the conditions prevailing under a house. This indicates the important result, that fractures in soil have no impact on radon entry into a house beyond that of an increased gas permeability, but a more thorough investigation of this subject is needed. Only in the case where the soil is exposed to large pressure gradients, relative to gradients induced by a house, may it be possible to observe effects of radon exchange between fractures and matrix. (au) 52 tabs., 60 ill., 5 refs.

  6. Explicitly representing soil microbial processes in Earth system models

    Science.gov (United States)

    Wieder, William R.; Allison, Steven D.; Davidson, Eric A.; Georgiou, Katerina; Hararuk, Oleksandra; He, Yujie; Hopkins, Francesca; Luo, Yiqi; Smith, Matthew J.; Sulman, Benjamin; Todd-Brown, Katherine; Wang, Ying-Ping; Xia, Jianyang; Xu, Xiaofeng

    2015-10-01

    Microbes influence soil organic matter decomposition and the long-term stabilization of carbon (C) in soils. We contend that by revising the representation of microbial processes and their interactions with the physicochemical soil environment, Earth system models (ESMs) will make more realistic global C cycle projections. Explicit representation of microbial processes presents considerable challenges due to the scale at which these processes occur. Thus, applying microbial theory in ESMs requires a framework to link micro-scale process-level understanding and measurements to macro-scale models used to make decadal- to century-long projections. Here we review the diversity, advantages, and pitfalls of simulating soil biogeochemical cycles using microbial-explicit modeling approaches. We present a roadmap for how to begin building, applying, and evaluating reliable microbial-explicit model formulations that can be applied in ESMs. Drawing from experience with traditional decomposition models, we suggest the following: (1) guidelines for common model parameters and output that can facilitate future model intercomparisons; (2) development of benchmarking and model-data integration frameworks that can be used to effectively guide, inform, and evaluate model parameterizations with data from well-curated repositories; and (3) the application of scaling methods to integrate microbial-explicit soil biogeochemistry modules within ESMs. With contributions across scientific disciplines, we feel this roadmap can advance our fundamental understanding of soil biogeochemical dynamics and more realistically project likely soil C response to environmental change at global scales.

  7. Salt-Water Transport in Unsaturated Soils Under Crop Planting: Dynamics and Numerical Simulation

    Institute of Scientific and Technical Information of China (English)

    XU Li-Gang; YANG Jing-Song; ZHANG Qi; LIU Guang-Ming

    2005-01-01

    A laboratory salt-water dynamics experiment using unsaturated soils in packed silt loam and clay soil columns with different soil texture profiles and groundwater levels under crops were conducted to study the changes of salt-water dynamics induced by water uptake of crops and to propose the theoretical basis for the regulation and control of saltwater dynamics as well as to predict salinity levels. The HYDRUS 1D model was applied to simulate the one-dimensional movement of water and salt transport in the soil columns. The results showed that the salts mainly accumulated in the plow layer in the soil columns under crops. Soil water and salt both moved towards the plow layer due to soil water absorption by the crop root system. The salt contents in the column with lower groundwater were mostly greater than those with high groundwater. The water contents in the soil columns increased from top to the bottom due to plant root water uptake. The changes in groundwater level had little influence on water content of the root zone in the soil columns with crop planting. Comparison between the simulated and the determined values showed that model simulation results were ideal, so it is practicable to do numerical simulation of soil salt and water transport by the HYDRUS 1D model.Furthermore, if the actual movement of salt and water in fields is to be described in detail, much work needs to be done.The most important thing is to refine the parameters and select precise boundary conditions.

  8. Single Plant Root System Modeling under Soil Moisture Variation

    Science.gov (United States)

    Yabusaki, S.; Fang, Y.; Chen, X.; Scheibe, T. D.

    2016-12-01

    A prognostic Virtual Plant-Atmosphere-Soil System (vPASS) model is being developed that integrates comprehensively detailed mechanistic single plant modeling with microbial, atmospheric, and soil system processes in its immediate environment. Three broad areas of process module development are targeted: Incorporating models for root growth and function, rhizosphere interactions with bacteria and other organisms, litter decomposition and soil respiration into established porous media flow and reactive transport models Incorporating root/shoot transport, growth, photosynthesis and carbon allocation process models into an integrated plant physiology model Incorporating transpiration, Volatile Organic Compounds (VOC) emission, particulate deposition and local atmospheric processes into a coupled plant/atmosphere model. The integrated plant ecosystem simulation capability is being developed as open source process modules and associated interfaces under a modeling framework. The initial focus addresses the coupling of root growth, vascular transport system, and soil under drought scenarios. Two types of root water uptake modeling approaches are tested: continuous root distribution and constitutive root system architecture. The continuous root distribution models are based on spatially averaged root development process parameters, which are relatively straightforward to accommodate in the continuum soil flow and reactive transport module. Conversely, the constitutive root system architecture models use root growth rates, root growth direction, and root branching to evolve explicit root geometries. The branching topologies require more complex data structures and additional input parameters. Preliminary results are presented for root model development and the vascular response to temporal and spatial variations in soil conditions.

  9. Competitive and synergistic effects in pH dependent phosphate adsorption in soils: LCD modeling

    NARCIS (Netherlands)

    Weng, L.P.; Vega, F.A.; Riemsdijk, van W.H.

    2011-01-01

    The pH dependency of soluble phosphate in soil was measured for six agricultural soils over a pH range of 3–10. A mechanistic model, the LCD (ligand charge distribution) model, was used to simulate this change, which considers phosphate adsorption to metal (hydr)oxides in soils under the influence o

  10. Shear creep parameters of simulative soil for deep-sea sediment

    Institute of Scientific and Technical Information of China (English)

    马雯波; 饶秋华; 李鹏; 郭帅成; 冯康

    2014-01-01

    Based on mineral component and in-situ vane shear strength of deep-sea sediment, four kinds of simulative soils were prepared by mixing different bentonites with water in order to find the best simulative soil for the deep-sea sediment collected from the Pacific C-C area. Shear creep characteristics of the simulative soil were studied by shear creep test and shear creep parameters were determined by Burgers creep model. Research results show that the shear creep curves of the simulative soil can be divided into transient creep, unstable creep and stable creep, where the unstable creep stage is very short due to its high water content. The shear creep parameters increase with compressive stress and change slightly or fluctuate to approach a constant value with shear stress, and thus average creep parameters under the same compressive stress are used as the creep parameters of the simulative soil. Traction of the deep-sea mining machine walking at a constant velocity can be calculated by the shear creep constitutive equation of the deep-sea simulative soil, which provides a theoretical basis for safe operation and optimal design of the deep-sea mining machine.

  11. Simulating the influence of snow surface processes on soil moisture dynamics and streamflow generation in an alpine catchment

    Science.gov (United States)

    Wever, Nander; Comola, Francesco; Bavay, Mathias; Lehning, Michael

    2017-08-01

    The assessment of flood risks in alpine, snow-covered catchments requires an understanding of the linkage between the snow cover, soil and discharge in the stream network. Here, we apply the comprehensive, distributed model Alpine3D to investigate the role of soil moisture in the predisposition of the Dischma catchment in Switzerland to high flows from rainfall and snowmelt. The recently updated soil module of the physics-based multilayer snow cover model SNOWPACK, which solves the surface energy and mass balance in Alpine3D, is verified against soil moisture measurements at seven sites and various depths inside and in close proximity to the Dischma catchment. Measurements and simulations in such terrain are difficult and consequently, soil moisture was simulated with varying degrees of success. Differences between simulated and measured soil moisture mainly arise from an overestimation of soil freezing and an absence of a groundwater description in the Alpine3D model. Both were found to have an influence in the soil moisture measurements. Using the Alpine3D simulation as the surface scheme for a spatially explicit hydrologic response model using a travel time distribution approach for interflow and baseflow, streamflow simulations were performed for the discharge from the catchment. The streamflow simulations provided a closer agreement with observed streamflow when driving the hydrologic response model with soil water fluxes at 30 cm depth in the Alpine3D model. Performance decreased when using the 2 cm soil water flux, thereby mostly ignoring soil processes. This illustrates that the role of soil moisture is important to take into account when understanding the relationship between both snowpack runoff and rainfall and catchment discharge in high alpine terrain. However, using the soil water flux at 60 cm depth to drive the hydrologic response model also decreased its performance, indicating that an optimal soil depth to include in surface simulations exists and

  12. Semiempirical model of soil water hysteresis

    Science.gov (United States)

    Nimmo, J.R.

    1992-01-01

    In order to represent hysteretic soil water retention curves accurately using as few measurements as possible, a new semiempirical model has been developed. It has two postulates related to physical characteristics of the medium, and two parameters, each with a definite physical interpretation, whose values are determined empirically for a given porous medium. Tests of the model show that it provides high-quality optimized fits to measured water content vs. matric pressure wetting curves for a wide variety of media. A practical use of this model is to provide a complete simulated main wetting curve for a medium where only a main drying curve and two points on the wetting curve have been measured. -from Author

  13. SOIL QUALITY ASSESSMENT USING FUZZY MODELING

    Science.gov (United States)

    Maintaining soil productivity is essential if agriculture production systems are to be sustainable, thus soil quality is an essential issue. However, there is a paucity of tools for measurement for the purpose of understanding changes in soil quality. Here the possibility of using fuzzy modeling t...

  14. Residue cover effects on soil erosion and the infiltration in black soil under simulated rainfall experiments

    Science.gov (United States)

    Xin, Yan; Xie, Yun; Liu, Yuxin; Liu, Hongyuan; Ren, Xiaoyu

    2016-12-01

    Residue cover is widely used in the Northeastern China Black Soil Region for soil erosion control due to the large annual production of crop residues. Quantitative evaluations of the residue cover effects on preventing soil loss and on the cumulative infiltration amount are thus desirable. Herein, rainfall simulation experiments were conducted using simulators and soil flumes to study the effects of residue cover on soil erosion and infiltration under various rainfall events. Laboratory experiments were designed utilizing five levels of residue cover (bare, 15%, 35%, 55% and 75%), four rainfall intensities (30 mm/h, 60 mm/h, 90 mm/h and 120 mm/h), two soil moistures (dry and wet run) and a fixed slope of 7%. The results indicated that residue cover strongly affects runoff, soil loss and infiltration. Equations for predicting the soil loss ratio and infiltration ratio (the ratio of residue cover soil to bare soil) are herein proposed based on nonlinear curve regression. An empirical approach presented as the infiltration ratios multiplied Philip's equation derived from bare soil was established for estimating the cumulative infiltration amounts under various residue covers. The equation was demonstrated to be suitable for infiltration prediction for black soil by the root mean square error value and 1:1 line method. In addition, the relationship between the residue cover and biomass of corn residues was provided in order to enable accurate measurement of the residue coverage. These derived equations could be used for soil erosion and infiltration prediction under no-till and residue cover management conditions in the black soil region.

  15. Numerical simulation of PAHs sorption/desorption on soil with the influence of Tween80

    Institute of Scientific and Technical Information of China (English)

    CHEN Jing; WANG Xue-jun; HU Jun-dong; XU Fu-liu; TAO Shu

    2006-01-01

    In this paper, the influences of inionic surfactant Tween80 on polycyclic aromatic hydrocarbons (PAHs) sorption/desorption on artificially contaminated soil were studied, and γ model was applied to simulate the influences. Results showed that, with the use of Tween 80, the sorption behaviors of PAHs on soil altered significantly. Adsorbed Tween 80 increased the sorption amount of PAHs while the dissolved Tween80 increased the apparent solubility of PAHs. These two processes exert influences on the sorption coefficient of PAHs in soil-water system, which can be depicted by apparent sorption coefficient. The partition coefficients (the soil/water partition coefficient of PAHs and surfactants obtained from sorption experiments) and statistical parameters used in the amended γ model were obtained in independent experiments. With these parameters, the γ model could provide a satisfactory independent prediction of PAHs release from soil to aqueous phase at two surfactant concentrations.

  16. Pile-soil interface shear model of super long bored pile and its FEM simulation%超长灌注桩桩-土界面剪切模型及其有限元模拟

    Institute of Scientific and Technical Information of China (English)

    王卫东; 李永辉; 吴江斌

    2012-01-01

    Super long bored piles are friction piles; thus establishing the appropriate pile-soil interface shear model is the key to reasonable and effective simulation analyze the load-movement characteristics of the pile. According to working trait of the super long bored pile shaft friction (r) with the increasing of pile-soil relative movement (w),ι-w relationships are divided into the hardening and the softening types. Furthermore, the mobilized patterns of the pile shaft friction are divided into three types: the full hardening mobilized pattern, full softening mobilized pattern and hardening-softening mixed mobilized pattern. Hardening type and softening type pile-soil interface shear models are established for super long bored pile. The pile-soil interface shear models are introduced into FEM software using subroutine FRIC of ABAQUS. Single pile simulation example shows that the interface shear models are implemented in ABAQUS successfully. FEM simulation of field test piles is carried out using the established pile-soil interface shear models. The simulation results are similar to the measured results. It is shown that the established pile-soil interface shear models and FEM simulation have the rationality and feasibility to calculate the load-movement behavior of super long bored pile.%由于超长灌注桩为摩擦型桩,建立合适的桩-土界面剪切模型将成为合理且有效地模拟分析其承载变形特性的关键.基于超长灌注桩桩侧摩阻力τ随桩-土相对位移w发挥性状,将τ-W关系定义为硬化和软化两种类型,进而将桩侧摩阻力发挥模式分为全硬化模式、全软化模式和混合模式.建立超长灌注桩桩-土界面剪切硬化模型和软化模型,运用ABAQUS二次开发子程序FRIC将建立的剪切模型嵌入有限元,实现剪切模型的有限元模拟,单桩算例表明,剪切模型在ABAQUS中实现是成功的.运用建立的桩-土界面剪切模型对现场试验试桩进行有限元模拟,

  17. Establishing an International Soil Modelling Consortium

    Science.gov (United States)

    Vereecken, Harry; Schnepf, Andrea; Vanderborght, Jan

    2015-04-01

    Soil is one of the most critical life-supporting compartments of the Biosphere. Soil provides numerous ecosystem services such as a habitat for biodiversity, water and nutrients, as well as producing food, feed, fiber and energy. To feed the rapidly growing world population in 2050, agricultural food production must be doubled using the same land resources footprint. At the same time, soil resources are threatened due to improper management and climate change. Soil is not only essential for establishing a sustainable bio-economy, but also plays a key role also in a broad range of societal challenges including 1) climate change mitigation and adaptation, 2) land use change 3) water resource protection, 4) biotechnology for human health, 5) biodiversity and ecological sustainability, and 6) combating desertification. Soils regulate and support water, mass and energy fluxes between the land surface, the vegetation, the atmosphere and the deep subsurface and control storage and release of organic matter affecting climate regulation and biogeochemical cycles. Despite the many important functions of soil, many fundamental knowledge gaps remain, regarding the role of soil biota and biodiversity on ecosystem services, the structure and dynamics of soil communities, the interplay between hydrologic and biotic processes, the quantification of soil biogeochemical processes and soil structural processes, the resilience and recovery of soils from stress, as well as the prediction of soil development and the evolution of soils in the landscape, to name a few. Soil models have long played an important role in quantifying and predicting soil processes and related ecosystem services. However, a new generation of soil models based on a whole systems approach comprising all physical, mechanical, chemical and biological processes is now required to address these critical knowledge gaps and thus contribute to the preservation of ecosystem services, improve our understanding of climate

  18. Irrigation Optimization by Modeling of Plant-Soil Interaction

    OpenAIRE

    2011-01-01

    Irrigation scheduling is an important issue for crop management, in a general context of limited water resources and increasing concern about agricultural productivity. Methods to optimize crop irrigation should take into account the impact of water stress on plant growth and the water balance in the plant-soil-atmosphere system. In this article, we propose a methodology to solve the irrigation scheduling problem. For this purpose, a plant-soil interaction model is used to simulate the struct...

  19. Wake modeling and simulation

    DEFF Research Database (Denmark)

    Larsen, Gunner Chr.; Madsen Aagaard, Helge; Larsen, Torben J.;

    , have the potential to include also mutual wake interaction phenomenons. The basic conjecture behind the dynamic wake meandering (DWM) model is that wake transportation in the atmospheric boundary layer is driven by the large scale lateral- and vertical turbulence components. Based on this conjecture...... and trailed vorticity, has been approached by a simple semi-empirical model essentially based on an eddy viscosity philosophy. Contrary to previous attempts to model wake loading, the DWM approach opens for a unifying description in the sense that turbine power- and load aspects can be treated simultaneously...... methodology has been implemented in the aeroelastic code HAWC2, and example simulations of wake situations, from the small Tjæreborg wind farm, have been performed showing satisfactory agreement between predictions and measurements...

  20. A discrete element model for soil-sweep interaction in three different soils

    DEFF Research Database (Denmark)

    Chen, Y; Munkholm, Lars Juhl; Nyord, Tavs

    2013-01-01

    Soil–tool interactions are at the centre of many agricultural field operations, including slurry injection. Understanding of soil–tool interaction behaviours (soil cutting forces and soil disturbance) is important for designing high performance injection tools. A discrete element model was develo....... The calibrated model was validated using the soil disturbance characteristics measured in those three soils. The simulations agreed well with the measurements with relative errors below 10% in most cases....... were measured. The measured draught and vertical forces were used in calibrations of the most sensitive model parameter, particle stiffness. The calibrated particle stiffness was 0.75 × 103 N m−1 for the coarse sand, 2.75 × 103 N m−1 for the loamy sand, and 6 × 103 N m−1 for the sandy loam...

  1. Nonlinear soil-structure interaction calculations simulating the SIMQUAKE experiment using STEALTH 2D

    Science.gov (United States)

    Tang, H. T.; Hofmann, R.; Yee, G.; Vaughan, D. K.

    1980-01-01

    Transient, nonlinear soil-structure interaction simulations of an Electric Power Research Institute, SIMQUAKE experiment were performed using the large strain, time domain STEALTH 2D code and a cyclic, kinematically hardening cap soil model. Results from the STEALTH simulations were compared to identical simulations performed with the TRANAL code and indicate relatively good agreement between all the STEALTH and TRANAL calculations. The differences that are seen can probably be attributed to: (1) large (STEALTH) vs. small (TRANAL) strain formulation and/or (2) grid discretization differences.

  2. Modelling and simulations of controlled release fertilizer

    Science.gov (United States)

    Irfan, Sayed Ameenuddin; Razali, Radzuan; Shaari, Ku Zilati Ku; Mansor, Nurlidia

    2016-11-01

    The recent advancement in controlled release fertilizer has provided an alternative solution to the conventional urea, controlled release fertilizer has a good plant nutrient uptake they are environment friendly. To have an optimum plant intake of nutrients from controlled release fertilizer it is very essential to understand the release characteristics. A mathematical model is developed to predict the release characteristics from polymer coated granule. Numerical simulations are performed by varying the parameters radius of granule, soil water content and soil porosity to study their effect on fertilizer release. Understanding these parameters helps in the better design and improve the efficiency of controlled release fertilizer.

  3. Transport of Pathogen Surrogates in Soil Treatment Units: Numerical Modeling

    Directory of Open Access Journals (Sweden)

    Ivan Morales

    2014-04-01

    Full Text Available Segmented mesocosms (n = 3 packed with sand, sandy loam or clay loam soil were used to determine the effect of soil texture and depth on transport of two septic tank effluent (STE-borne microbial pathogen surrogates—green fluorescent protein-labeled E. coli (GFPE and MS-2 coliphage—in soil treatment units. HYDRUS 2D/3D software was used to model the transport of these microbes from the infiltrative surface. Mesocosms were spiked with GFPE and MS-2 coliphage at 105 cfu/mL STE and 105–106 pfu/mL STE, respectively. In all soils, removal rates were >99.99% at 25 cm. The transport simulation compared (1 optimization; and (2 trial-and-error modeling approaches. Only slight differences between the transport parameters were observed between these approaches. Treating both the die-off rates and attachment/detachment rates as variables resulted in an overall better model fit, particularly for the tailing phase of the experiments. Independent of the fitting procedure, attachment rates computed by the model were higher in sandy and sandy loam soils than clay, which was attributed to unsaturated flow conditions at lower water content in the coarser-textured soils. Early breakthrough of the bacteria and virus indicated the presence of preferential flow in the system in the structured clay loam soil, resulting in faster movement of water and microbes through the soil relative to a conservative tracer (bromide.

  4. Soils apart from equilibrium – consequences for soil carbon balance modelling

    Directory of Open Access Journals (Sweden)

    T. Wutzler

    2006-10-01

    Full Text Available Many projections of the soil carbon sink or source are based on kinetically defined carbon pool models. Parameters of these models are often determined in a way that the steady state of the model matches observed carbon stocks. The underlying simplifying assumption is that observed carbon stocks are near equilibrium. This assumption is challenged by observations of very old soils that do still accumulate carbon. In this modelling study we explored the consequences of the case where soils are apart from equilibrium. Calculation of equilibrium states of soils that are currently accumulating small amounts of carbon were performed using the Yasso model. It was found that already very small current accumulation rates cause big changes in theoretical equilibrium stocks, which can virtually approach infinity. We conclude that soils that have been disturbed several centuries ago are not in equilibrium but in a transient state because of the slowly ongoing accumulation of the slowest pool. A first consequence is that model calibrations to current carbon stocks that assume equilibrium state, overestimate the decay rate of the slowest pool. A second consequence is that spin-up runs (simulations until equilibrium overestimate stocks of recently disturbed sites. In order to account for these consequences, we propose a transient correction. This correction prescribes a lower decay rate of the slowest pool and accounts for disturbances in the past by decreasing the spin-up-run predicted stocks to match an independent estimate of current soil carbon stocks. Application of this transient correction at a Central European beech forest site with a typical disturbance history resulted in an additional carbon fixation of 5.7±1.5 tC/ha within 100 years. Carbon storage capacity of forest soils is potentially much higher than currently assumed. Simulations that do not adequately account for the transient state of soil carbon stocks neglect a substantial amount of

  5. Soil fauna: key to new carbon models

    Science.gov (United States)

    Filser, Juliane; Faber, Jack H.; Tiunov, Alexei V.; Brussaard, Lijbert; Frouz, Jan; De Deyn, Gerlinde; Uvarov, Alexei V.; Berg, Matty P.; Lavelle, Patrick; Loreau, Michel; Wall, Diana H.; Querner, Pascal; Eijsackers, Herman; José Jiménez, Juan

    2016-11-01

    Soil organic matter (SOM) is key to maintaining soil fertility, mitigating climate change, combatting land degradation, and conserving above- and below-ground biodiversity and associated soil processes and ecosystem services. In order to derive management options for maintaining these essential services provided by soils, policy makers depend on robust, predictive models identifying key drivers of SOM dynamics. Existing SOM models and suggested guidelines for future SOM modelling are defined mostly in terms of plant residue quality and input and microbial decomposition, overlooking the significant regulation provided by soil fauna. The fauna controls almost any aspect of organic matter turnover, foremost by regulating the activity and functional composition of soil microorganisms and their physical-chemical connectivity with soil organic matter. We demonstrate a very strong impact of soil animals on carbon turnover, increasing or decreasing it by several dozen percent, sometimes even turning C sinks into C sources or vice versa. This is demonstrated not only for earthworms and other larger invertebrates but also for smaller fauna such as Collembola. We suggest that inclusion of soil animal activities (plant residue consumption and bioturbation altering the formation, depth, hydraulic properties and physical heterogeneity of soils) can fundamentally affect the predictive outcome of SOM models. Understanding direct and indirect impacts of soil fauna on nutrient availability, carbon sequestration, greenhouse gas emissions and plant growth is key to the understanding of SOM dynamics in the context of global carbon cycling models. We argue that explicit consideration of soil fauna is essential to make realistic modelling predictions on SOM dynamics and to detect expected non-linear responses of SOM dynamics to global change. We present a decision framework, to be further developed through the activities of KEYSOM, a European COST Action, for when mechanistic SOM models

  6. Hygrothermal Simulation of Foundations: Part 1 - Soil Material Properties

    Energy Technology Data Exchange (ETDEWEB)

    Kehrer, Manfred [ORNL; Pallin, Simon B [ORNL

    2012-10-01

    The hygrothermal performance of soils coupled to buildings is a complicated process. A computational approach for heat transfer through the ground has been well defined (EN ISO 13370:2007, 2007), and simplified methods have been developed (Staszczuk, Radon, and Holm 2010). However, these approaches generally ignore the transfer of soil moisture, which is not negligible (Janssen, Carmeliet, and Hens 2004). This study is divided into several parts. The intention of the first part is to gather, comprehend and adapt soil properties from Soil Science. The obtained information must be applicable to related tasks in Building Science and validated with hygrothermal calculation tools. Future parts of this study will focus on the validation aspect of the soil properties to be implemented. Basic changes in the software code may be requested at this time. Different types of basement construction will be created with a hygrothermal calculation tool, WUFI. Simulations from WUFI will be compared with existing or ongoing measurements. The intentions of the first part of this study have been fulfilled. The soil properties of interest in Building Science have been defined for 12 different soil textures. These properties will serve as input parameters when performing hygrothermal calculations of building constructions coupled to soil materials. The reliability of the soil parameters will be further evaluated with measurements in Part 2.

  7. Delay modeling in logic simulation

    Energy Technology Data Exchange (ETDEWEB)

    Acken, J. M.; Goldstein, L. H.

    1980-01-01

    As digital integrated circuit size and complexity increases, the need for accurate and efficient computer simulation increases. Logic simulators such as SALOGS (SAndia LOGic Simulator), which utilize transition states in addition to the normal stable states, provide more accurate analysis than is possible with traditional logic simulators. Furthermore, the computational complexity of this analysis is far lower than that of circuit simulation such as SPICE. An eight-value logic simulation environment allows the use of accurate delay models that incorporate both element response and transition times. Thus, timing simulation with an accuracy approaching that of circuit simulation can be accomplished with an efficiency comparable to that of logic simulation. 4 figures.

  8. Geopolymers from lunar and Martian soil simulants

    Science.gov (United States)

    Alexiadis, Alessio; Alberini, Federico; Meyer, Marit E.

    2017-01-01

    This work discusses the geopolymerization of lunar dust simulant JSC LUNAR-1A and Martian dust simulant JSC MARS-1A. The geopolymerization of JSC LUNAR-1A occurs easily and produces a hard, rock-like, material. The geopolymerization of JSC MARS-1A requires milling to reduce the particle size. Tests were carried out to measure, for both JSC LUNAR-1A and JSC MARS-1A geopolymers, the maximum compressive and flexural strengths. In the case of the lunar simulant, these are higher than those of conventional cements. In the case of the Martian simulant, they are close to those of common building bricks.

  9. Grassland Evolution Under Soil Degradation: Numerical Simulation and Test

    Institute of Scientific and Technical Information of China (English)

    QI Xiang-Zhen; LIN Zhen-Shan

    2005-01-01

    Both theoretical and field observations were examined to study the close relationship between soil degeneration and the evolution of grassland vegetation. A general n-species model of equal competition under different degrees of soil degradation was applied to field data in order to probe the dynamic processes and mechanisms of vegetation evolution due to the effects of the soil's ecological deterioration on grassland vegetation. Comparisons were made between the theoretical results and the practical surveys with satisfactory results.

  10. Phytoremediation and its models for organic contaminated soils

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Soil pollution has been attracting considerable public attentions over the last decades. Sorts of traditional physiochemical methods have been used to remove the organic pollutants from soils. However, the enormous costs and low efficiencies associated with these remediation technologies limit their availabilities. Phytoremediation is an emerging technology that uses plants to cleanup pollutants in soils. As overwhelmingly positive results have been shown, phytoremediation is a most economical and effective remediation technique for organic contaminated soils. In this paper phytoremediation and its models for organic contaminated soils is overviewed. The mechanisms of phytoremediation mainly include the direct plant uptake of organic pollutants, degradation by plant-derived degradative enzymes, and stimulated biodegradation in plant rhizosphere. Phytoremediation efficiency is tightly related to physicochemical properties of organic pollutants, environmental characteristics, and plant types. It is no doubt that soil amendments such as surfactants change the solubilities and availabilities of organic pollutants in soils. However, little information is available about effects of soil amendments on phytoremediation efficiencies. Phytoremediation models have been developed to simulate and predict the environmental behavior of organic pollutants, and progress of models is illustrated. In many ways phytoremediation is still in its initial stage, and recommendations for the future research on phytoremediation are presented.

  11. Deep Soil: Quantifying and Modeling Subsurface Carbon

    Science.gov (United States)

    James, J. N.; Devine, W.; Harrison, R. B.

    2014-12-01

    Some soil carbon datasets that are spatially rich, such as the USDA Forest Service Inventory and Analysis National Program dataset, sample soil to only 20 cm (8 inches), despite evidence that substantial stores of soil C can be found deeper in the soil profile. The maximum extent of tree rooting is typically many meters deep and provides: direct exchange with the soil solution; redistribution of water from deep horizons toward the surface during times of drought; resources for active microbial communities in deep soil around root channels; and direct carbon inputs through exudates and root turnover. This study examined soil carbon to a depth of 2.5 meters across 22 soils in Pacific Northwest Douglas-fir forests. Excavations at 20 additional sites took place in summer 2014, greatly expanding the spatial coverage and extent of the data set. Forest floor and mineral soil bulk density samples were collected at depths of 0.1, 0.5, 1.0, 1.5, 2.0 and 2.5 meters. Pool estimates from systematic sampling depths shallower than 1.5 m yielded significantly smaller estimates than the total soil stock to 2.5 meters (P<0.01). On average, only 5% of soil C was found in the litter layer, 35% was found below 0.5 meter, and 21% was found below 1.0 meter. Due to the difficulty of excavating and measuring deep soil carbon, a series of nonlinear mixed effect models were fit to the data to predict deep soil carbon stocks given sampling to 1.0 meter. A model using an inverse polynomial function predicted soil carbon to 2.5 meters with -5.6% mean error. The largest errors occurred in Andisols with non-crystalline minerals, which can adsorb large quantities of carbon on mineral surfaces and preserve it from decomposition. An accurate spatial dataset of soil depth to bedrock would be extremely useful to constrain models of the vertical distribution of soil carbon. Efforts to represent carbon in spatial models would benefit from considering the vertical distribution of carbon in soil. Sampling

  12. Simulation of soil water dynamics in a Caragana intermedia woodland in Huangfuchuan watershed

    Institute of Scientific and Technical Information of China (English)

    JIA Haikun; LIU Yinghui; XU Xia; WANG Kun; GAO Qiong

    2007-01-01

    As vegetation coverage increases,soil water content can decrease due to water uptake and evapotranspiration.At a very high level of plant density,poor growth and even mortality can occur due to the decrease of soil water content.Hence,a better understanding of the relationship between soil water content and the density of plants is important to design effective restoration projects.To study these relationships,we developed a soil water dynamic simulation model of a Caragana intermedia woodland under different slope gradient and slope aspect conditions in the Huangfuchuan watershed on the basis of the previous studies and field experiments.The model took into account the major processes that address the relationships of plants and the environment,including soil characteristics,precipitation,infiltration,vegetation transpiration,and soil evaporation.Daily changes in soil water content,transpiration,and evaporation of the Caragana intermedia woodland with different vegetation coverage,slope gradient,and slope aspect were simulated from 1971 to 2000.Based on the model simulations,we determined the functional relationships among soil water content,plant coverage and slope as well as the optimal plant density on flat slopes.We also determined the effects of slope gradient and slope aspect on soil water content.When slope gradient was less than l0~,the optimal plant density was sensitive to slope gradient.In the slope range from 10° to 30°,plant density was not sensitive to slope gradient.Therefore,it is important to consider planting densities on the hillsides with slope gradients less than 10° for reconstructing vegetation.

  13. Dynamics of soil organic matter in primary and secondary forest succession on sandy soils in The Netherlands: An application of the ROMUL model

    NARCIS (Netherlands)

    Nadporozhskaya, M.A.; Mohren, G.M.J.; Chertov, O.G.; Komarov, A.S.; Mikhailov, A.V.

    2006-01-01

    We applied the simulation model ROMUL of soil organic matter dynamics in order to analyse and predict forest soil organic matter (SOM) changes following stand growth and also to identify gaps of data and modelling problems. SOM build-up was analysed (a) from bare sand to forest soil during a primary

  14. Dynamics of soil organic matter in primary and secondary forest succession on sandy soils in The Netherlands: An application of the ROMUL model

    NARCIS (Netherlands)

    Nadporozhskaya, M.A.; Mohren, G.M.J.; Chertov, O.G.; Komarov, A.S.; Mikhailov, A.V.

    2006-01-01

    We applied the simulation model ROMUL of soil organic matter dynamics in order to analyse and predict forest soil organic matter (SOM) changes following stand growth and also to identify gaps of data and modelling problems. SOM build-up was analysed (a) from bare sand to forest soil during a primary

  15. Modelo para simulação da dinâmica de nitrato em colunas verticais de solo não saturado A simulation model of nitrate displacement in vertical columns in a non-saturated soil

    Directory of Open Access Journals (Sweden)

    Jarbas H. de Miranda

    2002-01-01

    Full Text Available A agricultura intensiva está sempre em busca de incrementos de produtividade mas, em contrapartida, pouca atenção é dedicada a possíveis impactos ambientais. Portanto, o entendimento sobre processos de transporte de solutos no solo auxilia na redução da sua lixiviação para as camadas subsuperficiais. Neste sentido, objetivou-se, com o presente trabalho, desenvolver e avaliar um modelo computacional aplicado para simulação da dinâmica de solutos no solo por meio de soluções numéricas de equações diferenciais que descrevam esse transporte. Pelos resultados obtidos, o modelo apresentou bom ajuste das concentrações de nitrato e dos perfis de umidade, simulados com relação aos medidos em condições de laboratório em coluna vertical de solo não saturado.Intensive agriculture always aims at increased productivity, with limited or no attention dedicated to possible impacts on the environment. Therefore, the understanding of processes of solute transport in the soil contributes to reduction of leaching to the deep layers. In this connection, the present study had the objective of developing and evaluating a computational model for solute displacement simulation in the soil based on numerical solutions of differential equations describing this displacement. From the results obtained, the model presented a good agreement of nitrate concentrations as well as soil moisture profile when compared with the results obtained on a vertical column of non-saturated soil under laboratory conditions.

  16. Improving Simulated Soil Moisture Fields Through Assimilation of AMSR-E Soil Moisture Retrievals with an Ensemble Kalman Filter and a Mass Conservation Constraint

    Science.gov (United States)

    Li, Bailing; Toll, David; Zhan, Xiwu; Cosgrove, Brian

    2011-01-01

    Model simulated soil moisture fields are often biased due to errors in input parameters and deficiencies in model physics. Satellite derived soil moisture estimates, if retrieved appropriately, represent the spatial mean of soil moisture in a footprint area, and can be used to reduce model bias (at locations near the surface) through data assimilation techniques. While assimilating the retrievals can reduce model bias, it can also destroy the mass balance enforced by the model governing equation because water is removed from or added to the soil by the assimilation algorithm. In addition, studies have shown that assimilation of surface observations can adversely impact soil moisture estimates in the lower soil layers due to imperfect model physics, even though the bias near the surface is decreased. In this study, an ensemble Kalman filter (EnKF) with a mass conservation updating scheme was developed to assimilate the actual value of Advanced Microwave Scanning Radiometer (AMSR-E) soil moisture retrievals to improve the mean of simulated soil moisture fields by the Noah land surface model. Assimilation results using the conventional and the mass conservation updating scheme in the Little Washita watershed of Oklahoma showed that, while both updating schemes reduced the bias in the shallow root zone, the mass conservation scheme provided better estimates in the deeper profile. The mass conservation scheme also yielded physically consistent estimates of fluxes and maintained the water budget. Impacts of model physics on the assimilation results are discussed.

  17. Preparations, models, and simulations.

    Science.gov (United States)

    Rheinberger, Hans-Jörg

    2015-01-01

    This paper proposes an outline for a typology of the different forms that scientific objects can take in the life sciences. The first section discusses preparations (or specimens)--a form of scientific object that accompanied the development of modern biology in different guises from the seventeenth century to the present: as anatomical-morphological specimens, as microscopic cuts, and as biochemical preparations. In the second section, the characteristics of models in biology are discussed. They became prominent from the end of the nineteenth century onwards. Some remarks on the role of simulations--characterising the life sciences of the turn from the twentieth to the twenty-first century--conclude the paper.

  18. [Simulation of soil water dynamics in triploid Populus tomentosa root zone under subsurface drip irrigation].

    Science.gov (United States)

    Xi, Ben-Ye; Jia, Li-Ming; Wang, Ye; Li, Guang-De

    2011-01-01

    Based on the observed data of triploid Populus tomentosa root distribution, a one-dimensional root water uptake model was proposed. Taking the root water uptake into account, the soil water dynamics in triploid P. tomentosa root zone under subsurface drip irrigation was simulated by using HYDRUS model, and the results were validated with field experiment. Besides, the HYDRUS model was used to study the effects of various irrigation technique parameters on soil wetting patterns. The RMAE for the simulated soil water content by the end of irrigation and approximately 24 h later was 7.8% and 6.0%, and the RMSE was 0.036 and 0.026 cm3 x cm(-3), respectively, illustrating that the HYDRUS model performed well in simulating the short-term soil water dynamics in triploid P. tomentosa root zone under drip irrigation, and the root water uptake model was reasonable. Comparing with 2 and 4 L x h(-1) of drip discharge and continuous irrigation, both the 1 L x h(-1) of drip discharge and the pulsed irrigation with water applied intermittently in 30 min periods could increase the volume of wetted soil and reduce deep percolation. It was concluded that the combination of 1 L x h(-1) of drip discharge and pulsed irrigation should be the first choice when applying drip irrigation to triploid P. tomentosa root zone at the experiment site.

  19. Retrieval of Surface and Subsurface Moisture of Bare Soil Using Simulated Annealing

    Science.gov (United States)

    Tabatabaeenejad, A.; Moghaddam, M.

    2009-12-01

    Soil moisture is of fundamental importance to many hydrological and biological processes. Soil moisture information is vital to understanding the cycling of water, energy, and carbon in the Earth system. Knowledge of soil moisture is critical to agencies concerned with weather and climate, runoff potential and flood control, soil erosion, reservoir management, water quality, agricultural productivity, drought monitoring, and human health. The need to monitor the soil moisture on a global scale has motivated missions such as Soil Moisture Active and Passive (SMAP) [1]. Rough surface scattering models and remote sensing retrieval algorithms are essential in study of the soil moisture, because soil can be represented as a rough surface structure. Effects of soil moisture on the backscattered field have been studied since the 1960s, but soil moisture estimation remains a challenging problem and there is still a need for more accurate and more efficient inversion algorithms. It has been shown that the simulated annealing method is a powerful tool for inversion of the model parameters of rough surface structures [2]. The sensitivity of this method to measurement noise has also been investigated assuming a two-layer structure characterized by the layers dielectric constants, layer thickness, and statistical properties of the rough interfaces [2]. However, since the moisture profile varies with depth, it is sometimes necessary to model the rough surface as a layered structure with a rough interface on top and a stratified structure below where each layer is assumed to have a constant volumetric moisture content. In this work, we discretize the soil structure into several layers of constant moisture content to examine the effect of subsurface profile on the backscattering coefficient. We will show that while the moisture profile could vary in deeper layers, these layers do not affect the scattered electromagnetic field significantly. Therefore, we can use just a few layers

  20. Simulation of Effect of Irrigation with Reclaimed Water on Soil Water-Salt Movement by ENVIRO-GRO Model%模型模拟再生水灌溉对土壤水盐运动的影响

    Institute of Scientific and Technical Information of China (English)

    吕斯丹; 陈卫平; 王美娥

    2012-01-01

    As the conflict between water supply and demand,wastewater reuse has become an important measure,which can relieve the water shortage in Beijing.In order to promote safe irrigation with reclaimed water and prevent soil salinisation,the dynamic transport of salts in urban soils of Beijing,a city of water shortage,under irrigation of reclaimed water was simulated by ENVIRO-GRO model in this research.The accumulation trends of soil salinity were predicted.Simultaneously,it investigated the effects of different irrigation practices on soil water-salt movement and salt accumulation.Results indicated that annual averages of soil salinity(ECe) increased 29.5%,97.2%,197.8% respectively,with the higher irrigation,normal irrigation,and low irrigation under equilibrium conditions.Irrigation frequency had little effect on soil salt-water movement,and soil salt accumulation was in a downward trend with low frequency of irrigation.Under equilibrium conditions,annual averages of ECe increased 23.7%,97.2%,208.5% respectively,with irrigation water salinity(ECw) 0.6,1.2,2.4 dS·m-1.Soil salinity increased slightly with ECw=0.6 dS·m-1,while soil salinization did not appear.Totally,the growth of Blue grass was not influenced by soil salinity under equilibrium conditions with the regular irrigation in Beijing,but mild soil salinization appeared.%随着水资源供需矛盾日益尖锐,污水再生利用成为了缓解北京水资源紧缺的重要举措.为推动北京再生水安全灌溉,本研究运用ENVIRO-GRO模型模拟缺水城市北京再生水灌溉土壤水盐运动规律,并对土壤盐分累积进行预测,探讨了不同灌溉措施对土壤水盐运动规律和盐分累积的影响.结果表明,高水量、常规、低水量灌溉,平衡时土壤含盐量(ECe)年均值分别增加了29.5%、97.2%、197.8%;灌溉频率对土壤水盐运动规律影响不大,但低频灌溉下土壤中盐分的累积有减少的趋势;灌溉水含盐量(ECw)为0.6、1.2、2.4 d

  1. Numerical Simulation of Heat Transfer Characteristics of Horizontal Ground Heat Exchanger in Frozen Soil Layer

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A simplified numerical model of heat transfer characteristics of horizontal ground heat exchanger (GHE) in the frozen soil layer is presented and the steady-state distribution of temperature field is simulated. Numerical results show that the frozen depth mainly depends on the soil's moisture content and ambient temperature. The heat transfer loss of horizontal GHE tends to grow with the increase of the soil's moisture content and the decrease of ambient temperature. Backfilled materials with optimal thermal conductivity can reduce the thermal loss effectively in the frozen soil. The applicability of the Chinese national standard "Technical Code for Ground Source Heat Pump (GB 50366-2005)" is verified. For a ground source heat pump project, the feasible layout of horizontal GHE should be determined based on the integration of the soil's structure, backfilled materials,weather data, and economic analysis.

  2. Constraining Parameter Uncertainty in Simulations of Water and Heat Dynamics in Seasonally Frozen Soil Using Limited Observed Data

    Directory of Open Access Journals (Sweden)

    Mousong Wu

    2016-02-01

    Full Text Available Water and energy processes in frozen soils are important for better understanding hydrologic processes and water resources management in cold regions. To investigate the water and energy balance in seasonally frozen soils, CoupModel combined with the generalized likelihood uncertainty estimation (GLUE method was used. Simulation work on water and heat processes in frozen soil in northern China during the 2012/2013 winter was conducted. Ensemble simulations through the Monte Carlo sampling method were generated for uncertainty analysis. Behavioral simulations were selected based on combinations of multiple model performance index criteria with respect to simulated soil water and temperature at four depths (5 cm, 15 cm, 25 cm, and 35 cm. Posterior distributions for parameters related to soil hydraulic, radiation processes, and heat transport indicated that uncertainties in both input and model structures could influence model performance in modeling water and heat processes in seasonally frozen soils. Seasonal courses in water and energy partitioning were obvious during the winter. Within the day-cycle, soil evaporation/condensation and energy distributions were well captured and clarified as an important phenomenon in the dynamics of the energy balance system. The combination of the CoupModel simulations with the uncertainty-based calibration method provides a way of understanding the seasonal courses of hydrology and energy processes in cold regions with limited data. Additional measurements may be used to further reduce the uncertainty of regulating factors during the different stages of freezing–thawing.

  3. Soil-vegetation-atmosphere transfer modeling

    Energy Technology Data Exchange (ETDEWEB)

    Ikonen, J.P.; Sucksdorff, Y. [Finnish Environment Agency, Helsinki (Finland)

    1996-12-31

    In this study the soil/vegetation/atmosphere-model based on the formulation of Deardorff was refined to hour basis and applied to a field in Vihti. The effect of model parameters on model results (energy fluxes, temperatures) was also studied as well as the effect of atmospheric conditions. The estimation of atmospheric conditions on the soil-vegetation system as well as an estimation of the effect of vegetation parameters on the atmospheric climate was estimated. Areal surface fluxes, temperatures and moistures were also modelled for some river basins in southern Finland. Land-use and soil parameterisation was developed to include properties and yearly variation of all vegetation and soil types. One classification was selected to describe the hydrothermal properties of the soils. Evapotranspiration was verified against the water balance method

  4. Stratified drought analysis using a stochastic ensemble of simulated and in-situ soil moisture observations

    Science.gov (United States)

    Sehgal, Vinit; Sridhar, Venkataramana; Tyagi, Aditya

    2017-02-01

    This study proposes a multi-wavelet Bayesian ensemble of two Land Surface Models (LSMs) using in-situ observations for accurate estimation of soil moisture for Contiguous United States (CONUS). In the absence of a continuous, accurate in-situ soil moisture dataset at high spatial resolution, an ensemble of Noah and Mosaic LSMs is derived by performing a Bayesian Model Averaging (BMA) of several wavelet-based multi-resolution regression models (WR) of the simulated soil moisture from the LSMs and in-situ volumetric soil moisture dataset obtained from the U.S. Climate Reference Network (USCRN) field stations. This provides a proxy to the in-situ soil moisture dataset at 1/8th degree spatial resolution called Hybrid Soil Moisture (HSM) for three soil layers (1-10 cm, 10-40 cm and 40-100 cm) for the CONUS. The derived HSM is used further to study the layer-wise response of soil moisture to drought, highlighting the necessity of the ensemble approach and soil profile perspective for drought analysis. A correlation analysis between HSM, the long-term (PDSI, PHDI, SPI-9, SPI-12 and SPI-24) and the short-term (Palmer Z index, SPI-1 and SPI-6) drought indices is carried out for the nine climate regions of the U.S. indicating a higher sensitivity of soil moisture to drought conditions for the Southern U.S. Furthermore, a layer-wise soil moisture percentile approach is proposed and applied for drought reconstruction in CONUS with a focus on the Southern U.S. for the year 2011.

  5. Statistical Modelling of the Soil Dielectric Constant

    Science.gov (United States)

    Usowicz, Boguslaw; Marczewski, Wojciech; Bogdan Usowicz, Jerzy; Lipiec, Jerzy

    2010-05-01

    The dielectric constant of soil is the physical property being very sensitive on water content. It funds several electrical measurement techniques for determining the water content by means of direct (TDR, FDR, and others related to effects of electrical conductance and/or capacitance) and indirect RS (Remote Sensing) methods. The work is devoted to a particular statistical manner of modelling the dielectric constant as the property accounting a wide range of specific soil composition, porosity, and mass density, within the unsaturated water content. Usually, similar models are determined for few particular soil types, and changing the soil type one needs switching the model on another type or to adjust it by parametrization of soil compounds. Therefore, it is difficult comparing and referring results between models. The presented model was developed for a generic representation of soil being a hypothetical mixture of spheres, each representing a soil fraction, in its proper phase state. The model generates a serial-parallel mesh of conductive and capacitive paths, which is analysed for a total conductive or capacitive property. The model was firstly developed to determine the thermal conductivity property, and now it is extended on the dielectric constant by analysing the capacitive mesh. The analysis is provided by statistical means obeying physical laws related to the serial-parallel branching of the representative electrical mesh. Physical relevance of the analysis is established electrically, but the definition of the electrical mesh is controlled statistically by parametrization of compound fractions, by determining the number of representative spheres per unitary volume per fraction, and by determining the number of fractions. That way the model is capable covering properties of nearly all possible soil types, all phase states within recognition of the Lorenz and Knudsen conditions. In effect the model allows on generating a hypothetical representative of

  6. Modeling the influence of organic acids on soil weathering

    Science.gov (United States)

    Lawrence, Corey; Harden, Jennifer; Maher, Kate

    2014-08-01

    Biological inputs and organic matter cycling have long been regarded as important factors in the physical and chemical development of soils. In particular, the extent to which low molecular weight organic acids, such as oxalate, influence geochemical reactions has been widely studied. Although the effects of organic acids are diverse, there is strong evidence that organic acids accelerate the dissolution of some minerals. However, the influence of organic acids at the field-scale and over the timescales of soil development has not been evaluated in detail. In this study, a reactive-transport model of soil chemical weathering and pedogenic development was used to quantify the extent to which organic acid cycling controls mineral dissolution rates and long-term patterns of chemical weathering. Specifically, oxalic acid was added to simulations of soil development to investigate a well-studied chronosequence of soils near Santa Cruz, CA. The model formulation includes organic acid input, transport, decomposition, organic-metal aqueous complexation and mineral surface complexation in various combinations. Results suggest that although organic acid reactions accelerate mineral dissolution rates near the soil surface, the net response is an overall decrease in chemical weathering. Model results demonstrate the importance of organic acid input concentrations, fluid flow, decomposition and secondary mineral precipitation rates on the evolution of mineral weathering fronts. In particular, model soil profile evolution is sensitive to kaolinite precipitation and oxalate decomposition rates. The soil profile-scale modeling presented here provides insights into the influence of organic carbon cycling on soil weathering and pedogenesis and supports the need for further field-scale measurements of the flux and speciation of reactive organic compounds.

  7. Modeling the influence of organic acids on soil weathering

    Science.gov (United States)

    Lawrence, Corey R.; Harden, Jennifer W.; Maher, Kate

    2014-01-01

    Biological inputs and organic matter cycling have long been regarded as important factors in the physical and chemical development of soils. In particular, the extent to which low molecular weight organic acids, such as oxalate, influence geochemical reactions has been widely studied. Although the effects of organic acids are diverse, there is strong evidence that organic acids accelerate the dissolution of some minerals. However, the influence of organic acids at the field-scale and over the timescales of soil development has not been evaluated in detail. In this study, a reactive-transport model of soil chemical weathering and pedogenic development was used to quantify the extent to which organic acid cycling controls mineral dissolution rates and long-term patterns of chemical weathering. Specifically, oxalic acid was added to simulations of soil development to investigate a well-studied chronosequence of soils near Santa Cruz, CA. The model formulation includes organic acid input, transport, decomposition, organic-metal aqueous complexation and mineral surface complexation in various combinations. Results suggest that although organic acid reactions accelerate mineral dissolution rates near the soil surface, the net response is an overall decrease in chemical weathering. Model results demonstrate the importance of organic acid input concentrations, fluid flow, decomposition and secondary mineral precipitation rates on the evolution of mineral weathering fronts. In particular, model soil profile evolution is sensitive to kaolinite precipitation and oxalate decomposition rates. The soil profile-scale modeling presented here provides insights into the influence of organic carbon cycling on soil weathering and pedogenesis and supports the need for further field-scale measurements of the flux and speciation of reactive organic compounds.

  8. MICHIGAN SOIL VAPOR EXTRACTION REMEDIATION (MISER) MODEL: A COMPUTER PROGRAM TO MODEL SOIL VAPORT EXTRACTION AND BIOVENTING OF ORGANIC MATERIALS IN UNSATURATED GEOLOGICAL MATERIAL

    Science.gov (United States)

    This report describes the formulation, numerical development, and use of a multiphase, multicomponent, biodegradation model designed to simulate physical, chemical, and biological interactions occurring primarily in field scale soil vapor extraction (SVE) and bioventing (B...

  9. Snow modeling within a multi-layer soil-vegetation-atmosphere model

    Science.gov (United States)

    McGowan, L. E.; Paw U, K. T.; Pyles, D. R.

    2014-12-01

    Estimates of snow depth, extent, and melt in the Sierra Nevada Mountain Range are critical to estimating the amount of water that will be available for crops during the growing season within California's Central Valley. Numerical simulations utilizing a fourth order turbulent closure transport scheme in a multi-layer soil-vegetation-atmosphere model, Advanced Canopy-Atmosphere-Soil algorithm (ACASA), were used to explore snow model improvements in the physics-based parameterization for the Sierra Nevada Range. A set of alterations were made separately to the existing snowpack model within ACASA focusing on improvements to snow cover simulations on complex terrain slopes and over varying canopy cover. Three winter seasons were simulated; a climatological average, dry, and wet winter. The simulated output from the models are compared to observations to determine which model alterations made the largest improvements to snow simulations.

  10. Dynamics of partial anaerobiosis denitrification, and water in soil : experiments and simulation

    NARCIS (Netherlands)

    Leffelaar, P.A.

    1987-01-01

    Dynamic interactions between biological respiration and denitrification, and physical transport processes that modify the abiotic soil environment in which bacteria live, were studied through the development of a new type of experimental respirometer system and an explanatory simulation model.

  11. Nonlinear genetic-based simulation of soil shear strength parameters

    Indian Academy of Sciences (India)

    Seyyed Mohammad Mousavi; Amir Hossein Alavi; Amir Hossein Gandomi; Ali Mollahasani

    2011-12-01

    New nonlinear solutions were developed to estimate the soil shear strength parameters utilizing linear genetic programming (LGP). The soil cohesion intercept () and angle of shearing resistance () were formulated in terms of the basic soil physical properties. The best models were selected after developing and controlling several models with different combinations of influencing parameters. Comprehensive experimental database used for developing the models was established upon a series of unconsolidated, undrained, and unsaturated triaxial tests conducted in this study. Further, sensitivity and parametric analyses were carried out. and were found to be mostly influenced by the soil unit weight and liquid limit. In order to benchmark the proposed models, a multiple least squares regression (MLSR) analysis was performed. The validity of the models was proved on portions of laboratory results that were not included in the modelling process. The developed models are able to effectively learn the complex relationship between the soil strength parameters and their contributing factors. The LGP models provide a significantly better prediction performance than the regression models.

  12. DAYCENT national-scale simulations of nitrous oxide emissions from cropped soils in the United States.

    Science.gov (United States)

    Del Grosso, S J; Parton, W J; Mosier, A R; Walsh, M K; Ojima, D S; Thornton, P E

    2006-01-01

    Until recently, Intergovernmental Panel on Climate Change (IPCC) emission factor methodology, based on simple empirical relationships, has been used to estimate carbon (C) and nitrogen (N) fluxes for regional and national inventories. However, the 2005 USEPA greenhouse gas inventory includes estimates of N2O emissions from cultivated soils derived from simulations using DAYCENT, a process-based biogeochemical model. DAYCENT simulated major U.S. crops at county-level resolution and IPCC emission factor methodology was used to estimate emissions for the approximately 14% of cropped land not simulated by DAYCENT. The methodology used to combine DAYCENT simulations and IPCC methodology to estimate direct and indirect N2O emissions is described in detail. Nitrous oxide emissions from simulations of presettlement native vegetation were subtracted from cropped soil N2O to isolate anthropogenic emissions. Meteorological data required to drive DAYCENT were acquired from DAYMET, an algorithm that uses weather station data and accounts for topography to predict daily temperature and precipitation at 1-km2 resolution. Soils data were acquired from the State Soil Geographic Database (STATSGO). Weather data and dominant soil texture class that lie closest to the geographical center of the largest cluster of cropped land in each county were used to drive DAYCENT. Land management information was implemented at the agricultural-economic region level, as defined by the Agricultural Sector Model. Maps of model-simulated county-level crop yields were compared with yields estimated by the USDA for quality control. Combining results from DAYCENT simulations of major crops and IPCC methodology for remaining cropland yielded estimates of approximately 109 and approximately 70 Tg CO2 equivalents for direct and indirect, respectively, mean annual anthropogenic N2O emissions for 1990-2003.

  13. Migration of infiltrated NH4 and NO3 in a soil and groundwater system simulated by a soil tank

    Institute of Scientific and Technical Information of China (English)

    WANG Chao; WANG Pei-Fang

    2008-01-01

    The infiltration of water contaminants into soil and groundwater systems can greatly affect the quality of groundwater.A laboratory-designed large soil tank with periodic and continuous infiltration models,respectively,was used to simulate the migration of the contaminants NHa and NO3 in a soil and groundwater system,including unsaturated and saturated zones.The unsaturated soil zone had a significant effect on removing NH4 and NO3 infiltrated from the surface water.The patterns of breakthrough curves of NH4 and NO3 in the unsaturated zone were related to the infiltration time.A short infiltration time resulted in a single sharp peak in the breakthrough curve,while a long infiltration time led to a plateau curve.When NHa and NO3 migrated from the unsaturated zone to the saturated zone,an interfacial retardation was formed,resulting in an increased contaminant concentration on the interface.Under the influence of horizontal groundwater movement,the infiltrated contaminants formed a contamination-prone area downstream.As the contaminants migrated downstream,their concentrations were significantly reduced.Under the same infiltration concentration,the concentration of NO3 was greater than that of NH4 at every corresponding cross-section in the soil and groundwater tank,suggesting that the removal efficiency of NH4 was greater than that of NO3 in the soil and groundwater system.

  14. 土的基本特性、本构关系及数值模拟研究综述%Behaviors, constitutive models and numerical simulation of soils

    Institute of Scientific and Technical Information of China (English)

    姚仰平; 张丙印; 朱俊高

    2012-01-01

    expressional behaviors include such as stress history dependence, stress path dependence, softening, anisotropy, structure, creep, particle crushing, and temperature effect. They indirectly influence the stress-strain relationship of soils through affecting the essential behaviors of soils. The relative behaviors consist of such as yielding, normality flow, associated flow, eoaxiality, and critical state. They are basic concepts or assumptions to be incorporated into an elasto- plastic constitutive model if such model is desired. Following a detailed discussion on the soil behaviors and their mutual relations, a comprehensive review is provided on a few representative constitutive models, e. g., the Duncan-Chang nonlinear elastic model, the Cam-clay elastio-plastic model and the UH model, the Asaoka model, the Li-Dafalias model, the Yin-Graham EVP model and other constitutive models developed by Chinese researchers. The focus is placed mainly on how to conceptualize the intrinsic soil behaviors and lead to constitutive models, and which behaviors can be reflected by each constitutive mode] and how. Afterwards some considerations and personal experiences are shared on implementing constitutive models into numerical simulation. The discussion focuses on the accuracy of numerical simulation and the influencing factors, selection of proper constitutive models and parameters, consideration of spatial variation of soil modulus in deformation calculation, the strain localization and some solutions for fixing the problems caused by displacement discontinuity at soil-structure contacts in numerical simulation.

  15. Modeling Water Pollution of Soil

    Directory of Open Access Journals (Sweden)

    V. Doležel

    2008-01-01

    Full Text Available The government of the Czech Republic decided that in the location to the west of Prague, capital city of the Czech Republic, some deep mines should be closed because of their low efficiency of coal mined i.e. small amounts and low quality of the coal extracted in the final stage of mining. The locations near Prague influenced the decision to do maintenance on the abandoned mines, as the thread of soil pollution was unacceptably high in the neighborhood of the capital city. Before the mines were closed it was necessary to separate existed extensive horizontal location of salt water below a clay layer in order not to deteriorate the upper fresh water. The salt water could not be allowed to pollute the upper layer with the fresh water, as many wells in villages in the neighborhood of the former mines would be contaminated. Two horizontal clay layers (an insulator and a semi-insulator separated the two horizons containing salt water and fresh water. Before starting deep mining, vertical shafts had to be constructed with concrete linings to enable the miners to access the depths. The salt water was draining away throughout the existence of the mine. The drainage was designed very carefully to avoid possible infiltration of salt water into the upper horizon. Before the mines were abandoned it was necessary to prevent contact between the two kinds of waters in the shafts. Several options were put forward, the most efficient of which appeared to be one that proposed filling the shafts with spoil soil and creating a joint seal made of disparate material at the interface between the salt water and fresh water to create a reliable stopper. The material for the spoil soil was delivered from deposits located not far from the shafts. This material consisted of a variety of grains of sand, big boulders of slate, slaty clay, sandstone, etc.. Chemical admixtures were considered to improve the flocculation of the filling material. The stopper was positioned at a

  16. Notes on modeling and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Redondo, Antonio [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-10

    These notes present a high-level overview of how modeling and simulation are carried out by practitioners. The discussion is of a general nature; no specific techniques are examined but the activities associated with all modeling and simulation approaches are briefly addressed. There is also a discussion of validation and verification and, at the end, a section on why modeling and simulation are useful.

  17. Modeling soil moisture processes and recharge under a melting snowpack

    Science.gov (United States)

    Flint, A.L.; Flint, L.E.; Dettinger, M.D.

    2008-01-01

    Recharge into granitic bedrock under a melting snowpack is being investigated as part of a study designed to understand hydrologic processes involving snow at Yosemite National Park in the Sierra Nevada Mountains of California. Snowpack measurements, accompanied by water content and matric potential measurements of the soil under the snowpack, allowed for estimates of infiltration into the soil during snowmelt and percolation into the bedrock. During portions of the snowmelt period, infiltration rates into the soil exceeded the permeability of the bedrock and caused ponding to be sustained at the soil-bedrock interface. During a 5-d period with little measured snowmelt, drainage of the ponded water into the underlying fractured granitic bedrock was estimated to be 1.6 cm d?1, which is used as an estimate of bedrock permeability. The numerical simulator TOUGH2 was used to reproduce the field data and evaluate the potential for vertical flow into the fractured bedrock or lateral flow at the bedrock-soil interface. During most of the snowmelt season, the snowmelt rates were near or below the bedrock permeability. The field data and model results support the notion that snowmelt on the shallow soil overlying low permeability bedrock becomes direct infiltration unless the snowmelt rate greatly exceeds the bedrock permeability. Late in the season, melt rates are double that of the bedrock permeability (although only for a few days) and may tend to move laterally at the soil-bedrock interface downgradient and contribute directly to streamflow. ?? Soil Science Society of America.

  18. River basin soil-vegetation condition assessment applying mathematic simulation methods

    Science.gov (United States)

    Mishchenko, Natalia; Trifonova, Tatiana; Shirkin, Leonid

    2013-04-01

    Meticulous attention paid nowadays to the problem of vegetation cover productivity changes is connected also to climate global transformation. At the same time ecosystems anthropogenic transformation, basically connected to the changes of land use structure and human impact on soil fertility, is developing to a great extent independently from climatic processes and can seriously influence vegetation cover productivity not only at the local and regional levels but also globally. Analysis results of land use structure and soil cover condition influence on river basin ecosystems productive potential is presented in the research. The analysis is carried out applying integrated characteristics of ecosystems functioning, space images processing results and mathematic simulation methods. The possibility of making permanent functional simulator defining connection between macroparameters of "phytocenosis-soil" system condition on the basis of basin approach is shown. Ecosystems of river catchment basins of various degrees located in European part of Russia were chosen as research objects. For the integrated assessment of ecosystems soil and vegetation conditions the following characteristics have been applied: 1. Soil-productional potential, characterizing the ability of natural and natural-anthropogenic ecosystem in certain soil-bioclimatic conditions for long term reproduction. This indicator allows for specific phytomass characteristics and ecosystem produce, humus content in soil and bioclimatic parameters. 2. Normalized difference vegetation index (NDVI) has been applied as an efficient, remotely defined, monitoring indicator characterizing spatio-temporal unsteadiness of soil-productional potential. To design mathematic simulator functional simulation methods and principles on the basis of regression, correlation and factor analysis have been applied in the research. Coefficients values defining in the designed static model of phytoproductivity distribution has been

  19. Modelo de simulación del balance hídrico en suelos con freática poco profunda Water balance simulation model in shallow watertable soils

    Directory of Open Access Journals (Sweden)

    Américo Degioanni

    2006-07-01

    Full Text Available Los suelos con capa freática poco profunda poseen mayor probabilidad de ser afectados por anegamiento. La predicción de la oscilación temporal del nivel freático constituye una importante herramienta para valorar el riesgo de ocurrencia de tal proceso. El objetivo de este trabajo es presentar los fundamentos teóricos, la estructura operativa y la capacidad predictiva del modelo de simulación del balance hídrico Freat.1. El modelo se fundamenta en el cálculo de la transferencia de agua entre la atmósfera, el perfil del suelo, la vegetación y la capa freática. Los procesos de transferencia simulados son: escurrimiento superficial saliente, ascenso del nivel freático por efecto de la lluvia neta y del escurrimiento subterráneo entrante y descenso del nivel freático por efectos del escurrimiento subterráneo saliente, evaporación, ascenso capilar desde la capa freática y transpiración de la vegetación. Se evalúan los resultados de su aplicación en un Haplustol udorténtico y en un Natralbol típico ambos con freática oscilando a menos de tres metros de profundidad. El error de predicción estimado como la raíz del error cuadrático medio entre registros freáticos observados y simulados es menor de 15 cm para ambos suelos. Se concluye que el modelo resulta apropiado para predecir oscilaciones temporales de capa freática y evaluar el riesgo de inundación por anegamiento en suelos con capa freática cercana a la superficie.Soils with shallow water table have greater probability of being affected by waterlogging. The prediction of the water table depth temporal oscillation is an important tool to assess the risk of occurrence of such processes. The goal of this paper is to present the theoretical foundations, operative structure and predictive capacity of the water balance simulation model Freat.1. This model is based on the calculus of water transference between atmosphere, soil profile, vegetation and water table. The

  20. Validation and Scenario Analysis of a Soil Organic Carbon Model

    Institute of Scientific and Technical Information of China (English)

    HUANG Yao; LIU Shi-liang; SHEN Qi-rong; ZONG Liang-gang; JIANG Ding-an; HUANG Hong-guang

    2002-01-01

    A model developed by the authors was validated against independent data sets. The data sets were obtained from field experiments of crop residue decomposition and a 7-year soil improvement in Yixing City, Jiangsu Province. Model validation indicated that soil organic carbon dynamics can be simulated from the weather variables of temperature, sunlight and precipitation, soil clay content and bulk density, grain yield of previous crops, qualities and quantities of the added organic matter. Model simulation in general agreed with the measurements. The comparison between computed and measured resulted in correlation coefficient γ2 values of 0.9291 * * * (n = 48) and 0. 6431 * * (n = 65) for the two experiments, respectively. Model prediction under three scenarios of no additional organic matter input, with an annual incorporation of rice and wheat straw at rates of 6.75t/ha and 9.0t/ha suggested that the soil organic carbon in Wanshi Township of Yixing City would be from an initial value of 7.85g/kg in 1983 to 6.30g/kg, 11.42g/kg and 13g/kg in 2014, respectively. Consequently, total nitrogen content of the soil was predicted to be respectively 0.49g/kg,0.89g/kg and 1.01g/kg under the three scenarios.

  1. Modeling of soil-water-structure interaction

    DEFF Research Database (Denmark)

    Tang, Tian

    to dynamic ocean waves. The goal of this research project is to develop numerical soil models for computing realistic seabed response in the interacting offshore environment, where ocean waves, seabed and offshore structure highly interact with each other. The seabed soil models developed are based...... as the developed nonlinear soil displacements and stresses under monotonic and cyclic loading. With the FVM nonlinear coupled soil models as a basis, multiphysics modeling of wave-seabed-structure interaction is carried out. The computations are done in an open source code environment, OpenFOAM, where FVM models...... of Computational Fluid Dynamics (CFD) and structural mechanics are available. The interaction in the system is modeled in a 1-way manner: First detailed free surface CFD calculations are executed to obtain a realistic wave field around a given structure. Then the dynamic structural response, due to the motions...

  2. 模型模拟土壤性质和植被种类对再生水灌溉水盐运移的影响%Simulation of Effects of Soil Properties and Plants on Soil Water-salt Movement with Reclaimed Water Irrigation by ENVIRO-GRO Model

    Institute of Scientific and Technical Information of China (English)

    吕斯丹; 陈卫平; 王美娥

    2012-01-01

    为推动再生水安全灌溉,本研究运用ENVIRO-GRO模型模拟了不同土壤性质、植被条件下土壤盐分的分布规律及累积趋势,探讨了土壤性质和植被种类对再生水灌溉水盐运移的影响.研究发现,不同土壤初始含盐量下,经多年重复模拟后最终达到统一的平衡状态;而不同土壤质地下,随着灌溉年份的增加,壤土、黏壤土中的土壤ECe年均值逐渐增加直到平衡,砂壤土中的土壤ECe年均值逐渐减少直到平衡,平衡时土层中的ECe值砂壤土〈壤土〈黏壤土.3种植被下,大叶黄杨、油松的土壤ECe值增加量小于早熟禾;土壤盐分在土层中的空间、时间分布也均有所不同.此外,不同模拟情景下,土壤盐分累积都不会影响植被的生长(黏壤土除外),但均出现轻度盐渍化(砂壤土除外).%In order to promote safe irrigation with reclaimed water and prevent soil salinisation,the dynamic transport of salts in urban soils of Beijing under irrigation of reclaimed water was simulated by ENVIRO-GRO model in this study.The accumulation trends and profile distribution of soil salinity were predicted.Simultaneously,the effects of different soil properties and plants on soil water-salt movement and salt accumulation were investigated.Results indicated that soil salinity in the profiles reached uniform equilibrium conditions by repeated simulation,with different initial soil salinity.Under the conditions of loam and clay loam soil,salinity in the profiles increased over time until reaching equilibrium conditions,while under the condition of sandy loam soil,salinity in the profiles decreased over time until reaching equilibrium conditions.The saturated soil salinity(ECe) under equilibrium conditions followed an order of sandy loamloamclay loam.Salt accumulations in Japan euonymus and Chinese pine were less than that in Blue grass.The temporal and spatial distributions of soil salinity were also different in these three

  3. Impact of Sub-grid Soil Textural Properties on Simulations of Hydrological Fluxes at the Continental Scale Mississippi River Basin

    Science.gov (United States)

    Kumar, R.; Samaniego, L. E.; Livneh, B.

    2013-12-01

    Knowledge of soil hydraulic properties such as porosity and saturated hydraulic conductivity is required to accurately model the dynamics of near-surface hydrological processes (e.g. evapotranspiration and root-zone soil moisture dynamics) and provide reliable estimates of regional water and energy budgets. Soil hydraulic properties are commonly derived from pedo-transfer functions using soil textural information recorded during surveys, such as the fractions of sand and clay, bulk density, and organic matter content. Typically large scale land-surface models are parameterized using a relatively coarse soil map with little or no information on parametric sub-grid variability. In this study we analyze the impact of sub-grid soil variability on simulated hydrological fluxes over the Mississippi River Basin (≈3,240,000 km2) at multiple spatio-temporal resolutions. A set of numerical experiments were conducted with the distributed mesoscale hydrologic model (mHM) using two soil datasets: (a) the Digital General Soil Map of the United States or STATSGO2 (1:250 000) and (b) the recently collated Harmonized World Soil Database based on the FAO-UNESCO Soil Map of the World (1:5 000 000). mHM was parameterized with the multi-scale regionalization technique that derives distributed soil hydraulic properties via pedo-transfer functions and regional coefficients. Within the experimental framework, the 3-hourly model simulations were conducted at four spatial resolutions ranging from 0.125° to 1°, using meteorological datasets from the NLDAS-2 project for the time period 1980-2012. Preliminary results indicate that the model was able to capture observed streamflow behavior reasonably well with both soil datasets, in the major sub-basins (i.e. the Missouri, the Upper Mississippi, the Ohio, the Red, and the Arkansas). However, the spatio-temporal patterns of simulated water fluxes and states (e.g. soil moisture, evapotranspiration) from both simulations, showed marked

  4. Advancement of a soil parameters geodatabase for the modeling assessment of conservation practice outcomes in the United States

    Science.gov (United States)

    US-ModSoilParms-TEMPLE is a database composed of a set of geographic databases functionally storing soil-spatial units and soil hydraulic, physical, and chemical parameters for three agriculture management simulation models, SWAT, APEX, and ALMANAC. This paper introduces the updated US-ModSoilParms-...

  5. An integrated soil-crop system model for water and nitrogen management in North China

    Science.gov (United States)

    Liang, Hao; Hu, Kelin; Batchelor, William D.; Qi, Zhiming; Li, Baoguo

    2016-05-01

    An integrated model WHCNS (soil Water Heat Carbon Nitrogen Simulator) was developed to assess water and nitrogen (N) management in North China. It included five main modules: soil water, soil temperature, soil carbon (C), soil N, and crop growth. The model integrated some features of several widely used crop and soil models, and some modifications were made in order to apply the WHCNS model under the complex conditions of intensive cropping systems in North China. The WHCNS model was evaluated using an open access dataset from the European International Conference on Modeling Soil Water and N Dynamics. WHCNS gave better estimations of soil water and N dynamics, dry matter accumulation and N uptake than 14 other models. The model was tested against data from four experimental sites in North China under various soil, crop, climate, and management practices. Simulated soil water content, soil nitrate concentrations, crop dry matter, leaf area index and grain yields all agreed well with measured values. This study indicates that the WHCNS model can be used to analyze and evaluate the effects of various field management practices on crop yield, fate of N, and water and N use efficiencies in North China.

  6. Simulating global soil-CO2 flux and its response to climate change

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    It has been argued that increased soil respiration would become a major atmospheric source of CO2 in the event of global warming. The simple statistical models were developed based on a georeferenced database with 0.5°× 0.5° longitude/latitude resolution to simulate global soil-CO2 fluxes, to investigate climatic effects on these fluxes using sensitivity experiments, and to assess possible responses of soil-CO2 fluxes to various climate change scenarios. The statistical models yield a value of 69 PgC/a of global soil CO2 fluxes for current condition. Sensitivity experiments confirm that the fluxes are responsive to changes in temperature,precipitation and actual evapotranspiration, but increases in temperature and actual evapotranspiration affect soil-CO2 fluxes more than increases in precipitation. Using climatic change projections from four global circulation models, each corresponding to an equilibrium doubling of CO2, it can be found that the largest increases in soil-CO2 fluxes were associated with the boreal and tundra regions. The globally averaged soil-CO2 fluxes were estimated to increase by about 35 % above current values, providing a positive feedback to the greenhouse effect.

  7. Simulating global soil-CO2 flux and its response to climate change

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    It has been argued that increased soil respiration would become a major atmospheric source of CO2 in the event of global warming. The simple statistical models were developed based on a georeferenced database with 0.5° × 0.5° longitude/latitude resolution to simulate global soil-CO2 fluxes, to investigate climatic effects on these fluxes using sensitivity experiments, and to assess possible responses of soil-CO2 fluxes to various climate change scenarios. The statistical models yield a value of 69 PgC/a of global soil CO2 fluxes for current condition. Sensitivity experiments confirm that the fluxes are responsive to changes in temperature,precipitation and actual evapotranspiration, but increases in temperature and actual evapotranspiration affect soil-CO2 fluxes more than increases in precipitation. Using climatic change projections from four global circulation models, each corresponding to an equilibrium doubling of CO2, it can be found that the largest increases in soil-CO2 fluxes were associated with the boreal and tundra regions. The globally averaged soil-CO2 fluxes were estimated to increase by about 35 % above current values, providing a positive feedback to the greenhouse effect.

  8. The consumption of atmospheric methane by soil in a simulated future climate

    Directory of Open Access Journals (Sweden)

    C. L. Curry

    2009-11-01

    Full Text Available A recently developed model for the consumption of atmospheric methane by soil (Curry, 2007 is used to investigate the global magnitude and distribution of methane uptake in a simulated future climate. In addition to solving the one-dimensional diffusion-reaction equation, the model includes a parameterization of biological CH4 oxidation that is sensitive to soil temperature and moisture content, along with specified reduction factors for land cultivation and wetland fractional coverage. Under the SRES emission scenario A1B, the model projects an 8% increase in the global annual mean CH4 soil sink by 2100, over and above the 15% increase expected from increased CH4 concentration alone. While the largest absolute increases occur in cool temperate and subtropical forest ecosystems, the largest relative increases in consumption (>40% are seen in the boreal forest, tundra and polar desert environments of the high northern latitudes. Methane uptake at mid- to high northern latitudes increases year-round in 2100, with a 68% increase over present-day values in June. This increase is primarily due to enhanced soil diffusivity resulting from lower soil moisture produced by increased evaporation and reduced snow cover. At lower latitudes, uptake is enhanced mainly by elevated soil temperatures and/or reduced soil moisture stress, with the dominant influence determined by the local climate.

  9. Informing soil models using pedotransfer functions: challenges and perspectives

    Science.gov (United States)

    Pachepsky, Yakov; Romano, Nunzio

    2015-04-01

    Pedotransfer functions (PTFs) are empirical relationships between parameters of soil models and more easily obtainable data on soil properties. PTFs have become an indispensable tool in modeling soil processes. As alternative methods to direct measurements, they bridge the data we have and data we need by using soil survey and monitoring data to enable modeling for real-world applications. Pedotransfer is extensively used in soil models addressing the most pressing environmental issues. The following is an attempt to provoke a discussion by listing current issues that are faced by PTF development. 1. As more intricate biogeochemical processes are being modeled, development of PTFs for parameters of those processes becomes essential. 2. Since the equations to express PTF relationships are essentially unknown, there has been a trend to employ highly nonlinear equations, e.g. neural networks, which in theory are flexible enough to simulate any dependence. This, however, comes with the penalty of large number of coefficients that are difficult to estimate reliably. A preliminary classification applied to PTF inputs and PTF development for each of the resulting groups may provide simple, transparent, and more reliable pedotransfer equations. 3. The multiplicity of models, i.e. presence of several models producing the same output variables, is commonly found in soil modeling, and is a typical feature in the PTF research field. However, PTF intercomparisons are lagging behind PTF development. This is aggravated by the fact that coefficients of PTF based on machine-learning methods are usually not reported. 4. The existence of PTFs is the result of some soil processes. Using models of those processes to generate PTFs, and more general, developing physics-based PTFs remains to be explored. 5. Estimating the variability of soil model parameters becomes increasingly important, as the newer modeling technologies such as data assimilation, ensemble modeling, and model

  10. The influence of soil type, vegetation cover and soil moisture on spin up behaviour of a land surface model in a monsoonal region

    Science.gov (United States)

    Bhattacharya, Anwesha; Mandal, Manabottam

    2015-04-01

    Model spin-up is the process through which the model is adequately equilibrated to ensure balance between the mass fields and velocity fields. In this study, an offline one dimensional Noah land surface model is integrated recursively for three years to assess its spin-up behavior at different sites over the Indian Monsoon domain. Several numerical experiments are performed to investigate the impact of soil category, vegetation cover, initial soil moisture and subsequent dry or wet condition on model spin-up. These include simulations with the dominant soil and vegetation covers of this region, different initial soil moisture content (observed soil moisture; dry soil; moderately wet soil; saturated soil), simulations initialized at different rain conditions (no rain; infrequent rain; continuous rain) and different seasons (Winter, Spring, Summer/Pre-Monsoon, Monsoon and Autumn). It is seen that the spin-up behavior of the model depends on the soil type and vegetation cover with soil characteristics having the larger influence. Over India, the model has the longest spin-up in the case of simulations with loamy soil covered with mixed-shrub. It is noted that the model has a significantly longer spin-up when initialized with very low initial soil moisture content than with higher soil moisture content. It is also seen that in general, simulations initialized just before a continuous rainfall event have the least spin-up time. This observation is reinforced by the results from the simulations initialized in different seasons. It is seen that for monsoonal region, the model spin-up time is least for simulations initialized just before the Monsoon. Model initialized during the Monsoon rain episodes has a longer spin-up than that initialized in any other season. Furthermore, it is seen that the model has a shorter spin-up if it reaches the equilibrium state predominantly via drying process and could be as low as two months under quasi-equilibrium condition depending on

  11. Simulation study on vertical transport of atrazine in soil column

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A simulation experiment on vertical transport of herbicide atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) in soil column was conducted using lysimeter system. The atrazine concentrations in leaching water and soil samples in column at 8 layers with 10 cm thick of each layer were detected by high-performance liquid chromatography. The results show total atrazine amount in leaching water increases nonlinearly with the leaching time and the herbicide application rate, and the atrazine concentrations in column soil decrease with the vertical depth after water leaching. The distribution of atrazine mass in the system after 154 days were that among the applied atrazine, 0.3 % is out through leaching water, 1% is methanol extractable residues in soil, 46 % is methanol nonextractable residues in soil, and 52 % is other loss (including volatilization and degradation). The study indicates movement of atrazine in agriculture soil may not only have relation to the properties of herbicide, but also to the herbicide application history.

  12. Simulation study on vertical transport of atrazine in soil column

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A simulation experiment on vertical transport of herbicide atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) in soil column was conducted using lysimeter system. The atrazine concentrations in leaching water and soil samples in column at 8 layers with 10 cm thick of each layer were detected by high-performance liquid chromatography. The results show total atrazine amount in leaching water increases nonlinearly with the leaching time and the herbicide application rate, and the atrazine concentrations in column soil decrease with the vertical depth after water leaching. The distribution of atrazine mass in the system after 154 days were that among the applied atrazine, 0.3 % is out through leaching water, 1% is methanol extractable residues in soil, 46 % is methanol nonextractable residues in soil, and 52 % is other loss (including volatilization and degradation). The study indicates movement of atrazine in agriculture soil may not only have relation to the properties of herbicide, but also to the herbicide application history.

  13. Modeling of soil-water-structure interaction

    DEFF Research Database (Denmark)

    Tang, Tian

    The trend towards the installation of more offshore constructions for the production and transmission of marine oil, gas and wind power is expected to continue over the coming years. An important process in the offshore construction design is the assessment of seabed soil stability exposed...... to dynamic ocean waves. The goal of this research project is to develop numerical soil models for computing realistic seabed response in the interacting offshore environment, where ocean waves, seabed and offshore structure highly interact with each other. The seabed soil models developed are based...... on the ’modified’ Biot’s consolidation equations, in which the soil-pore fluid coupling is extended to account for the various nonlinear soil stress-strain relations included. The Finite volume method (FVM) together with a segregated solution strategy has been used to numerically solve the governing equations...

  14. Modelling Soil Profiles in their Landscape Context.

    Science.gov (United States)

    Kirkby, M. J.

    2015-12-01

    Through models, explores the relationships between the interacting drivers of soil profile evolution. Soil hydrology drives the partition of precipitation between overland flow, shallow subsurface flow and deeper percolation/ lateral flow. Critical parts of this interchange occurs close to the surface, within the zone of strong bioturbation, where inorganic composition is determined by the balance between erosion and weathering rates expressed in the chemical depletion ratio. The intensity of organic matter cycling may also limit the final composition of weathering products. Erosion rates are partly driven by the geomorphic environment, through gradient and hydrology, but also constrained by the degree of soil weathering, through particle size and mineralogy. Weathering rates are determined by water movement below the bioturbation zone and ionic diffusion from parent material, which control the rate of decline with soil depth. These interactions are explored through simple equilibrium and evolutionary models for the soil profile that are applicable across a wide range of geological and climatic environments.

  15. Modelling Analysis of Sewage Sludge Amended Soil

    DEFF Research Database (Denmark)

    Sørensen, P. B.; Carlsen, L.; Vikelsøe, J.

    The topic is risk assessment of sludge supply to agricultural soil in relation to xenobiotics. A large variety of xenobiotics arrive to the wastewater treatment plant in the wastewater. Many of these components are hydrophobic and thus will accumulate in the sludge solids and are removed from...... the plant effluent. The focus in this work is the top soil as this layer is important for the fate of a xenobiotic substance due to the high biological activity. A simple model for the top soil is used where the substance is assumed homogeneously distributed as suggested in the European Union System...... for the Evaluation of Substances (EUSES). It is shown how the fraction of substance mass, which is leached, from the top soil is a simple function of the ratio between the degradation half lifetime and the adsorption coefficient. This model can be used in probabilistic risk assessment of agricultural soils...

  16. Simulated responses of soil organic carbon stock to tillage management scenarios in the Northwest Great Plains

    Directory of Open Access Journals (Sweden)

    Li Zhengpeng

    2007-07-01

    Full Text Available Abstract Background Tillage practices greatly affect carbon (C stocks in agricultural soils. Quantification of the impacts of tillage on C stocks at a regional scale has been challenging because of the spatial heterogeneity of soil, climate, and management conditions. We evaluated the effects of tillage management on the dynamics of soil organic carbon (SOC in croplands of the Northwest Great Plains ecoregion of the United States using the General Ensemble biogeochemical Modeling System (GEMS. Tillage management scenarios included actual tillage management (ATM, conventional tillage (CT, and no-till (NT. Results Model simulations show that the average amount of C (kg C ha-1yr-1 released from croplands between 1972 and 2000 was 246 with ATM, 261 with CT, and 210 with NT. The reduction in the rate of C emissions with conversion of CT to NT at the ecoregion scale is much smaller than those reported at plot scale and simulated for other regions. Results indicate that the response of SOC to tillage practices depends significantly on baseline SOC levels: the conversion of CT to NT had less influence on SOC stocks in soils having lower baseline SOC levels but would lead to higher potentials to mitigate C release from soils having higher baseline SOC levels. Conclusion For assessing the potential of agricultural soils to mitigate C emissions with conservation tillage practices, it is critical to consider both the crop rotations being used at a local scale and the composition of all cropping systems at a regional scale.

  17. ISRU Soil Mechanics Vacuum Facility: Soil Bin Preparation and Simulant Strength Characterization

    Science.gov (United States)

    Kleinhenz, Julie; Wilkinson, Allen

    2012-01-01

    Testing in relevant environments is key to exploration mission hardware development. This is true on both the component level (in early development) and system level (in late development stages). During ISRU missions the hardware will interface with the soil (digging, roving, etc) in a vacuum environment. A relevant test environment will therefore involve a vacuum chamber with a controlled, conditioned simulant bed. However, in earth-based granular media, such as lunar soil simulant, gases trapped within the material pore structures and water adsorbed to all particle surfaces will release when exposed to vacuum. Early vacuum testing has shown that this gas release can occur violently, which loosens and weakens the simulant, altering the consolidation state. The Vacuum Facility #13, a mid-size chamber (3.66m tall, 1.5m inner diameter) at the NASA Glenn Research Center has been modified to create a soil mechanics test facility. A 0.64m deep by 0.914m square metric ton bed of lunar simulant was placed under vacuum using a variety of pumping techniques. Both GRC-3 and LHT-3M simulant types have been used. An electric cone penetrometer was used to measure simulant strength properties at vacuum including: cohesion, friction angle, bulk density and shear modulus. Simulant disruptions, caused by off gassing, affected the strength properties, but could be mitigated by reducing pump rate. No disruptions were observed at pressures below 2.5Torr, regardless of the pump rate. However, slow off gassing of the soil lead to long test times, a full week, to reach 10-5Torr. This work highlights the need for robotic machine-simulant hardware and operations in vacuum to expeditiously perform (sub-)systems tests.

  18. Fate of invading bacteria in soil and survival of transformants after simulated uptake of transgenes, as evaluated by a model system based on lindane degradation.

    Science.gov (United States)

    Zhang, Xiaojun; Nesme, Joseph; Simonet, Pascal; Frostegård, Asa

    2012-04-01

    Emergence of bacteria carrying new traits resulting from mutations, gene synthesis by gene-shuffling or acquisition of exogenous DNA underpins the need to better understand factors influencing their spread and establishment. Studies of soils may be difficult, since the gene of interest is often already present in high numbers. The gene linA, responsible for the first dechlorination steps during degradation of lindane (γ-hexachlorocyclohexane), has low background levels in soil and is simple to detect. Development of transgenic plants containing linA and newly proposed approaches to bioremediation by in situ electrotransformation after addition of a vector carrying this gene call for documentation on the fate of bacteria that incorporate it. We inserted linA into the broad-host-range conjugative RP4-plasmid and transferred it to different soil bacteria which were inoculated into soil microcosms in the presence/absence of lindane. Similar experiments were performed using Sphingobium francense Sp+, which carries all genes for complete lindane degradation. This strain increased in numbers during lindane mineralization, but other bacteria increased more, resulting in a modified bacterial community structure. The engineered strains decreased below the detection limit, but rose in numbers after nutrient addition, demonstrating that new invading bacteria may persist in soil in the form of small populations over extended time periods.

  19. Evaluating uncertainty in simulation models

    Energy Technology Data Exchange (ETDEWEB)

    McKay, M.D.; Beckman, R.J.; Morrison, J.D.; Upton, S.C.

    1998-12-01

    The authors discussed some directions for research and development of methods for assessing simulation variability, input uncertainty, and structural model uncertainty. Variance-based measures of importance for input and simulation variables arise naturally when using the quadratic loss function of the difference between the full model prediction y and the restricted prediction {tilde y}. The concluded that generic methods for assessing structural model uncertainty do not now exist. However, methods to analyze structural uncertainty for particular classes of models, like discrete event simulation models, may be attainable.

  20. Numerical simulation of liquefaction susceptibility of soil interacting by single pile

    Directory of Open Access Journals (Sweden)

    Ahmad Asaadi

    2015-06-01

    Full Text Available Previous case histories have shown that soil liquefaction severely damaged many structures supported on pile foundations during earthquakes. As a result, evaluating the potential for instability is an important consideration for the safe and resistant design of deep foundation against earthquakes. In this study, the liquefaction susceptibility of saturated sand interacting by single concrete pile was simulated by means of finite difference method. A nonlinear effective stress analysis was used to evaluate soil liquefaction, and the soil-pile interaction was considered using interface elements. The parameter Ru was defined as the pore water pressure ratio to investigate liquefaction in the soil mass during time. A set of numerical models were carried out by three types of soil mass with various condensation (loose, semi-dense and dense under three ground motion with different predominant frequencies and peak accelerations. The effect of these parameters was studied using excess pore pressure, lateral movement and settlement time histories. It was found that the pile can affect the liquefaction susceptibility of soil by comparing the near pile and free field responses. However, for various soil and earthquake characteristics, it was found that the depth of soil liquefaction and triggering, varies.

  1. Subsurface flow in a soil-mantled subtropical dolomite karst slope: A field rainfall simulation study

    Science.gov (United States)

    Fu, Z. Y.; Chen, H. S.; Zhang, W.; Xu, Q. X.; Wang, S.; Wang, K. L.

    2015-12-01

    Soil and epikarst co-evolve resulting in complex structures, but their coupled structural effects on hydrological processes are poorly understood in karst regions. This study examined the plot-scale subsurface flow characteristics from an integrated soil-epikarst system perspective in a humid subtropical cockpit karst region of Southwest China. A trench was excavated to the epikarst lower boundary for collecting individual subsurface flows in five sections with different soil thicknesses. Four field rainfall simulation experiments were carried out under different initial moisture conditions (dry and wet) and rainfall intensities (114 mm h- 1 (high) and 46 mm h- 1 (low) on average). The soil-epikarst system was characterized by shallow soil overlaying a highly irregular epikarst surface with a near-steady infiltration rate of about 35 mm h- 1. The subsurface flows occurred mainly along the soil-epikarst interface and were dominated by preferential flow. The subsurface flow hydrographs showed strong spatial variability and had high steady-state coefficients (0.52 and 0.36 for high and low rainfall intensity events). Irregular epikarst surface combining with high vertical drainage capacity resulted in high threshold rainfall depths for subsurface flows: 67 mm and 263 mm for initial wet and dry conditions, respectively. The above results evidenced that the irregular and permeable soil-epikarst interface was a crucial component of soil-epikarst architecture and consequently should be taken into account in the hydrological modeling for karst regions.

  2. Simulation Model of a Transient

    DEFF Research Database (Denmark)

    Jauch, Clemens; Sørensen, Poul; Bak-Jensen, Birgitte

    2005-01-01

    This paper describes the simulation model of a controller that enables an active-stall wind turbine to ride through transient faults. The simulated wind turbine is connected to a simple model of a power system. Certain fault scenarios are specified and the turbine shall be able to sustain operation...... in case of such faults. The design of the controller is described and its performance assessed by simulations. The control strategies are explained and the behaviour of the turbine discussed....

  3. Simulation Model of a Transient

    DEFF Research Database (Denmark)

    Jauch, Clemens; Sørensen, Poul; Bak-Jensen, Birgitte

    2005-01-01

    This paper describes the simulation model of a controller that enables an active-stall wind turbine to ride through transient faults. The simulated wind turbine is connected to a simple model of a power system. Certain fault scenarios are specified and the turbine shall be able to sustain operation...

  4. Soil carbonyl sulfide fluxes in a Mediterranean ecosystem: insights from model-data fusion analysis

    Science.gov (United States)

    Sun, W.; Seibt, U. H.; Maseyk, K. S.; Lett, C.

    2013-12-01

    Carbonyl sulfide (COS) is linked to biosphere components of the carbon cycle, due in large part to its hydrolysis by the enzyme carbonic anhydrase (CA). Stomatal diffusion models and observations at leaf and ecosystem scales have demonstrated the potential of COS as a tracer for Gross Primary Production (GPP). Although considered small relative to canopy COS fluxes, accurate knowledge of soil COS fluxes is required for the use of net ecosystem COS fluxes in carbon flux partitioning. However, extensive field measurements of soil COS fluxes are rare and process-based modeling is limited. Here we report continuous chamber measurements of soil COS fluxes in a Mediterranean ecosystem in the Santa Monica Mountains, California during April and early May 2013. Both COS uptake and emissions were observed, but the soil acted as a net sink in most conditions and was a net source only when soil temperatures were above 22 C. COS sink fluxes were positively correlated with soil water content and CO2 fluxes. COS uptake had a maximum at a temperature around 15 C. However, no single environmental variable could be correlated to COS fluxes with an r-square > 0.6. COS fluxes from soil chambers ranged from -9 to 2.5 pmol m-2 s-1. Leaf litter appeared to increase soil COS metabolic activity. We observed huge bursts of soil COS uptake induced by a precipitation event, probably due to enhanced soil microbial activity resulting from alleviated water limitation and a decrease in soil temperature towards the optimum. We used a soil gas exchange model coupled with CA enzyme kinetics to simulate the soil COS fluxes. Micrometeorological and soil data were used to drive the soil flux model. Model simulations indicated that diurnal and synoptic variations of COS fluxes were driven by soil temperature and water content, controlling both CA activity and diffusion. We suggest that multiple parameters need to be optimized to reduce uncertainties in models of soil COS fluxes at larger scales.

  5. Rapid immobilization of simulated radioactive soil waste by microwave sintering.

    Science.gov (United States)

    Zhang, Shuai; Shu, Xiaoyan; Chen, Shunzhang; Yang, Huimin; Hou, Chenxi; Mao, Xueli; Chi, Fangting; Song, Mianxin; Lu, Xirui

    2017-09-05

    A rapid and efficient method is particularly necessary in the timely disposal of seriously radioactive contaminated soil. In this paper, a series of simulated radioactive soil waste containing different contents of neodymium oxide (3-25wt.%) has been successfully vitrified by microwave sintering at 1300°C for 30min. The microstructures, morphology, element distribution, density and chemical durability of as obtained vitrified forms have been analyzed. The results show that the amorphous structure, homogeneous element distribution, and regular density improvement are well kept, except slight cracks emerge on the magnified surface for the 25wt.% Nd2O3-containing sample. Moreover, all the vitrified forms exhibit excellent chemical durability, and the leaching rates of Nd are kept as ∼10(-4)-10(-6)g/(m(2)day) within 42days. This demonstrates a potential application of microwave sintering in radioactive contaminated soil disposal. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Modeling the Effects of Soil Moisture at a GPS-Interferometric Reflectometry Station

    Science.gov (United States)

    Chew, C.; Small, E. E.; Larson, K. M.; Nievinski, F. G.; Zavorotny, V.

    2011-12-01

    GPS-Interferometric Reflectometry (GPS-IR) uses ground-reflected GPS signals to estimate near-surface soil moisture. Data are recorded by high-precision, geodetic-quality GPS antennas/receivers, for example those that comprise NSF's EarthScope Plate Boundary Observatory. The ground reflections used in GPS-IR are representative of a ~1000 m2 area around an antenna. As the dielectric constant of the surface fluctuates, the phase, amplitude, and frequency of signal-to-noise ratio (SNR) data recorded by the GPS unit change. Based on field observations, it has been shown that these characteristics of the SNR data are sensitive to shallow soil moisture. A single-scattering, electrodynamic model was used to simulate SNR output over a range of soil moisture conditions. All simulations were for a 2.4 m tall antenna surrounded by a surface free of roughness or vegetation. The model was run using three different types of soil moisture profiles: constant with depth, monotonic variations with depth, and observed profiles interpolated from field data. For all profiles, amplitude, phase shift, and frequency changes were calculated from simulated SNR data. The three GPS metrics are well correlated with soil moisture content modeled at the soil surface because a majority of the incident microwave energy is reflected at the air-soil interface. When surface soil is dry relative to the underlying soil, GPS metrics are also strongly correlated with soil moisture averaged over the top 5 cm of the soil column. The relationship between GPS metrics and soil moisture averaged over 5 cm is not as strong when surface soil is relatively wet (>35% volumetric soil moisture). Interpolated profiles from field data resulted in a very strong correlation between SNR metrics and soil moisture averaged over the top 5 cm of soil, suggesting that soil moisture estimated from SNR data is useful for various hydrologic applications.

  7. Uncertainty in the fate of soil organic carbon: A comparison of three conceptually different soil decomposition models

    Science.gov (United States)

    He, Yujie; Yang, Jinyan; Zhuang, Qianlai; McGuire, Anthony; Zhu, Qing; Liu, Yaling; Teskey, Robert O.

    2014-01-01

    Conventional Q10 soil organic matter decomposition models and more complex microbial models are available for making projections of future soil carbon dynamics. However, it is unclear (1) how well the conceptually different approaches can simulate observed decomposition and (2) to what extent the trajectories of long-term simulations differ when using the different approaches. In this study, we compared three structurally different soil carbon (C) decomposition models (one Q10 and two microbial models of different complexity), each with a one- and two-horizon version. The models were calibrated and validated using 4 years of measurements of heterotrophic soil CO2 efflux from trenched plots in a Dahurian larch (Larix gmelinii Rupr.) plantation. All models reproduced the observed heterotrophic component of soil CO2 efflux, but the trajectories of soil carbon dynamics differed substantially in 100 year simulations with and without warming and increased litterfall input, with microbial models that produced better agreement with observed changes in soil organic C in long-term warming experiments. Our results also suggest that both constant and varying carbon use efficiency are plausible when modeling future decomposition dynamics and that the use of a short-term (e.g., a few years) period of measurement is insufficient to adequately constrain model parameters that represent long-term responses of microbial thermal adaption. These results highlight the need to reframe the representation of decomposition models and to constrain parameters with long-term observations and multiple data streams. We urge caution in interpreting future soil carbon responses derived from existing decomposition models because both conceptual and parameter uncertainties are substantial.

  8. Simulation - modeling - experiment; Simulation - modelisation - experience

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    After two workshops held in 2001 on the same topics, and in order to make a status of the advances in the domain of simulation and measurements, the main goals proposed for this workshop are: the presentation of the state-of-the-art of tools, methods and experiments in the domains of interest of the Gedepeon research group, the exchange of information about the possibilities of use of computer codes and facilities, about the understanding of physical and chemical phenomena, and about development and experiment needs. This document gathers 18 presentations (slides) among the 19 given at this workshop and dealing with: the deterministic and stochastic codes in reactor physics (Rimpault G.); MURE: an evolution code coupled with MCNP (Meplan O.); neutronic calculation of future reactors at EdF (Lecarpentier D.); advance status of the MCNP/TRIO-U neutronic/thermal-hydraulics coupling (Nuttin A.); the FLICA4/TRIPOLI4 thermal-hydraulics/neutronics coupling (Aniel S.); methods of disturbances and sensitivity analysis of nuclear data in reactor physics, application to VENUS-2 experimental reactor (Bidaud A.); modeling for the reliability improvement of an ADS accelerator (Biarotte J.L.); residual gas compensation of the space charge of intense beams (Ben Ismail A.); experimental determination and numerical modeling of phase equilibrium diagrams of interest in nuclear applications (Gachon J.C.); modeling of irradiation effects (Barbu A.); elastic limit and irradiation damage in Fe-Cr alloys: simulation and experiment (Pontikis V.); experimental measurements of spallation residues, comparison with Monte-Carlo simulation codes (Fallot M.); the spallation target-reactor coupling (Rimpault G.); tools and data (Grouiller J.P.); models in high energy transport codes: status and perspective (Leray S.); other ways of investigation for spallation (Audoin L.); neutrons and light particles production at intermediate energies (20-200 MeV) with iron, lead and uranium targets (Le Colley F

  9. Use of Crop Models in Assessment of Soil Drought

    Directory of Open Access Journals (Sweden)

    Milada Stastna

    2007-03-01

    Full Text Available The aims of the study were to apply, test and to present the ability of the deterministic simulation models SIMWASER and CERES-Wheat computing soil-water balance components, percolation losses, ground water recharge and capillary rise. Two case studies for the assessment of percolation losses from irrigated carrots to deep groundwater at Obersiebenbrunn in the Marchfeld (Austria and ground water recharge and capillary rise from shallow groundwater in grass lysimeters at Berlin-Dahlem (Germany together with two test sites with similar climatic conditions and soil water storage potential but with (Grossenzesdorf, Austria and without (Zabcice, Czech Republic groundwater impact in a semi-arid agricultural area in central Europe were chosen. At Obersiebenbrunn, simulated percolation and evapotranspiration were 183 and 629 mm, while the respective measured values amounted to 198 and 635 mm. Up to 42% (194 mm of evapotranspiration was provided by groundwater at s Grossenzesdorf and only 126 mm was used for the worst case comparing to observed data. Th ese results showed both models as proper applicable tools to demonstrate crop – soil – water relations. However, the availability and management of soil water reserves will remain important, especially when extreme events such as droughts occur more frequently and annual soil and groundwater recharge decrease.

  10. Scaling and Pedotransfer in Numerical Simulations of Flow and Transport in Soils

    Science.gov (United States)

    Pachepsky, Y. A.; Yakirevich, A.; Guber, A.; Gish, T.; Cady, R.; Nicholson, T. J.

    2013-12-01

    Flow and transport parameters in numerical simulations need to be defined at the support volume of computational cells. This volume can be substantially larger than the support volume in laboratory of field measurements of those parameters. Parameter estimates obtained from measured values with pedotransfer functions are also defined at the measurement rather than simulation cell support scale. The scale dependence of flow and transport parameters essentially precludes the direct use of measured or pedotransfer estimated parameter values in numerical simulations. The hypothesis of this work was that a support volume-based scaling law could be introduced that could convert pedotransfer-estimated saturated hydraulic conductivity values into values to be used over grid cells for finite element-based simulations of water flow and tracer transport in variable saturated soils. A four month-long experiment was conducted at the USDA-ARS experimental site where tracer was applied with a pulse of irrigation water and its transport in groundwater and variably saturated shallow soils was monitored in three rows of wells on daily basis. The complementary weather data collection and runoff volume measurements were performed. The HYDRUS-3D software was used to set and calibrate the Richards model for flow simulations and the convective-dispersive equation for transport simulations. Saturated hydraulic conductivity values were estimated with class pedotransfer functions derived from the USDA database containing results of about 1000 measurements in soils of different textures and bulk density. A power law scaling law for the saturated hydraulic conductivity was derived from literature data and was applied at the OPE3 site. Using the scaled saturated hydraulic conductivity values resulted in the accuracy of simulations that was similar to the accuracy of the calibrated model results. Scaling of pedotransfer-estimated saturated hydraulic conductivities can provide reasonable

  11. Advances of modeling water flow in variably saturated soils with SWAP

    NARCIS (Netherlands)

    Dam, van J.C.; Groenendijk, P.; Hendriks, R.F.A.; Kroes, J.G.

    2008-01-01

    The Soil Water Atmosphere Plant (SWAP) model simulates transport of water, solutes, and heat in the vadose zone in interaction with vegetation development. Special features of the model are generic crop growth, versatile top boundary conditions, macroporous flow, and interaction of soil water with g

  12. Advances of modeling water flow in variably saturated soils with SWAP

    NARCIS (Netherlands)

    Dam, van J.C.; Groenendijk, P.; Hendriks, R.F.A.; Kroes, J.G.

    2008-01-01

    The Soil Water Atmosphere Plant (SWAP) model simulates transport of water, solutes, and heat in the vadose zone in interaction with vegetation development. Special features of the model are generic crop growth, versatile top boundary conditions, macroporous flow, and interaction of soil water with

  13. IVOA Recommendation: Simulation Data Model

    CERN Document Server

    Lemson, Gerard; Cervino, Miguel; Gheller, Claudio; Gray, Norman; LePetit, Franck; Louys, Mireille; Ooghe, Benjamin; Wagner, Rick; Wozniak, Herve

    2014-01-01

    In this document and the accompanying documents we describe a data model (Simulation Data Model) describing numerical computer simulations of astrophysical systems. The primary goal of this standard is to support discovery of simulations by describing those aspects of them that scientists might wish to query on, i.e. it is a model for meta-data describing simulations. This document does not propose a protocol for using this model. IVOA protocols are being developed and are supposed to use the model, either in its original form or in a form derived from the model proposed here, but more suited to the particular protocol. The SimDM has been developed in the IVOA Theory Interest Group with assistance of representatives of relevant working groups, in particular DM and Semantics.

  14. Updated global soil map for the Weather Research and Forecasting model and soil moisture initialization for the Noah land surface model

    Science.gov (United States)

    DY, C. Y.; Fung, J. C. H.

    2016-08-01

    A meteorological model requires accurate initial conditions and boundary conditions to obtain realistic numerical weather predictions. The land surface controls the surface heat and moisture exchanges, which can be determined by the physical properties of the soil and soil state variables, subsequently exerting an effect on the boundary layer meteorology. The initial and boundary conditions of soil moisture are currently obtained via National Centers for Environmental Prediction FNL (Final) Operational Global Analysis data, which are collected operationally in 1° by 1° resolutions every 6 h. Another input to the model is the soil map generated by the Food and Agriculture Organization of the United Nations - United Nations Educational, Scientific and Cultural Organization (FAO-UNESCO) soil database, which combines several soil surveys from around the world. Both soil moisture from the FNL analysis data and the default soil map lack accuracy and feature coarse resolutions, particularly for certain areas of China. In this study, we update the global soil map with data from Beijing Normal University in 1 km by 1 km grids and propose an alternative method of soil moisture initialization. Simulations of the Weather Research and Forecasting model show that spinning-up the soil moisture improves near-surface temperature and relative humidity prediction using different types of soil moisture initialization. Explanations of that improvement and improvement of the planetary boundary layer height in performing process analysis are provided.

  15. Developing High-resolution Soil Database for Regional Crop Modeling in East Africa

    Science.gov (United States)

    Han, E.; Ines, A. V. M.

    2014-12-01

    The most readily available soil data for regional crop modeling in Africa is the World Inventory of Soil Emission potentials (WISE) dataset, which has 1125 soil profiles for the world, but does not extensively cover countries Ethiopia, Kenya, Uganda and Tanzania in East Africa. Another dataset available is the HC27 (Harvest Choice by IFPRI) in a gridded format (10km) but composed of generic soil profiles based on only three criteria (texture, rooting depth, and organic carbon content). In this paper, we present a development and application of a high-resolution (1km), gridded soil database for regional crop modeling in East Africa. Basic soil information is extracted from Africa Soil Information Service (AfSIS), which provides essential soil properties (bulk density, soil organic carbon, soil PH and percentages of sand, silt and clay) for 6 different standardized soil layers (5, 15, 30, 60, 100 and 200 cm) in 1km resolution. Soil hydraulic properties (e.g., field capacity and wilting point) are derived from the AfSIS soil dataset using well-proven pedo-transfer functions and are customized for DSSAT-CSM soil data requirements. The crop model is used to evaluate crop yield forecasts using the new high resolution soil database and compared with WISE and HC27. In this paper we will present also the results of DSSAT loosely coupled with a hydrologic model (VIC) to assimilate root-zone soil moisture. Creating a grid-based soil database, which provides a consistent soil input for two different models (DSSAT and VIC) is a critical part of this work. The created soil database is expected to contribute to future applications of DSSAT crop simulation in East Africa where food security is highly vulnerable.

  16. Influence of Soil Water Retention Properties on Hydrological Cycle and Water Budgeting Module Simulation

    Directory of Open Access Journals (Sweden)

    Hamid Čustović

    2011-03-01

    Full Text Available The complexity of water budgeting module as shown in this paper is represented in phases. By experimental measurement of precipitation and lysimetric measurement of percolation runoff the fi rst phase establishes monthly and annual soil-water budgets of skeletal and clayey soils, and hence the influence of soil water-retention potential on hydrologic cycle and water budget over a four year period in the area of Mostar. Then, a soil-water budget model is simulated in a simplified procedure in order to determine the corresponding soil productive water reserve (R for given soils.In this way, depending on R values, the output parameters of the simulated model may produce different results in: calculated surplus or percolation runoff, real evapotranspiration (RET and water deficit.The lysimetric measuring of the water input and output in skeletal and clayey soils determined significant differences in the water budgets of these, by physical properties, divergent soils. Such correlations indicate that there is a realistic possibility of computing new, relatively reliable and pragmatically significant agro-hydrological parameters using measured precipitation and calculated PET.Also, this paper addresses a correlative analysis between the apple and maize ET on one side, and evaporation measured by Piche and by Class A, as well as PET calculated by Thornthwaite, Turc and Penman, on the other side. The results show a reliable reaction between ET of apple and maize with E by Piche, while the same relation is even more reliable with Class A. Other methods in this correlative analysis are less reliable.

  17. A GPU Reaction Diffusion Soil-Microbial Model

    Science.gov (United States)

    Falconer, Ruth; Houston, Alasdair; Schmidt, Sonja; Otten, Wilfred

    2014-05-01

    Parallelised algorithms are frequent in bioinformatics as a consequence of the close link to informatics - however in the field of soil science and ecology they are less prevalent. A current challenge in soil ecology is to link habitat structure to microbial dynamics. Soil science is therefore entering the 'big data' paradigm as a consequence of integrating data pertinent to the physical soil environment obtained via imaging and theoretical models describing growth and development of microbial dynamics permitting accurate analyses of spatio-temporal properties of different soil microenvironments. The microenvironment is often captured by 3D imaging (CT tomography) which yields large datasets and when used in computational studies the physical sizes of the samples that are amenable to computation are less than 1 cm3. Today's commodity graphics cards are programmable and possess a data parallel architecture that in many cases is capable of out-performing the CPU in terms of computational rates. The programmable aspect is achieved via a low-level parallel programming language (CUDA, OpenCL and DirectX). We ported a Soil-Microbial Model onto the GPU using the DirectX Compute API. We noted a significant computational speed up as well as an increase in the physical size that can be simulated. Some of the drawbacks of such an approach were concerned with numerical precision and the steep learning curve associated with GPGPU technologies.

  18. The consumption of atmospheric methane by soil in a simulated future climate

    Directory of Open Access Journals (Sweden)

    C. L. Curry

    2009-06-01

    Full Text Available A recently developed model for the consumption of atmospheric methane by soil (Curry, 2007 is used to investigate the global magnitude and distribution of methane uptake in a simulated future climate. In addition to solving the one-dimensional diffusion-reaction equation, the model includes a parameterization of biological CH4 oxidation that is sensitive to soil temperature and moisture content, along with simple scalings for land cultivation and wetland fractional coverage. Under the SRES emission scenario A1B, the model projects an 8% increase in the global annual mean CH4 soil sink by 2100, over and above the 15% increase expected from increased CH4 concentration alone. While the largest absolute increases occur in cool temperate and subtropical forest ecosystems, the largest relative increases in consumption (>40% are seen in the boreal forest, tundra and polar desert environments of the high northern latitudes. Methane uptake at mid- to high northern latitudes increases year-round in 2100, with a 68% increase over present-day values in June. This increase is primarily due to enhanced soil diffusivity resulting from increased evaporation and reduced snow cover. At lower latitudes, uptake is enhanced mainly by elevated soil temperatures and/or reduced soil moisture stress, with the dominant influence determined by the local climate.

  19. Potential for monitoring soil erosion features and soil erosion modeling components from remotely sensed data

    Science.gov (United States)

    Langran, K. J.

    1983-01-01

    Accurate estimates of soil erosion and its effects on soil productivity are essential in agricultural decision making and planning from the field scale to the national level. Erosion models have been primarily developed for designing erosion control systems, predicting sediment yield for reservoir design, predicting sediment transport, and simulating water quality. New models proposed are more comprehensive in that the necessary components (hydrology, erosion-sedimentation, nutrient cycling, tillage, etc.) are linked in a model appropriate for studying the erosion-productivity problem. Recent developments in remote sensing systems, such as Landsat Thematic Mapper, Shuttle Imaging Radar (SIR-B), etc., can contribute significantly to the future development and operational use of these models.

  20. Deriving pedotransfer functions for soil quartz fraction in southern France from reverse modeling

    Science.gov (United States)

    Calvet, Jean-Christophe; Fritz, Noureddine; Berne, Christine; Piguet, Bruno; Maurel, William; Meurey, Catherine

    2016-12-01

    The quartz fraction in soils is a key parameter of soil thermal conductivity models. Because it is difficult to measure the quartz fraction in soils, this information is usually unavailable. This source of uncertainty impacts the simulation of sensible heat flux, evapotranspiration and land surface temperature in numerical simulations of the Earth system. Improving the estimation of soil quartz fraction is needed for practical applications in meteorology, hydrology and climate modeling. This paper investigates the use of long time series of routine ground observations made in weather stations to retrieve the soil quartz fraction. Profile soil temperature and water content were monitored at 21 weather stations in southern France. Soil thermal diffusivity was derived from the temperature profiles. Using observations of bulk density, soil texture, and fractions of gravel and soil organic matter, soil heat capacity and thermal conductivity were estimated. The quartz fraction was inversely estimated using an empirical geometric mean thermal conductivity model. Several pedotransfer functions for estimating quartz content from gravimetric or volumetric fractions of soil particles (e.g., sand) were analyzed. The soil volumetric fraction of quartz (fq) was systematically better correlated with soil characteristics than the gravimetric fraction of quartz. More than 60 % of the variance of fq could be explained using indicators based on the sand fraction. It was shown that soil organic matter and/or gravels may have a marked impact on thermal conductivity values depending on which predictor of fq is used. For the grassland soils examined in this study, the ratio of sand-to-soil organic matter fractions was the best predictor of fq, followed by the gravimetric fraction of sand. An error propagation analysis and a comparison with independent data from other tested models showed that the gravimetric fraction of sand is the best predictor of fq when a larger variety of soil types

  1. Research on Impact Process of Lander Footpad against Simulant Lunar Soils

    Directory of Open Access Journals (Sweden)

    Bo Huang

    2015-01-01

    Full Text Available The safe landing of a Moon lander and the performance of the precise instruments it carries may be affected by too heavy impact on touchdown. Accordingly, landing characteristics have become an important research focus. Described in this paper are model tests carried out using simulated lunar soils of different relative densities (called “simulant” lunar soils below, with a scale reduction factor of 1/6 to consider the relative gravities of the Earth and Moon. In the model tests, the lander was simplified as an impact column with a saucer-shaped footpad with various impact landing masses and velocities. Based on the test results, the relationships between the footpad peak feature responses and impact kinetic energy have been analyzed. Numerical simulation analyses were also conducted to simulate the vertical impact process. A 3D dynamic finite element model was built for which the material parameters were obtained from laboratory test data. When compared with the model tests, the numerical model proved able to effectively simulate the dynamic characteristics of the axial forces, accelerations, and penetration depths of the impact column during landing. This numerical model can be further used as required for simulating oblique landing impacts.

  2. Effects of modeling decisions on cold region hydrological model performance: snow, soil and streamflow

    Science.gov (United States)

    Musselman, Keith; Clark, Martyn; Endalamaw, Abraham; Bolton, W. Robert; Nijssen, Bart; Arnold, Jeffrey

    2017-04-01

    Cold regions are characterized by intense spatial gradients in climate, vegetation and soil properties that determine the complex spatiotemporal patterns of snowpack evolution, frozen soil dynamics, catchment connectivity, and streamflow. These spatial gradients pose unique challenges for hydrological models, including: 1) how the spatial variability of the physical processes are best represented across a hierarchy of scales, and 2) what algorithms and parameter sets best describe the biophysical and hydrological processes at the spatial scale of interest. To address these topics, we apply the Structure for Unifying Multiple Modeling Alternatives (SUMMA) to simulate hydrological processes at the Caribou - Poker Creeks Research Watershed in the Alaskan sub-arctic Boreal forest. The site is characterized by numerous gauged headwater catchments ranging in size from 5 sq. km to 106 sq. km with varying extents (3% to 53%) of discontinuous permafrost that permits a multi-scale paired watershed analysis of the hydrological impacts of frozen soils. We evaluate the effects of model decisions on the skill of SUMMA to simulate observed snow and soil dynamics, and the spatial integration of these processes as catchment streamflow. Decisions such as the number of soil layers, total soil column depth, and vertical soil discretization are shown to have profound impacts on the simulation of seasonal active layer dynamics. Decisions on the spatial organization (lateral connectivity, representation of riparian response units, and the spatial discretization of the hydrological landscape) are shown to be as important as accurate snowpack and soil process representation in the simulation of streamflow. The work serves to better inform hydrological model decisions for cold region hydrologic evaluation and to improve predictive capacity for water resource planning.

  3. Modelling Analysis of Sewage Sludge Amended Soil

    DEFF Research Database (Denmark)

    Sørensen, P. B.; Carlsen, L.; Vikelsøe, J.;

    The topic is risk assessment of sludge supply to agricultural soil in relation to xenobiotics. A large variety of xenobiotics arrive to the wastewater treatment plant in the wastewater. Many of these components are hydrophobic and thus will accumulate in the sludge solids and are removed from...... for the Evaluation of Substances (EUSES). It is shown how the fraction of substance mass, which is leached, from the top soil is a simple function of the ratio between the degradation half lifetime and the adsorption coefficient. This model can be used in probabilistic risk assessment of agricultural soils...

  4. 4Mx Soil-Plant Model: Applications, Opportunities and Challenges

    Directory of Open Access Journals (Sweden)

    Nándor Fodor

    2012-12-01

    Full Text Available Crop simulation models describe the main processes of the soil-plant system in a dynamic way usually in a daily time-step. With the help of these models we may monitor the soil- and plant-related processes of the simulated system as they evolve according to the atmospheric and environmental conditions. Crop models could be successfully applied in the following areas: (1 Education: by promoting the system-oriented thinking a comprehensive overview of the interrelations of the soil-plant system as well as of the environmental protection related aspects of the human activities could be presented. (2 Research: The results of observations as well as of experiments could be extrapolated in time and space, thus, for example, the possible effects of the global climate change could be estimated. (3 Practice: Model calculations could be used in intelligent irrigation control and decision supporting systems as well as for providing scientific background for policy makers. The most spectacular feature of the 4Mx crop model is that its graphical user interface enables the user to alter not only the parameters of the model but the function types of its governing equations as well. The applicability of the 4Mx model is presented via several case-studies.

  5. Modeling and Simulation with INS.

    Science.gov (United States)

    Roberts, Stephen D.; And Others

    INS, the Integrated Network Simulation language, puts simulation modeling into a network framework and automatically performs such programming activities as placing the problem into a next event structure, coding events, collecting statistics, monitoring status, and formatting reports. To do this, INS provides a set of symbols (nodes and branches)…

  6. Simulation modeling of estuarine ecosystems

    Science.gov (United States)

    Johnson, R. W.

    1980-01-01

    A simulation model has been developed of Galveston Bay, Texas ecosystem. Secondary productivity measured by harvestable species (such as shrimp and fish) is evaluated in terms of man-related and controllable factors, such as quantity and quality of inlet fresh-water and pollutants. This simulation model used information from an existing physical parameters model as well as pertinent biological measurements obtained by conventional sampling techniques. Predicted results from the model compared favorably with those from comparable investigations. In addition, this paper will discuss remotely sensed and conventional measurements in the framework of prospective models that may be used to study estuarine processes and ecosystem productivity.

  7. Density-Corrected Models for Gas Diffusivity and Air Permeability in Unsaturated Soil

    DEFF Research Database (Denmark)

    Chamindu, Deepagoda; Møldrup, Per; Schjønning, Per

    2011-01-01

    Accurate prediction of gas diffusivity (Dp/Do) and air permeability (ka) and their variations with air-filled porosity (e) in soil is critical for simulating subsurface migration and emission of climate gases and organic vapors. Gas diffusivity and air permeability measurements from Danish soil...... in subsurface soil. The data were regrouped into four categories based on compaction (total porosity F 0.4 m3 m-3) and soil texture (volume-based content of clay, silt, and organic matter 15%). The results suggested that soil compaction more than soil type was the major control on gas...... diffusivity and to some extent also on air permeability. We developed a density-corrected (D-C) Dp(e)/Do model as a generalized form of a previous model for Dp/ Do at -100 cm H2O of matric potential (Dp,100/Do). The D-C model performed well across soil types and density levels compared with existing models...

  8. Soil process modelling in CZO research: gains in data harmonisation and model validation

    Science.gov (United States)

    van Gaans, Pauline; Andrianaki, Maria; Kobierska, Florian; Kram, Pavel; Lamacova, Anna; Lair, Georg; Nikolaidis, Nikos; Duffy, Chris; Regelink, Inge; van Leeuwen, Jeroen P.; de Ruiter, Peter

    2014-05-01

    Various soil process models were applied to four European Critical Zone observatories (CZOs), the core research sites of the FP7 project SoilTrEC: the Damma glacier forefield (CH), a set of three forested catchments on geochemically contrasing bedrocks in the Slavkov Forest (CZ), a chronosequence of soils in the former floodplain of the Danube of Fuchsenbigl/Marchfeld (AT), and the Koiliaris catchments in the north-western part of Crete, (GR). The aim of the modelling exercises was to apply and test soil process models with data from the CZOs for calibration/validation, identify potential limits to the application scope of the models, interpret soil state and soil functions at key stages of the soil life cycle, represented by the four SoilTrEC CZOs, contribute towards harmonisation of data and data acquisition. The models identified as specifically relevant were: The Penn State Integrated Hydrologic Model (PIHM), a fully coupled, multiprocess, multi-scale hydrologic model, to get a better understanding of water flow and pathways, The Soil and Water Assessment Tool (SWAT), a deterministic, continuous time (daily time step) basin scale model, to evaluate the impact of soil management practices, The Rothamsted Carbon model (Roth-C) to simulate organic carbon turnover and the Carbon, Aggregation, and Structure Turnover (CAST) model to include the role of soil aggregates in carbon dynamics, The Ligand Charge Distribution (LCD) model, to understand the interaction between organic matter and oxide surfaces in soil aggregate formation, and The Terrestrial Ecology Model (TEM) to obtain insight into the link between foodweb structure and carbon and nutrient turnover. With some exceptions all models were applied to all four CZOs. The need for specific model input contributed largely to data harmonisation. The comparisons between the CZOs turned out to be of great value for understanding the strength and limitations of the models, as well as the differences in soil conditions

  9. Modeling and Simulating Environmental Effects

    OpenAIRE

    Guest, Peter S.; Murphree, Tom; Frederickson, Paul A.; Guest, Arlene A.

    2012-01-01

    MOVES Research & Education Systems Seminar: Presentation; Session 4: Collaborative NWDC/NPS M&S Research; Moderator: Curtis Blais; Modeling and Simulating Environmental Effects; speakers: Peter Guest, Paul Frederickson & Tom Murphree Environmental Effects Group

  10. Assessing soil surface roughness decay during simulated rainfall by multifractal analysis

    Directory of Open Access Journals (Sweden)

    E. Vidal Vázquez

    2008-06-01

    Full Text Available Understanding and describing the spatial characteristics of soil surface microrelief are required for modelling overland flow and erosion. We employed the multifractal approach to characterize topographical point elevation data sets acquired by high resolution laser scanning for assessing the effect of simulated rainfall on microrelief decay. Three soil surfaces with different initial states or composition and rather smooth were prepared on microplots and subjected to successive events of simulated rainfall. Soil roughness was measured on a 2×2 mm2 grid, initially, i.e. before rain, and after each simulated storm, yielding a total of thirteen data sets for three rainfall sequences. The vertical microrelief component as described by the statistical index random roughness (RR exhibited minor changes under rainfall in two out of three study cases, which was due to the imposed wet initial state constraining aggregate breakdown. The effect of cumulative rainfall on microrelief decay was also assessed by multifractal analysis performed with the box-count algorithm. Generalized dimension, Dq, spectra allowed characterization of the spatial variation of soil surface microrelief measured at the microplot scale. These Dq spectra were also sensitive to temporal changes in soil surface microrelief, so that in all the three study rain sequences, the initial soil surface and the surfaces disturbed by successive storms displayed great differences in their degree of multifractality. Therefore, Multifractal parameters best discriminate between successive soil stages under a given rain sequence. Decline of RR and multifractal parameters showed little or no association.

  11. TREAT Modeling and Simulation Strategy

    Energy Technology Data Exchange (ETDEWEB)

    DeHart, Mark David [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-09-01

    This report summarizes a four-phase process used to describe the strategy in developing modeling and simulation software for the Transient Reactor Test Facility. The four phases of this research and development task are identified as (1) full core transient calculations with feedback, (2) experiment modeling, (3) full core plus experiment simulation and (4) quality assurance. The document describes the four phases, the relationship between these research phases, and anticipated needs within each phase.

  12. An Expert support model for ex situ soil remediation

    NARCIS (Netherlands)

    Okx, J.P.; Frankhuizen, E.M.; Wit, de J.C.; Pijls, C.G.J.M.; Stein, A.

    2000-01-01

    This paper presents an expert support model recombining knowledge and experience obtained during ex situ soil remediation. To solve soil remediation problems, an inter-disciplinary approach is required. Responsibilities during the soil remediation process, however, are increasingly decentralised, wh

  13. Implicit numerical integration for a kinematic hardening soil plasticity model

    Science.gov (United States)

    Rouainia, M.; Muir Wood, D.

    2001-11-01

    Soil models based on kinematic hardening together with elements of bounding surface plasticity, provide a means of introducing some memory of recent history and stiffness variation in the predicted response of soils. Such models provide an improvement on simple elasto-plastic models in describing soil behaviour under non-monotonic loading. Routine use of such models requires robust numerical integration schemes. Explicit integration of highly non-linear models requires extremely small steps in order to guarantee convergence. Here, a fully implicit scheme is presented for a simple kinematic hardening extension of the Cam clay soil model. The algorithm is based on the operator split methodology and the implicit Euler backward integration scheme is proposed to integrate the rate form of the constitutive relations. This algorithm maintains a quadratic rate of asymptotic convergence when used with a Newton-Raphson iterative procedure. Various strain-driven axisymmetric triaxial paths are simulated in order to demonstrate the efficiency and good performance of the proposed algorithm.

  14. A New Model for Simulating TSS Washoff in Urban Areas

    Directory of Open Access Journals (Sweden)

    E. Crobeddu

    2011-01-01

    Full Text Available This paper presents the formulation and validation of the conceptual Runoff Quality Simulation Model (RQSM that was developed to simulate the erosion and transport of solid particles in urban areas. The RQSM assumes that solid particle accumulation on pervious and impervious areas is infinite. The RQSM simulates soil erosion using rainfall kinetic energy and solid particle transport with linear system theory. A sensitivity analysis was conducted on the RQSM to show the influence of each parameter on the simulated load. Total suspended solid (TSS loads monitored at the outlet of the borough of Verdun in Canada and at three catchment outlets of the City of Champaign in the United States were used to validate the RQSM. TSS loads simulated by the RQSM were compared to measured loads and to loads simulated by the Rating Curve model and the Exponential model of the SWMM software. The simulation performance of the RQSM was comparable to the Exponential and Rating Curve models.

  15. An Approach for Simulating Soil Loss from an Agro-Ecosystem Using Multi-Agent Simulation: A Case Study for Semi-Arid Ghana

    Directory of Open Access Journals (Sweden)

    Biola K. Badmos

    2015-07-01

    Full Text Available Soil loss is not limited to change from forest or woodland to other land uses/covers. It may occur when there is agricultural land-use/cover modification or conversion. Soil loss may influence loss of carbon from the soil, hence implication on greenhouse gas emission. Changing land use could be considered actually or potentially successful in adapting to climate change, or may be considered maladaptation if it creates environmental degradation. In semi-arid northern Ghana, changing agricultural practices have been identified amongst other climate variability and climate change adaptation measures. Similarly, some of the policies aimed at improving farm household resilience toward climate change impact might necessitate land use change. The heterogeneity of farm household (agents cannot be ignored when addressing land use/cover change issues, especially when livelihood is dependent on land. This paper therefore presents an approach for simulating soil loss from an agro-ecosystem using multi-agent simulation (MAS. We adapted a universal soil loss equation as a soil loss sub-model in the Vea-LUDAS model (a MAS model. Furthermore, for a 20-year simulation period, we presented the impact of agricultural land-use adaptation strategy (maize cultivation credit i.e., maize credit scenario on soil loss and compared it with the baseline scenario i.e., business-as-usual. Adoption of maize as influenced by maize cultivation credit significantly influenced agricultural land-use change in the study area. Although there was no significant difference in the soil loss under the tested scenarios, the incorporation of human decision-making in a temporal manner allowed us to view patterns that cannot be seen in single step modeling. The study shows that opening up cropland on soil with a high erosion risk has implications for soil loss. Hence, effective measures should be put in place to prevent the opening up of lands that have high erosion risk.

  16. Stochastic modeling analysis and simulation

    CERN Document Server

    Nelson, Barry L

    1995-01-01

    A coherent introduction to the techniques for modeling dynamic stochastic systems, this volume also offers a guide to the mathematical, numerical, and simulation tools of systems analysis. Suitable for advanced undergraduates and graduate-level industrial engineers and management science majors, it proposes modeling systems in terms of their simulation, regardless of whether simulation is employed for analysis. Beginning with a view of the conditions that permit a mathematical-numerical analysis, the text explores Poisson and renewal processes, Markov chains in discrete and continuous time, se

  17. Karst bare slope soil erosion and soil quality: a simulation case study

    Directory of Open Access Journals (Sweden)

    Q. Dai

    2015-06-01

    Full Text Available The influence on soil erosion by different bedrock bareness ratios, different rainfall intensities, different underground pore fissure degrees and rainfall duration are researched through manual simulation of microrelief characteristics of karst bare slopes and underground karst crack construction in combination with artificial simulation of rainfall experiment. The results show that firstly, when the rainfall intensity is small (30 and 50 mm h−1, no bottom load loss is produced on the surface, and surface and underground runoff and sediment production is increased with the increasing of rainfall intensity; secondly, surface runoff and sediment production reduced with increased underground pore fissure degree, while underground runoff and sediment production increased; thirdly, raindrops hit the surface, forming a crust with rainfall duration. The formation of crusts increases surface runoff erosion and reduces soil infiltration rate. Increasing of surface runoff erosion damaged crust and increased soil seepage rate. Raindrops continued to hit the surface, leading the formation of crust. Soil permeability showed volatility which were from reduction to increases and reduction, and so on. Surface and subsurface runoff were volatility with rainfall duration; fourthly, when rock bareness ratio is 50% and rainfall intensities are 30 and 50 mm h−1, runoff is not produced on the surface, and the slope runoff and sediment production presents a fluctuating change with increased rock bareness ratio; fifthly, the correlation degree between the slope runoff and sediment production and all factors are as follows: rainfall intensity > rainfall duration > underground pore fissure degree > bed rock bareness ratio.

  18. Model reduction for circuit simulation

    CERN Document Server

    Hinze, Michael; Maten, E Jan W Ter

    2011-01-01

    Simulation based on mathematical models plays a major role in computer aided design of integrated circuits (ICs). Decreasing structure sizes, increasing packing densities and driving frequencies require the use of refined mathematical models, and to take into account secondary, parasitic effects. This leads to very high dimensional problems which nowadays require simulation times too large for the short time-to-market demands in industry. Modern Model Order Reduction (MOR) techniques present a way out of this dilemma in providing surrogate models which keep the main characteristics of the devi

  19. A land surface soil moisture data assimilation framework in consideration of the model subgrid-scale heterogeneity and soil water thawing and freezing

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The Ensemble Kalman Filter (EnKF) is well known and widely used in land data assimilation for its high precision and simple operation. The land surface models used as the forecast operator in a land data assimilation system are usually designed to consider the model subgrid-heterogeneity and soil water thawing and freezing. To neglect their effects could lead to some errors in soil moisture assimilation. The dual EnKF method is employed in soil moisture data assimilation to build a soil moisture data as- similation framework based on the NCAR Community Land Model version 2.0 (CLM 2.0) in considera- tion of the effects of the model subgrid-heterogeneity and soil water thawing and freezing: Liquid volumetric soil moisture content in a given fraction is assimilated through the state filter process, while solid volumetric soil moisture content in the same fraction and solid/liquid volumetric soil moisture in the other fractions are optimized by the parameter filter. Preliminary experiments show that this dual EnKF-based assimilation framework can assimilate soil moisture more effectively and precisely than the usual EnKF-based assimilation framework without considering the model subgrid-scale heteroge- neity and soil water thawing and freezing. With the improvement of soil moisture simulation, the soil temperature-simulated precision can be also improved to some extent.

  20. A land surface soil moisture data assimilation framework in consideration of the model subgrid-scale heterogeneity and soil water thawing and freezing

    Institute of Scientific and Technical Information of China (English)

    TIAN XiangJun; XIE ZhengHui

    2008-01-01

    The Ensemble Kalman Filter (EnKF) is well known and widely used in land data assimilation for its high precision and simple operation. The land surface models used as the forecast operator in a land data assimilation system are usually designed to consider the model subgrid-heterogeneity and soil water thawing and freezing. To neglect their effects could lead to some errors in soil moisture assimilation.The dual EnKF method is employed in soil moisture data assimilation to build a soil moisture data assimilation framework based on the NCAR Community Land Model version 2.0 (CLM 2.0) in consideration of the effects of the model subgrid-heterogeneity and soil water thawing and freezing: Liquid volumetric soil moisture content in a given fraction is assimilated through the state filter process,while solid volumetric soil moisture content in the same fraction and solid/liquid volumetric soil moisture in the other fractions are optimized by the parameter filter. Preliminary experiments show that this dual EnKF-based assimilation framework can assimilate soil moisture more effectively and precisely than the usual EnKF-based assimilation framework without considering the model subgrid-scale heterogeneity and soil water thawing and freezing. With the improvement of soil moisture simulation,the soil temperature-simulated precision can be also improved to some extent.

  1. An event-based hydrologic simulation model for bioretention systems.

    Science.gov (United States)

    Roy-Poirier, A; Filion, Y; Champagne, P

    2015-01-01

    Bioretention systems are designed to treat stormwater and provide attenuated drainage between storms. Bioretention has shown great potential at reducing the volume and improving the quality of stormwater. This study introduces the bioretention hydrologic model (BHM), a one-dimensional model that simulates the hydrologic response of a bioretention system over the duration of a storm event. BHM is based on the RECARGA model, but has been adapted for improved accuracy and integration of pollutant transport models. BHM contains four completely-mixed layers and accounts for evapotranspiration, overflow, exfiltration to native soils and underdrain discharge. Model results were evaluated against field data collected over 10 storm events. Simulated flows were particularly sensitive to antecedent water content and drainage parameters of bioretention soils, which were calibrated through an optimisation algorithm. Temporal disparity was observed between simulated and measured flows, which was attributed to preferential flow paths formed within the soil matrix of the field system. Modelling results suggest that soil water storage is the most important short-term hydrologic process in bioretention, with exfiltration having the potential to be significant in native soils with sufficient permeability.

  2. Modelling Soil Water Characteristic Curves for the Investigation of Hydrophobicity

    Science.gov (United States)

    Hallin, Ingrid; Matthews, Peter; Laudone, Maurizio; Van Keulen, Geertje; Doerr, Stefan; Francis, Lewis; Dudley, Ed; Gazze, Andrea; Quinn, Gerry; Whalley, Richard; Ashton, Rhys

    2016-04-01

    Soil hydrophobicity presents a major challenge for the future, as it reduces both plant-available water and irrigation efficiency, and can increase flooding hazards and erosion. A collaborative research project has been set up in the UK to study hydrophobicity over a wide range of length scales. At core scale, we are investigating the wetting behaviour of water repellent soils in order to model percolation through hydrophobic pore spaces. To that end, water retention measurements were carried out on both wettable and forcibly-wetted water-repellent soils collected from three locations in England and Wales. The data were then fitted with both the commonly used Van Genuchten model and an alternative model from PoreXpert, a software program that analyses and models porous materials. The Van Genuchten model fits a curve to the data using parameters related to air entry suction, irreducible water content and pore size distribution. By contrast, PoreXpert uses a Boltzmann-annealed simplex to find a best-fit curve based on parameters directly related to the void structure of the soil: the size of the voids, the shape of the void size distribution, and how the voids are connected to each other. Both Van Genuchten and PoreXpert fit the experimental data well, but where Van Genuchten forces an S-shaped curve that can mask small variations, PoreXpert gives a closer fit of no pre-defined shape that captures subtle differences between data points. This allows us to calculate differences in the effective pore and throat size distributions, and provides a mechanistic framework from which to model additional hydrologic behaviour in water repellent soil. Simulations of capillary induced wetting based on these mechanistic postulates are then compared to wicking experiments at the core scale, which can then be upscaled and applied to other soils.

  3. Partitioning of simulated rainfall in a kaolinitic soil under improved fallow-maize rotation in Zimbabwe

    NARCIS (Netherlands)

    Nyamadzawo, G.; Nyamugafata, P.; Chikowo, R.; Giller, K.E.

    2003-01-01

    Research on improved fallows has concentrated on soil fertility benefits neglecting possible benefits to soil and water conservation. The effects of improved fallows on rainfall partitioning and associated soil loss were investigated using simulated rainfall on a kaolinitic soil in Zimbabwe.

  4. Pore - to - Core Modeling of Soil Organic Matter Decomposition in 3D Soil Structures

    Science.gov (United States)

    Falconer, R. E.; Battaia, G.; Baveye, P.; Otten, W.

    2013-12-01

    There is a growing body of literature supporting the need for microbial contributions to be considered explicitly in carbon-climate models. There is also overwhelming evidence that physical protection within aggregates can play a significant role in organic matter dynamics. Yet current models of soil organic matter dynamics divide soil organic matter into conceptual pools with distinct turnover times, assuming that a combination of biochemical and physical properties control decay without explicit description. Albeit robust in their application, such models are not capable to account for changes in soil structure or microbial populations, or accurately predict the effect of wetness or priming. A spatially explicit model is presented that accounts for microbial dynamics and physical processes, permitting consideration of the heterogeneity of the physical and chemical microenvironments at scales relevant for microbes. Exemplified for fungi, we investigate how micro-scale processes manifest at the core scale with particular emphasis on evolution of CO2 and biomass distribution. The microbial model is based upon previous (Falconer et al, 2012) and includes the following processes: uptake, translocation, recycling, enzyme production, growth, spread and respiration. The model is parameterised through a combination of literature data and parameter estimation (Cazelles et al., 2012).The Carbon model comprises two pools, particulate organic matter which through enzymatic activity is converted into dissolved organic matter. The microbial and carbon dynamics occur within a 3D soil structure obtained by X-ray CT. We show that CO2 is affected not only by the amount of Carbon in the soil but also by microbial dynamics, soil structure and the spatial distribution of OM. The same amount of OM can result in substantially different respiration rates, with surprisingly more CO2 with increased clustering of OM. We can explain this from the colony dynamics, production of enzymes and

  5. On integration of a cyclic soil plasticity model

    Science.gov (United States)

    Manzari, Majid T.; Prachathananukit, Rung

    2001-05-01

    Performance of three classes of explicit and implicit time-stepping integrators is assessed for a cyclic plasticity constitutive model for sands. The model is representative of an important class of cyclic plasticity models for soils and includes both isotropic and nonlinear kinematic hardening. The implicit algorithm is based on the closest point projection method and the explicit algorithm follows a cutting-plane integration procedure. A sub-stepping technique was also implemented. The performance of these algorithms is assessed through a series of numerical simulations ranging from simulations of laboratory tests (such as triaxial and bi-axial compression, direct shear, and cyclic triaxial tests) to the analysis of a typical boundary value problem of geotechnical earthquake engineering. These simulations show that the closest point projection algorithm remains stable and accurate for relatively large strain increments and for cases where the mean effective stress in a soil element reaches very small values leading to a liquefaction state. It is also shown that while the cutting plane (CP) and sub-stepping (SS) algorithms provide high efficiency and good accuracy for small to medium size strain increments, their accuracy and efficiency deteriorate faster than the closest point projection method for large strain increments. The CP and SS algorithms also face convergence difficulties in the liquefaction analysis when the soil approaches very small mean effective stresses.

  6. [Effects of simulated warming on soil enzyme activities in two subalpine coniferous forests in west Sichuan].

    Science.gov (United States)

    Xu, Zhen-feng; Tang, Zheng; Wan, Chuan; Xiong, Pei; Cao, Gang; Liu, Qing

    2010-11-01

    With open top chamber (OTC), this paper studied the effects of simulated warming on the activities of soil invertase, urease, catalase, polyphenol oxidase in two contrasting subalpine coniferous forests (a dragon spruce plantation and a natural conifer forest) in west Sichuan. The dynamic changes of soil temperature and soil moisture were monitored synchronously. In the whole growth season, simulated warming enhanced the daily mean temperature at soil depth 5 cm by 0.61 degrees C in the plantation, and by 0.55 degrees C in the natural forest. Conversely, the volumetric moisture at soil depth 10 cm was declined by 4.10% and 2.55%, respectively. Simulated warming also increased soil invertase, urease, catalase, and polyphenol oxidase activities. The interactive effect of warming and forest type was significant on soil urease and catalase, but not significant on soil invertase and polyphenol oxidase. The warming effect on soil catalase depended, to some extent, on season change. In all treatments, the soil enzyme activities in the natural forest were significantly higher than those in the plantation. The seasonal changes of test soil enzyme activities were highly correlated with soil temperature, but less correlated with soil moisture. This study indicated that warming could enhance soil enzyme activities, and the effect had definite correlations with forest type, enzyme category, and season change. The soil enzyme activities in the subalpine coniferous forests were mainly controlled by soil temperature rather than soil moisture.

  7. Simulation of Soil Organic Carbon Dynamics in Chinese Rice Paddies from 1980 to 2000

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wen; YU Yong-Qiang; SUN Wen-Juan; HUANG Yao

    2007-01-01

    Changes in soil organic carbon (SOC) of rice paddies in China were simulated from 1980 to 2000 by linking a coupled bio-physical model to GIS database. The coupled model consists of two sub-models including Crop-C for simulating net primary productivity and hence residue retention and Soil-C for computing the turnover rates of SOC. The GIS database included parameters of climate, soils and agricultural activities with the resolution of 10 km × 10 km. Model simulation indicated that Chinese rice paddies covering 22.6 Mha sequestrated a considerable amount of C, about 0.15 ± 0.07 Pg C from 1980 to 2000. Annual sequestration rate increased sharply from -180 ± 45 kg C ha-1 year-1 in 1980 to 440 ± 170kg C ha-1 year-1 in 1989. Thereafter, a steady sequestration rate of 460 ± 170 kg C ha-1 year-1 occurred till 1994 and declined since then. Approximately 84% of the Chinese rice paddies sequestrated carbon, while 15% lost carbon and 1%kept balance over the 20 years. Great SOC sequestration occurred in eastern, southern and central China, while a slight decline of SOC existed in some regions of northeastern and southwestern China.

  8. Runoff Simulation of Shitoukoumen Reservoir Basin Based on SWAT Model

    Institute of Scientific and Technical Information of China (English)

    XIE; Miao; LI; Hong-yan; LIU; Tie-juan; RU; Shi-rong

    2012-01-01

    [Objective]The study aimed to simulate the runoff of Shitoukoumen Reservoir basin by using SWAT model. [Method] Based on DEM elevation, land use type, soil type and hydrometeorological data, SWAT model, a distributed hydrological model was established to simulate the monthly runoff of Shitoukoumen Reservoir basin, and the years 2006 and 2010 were chosen as the calibration and validation period respectively. [Result] The simulation results indicated that SWAT model could be used to simulate the runoff of Shitoukoumen Reservoir basin, and the simulation effect was good. However, the response of the model to local rainstorm was not obvious, so that the actual runoff in June and July of 2010 was abnormally higher than the simulation value. [Conclusion] The research could provide theoretical references for the plan and management of water resources in Shitoukoumen Reservoir basin in future.

  9. Simulation of Vegetative Induced Deformation in an Unsaturated Soil

    Directory of Open Access Journals (Sweden)

    Nazri B. Ali

    2010-01-01

    Full Text Available Problem statement: Tree root water-uptake increases soil strength by increasing the soil matric suction due to pore pressure dissipation in a soil mass, inducing increases in vertical total stress or water extraction, the effective stress to which the soil strata is subjected to may also increase. This causes volume change which might be detrimental to geotechnical structures and shallow foundation. Approach: This study proposed a methodology that can be used for the prediction of the root water-uptake and deformation. It is suggested that negative pore-water pressures can be estimated through two-dimensional governing equation for unsaturated soil and was converted to axi-symmetrical form due radially nature of tree roots. Results: The results of the root water-uptake analysis are then used as input for the prediction of ground displacements in a stress-deformation analysis. A volume change was modeled as a result of matric suction change caused by vegetative induced moisture migration. The proposed method is studied and tested against data collected on a case history involving a mature Lime tree on Boulder clay at Stacey Hall, Wolverton, England and mechanical properties of Boulder Clay. The recommended safe planting distance of trees of height, H, from buildings a distance, L, away is in form of L: H≥0.5 m ratio. Conclusion: The predicted results from the two dimensional axi-symmetrical analyses agree well with the measured data in terms of both total vertical displacements and final water contents in the soil. Based on hypothesis, the numerical model developed provides practicing geotechnical engineers an effective tool for designing structures on vadose zones containing vegetation.

  10. Mathematical modeling in soil science

    Science.gov (United States)

    Tarquis, Ana M.; Gasco, Gabriel; Saa-Requejo, Antonio; Méndez, Ana; Andina, Diego; Sánchez, M. Elena; Moratiel, Rubén; Antón, Jose Manuel

    2015-04-01

    Teaching in context can be defined as teaching a mathematical idea or process by using a problem, situation, or data to enhance the teaching and learning process. The same problem or situation may be used many times, at different mathematical levels to teach different objectives. A common misconception exists that assigning/teaching applications is teaching in context. While both use problems, the difference is in timing, in purpose, and in student outcome. In this work, one problem situation is explored thoroughly at different levels of understanding and other ideas are suggested for classroom explorations. Some teachers, aware of the difficulties some students have with mathematical concepts, try to teach quantitative sciences without using mathematical tools. Such attempts are not usually successful. The answer is not in discarding the mathematics, but in finding ways to teach mathematically-based concepts to students who need them but who find them difficult. The computer is an ideal tool for this purpose. To this end, teachers of the Soil Science and Mathematics Departments of the UPM designed a common practice to teach to the students the role of soil on the carbon sequestration. The objective of this work is to explain the followed steps to the design of the practice. Acknowledgement Universidad Politécnica de Madrid (UPM) for the Projects in Education Innovation IE12_13-02009 and IE12_13-02012 is gratefully acknowledge.

  11. Model Test Based Soil Spring Model and Application in Pipeline Thermal Buckling Analysis

    Institute of Scientific and Technical Information of China (English)

    GAO Xi-feng; LIU Run; YAN Shu-wang

    2011-01-01

    The buckling of submarine pipelines may occur due to the action of axial soil frictional force caused by relative movement of soil and pipeline,which is induced by the thermal and internal pressure.The likelihood of occurrence of this buckling phenomenon is largely determined by soil resistance.A series of large-scale model tests were carried out to facilitate the establishment of substantial data base for a variety of burial pipeline relationships.Based on the test data,nonlinear soil spring can be adopted to simulate the soil behavior during the pipeline movement.For uplift resistance,an ideal elasticity plasticity model is recommended in the case of H/D (depth-to-diameter ratio)>5 and an elasticity softened model is recommended in the case of H/D≤5.The soil resistance along the pipeline axial direction can be simulated by an ideal elasticity plasticity model.The numerical analyzing results show that the capacity of pipeline against thermal buckling decreases with its initial imperfection enlargement and increases with the burial depth enhancement.

  12. A VRLA battery simulation model

    Energy Technology Data Exchange (ETDEWEB)

    Pascoe, P.E.; Anbuky, A.H. [Invensys Energy Systems NZ Limited, Christchurch (New Zealand)

    2004-05-01

    A valve regulated lead acid (VRLA) battery simulation model is an invaluable tool for the standby power system engineer. The obvious use for such a model is to allow the assessment of battery performance. This may involve determining the influence of cells suffering from state of health (SOH) degradation on the performance of the entire string, or the running of test scenarios to ascertain the most suitable battery size for the application. In addition, it enables the engineer to assess the performance of the overall power system. This includes, for example, running test scenarios to determine the benefits of various load shedding schemes. It also allows the assessment of other power system components, either for determining their requirements and/or vulnerabilities. Finally, a VRLA battery simulation model is vital as a stand alone tool for educational purposes. Despite the fundamentals of the VRLA battery having been established for over 100 years, its operating behaviour is often poorly understood. An accurate simulation model enables the engineer to gain a better understanding of VRLA battery behaviour. A system level multipurpose VRLA battery simulation model is presented. It allows an arbitrary battery (capacity, SOH, number of cells and number of strings) to be simulated under arbitrary operating conditions (discharge rate, ambient temperature, end voltage, charge rate and initial state of charge). The model accurately reflects the VRLA battery discharge and recharge behaviour. This includes the complex start of discharge region known as the coup de fouet. (author)

  13. Leaching of chromium from chromium contaminated soil: Speciation study and geochemical modeling

    Directory of Open Access Journals (Sweden)

    Anđelković Darko H.

    2012-01-01

    Full Text Available Distribution of chromium between soil and leachate was monitored. A natural process of percolating rainwater through the soil was simulated in the laboratory conditions and studied with column leaching extraction. Migration of chromium in the soil is conditioned by the level of chromium soil contamination, the soil organic matter content, and rainwater acidity. Chromium (III and chromium(VI were determined by spectrophotometric method with diphenilcarbazide in acidic media. Comparing the results of chromium speciation in leachate obtained by experimental model systems and geochemical modelling calculations using Visual MINTEQ model, a correlation was observed regarding the influence of the tested parameters. Leachate solutions showed that the concentration of Cr depended on the organic matter content. The influence of pH and soil organic matter content is in compliance after its definition through experimental and theoretical way. The computer model - Stockholm Humic Model used to evaluate the leaching results corresponded rather well with the measured values.

  14. Advances in Application of Models in Soil Quality Evaluation

    Institute of Scientific and Technical Information of China (English)

    SI Zhi-guo; WANG Ji-jie; YU Yuan-chun; LIANG Guan-feng; CHEN Chang-ren; SHU Hong-lan

    2012-01-01

    Soil quality is a comprehensive reflection of soil properties.Since the soil quality concept was put forward in the 1970s,the quality of different type soils in different regions have been evaluated through a variety of evaluation methods,but it still lacks universal soil quantity evaluation models and methods.In this paper,the applications and prospects of grey relevancy comprehensive evaluation model,attribute hierarchical model,fuzzy comprehensive evaluation model,matter-element model,RAGA-based PPC /PPE model and GIS model in soil quality evaluation are reviewed.

  15. Modelling and Simulation: An Overview

    NARCIS (Netherlands)

    M.J. McAleer (Michael); F. Chan (Felix); L. Oxley (Les)

    2013-01-01

    textabstractThe papers in this special issue of Mathematics and Computers in Simulation cover the following topics: improving judgmental adjustment of model-based forecasts, whether forecast updates are progressive, on a constrained mixture vector autoregressive model, whether all estimators are bor

  16. General introduction to simulation models

    DEFF Research Database (Denmark)

    Hisham Beshara Halasa, Tariq; Boklund, Anette

    2012-01-01

    Monte Carlo simulation can be defined as a representation of real life systems to gain insight into their functions and to investigate the effects of alternative conditions or actions on the modeled system. Models are a simplification of a system. Most often, it is best to use experiments and field...

  17. Modelling, simulating and optimizing Boilers

    DEFF Research Database (Denmark)

    Sørensen, Kim; Condra, Thomas Joseph; Houbak, Niels

    2003-01-01

    of the boiler has been developed and simulations carried out by means of the Matlab integration routines. The model is prepared as a dynamic model consisting of both ordinary differential equations and algebraic equations, together formulated as a Differential-Algebraic- Equation system. Being able to operate...

  18. Modeling Carbon Dynamics in Paddy Soils in Jiangsu Province of China with Soil Databases Differing in Spatial Resolution

    Institute of Scientific and Technical Information of China (English)

    XU Sheng-Xiang; SHI Xue-Zheng; ZHAO Yong-Cun; YU Dong-Sheng; WANG Shi-Hang; ZHANG Li-Ming; C. S. LI; TAN Man-Zhi

    2011-01-01

    A number of process-based models have been developed for quantifying carbon (C) sequestration in ago-ecosystems.The DeNitrification-DeComposition (DNDC) model was used to simulate and quantify long-term (1980-2008) soil organic carbon (SOC) dynamics in the important rice-producing province,Jiangsu,China.Changes in SOC storages were estimated from two soil databases differing in spatial resolution:a county database consisting of 68 polygons and a soil patch-based database of 701 polygons for all 3.7 Mha of rice fields in Jiangsu.The simulated SOC storage with the coarse resolution county database ranged between 131.0-320.6 Tg C in 1980 and 170.3-305.1 Tg C in 2008,respectively,while that estimated with the fine resolution database was 201.6 and 216.2 Tg C in 1980 and 2008,respectively.The results modeled with the soil databases differing in spatial resolution indicated that using the soil input data with higher resolution substantially increased the accuracy of the modeled results; and when lacking detailed soil datasets,the DNDC model,parameterized with the most sensitive factor (MSF) method to cope with attribute uncertainty,could still produce acceptable results although with deviations of up to 60% for the case study reported in this paper.

  19. Evaluation of soil CO2 production and transport in Duke Forest using a process-based modeling approach

    Science.gov (United States)

    Hui, Dafeng; Luo, Yiqi

    2004-12-01

    Soil surface CO2 efflux is an important component of the carbon cycle in terrestrial ecosystems. However, our understanding of mechanistic controls of soil CO2 production and transport is greatly limited. A multilayer process-based soil CO2 efflux model (PATCIS) was used to evaluate soil CO2 production and transport in the Duke Forest. CO2 production in the soil is the sum of root respiration and soil microbial respiration, and CO2 transport in the soil mainly simulates gaseous diffusion. Simulated soil CO2 efflux in the Duke Forest ranged from 5 g CO2 m-2 d-1 in the winter to 25 g CO2 m-2 d-1 in summer. Annual soil CO2 efflux was 997 and 1211 g C m-2 yr-1 in 1997 and 1998, respectively. These simulations were consistent with the observed soil CO2 efflux. Simulated root respiration contributed 53% to total soil respiration. Soil temperature had the dominant influence on soil CO2 production and CO2 efflux while soil moisture only regulated soil CO2 efflux in the summer when soil moisture was very low. Soil CO2 efflux was sensitive to the specific fine root respiratory rate and live fine root biomass. Elevated CO2 increased annual soil CO2 efflux by 26% in 1997 and 18% in 1998, due mainly to the enhanced live fine root biomass and litterfall. On a daily to yearly basis, CO2 production is almost identical to CO2 efflux, suggesting that CO2 transport is not a critical process regulating daily and long-term soil surface CO2 effluxes in the Duke Forest. We also developed a statistical model of soil CO2 efflux with soil temperature and moisture. Daily soil CO2 efflux estimation by the statistical model showed a similar pattern to the simulated soil CO2 efflux, but the total annual CO2 efflux was slightly lower. While the statistical model is simple, yet powerful, in simulating seasonal dynamics of soil CO2 efflux, the process-based model has the potential to advance our mechanistic understanding of soil CO2 efflux variations in the current and future worlds.

  20. Characterization of Apollo Bulk Soil Samples Under Simulated Lunar Conditions

    Science.gov (United States)

    Donaldson Hanna, K. L.; Pieters, C. M.; Thomas, I.; Bowles, N. E.; Greenhagen, B. T.

    2013-12-01

    Remote observations provide key insights into the composition and evolution of planetary surfaces. A fundamentally important component to any remote compositional analysis of planetary surfaces is laboratory measurements of well-characterized samples measured under the appropriate environmental conditions. The vacuum environment of airless bodies like the Moon creates a steep thermal gradient in the upper hundreds of microns of regolith. Lab studies of particulate rocks and minerals as well as selected lunar soils under vacuum and lunar-like conditions have identified significant effects of this thermal gradient on thermal infrared (TIR) spectral measurements [e.g. Logan et al. 1973, Salisbury and Walter 1989, Thomas et al. 2012, Donaldson Hanna et al. 2012]. Such lab studies demonstrate the high sensitivity of TIR emissivity spectra to environmental conditions under which they are measured. To best understand the effects of the near surface-environment of the Moon, a consortium of four institutions with the capabilities of characterizing lunar samples was created. The goal of the Thermal Infrared Emission Studies of Lunar Surface Compositions Consortium (TIRES-LSCC) is to characterize Apollo bulk soil samples with a range of compositions and maturities in simulated lunar conditions to provide better context for the spectral effects due to varying compositions and soil maturity as well as for the interpretation of data obtained by the LRO Diviner Lunar Radiometer and future lunar and airless body thermal emission spectrometers. An initial set of thermal infrared emissivity measurements of the bulk lunar soil samples will be made in three of the laboratories included in the TIRES-LSCC: the Asteroid and Lunar Environment Chamber (ALEC) in RELAB at Brown University, the Simulated Lunar Environment chamber in the Planetary Spectroscopy Facility (PSF) at the University of Oxford, and the Simulated Airless Body Emission Laboratory (SABEL) at the Jet Propulsion Laboratory

  1. Modeling atrazine transport in soil columns with HYDRUS-1D

    Directory of Open Access Journals (Sweden)

    John Leju CELESTINO LADU

    2011-09-01

    Full Text Available Both physical and chemical processes affect the fate and transport of herbicides. It is useful to simulate these processes with computer programs to predict solute movement. Simulations were run with HYDRUS-1D to identify the sorption and degradation parameters of atrazine through calibration from the breakthrough curves (BTCs. Data from undisturbed and disturbed soil column experiments were compared and analyzed using the dual-porosity model. The study results show that the values of dispersivity are slightly lower in disturbed columns, suggesting that the more heterogeneous the structure is, the higher the dispersivity. Sorption parameters also show slight variability, which is attributed to the differences in soil properties, experimental conditions and methods, or other ecological factors. For both of the columns, the degradation rates were similar. Potassium bromide was used as a conservative non-reactive tracer to characterize the water movement in columns. Atrazine BTCs exhibited significant tailing and asymmetry, indicating non-equilibrium sorption during solute transport. The dual-porosity model was verified to best fit the BTCs of the column experiments. Greater or lesser concentration of atrazine spreading to the bottom of the columns indicated risk of groundwater contamination. Overall, HYDRUS-1D successfully simulated the atrazine transport in soil columns.

  2. Modeling the impact of soil aggregate size on selenium immobilization

    Directory of Open Access Journals (Sweden)

    M. F. Kausch

    2012-09-01

    Full Text Available Soil aggregates are mm- to cm-sized microporous structures separated by macropores. Whereas fast advective transport prevails in macropores, advection is inhibited by the low permeability of intra-aggregate micropores. This can lead to mass transfer limitations and the formation of aggregate-scale concentration gradients affecting the distribution and transport of redox sensitive elements. Selenium (Se mobilized through irrigation of seleniferous soils has emerged as a major aquatic contaminant. In the absence of oxygen, the bioavailable oxyanions selenate, Se(VI, and selenite, Se(IV, can be microbially reduced to solid, elemental Se, Se(0, and anoxic microzones within soil aggregates are thought to promote this process in otherwise well aerated soils.

    To evaluate the impact of soil aggregate size on selenium retention, we developed a dynamic 2-D reactive transport model of selenium cycling in a single idealized aggregate surrounded by a macropore. The model was developed based on flow-through-reactor experiments involving artificial soil aggregates (diameter: 2.5 cm made of sand and containing Enterobacter cloacae SLD1a-1 that reduces Se(VI via Se(IV to Se(0. Aggregates were surrounded by a constant flow providing Se(VI and pyruvate under oxic or anoxic conditions. In the model, reactions were implemented with double-Monod rate equations coupled to the transport of pyruvate, O2, and Se-species. The spatial and temporal dynamics of the model were validated with data from experiments and predictive simulations were performed covering aggregate sizes between 1 and 2.5 cm diameter.

    Simulations predict that selenium retention scales with aggregate size. Depending on O2, Se(VI, and pyruvate concentrations, selenium retention was 4–23 times higher in 2.5-cm-aggregates compared to 1-cm-aggregates. Under oxic conditions, aggregate size and pyruvate-concentrations were found to have a positive synergistic

  3. Modeling the impact of soil aggregate size on selenium immobilization

    Science.gov (United States)

    Kausch, M. F.; Pallud, C. E.

    2013-03-01

    Soil aggregates are mm- to cm-sized microporous structures separated by macropores. Whereas fast advective transport prevails in macropores, advection is inhibited by the low permeability of intra-aggregate micropores. This can lead to mass transfer limitations and the formation of aggregate scale concentration gradients affecting the distribution and transport of redox sensitive elements. Selenium (Se) mobilized through irrigation of seleniferous soils has emerged as a major aquatic contaminant. In the absence of oxygen, the bioavailable oxyanions selenate, Se(VI), and selenite, Se(IV), can be microbially reduced to solid, elemental Se, Se(0), and anoxic microzones within soil aggregates are thought to promote this process in otherwise well-aerated soils. To evaluate the impact of soil aggregate size on selenium retention, we developed a dynamic 2-D reactive transport model of selenium cycling in a single idealized aggregate surrounded by a macropore. The model was developed based on flow-through-reactor experiments involving artificial soil aggregates (diameter: 2.5 cm) made of sand and containing Enterobacter cloacae SLD1a-1 that reduces Se(VI) via Se(IV) to Se(0). Aggregates were surrounded by a constant flow providing Se(VI) and pyruvate under oxic or anoxic conditions. In the model, reactions were implemented with double-Monod rate equations coupled to the transport of pyruvate, O2, and Se species. The spatial and temporal dynamics of the model were validated with data from experiments, and predictive simulations were performed covering aggregate sizes 1-2.5 cm in diameter. Simulations predict that selenium retention scales with aggregate size. Depending on O2, Se(VI), and pyruvate concentrations, selenium retention was 4-23 times higher in 2.5 cm aggregates compared to 1 cm aggregates. Under oxic conditions, aggregate size and pyruvate concentrations were found to have a positive synergistic effect on selenium retention. Promoting soil aggregation on

  4. Modeling the impact of soil aggregate size on selenium immobilization

    Directory of Open Access Journals (Sweden)

    M. F. Kausch

    2013-03-01

    Full Text Available Soil aggregates are mm- to cm-sized microporous structures separated by macropores. Whereas fast advective transport prevails in macropores, advection is inhibited by the low permeability of intra-aggregate micropores. This can lead to mass transfer limitations and the formation of aggregate scale concentration gradients affecting the distribution and transport of redox sensitive elements. Selenium (Se mobilized through irrigation of seleniferous soils has emerged as a major aquatic contaminant. In the absence of oxygen, the bioavailable oxyanions selenate, Se(VI, and selenite, Se(IV, can be microbially reduced to solid, elemental Se, Se(0, and anoxic microzones within soil aggregates are thought to promote this process in otherwise well-aerated soils. To evaluate the impact of soil aggregate size on selenium retention, we developed a dynamic 2-D reactive transport model of selenium cycling in a single idealized aggregate surrounded by a macropore. The model was developed based on flow-through-reactor experiments involving artificial soil aggregates (diameter: 2.5 cm made of sand and containing Enterobacter cloacae SLD1a-1 that reduces Se(VI via Se(IV to Se(0. Aggregates were surrounded by a constant flow providing Se(VI and pyruvate under oxic or anoxic conditions. In the model, reactions were implemented with double-Monod rate equations coupled to the transport of pyruvate, O2, and Se species. The spatial and temporal dynamics of the model were validated with data from experiments, and predictive simulations were performed covering aggregate sizes 1–2.5 cm in diameter. Simulations predict that selenium retention scales with aggregate size. Depending on O2, Se(VI, and pyruvate concentrations, selenium retention was 4–23 times higher in 2.5 cm aggregates compared to 1 cm aggregates. Under oxic conditions, aggregate size and pyruvate concentrations were found to have a positive synergistic effect on selenium retention. Promoting soil

  5. Multi-site assimilation of a terrestrial biosphere model (BETHY) using satellite derived soil moisture data

    Science.gov (United States)

    Wu, Mousong; Sholze, Marko

    2017-04-01

    We investigated the importance of soil moisture data on assimilation of a terrestrial biosphere model (BETHY) for a long time period from 2010 to 2015. Totally, 101 parameters related to carbon turnover, soil respiration, as well as soil texture were selected for optimization within a carbon cycle data assimilation system (CCDAS). Soil moisture data from Soil Moisture and Ocean Salinity (SMOS) product was derived for 10 sites representing different plant function types (PFTs) as well as different climate zones. Uncertainty of SMOS soil moisture data was also estimated using triple collocation analysis (TCA) method by comparing with ASCAT dataset and BETHY forward simulation results. Assimilation of soil moisture to the system improved soil moisture as well as net primary productivity(NPP) and net ecosystem productivity (NEP) when compared with soil moisture derived from in-situ measurements and fluxnet datasets. Parameter uncertainties were largely reduced relatively to prior values. Using SMOS soil moisture data for assimilation of a terrestrial biosphere model proved to be an efficient approach in reducing uncertainty in ecosystem fluxes simulation. It could be further used in regional an global assimilation work to constrain carbon dioxide concentration simulation by combining with other sources of measurements.

  6. WATSFAR: numerical simulation of soil WATer and Solute fluxes using a FAst and Robust method

    Science.gov (United States)

    Crevoisier, David; Voltz, Marc

    2013-04-01

    To simulate the evolution of hydro- and agro-systems, numerous spatialised models are based on a multi-local approach and improvement of simulation accuracy by data-assimilation techniques are now used in many application field. The latest acquisition techniques provide a large amount of experimental data, which increase the efficiency of parameters estimation and inverse modelling approaches. In turn simulations are often run on large temporal and spatial domains which requires a large number of model runs. Eventually, despite the regular increase in computing capacities, the development of fast and robust methods describing the evolution of saturated-unsaturated soil water and solute fluxes is still a challenge. Ross (2003, Agron J; 95:1352-1361) proposed a method, solving 1D Richards' and convection-diffusion equation, that fulfil these characteristics. The method is based on a non iterative approach which reduces the numerical divergence risks and allows the use of coarser spatial and temporal discretisations, while assuring a satisfying accuracy of the results. Crevoisier et al. (2009, Adv Wat Res; 32:936-947) proposed some technical improvements and validated this method on a wider range of agro- pedo- climatic situations. In this poster, we present the simulation code WATSFAR which generalises the Ross method to other mathematical representations of soil water retention curve (i.e. standard and modified van Genuchten model) and includes a dual permeability context (preferential fluxes) for both water and solute transfers. The situations tested are those known to be the less favourable when using standard numerical methods: fine textured and extremely dry soils, intense rainfall and solute fluxes, soils near saturation, ... The results of WATSFAR have been compared with the standard finite element model Hydrus. The analysis of these comparisons highlights two main advantages for WATSFAR, i) robustness: even on fine textured soil or high water and solute

  7. Disentangling residence time and temperature sensitivity of microbial decomposition in a global soil carbon model

    Science.gov (United States)

    Exbrayat, J.-F.; Pitman, A. J.; Abramowitz, G.

    2014-12-01

    Recent studies have identified the first-order representation of microbial decomposition as a major source of uncertainty in simulations and projections of the terrestrial carbon balance. Here, we use a reduced complexity model representative of current state-of-the-art models of soil organic carbon decomposition. We undertake a systematic sensitivity analysis to disentangle the effect of the time-invariant baseline residence time (k) and the sensitivity of microbial decomposition to temperature (Q10) on soil carbon dynamics at regional and global scales. Our simulations produce a range in total soil carbon at equilibrium of ~ 592 to 2745 Pg C, which is similar to the ~ 561 to 2938 Pg C range in pre-industrial soil carbon in models used in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). This range depends primarily on the value of k, although the impact of Q10 is not trivial at regional scales. As climate changes through the historical period, and into the future, k is primarily responsible for the magnitude of the response in soil carbon, whereas Q10 determines whether the soil remains a sink, or becomes a source in the future mostly by its effect on mid-latitude carbon balance. If we restrict our simulations to those simulating total soil carbon stocks consistent with observations of current stocks, the projected range in total soil carbon change is reduced by 42% for the historical simulations and 45% for the future projections. However, while this observation-based selection dismisses outliers, it does not increase confidence in the future sign of the soil carbon feedback. We conclude that despite this result, future estimates of soil carbon and how soil carbon responds to climate change should be more constrained by available data sets of carbon stocks.

  8. Simulation of the steady-state transport of radon from soil into houses with basements under constant negative pressure

    Energy Technology Data Exchange (ETDEWEB)

    de Oliveira Loureiro, C.

    1987-05-01

    A theoretical model was developed to simulate this phenomenon, under some specific assumptions. The model simulates: the generation and decay of radon within the soil; its transport throughout the soil due to diffusion and convection induced by the pressure disturbance applied at a crack in the basement; its entrance into the house through the crack; and the resultant indoor radon concentration. The most important assumptions adopted in the model were: a steady-state condition; a house with a basement; a geometrically well-defined crack at the wall-floor joint in the basement; and a constant negative pressure applied at the crack in relation to the outside atmospheric pressure. Two three-dimensional finite-difference computer programs were written to solve the mathematical equations of the model. The first program, called PRESSU, was used to calculate: the pressure distribution within the soil as a result of the applied disturbance pressure at the crack; and the resultant velocity distribution of the soil gas throughout the soil matrix. The second program, called MASTRA, was used to: solve the radon mass-transport equation, and to calculate the concentration distribution of radon in the soil gas within the whole soil; and to calculate the entry rate of radon through the crack into the basement, and the final indoor radon concentration. A parametric sensitivity analysis performed on the model, revealed several features of the mechanisms involved in the transport of radon into the house. 84 refs., 66 figs., 16 tabs.

  9. Micromechanical Behavior and Modelling of Granular Soil

    Science.gov (United States)

    1989-07-01

    elasticity, hypoelasticity , plasticity and viscoplasticity. Despite the large number of models , there is no consensus yet within the research community on...Classification) (U) Micromechanical Behavior and Modelling of Granular MOWo I... 12. PERSONAL AUTHOR(S) Emmanuel Petrakis and Ricardo Dobry 13a. TYPE OF...Institute (RPI) on the behavior and modelling of granular media is summarized. The final objective is to develol a constitutive law for granular soil

  10. SIMULATED MACHINES FOR SOIL TREATMENT FOR FELLING AND SLASH AREAS

    Directory of Open Access Journals (Sweden)

    Alekseev A. E.

    2013-10-01

    Full Text Available The article presents the results of a simulation of functioning machines for tillage in AutoCAD Mechanical environment, the algorithm of machine work and the results of numerical experiments on the developed model

  11. Vehicle dynamics modeling and simulation

    CERN Document Server

    Schramm, Dieter; Bardini, Roberto

    2014-01-01

    The authors examine in detail the fundamentals and mathematical descriptions of the dynamics of automobiles. In this context different levels of complexity will be presented, starting with basic single-track models up to complex three-dimensional multi-body models. A particular focus is on the process of establishing mathematical models on the basis of real cars and the validation of simulation results. The methods presented are explained in detail by means of selected application scenarios.

  12. Numerical Simulation Of The Treatment Of Soil Swelling Using Grid Geocell Columns

    Directory of Open Access Journals (Sweden)

    Fattah Mohammed Y.

    2015-06-01

    Full Text Available In this paper, a method for the treatment of the swelling of expansive soil is numerically simulated. The method is simply based on the embedment of a geogrid (or a geomesh in the soil. The geogrid is extended continuously inside the volume of the soil where the swell is needed to be controlled and orientated towards the direction of the swell. Soils with different swelling potentials are employed: bentonite base-Na and bentonite base-Ca samples in addition to kaolinite mixed with bentonite. A numerical analysis was carried out by the finite element method to study the swelling soil's behavior and investigate the distribution of the stresses and pore water pressures around the geocells beneath the shallow footings. The ABAQUS computer program was used as a finite element tool, and the soil is represented by the modified Drucker-Prager/cap model. The geogrid surrounding the geocell is assumed to be a linear elastic material throughout the analysis. The soil properties used in the modeling were experimentally obtained. It is concluded that the degree of saturation and the matric suction (the negative pore water pressure decrease as the angle of friction of the geocell column material increases due to the activity of the sand fill in the dissipation of the pore water pressure and the acceleration of the drainage through its function as a drain. When the plasticity index and the active depth (the active zone is considered to be equal to the overall depth of the clay model increase, the axial movement (swelling movement and matric suction, as a result of the increase in the axial forces, vary between this maximum value at the top of the layer and the minimum value in the last third of the active depth and then return to a consolidation at the end of the depth layer.

  13. A hydrometeorological approach for probabilistic simulation of monthly soil moisture under bare and crop land conditions

    Science.gov (United States)

    Das, Sarit Kumar; Maity, Rajib

    2015-04-01

    This study focuses on the probabilistic estimation of monthly soil moisture variation by considering (a) the influence of hydrometeorological forcing to model the temporal variation and (b) the information of Hydrological Soil Groups (HSGs) and Agro-Climatic Zones (ACZs) to capture the spatial variation. The innovative contributions of this study are: (i) development of a Combined Hydro-Meteorological (CHM) index to extract the information of different influencing hydrometeorological variables, (ii) consideration of soil-hydrologic characteristics (through HSGs) and climate regime-based zoning for agriculture (through ACZs), and (iii) quantification of uncertainty range of the estimated soil moisture. Usage of Supervised Principal Component Analysis (SPCA) in the development of the CHM index helps to eliminate the "curse of dimensionality," typically arises in the multivariate analysis. The usage of SPCA also ensures the maximum possible association between the developed CHM index and soil moisture variation. The association between these variables is modeled through their joint distribution which is obtained by using the theory of copula. The proposed approach is also spatially transferable, since the information on HSGs and ACZs is considered. The "leave-one-out" cross-validation (LOO-CV) approach is adopted for stations belong to a particular HSG to examine the spatial transferability. The simulated soil moisture values are also compared with a few existing soil moisture data sets, derived from different Land Surface Models (LSMs) or retrieved from different satellite-based missions. The potential of the proposed approach is found to be promising and even applicable to crop land also, though with a lesser degree of efficiency as compared to bare land conditions.

  14. Modelling autotrophic and heterotrophic components of soil respiration in wheat fields

    Science.gov (United States)

    Delogu, E.; LeDantec, V.; Buysse, P.; Mordelet, P.; Aubinet, M.

    2012-04-01

    Partitioning soil respiration into its heterotrophic and autotrophic components is a current key challenge to improve understanding of soil processes in croplands. For this purpose, we coupled a daily-time step soil organic carbon model derived from the CENTURY (Parton et al, 1987) calculating carbon turnover and carbon dioxide production in the soil with root sub-model from the plant process-based model CASTANEA (Dufrêne et al, 2005). In the Century model, soil organic carbon is divided into three major components including active, slow and passive soil carbon. Each pool has its own decomposition constant. Carbon flows between these pools are controlled by carbon inputs (crop residue), decomposition rate and microbial respiration loss parameters, both of which are a function of soil texture, soil temperature and soil water content. The model assumes that all C decompositions flows are associated with microbial activity and that microbial respiration occurs for each of these flows. Heterotrophic soil respiration is the sum of all these microbial respiration processes. To simulate autotrophic component, maintenance respiration is calculated from the nitrogen content and assuming an exponential relationship to account for temperature dependence. Growth respiration is calculated assuming that daily growth respiration depends on both growth rate and construction cost of the considered organ. To investigate model performances, simulations of soil CO2 efflux were compared with 3 datasets recorded in three different fields under different soil and climate conditions. Soil respiration measurements were performed on three winter wheat crops on Lamasquère (2007) and Auradé (2008), South-West France and in Lonzée (2007), Belgium. The French sites data come from manual measurement chambers, PP systems. The Belgium site is equipped with an automatic (half-hour resolution time) measurement system. The model was run on the three climatic years of data on bare soil and a first

  15. Explicit and implicit soil modelling for dynamic soil-structure interaction problems

    Science.gov (United States)

    Dasgupta, Aaron

    1986-10-01

    Increased application of nonlinear viscoelastic materials in structures and consideration of operating environments require modeling of interaction of such structures with the surrounding soil medium which significantly influences the dynamic response when subjected to an impulse or blast overpressure loading. The need is accentuated by the rapid advances in numerical modeling of dynamic problems using either finite difference or finite element techniques of structural analysis. An explicit modeling technique is recommended whereby a few layers of soil surrounding the base of the structure are modeled as an assembly of elements in contact with the structure. The interfacing contact elements for both structure and soil are allowed to stick, slide or separate from each other to simulate the appropriate boundary conditions. The explicit modeling technique using a finite element code requires characterization of constitutive relationship of geological materials from shock compression behavior of such materials and their Hugoniot characteristics. The characterization technique used here is currently restricted to materials with linear Hugoniot characteristics at all pressure ranges.

  16. Designing efficient nitrous oxide sampling strategies in agroecosystems using simulation models

    Science.gov (United States)

    Debasish Saha; Armen R. Kemanian; Benjamin M. Rau; Paul R. Adler; Felipe Montes

    2017-01-01

    Annual cumulative soil nitrous oxide (N2O) emissions calculated from discrete chamber-based flux measurements have unknown uncertainty. We used outputs from simulations obtained with an agroecosystem model to design sampling strategies that yield accurate cumulative N2O flux estimates with a known uncertainty level. Daily soil N2O fluxes were simulated for Ames, IA (...

  17. Stochastic models: theory and simulation.

    Energy Technology Data Exchange (ETDEWEB)

    Field, Richard V., Jr.

    2008-03-01

    Many problems in applied science and engineering involve physical phenomena that behave randomly in time and/or space. Examples are diverse and include turbulent flow over an aircraft wing, Earth climatology, material microstructure, and the financial markets. Mathematical models for these random phenomena are referred to as stochastic processes and/or random fields, and Monte Carlo simulation is the only general-purpose tool for solving problems of this type. The use of Monte Carlo simulation requires methods and algorithms to generate samples of the appropriate stochastic model; these samples then become inputs and/or boundary conditions to established deterministic simulation codes. While numerous algorithms and tools currently exist to generate samples of simple random variables and vectors, no cohesive simulation tool yet exists for generating samples of stochastic processes and/or random fields. There are two objectives of this report. First, we provide some theoretical background on stochastic processes and random fields that can be used to model phenomena that are random in space and/or time. Second, we provide simple algorithms that can be used to generate independent samples of general stochastic models. The theory and simulation of random variables and vectors is also reviewed for completeness.

  18. Simulation model for oxygen consumption flux and prediction of methane oxidation in landfill cover soil%覆盖层氧气消耗通量模型及甲烷氧化能力预测

    Institute of Scientific and Technical Information of China (English)

    邢志林; 赵天涛; 陈新安; 车轮; 张丽杰; 全学军

    2015-01-01

    填埋场覆盖层生物气扩散规律和甲烷氧化能力的评估是甲烷减排研究的重要组成部分。以数值模拟方法分析了氧气在覆盖层中的扩散规律,得到了指数方程形式的氧气扩散模型(R2范围0.8941~0.9975);通过检测有机碳和甲烷浓度变化进一步考察了模拟覆盖层不同深度的甲烷氧化能力,证实了在0.05~0.25 m范围内甲烷氧化活性最高;以Fick定律和轴向扩散模型推导了模拟覆盖层中氧气消耗通量模型,该模型计算得到的氧气消耗通量与覆盖层中微生物甲烷氧化经验方程相比无显著差异;结合以上模型推演出覆盖层甲烷消耗通量模型,与实际检测值相比,预测结果理想(R2=0.9983)。该成果可为揭示填埋场覆盖层生物气扩散规律、强化甲烷氧化能力以及预测甲烷排放提供新的思路和理论依据。%Diffusion process of biogas and evaluation of methane oxidation in landfill cover soil are important parts of research on methane emission. Diffusion process of oxygen in landfill cover soil was analyzed by simulation, and an oxygen diffusion model fitted by exponential equation (0.8941model in landfill cover was derived on the basis of Fick’s law and axial dispersion model. There was no significant difference between fitted values by oxygen consumption flux model and derived values by empirical equation of biological methane oxidation. Based on the above model, a methane consumption flux model was derived finally, and the prediction was consistent with detection. These results provided new ideas and theoretical basis for revealing biogas diffusion process in landfill cover soil

  19. Modeling soil bulk density through a complete data scanning procedure: Heuristic alternatives

    Science.gov (United States)

    Shiri, Jalal; Keshavarzi, Ali; Kisi, Ozgur; Karimi, Sepideh; Iturraran-Viveros, Ursula

    2017-06-01

    Soil bulk density (BD) is very important factor in land drainage and reclamation, irrigation scheduling (for estimating the soil volumetric water content), and assessing soil carbon and nutrient stock as well as determining the pollutant mass balance in soils. Numerous pedotransfer functions have been suggested so far to relate the soil BD values to soil parameters (e.g. soil separates, carbon content, etc). The present paper aims at simulating soil BD using easily measured soil variables through heuristic gene expression programming (GEP), neural networks (NN), random forest (RF), support vector machine (SVM), and boosted regression trees (BT) techniques. The statistical Gamma test was utilized to identify the most influential soil parameters on BD. The applied models were assessed through k-fold testing where all the available data patterns were involved in the both training and testing stages, which provide an accurate assessment of the models accuracy. Some existing pedotransfer functions were also applied and compared with the heuristic models. The obtained results revealed that the heuristic GEP model outperformed the other applied models globally and per test stage. Nevertheless, the performance accuracy of the applied heuristic models was much better than those of the applied pedotransfer functions. Using k-fold testing provides a more-in-detail judgment of the models.

  20. Global Change Simulations Affect Potential Methane Oxidation in Upland Soils

    Science.gov (United States)

    Blankinship, J. C.; Hungate, B. A.

    2004-12-01

    Atmospheric concentrations of methane (CH4) are higher now than they have ever been during the past 420,000 years. However, concentrations have remained stable since 1999. Emissions associated with livestock husbandry are unlikely to have changed, so some combination of reduced production in wetlands, more efficient capture by landfills, or increased consumption by biological CH4 oxidation in upland soils may be responsible. Methane oxidizing bacteria are ubiquitous in upland soils and little is known about how these bacteria respond to anthropogenic global change, and how they will influence - or already are influencing - the radiative balance of the atmosphere. Might ongoing and future global changes increase biological CH4 oxidation? Soils were sampled from two field experiments to assess changes in rates of CH4 oxidation in response to global change simulations. Potential activities of CH4 oxidizing bacterial communities were measured through laboratory incubations under optimal temperature, soil moisture, and atmospheric CH4 concentrations (~18 ppm, or 10x ambient). The ongoing 6-year multifactorial Jasper Ridge Global Change Experiment (JRGCE) simulates warming, elevated precipitation, elevated atmospheric CO2, elevated atmospheric N deposition, and increased wildfire frequency in an annual grassland in a Mediterranean-type climate in central California. The ongoing 1-year multifactorial Merriam Climate Change Experiment (MCCE) simulates warming, elevated precipitation, and reduced precipitation in four different types of ecosystems along an elevational gradient in a semi-arid climate in northern Arizona. The high desert grassland, pinyon-juniper woodland, ponderosa pine forest, and mixed conifer forest ecosystems range in annual precipitation from 100 to 1000 mm yr-1, and from productivity being strongly water limited to strongly temperature limited. Among JRGCE soils, elevated atmospheric CO2 increased potential CH4 oxidation rates (p=0.052) and wildfire

  1. Simulating sunflower canopy temperatures to infer root-zone soil water potential

    Science.gov (United States)

    Choudhury, B. J.; Idso, S. B.

    1983-01-01

    A soil-plant-atmosphere model for sunflower (Helianthus annuus L.), together with clear sky weather data for several days, is used to study the relationship between canopy temperature and root-zone soil water potential. Considering the empirical dependence of stomatal resistance on insolation, air temperature and leaf water potential, a continuity equation for water flux in the soil-plant-atmosphere system is solved for the leaf water potential. The transpirational flux is calculated using Monteith's combination equation, while the canopy temperature is calculated from the energy balance equation. The simulation shows that, at high soil water potentials, canopy temperature is determined primarily by air and dew point temperatures. These results agree with an empirically derived linear regression equation relating canopy-air temperature differential to air vapor pressure deficit. The model predictions of leaf water potential are also in agreement with observations, indicating that measurements of canopy temperature together with a knowledge of air and dew point temperatures can provide a reliable estimate of the root-zone soil water potential.

  2. Computational Modeling of Simulation Tests.

    Science.gov (United States)

    1980-06-01

    Mexico , March 1979. 14. Kinney, G. F.,.::. IeiN, .hoce 1h Ir, McMillan, p. 57, 1962. 15. Courant and Friedrichs, ,U: r. on moca an.: Jho...AD 79 275 NEW MEXICO UNIV ALBUGUERGUE ERIC H WANG CIVIL ENGINE-ETC F/6 18/3 COMPUTATIONAL MODELING OF SIMULATION TESTS.(U) JUN 80 6 LEIGH, W CHOWN, B...COMPUTATIONAL MODELING OF SIMULATION TESTS00 0G. Leigh W. Chown B. Harrison Eric H. Wang Civil Engineering Research Facility University of New Mexico

  3. Oxygen supply and consumption in soilless culture: evaluation of an oxygen simulation model for cucumber

    NARCIS (Netherlands)

    Baas, R.; Wever, G.; Koolen, A.J.; Tariku, E.; Stol, K.J.

    2001-01-01

    A soil oxygen simulation model (OXSI) was tested and evaluated for evaluating growing media with respect to aeration. In the model, local oxygen concentrations are calculated from coefficients of diffusion and consumption (respiration), assuming equilibrium conditions. Apparent oxygen diffusion coef

  4. A multi-scale ''soil water structure'' model based on the pedostructure concept

    Directory of Open Access Journals (Sweden)

    E. Braudeau

    2009-02-01

    Full Text Available Current soil water models do not take into account the internal organization of the soil medium and, a fortiori, the physical interaction between the water film surrounding the solid particles of the soil structure, and the surface charges of this structure. In that sense they empirically deal with the physical soil properties that are all generated from this soil water-structure interaction. As a result, the thermodynamic state of the soil water medium, which constitutes the local physical conditions, namely the pedo-climate, for biological and geo-chemical processes in soil, is not defined in these models. The omission of soil structure from soil characterization and modeling does not allow for coupling disciplinary models for these processes with soil water models. This article presents a soil water structure model, Kamel®, which was developed based on a new paradigm in soil physics where the hierarchical soil structure is taken into account allowing for defining its thermodynamic properties. After a review of soil physics principles which forms the basis of the paradigm, we describe the basic relationships and functionality of the model. Kamel® runs with a set of 15 soil input parameters, the pedohydral parameters, which are parameters of the physically-based equations of four soil characteristic curves that can be measured in the laboratory. For cases where some of these parameters are not available, we show how to estimate these parameters from commonly available soil information using published pedotransfer functions. A published field experimental study on the dynamics of the soil moisture profile following a pounded infiltration rainfall event was used as an example to demonstrate soil characterization and Kamel® simulations. The simulated soil moisture profile for a period of 60 days showed very good agreement with experimental field data. Simulations using input data calculated from soil texture and

  5. Disentangling residence time and temperature sensitivity of microbial decomposition in a global soil carbon model

    Directory of Open Access Journals (Sweden)

    J.-F. Exbrayat

    2014-03-01

    Full Text Available Recent studies have identified the first-order parameterization of microbial decomposition as a major source of uncertainty in simulations and projections of the terrestrial carbon balance. Here, we use a reduced complexity model representative of the current state-of-the-art parameterization of soil organic carbon decomposition. We undertake a systematic sensitivity analysis to disentangle the effect of the time-invariant baseline residence time (k and the sensitvity of microbial decomposition to temperature (Q10 on soil carbon dynamics at regional and global scales. Our simulations produce a range in total soil carbon at equilibrium of ~ 592 to 2745 Pg C which is similar to the ~ 561 to 2938 Pg C range in pre-industrial soil carbon in models used in the fifth phase of the Coupled Model Intercomparison Project. This range depends primarily on the value of k, although the impact of Q10 is not trivial at regional scales. As climate changes through the historical period, and into the future, k is primarily responsible for the magnitude of the response in soil carbon, whereas Q10 determines whether the soil remains a sink, or becomes a source in the future mostly by its effect on mid-latitudes carbon balance. If we restrict our simulations to those simulating total soil carbon stocks consistent with observations of current stocks, the projected range in total soil carbon change is reduced by 42% for the historical simulations and 45% for the future projections. However, while this observation-based selection dismisses outliers it does not increase confidence in the future sign of the soil carbon feedback. We conclude that despite this result, future estimates of soil carbon, and how soil carbon responds to climate change should be constrained by available observational data sets.

  6. A Device for Simulating Soil Nutrient Extraction and Plant Uptake

    Institute of Scientific and Technical Information of China (English)

    YANG Xu-Jian; LAI Yong-Lin; MO Jin-Yu; SHEN Hong

    2012-01-01

    In situ evaluating the availability of soil nutrients has been a challenge.In this study,a new type of Device for Simulating Soil Nutrient Extraction and Plant Uptake (DSSNEPU) and its operating procedures were introduced.The device consists of a sampling tube,a fluid supply system,a low pressure system,a tube sheath and an elution cylinder.The sampling tube was firstly soaked in the solution of 0.5 mol L-1 NaHCO3 and then buried into soils.The fluid supply system was connected to the sampling tube and the deionized water was supplied.During the period,low pressure system started a vacuum for 3 min every 10 min interval.After extraction,the sampling tube was removed and the nutrients on the sampling tube were eluted with 0.5 mol L-1 HC1.The elution solution was used for nutrient measurement.The amounts of P and K extracted by DSSNEPU reached the maximal values after 4 h.No significant increases of P and K were observed for longer extraction duration.The optimal temperature for extracting P and K was 30 ℃ in this experiment.Extracted P and K were increased by 83.3% and 84.6% with the employment of low pressure system in comparison to those without employing low pressure system.Correlation analysis indicated that P and K extracted by DSSNEPU were highly correlated with those by conventional chemical extraction and by plant uptake.The above results suggest that this device is applicable to assess the availability of nutrients in soils.

  7. A Numerical Model to Assess Soil Fluxes from Meteoric 10Be Data

    Science.gov (United States)

    Campforts, B.; Govers, G.; Vanacker, V.; Vanderborght, J.; Smolders, E.; Baken, S.

    2015-12-01

    Meteoric 10Be may be mobile in the soil system. The latter hampers a direct translation of meteoric 10Be inventories into spatial variations in erosion and deposition rates. Here, we present a spatially explicit 2D model that allows us to simulate the behaviour of meteoric 10Be in the soil system. The Be2D model is then used to analyse the potential impact of human-accelerated soil fluxes on meteoric 10Be inventories. The model consists of two parts. A first component deals with advective and diffusive mobility of meteoric 10Be within the soil profile including particle migration, chemical leaching and bioturbation, whereas a second component describes lateral soil (and meteoric 10Be) fluxes over the hillslope. Soil depth is calculated dynamically, accounting for soil production through weathering and lateral soil fluxes from creep, water and tillage erosion. Model simulations show that meteoric 10Be inventories can indeed be related to erosion and deposition, across a wide range of geomorphological and pedological settings. However, quantification of the effects of vertical mobility is essential for a correct interpretation of the observed spatial patterns in 10Be data. Moreover, our simulations suggest that meteoric 10Be can be used as a tracer to unravel human impact on soil fluxes when soils have a high retention capacity for meteoric meteoric 10Be. Application of the Be2D model to existing data sets shows that model parameters can reliably be constrained, resulting in a good agreement between simulated and observed meteoric 10Be concentrations and inventories. This confirms the suitability of the Be2D model as a robust tool to underpin quantitative interpretations of spatial variability in meteoric 10Be data for eroding landscapes.

  8. SIMULATION OF COLLECTIVE RISK MODEL

    Directory of Open Access Journals (Sweden)

    Viera Pacáková

    2007-12-01

    Full Text Available The article focuses on providing brief theoretical definitions of the basic terms and methods of modeling and simulations of insurance risks in non-life insurance by means of mathematical and statistical methods using statistical software. While risk assessment of insurance company in connection with its solvency is a rather complex and comprehensible problem, its solution starts with statistical modeling of number and amount of individual claims. Successful solution of these fundamental problems enables solving of curtail problems of insurance such as modeling and simulation of collective risk, premium an reinsurance premium calculation, estimation of probabiliy of ruin etc. The article also presents some essential ideas underlying Monte Carlo methods and their applications to modeling of insurance risk. Solving problem is to find the probability distribution of the collective risk in non-life insurance portfolio. Simulation of the compound distribution function of the aggregate claim amount can be carried out, if the distibution functions of the claim number process and the claim size are assumed given. The Monte Carlo simulation is suitable method to confirm the results of other methods and for treatments of catastrophic claims, when small collectives are studied. Analysis of insurance risks using risk theory is important part of the project Solvency II. Risk theory is analysis of stochastic features of non-life insurance process. The field of application of risk theory has grown rapidly. There is a need to develop the theory into form suitable for practical purposes and demostrate their application. Modern computer simulation techniques open up a wide field of practical applications for risk theory concepts, without requiring the restricive assumptions and sophisticated mathematics. This article presents some comparisons of the traditional actuarial methods and of simulation methods of the collective risk model.

  9. Theory, modeling and simulation: Annual report 1993

    Energy Technology Data Exchange (ETDEWEB)

    Dunning, T.H. Jr.; Garrett, B.C.

    1994-07-01

    Developing the knowledge base needed to address the environmental restoration issues of the US Department of Energy requires a fundamental understanding of molecules and their interactions in insolation and in liquids, on surfaces, and at interfaces. To meet these needs, the PNL has established the Environmental and Molecular Sciences Laboratory (EMSL) and will soon begin construction of a new, collaborative research facility devoted to advancing the understanding of environmental molecular science. Research in the Theory, Modeling, and Simulation program (TMS), which is one of seven research directorates in the EMSL, will play a critical role in understanding molecular processes important in restoring DOE`s research, development and production sites, including understanding the migration and reactions of contaminants in soils and groundwater, the development of separation process for isolation of pollutants, the development of improved materials for waste storage, understanding the enzymatic reactions involved in the biodegradation of contaminants, and understanding the interaction of hazardous chemicals with living organisms. The research objectives of the TMS program are to apply available techniques to study fundamental molecular processes involved in natural and contaminated systems; to extend current techniques to treat molecular systems of future importance and to develop techniques for addressing problems that are computationally intractable at present; to apply molecular modeling techniques to simulate molecular processes occurring in the multispecies, multiphase systems characteristic of natural and polluted environments; and to extend current molecular modeling techniques to treat complex molecular systems and to improve the reliability and accuracy of such simulations. The program contains three research activities: Molecular Theory/Modeling, Solid State Theory, and Biomolecular Modeling/Simulation. Extended abstracts are presented for 89 studies.

  10. Crop growth and two dimensional modeling of soil water transport in drip irrigated potatoes

    DEFF Research Database (Denmark)

    Plauborg, Finn; Iversen, Bo Vangsø; Mollerup, Mikkel

    2009-01-01

    Drip irrigation can be an effective way to improve water and nitrogen use efficiency in soil and hence to reduce the environmental pollution. In the EU project SAFIR ( http://www.safir4eu.org/ ) a potato experiment was carried out in lysimeters on three different soil types: coarse sand, loamy sand...... of abscisic acid (ABA). Model outputs from the mechanistic simulation model Daisy, in SAFIR developed to include 2D soil processes and gas exchange processes based on Ball et al. and Farquhar were compared with measured crop dynamics, final DM yield and volumetric water content in the soil measured by TDR...... probes. The probes were installed parallel to the tillage direction at different positions in the potato ridge. The new Daisy 2D model showed to be able to simulate crop growth, water use and soil water distribution fairly well...

  11. Modelling soil moisture at SMOS scale by use of a SVAT model over the Valencia Anchor Station

    Directory of Open Access Journals (Sweden)

    S. Juglea

    2010-01-01

    Full Text Available The main goal of the SMOS (Soil Moisture and Ocean Salinity mission is to deliver global fields of surface soil moisture and sea surface salinity using L-band (1.4 GHz radiometry. Within the context of the preparation for this mission over land, the Valencia Anchor Station experimental site, in Spain, was chosen to be one of the main test sites in Europe for the SMOS Calibration/Validation (Cal/Val activities. Ground and meteorological measurements over the area are used as the input of a Soil-Vegetation-Atmosphere-Transfer (SVAT model, SURFEX (Externalized Surface-module ISBA (Interactions between Soil-Biosphere-Atmosphere so as to simulate the surface soil moisture. The calibration as well as the validation of the ISBA model was made using in situ soil moisture measurements. It is shown that a good consistency was reached when point comparisons between simulated and in situ soil moisture measurements were made. In order to obtain an accurate soil moisture mapping over the Valencia Anchor Station (50×50 km2 area, a spatialization method has been applied. To validate the approach, a comparison with remote sensing data from the Advanced Microwave Scanning Radiometer on Earth observing System (AMSR-E and from the European Remote Sensing Satellites (ERS-Scat was performed. Despite the fact that AMSR-E surface soil moisture product is not reproducing accurately the absolute values, it provides trustworthy information on surface soil moisture temporal variability. However, during the vegetation growing season the signal is perturbed. By using the polarization ratio a better agreement is obtained. ERS-Scat soil moisture products were also used to be compared with the simulated spatialized soil moisture. The seasonal variations were well reproduced. However, the lack of soil moisture data over the area (45 observations for one year was a limit into completely understanding the soil moisture variability.

  12. Numerical Simulation of Hysteretic Live Load Effect in a Soil-Steel Bridge

    Directory of Open Access Journals (Sweden)

    Sobótka Maciej

    2014-03-01

    Full Text Available The paper presents numerical simulation of hysteretic live load effect in a soil-steel bridge. The effect was originally identified experimentally by Machelski [1], [2]. The truck was crossing the bridge one way and the other in the full-scale test performed. At the same time, displacements and stress in the shell were measured. The major conclusion from the research was that the measured quantities formed hysteretic loops. A numerical simulation of that effect is addressed in the present work. The analysis was performed using Flac finite difference code. The methodology of solving the mechanical problems implemented in Flac enables us to solve the problem concerning a sequence of load and non-linear mechanical behaviour of the structure. The numerical model incorporates linear elastic constitutive relations for the soil backfill, for the steel shell and the sheet piles, being a flexible substructure for the shell. Contact zone between the shell and the soil backfill is assumed to reflect elastic-plastic constitutive model. Maximum shear stress in contact zone is limited by the Coulomb condition. The plastic flow rule is described by dilation angle ψ = 0. The obtained results of numerical analysis are in fair agreement with the experimental evidence. The primary finding from the performed simulation is that the slip in the interface can be considered an explanation of the hysteresis occurrence in the charts of displacement and stress in the shell.

  13. Simulation of carrier-facilitated transport of phenanthrene in a layered soil profile

    Science.gov (United States)

    Prechtel, Alexander; Knabner, Peter; Schneid, Eckhard; Totsche, Kai Uwe

    2002-06-01

    The appropriate prediction of the fate of the contaminant is an essential step when evaluating the risk of severe groundwater pollutions—in particular in the context of natural attenuation. We numerically study the reactive transport of phenanthrene at the field scale in a multilayer soil profile based on experimental data. The effect of carrier facilitation by dissolved organic carbon is emphasized and incorporated in the model. Previously published simulations are restricted to the saturated zone and/or to homogeneous soil columns at the laboratory scale. A numerical flow and transport model is extended and applied to understand and quantify the relevant processes in the case of a strongly sorbing hydrophobic organic compound that is subject to carrier facilitation in the unsaturated zone. The contaminant migration is investigated on long- and short-term time scales and compared to predictions without carrier facilitation. The simulations demonstrate the importance of carrier facilitation and suggest strongly to take this aspect into account. By carrier facilitation breakthrough times at the groundwater level decreased from 500 to approximately 8 years and concentration peaks increased by two orders of magnitude in the long-term simulation assuming a temporary spill in an initially unpolluted soil with a non-sorbing carrier.

  14. Impact of modified soil thermal characteristic on the simulated monsoon climate over south Asia

    Indian Academy of Sciences (India)

    Pankaj Kumar; Ralf Podzun; Stefan Hagemann; Daniela Jacob

    2014-02-01

    In the present study, the influence of soil thermal characteristics (STC) on the simulated monsoon climate over south Asia is analyzed. The study was motivated by a common warm temperature bias over the plains of northern India that has been noticed in several global and regional climate models. To address this warm bias and its relation to STC, two sensitivity experiments have been performed with the regional climate model REMO of the Max Planck Institute for Meteorology. The control experiment uses the standard soil thermal characteristic of the model that corresponds to a moist soil. The second experiment uses modified STC that characterize a dry soil, which is more representative of the considered region, as a large part of the region has arid, semi-arid or subtropical summer wet conditions. Both experiments were conducted over 20 years using re-analysis data as lateral boundary conditions. Results show that using the modified STC the predominant regional warm bias has reduced substantially, leading to a better and more realistic surface temperature compared to observations over south Asia. Although, the magnitude of bias has reduced, the warm bias still exists over the region suggesting that other atmospheric and land surface processes also play a role, such as aerosols and irrigation. These need to be addressed adequately in future modeling studies over the region.

  15. Study of Soil-Water Characteristic Curve Using Microscopic Spherical Particle Model

    Institute of Scientific and Technical Information of China (English)

    YANG Song; LU Ting-Hao

    2012-01-01

    When variations occur in the water content or dry bulk density of soil,the contact angle hysteresis will affect the soil-water characteristic curve (SWCC).The occurrence of the contact angle hysteresis can be divided into slipping and pinning.It is difficult to determine the effect of pinning existence on SWCC by tests.In this study,the effect of contact angle hysteresis on SWCC was analyzed either in the case of no variations in soil dry bulk density with changes in soil water content or no variations in soil water content with changes in soil dry bulk density.In both cases,soil particles were simplified to the spherical particle model.Based on the geometrically mechanic relationship between the particles and connecting liquid bridges,a physical model for predicting the SWCC was derived from the spherical particle model.Adjusting parameters made the model applicable to various soils,that is,the cohesive soil was considered as micron-sized spherical particles.Through the simulations on SWCC test data of sand,silt,clay,and swelling soil,it was confirmed that the physical model possessed good reliability and practicability.Finally,the analysis of rationality of contact angle was performed based on the basic assumptions of the model.

  16. Longitudinal vibration of pile in layered soil based on Rayleigh-Love rod theory and fictitious soil-pile model

    Institute of Scientific and Technical Information of China (English)

    Lü Shu-hui; WANG Kui-hua; WU Wen-bing; C. J. LEO

    2015-01-01

    The dynamic response of pile in layered soil is theoretically investigated when considering the transverse inertia effect. Firstly, the fictitious soil-pile model is employed to simulate the dynamic interaction between the pile and the soil layers beneath pile toe. The dynamic interactions of adjacent soil layers along the vertical direction are simplified as distributed Voigt models. Meanwhile, the pile and fictitious soil-pile are assumed to be viscoelastic Rayleigh-Love rods, and both the radial and vertical displacement continuity conditions at the soil-pile interface are taken into consideration. On this basis, the analytical solution for dynamic response at the pile head is derived in the frequency domain and the corresponding quasi-analytical solution in the time domain is then obtained by means of the convolution theorem. Following this, the accuracy and parameter value of the hypothetical boundaries for soil-layer interfaces are discussed. Comparisons with published solution and measured data are carried out to verify the rationality of the present solution. Parametric analyses are further conducted by using the present solution to investigate the relationships between the transverse inertia effects and soil-pile parameters.

  17. MODELLING, SIMULATING AND OPTIMIZING BOILERS

    DEFF Research Database (Denmark)

    Sørensen, K.; Condra, T.; Houbak, Niels

    2003-01-01

    This paper describes the modelling, simulating and optimizing including experimental verification as being carried out as part of a Ph.D. project being written resp. supervised by the authors. The work covers dynamic performance of both water-tube boilers and fire tube boilers. A detailed dynamic...... model of the boiler has been developed and simulations carried out by means of the Matlab integration routines. The model is prepared as a dynamic model consisting of both ordinary differential equations and algebraic equations, together formulated as a Differential-Algebraic-Equation system. Being able...... to operate a boiler plant dynamically means that the boiler designs must be able to absorb any fluctuations in water level and temperature gradients resulting from the pressure change in the boiler. On the one hand a large water-/steam space may be required, i.e. to build the boiler as big as possible. Due...

  18. Modelling soil organic carbon concentration of mineral soils in arable lands using legacy soil data

    DEFF Research Database (Denmark)

    Suuster, E; Ritz, Christian; Roostalu, H

    2012-01-01

    as to the advantages and shortcomings of the different commonly used prediction methods. Therefore, we compared and evaluated the merits of the median approach, analysis of covariance, mixed models and random forests in the context of prediction of SOC concentrations of mineral soils under arable management in the A...

  19. Intelligent Mobility Modeling and Simulation

    Science.gov (United States)

    2015-03-04

    cog.cs.drexel.edu/act-r/index.html) •Models sensory / motor performance of human driver or teleoperator 27UNCLASSIFIED: Distribution Statement A. Approved for...U.S. ARMY TANK AUTOMOTIVE RESEARCH, DEVELOPMENT AND ENGINEERING CENTER Intelligent Mobility Modeling and Simulation 1 Dr. P. Jayakumar, S. Arepally...Prescribed by ANSI Std Z39-18 Contents 1. Mobility - Autonomy - Latency Relationship 2. Machine - Human Partnership 3. Development of Shared Control

  20. Current developments in soil organic matter modeling and the expansion of model applications: a review

    Science.gov (United States)

    Campbell, Eleanor E.; Paustian, Keith

    2015-12-01

    Soil organic matter (SOM) is an important natural resource. It is fundamental to soil and ecosystem functions across a wide range of scales, from site-specific soil fertility and water holding capacity to global biogeochemical cycling. It is also a highly complex material that is sensitive to direct and indirect human impacts. In SOM research, simulation models play an important role by providing a mathematical framework to integrate, examine, and test the understanding of SOM dynamics. Simulation models of SOM are also increasingly used in more ‘applied’ settings to evaluate human impacts on ecosystem function, and to manage SOM for greenhouse gas mitigation, improved soil health, and sustainable use as a natural resource. Within this context, there is a need to maintain a robust connection between scientific developments in SOM modeling approaches and SOM model applications. This need forms the basis of this review. In this review we first provide an overview of SOM modeling, focusing on SOM theory, data-model integration, and model development as evidenced by a quantitative review of SOM literature. Second, we present the landscape of SOM model applications, focusing on examples in climate change policy. We conclude by discussing five areas of recent developments in SOM modeling including: (1) microbial roles in SOM stabilization; (2) modeling SOM saturation kinetics; (3) temperature controls on decomposition; (4) SOM dynamics in deep soil layers; and (5) SOM representation in earth system models. Our aim is to comprehensively connect SOM model development to its applications, revealing knowledge gaps in need of focused interdisciplinary attention and exposing pitfalls that, if avoided, can lead to best use of SOM models to support policy initiatives and sustainable land management solutions.

  1. Searching for the right scale in catchment hydrology: the effect of soil spatial variability in simulated states and fluxes

    Science.gov (United States)

    Baroni, Gabriele; Zink, Matthias; Kumar, Rohini; Samaniego, Luis; Attinger, Sabine

    2017-04-01

    The advances in computer science and the availability of new detailed data-sets have led to a growing number of distributed hydrological models applied to finer and finer grid resolutions for larger and larger catchment areas. It was argued, however, that this trend does not necessarily guarantee better understanding of the hydrological processes or it is even not necessary for specific modelling applications. In the present study, this topic is further discussed in relation to the soil spatial heterogeneity and its effect on simulated hydrological state and fluxes. To this end, three methods are developed and used for the characterization of the soil heterogeneity at different spatial scales. The methods are applied at the soil map of the upper Neckar catchment (Germany), as example. The different soil realizations are assessed regarding their impact on simulated state and fluxes using the distributed hydrological model mHM. The results are analysed by aggregating the model outputs at different spatial scales based on the Representative Elementary Scale concept (RES) proposed by Refsgaard et al. (2016). The analysis is further extended in the present study by aggregating the model output also at different temporal scales. The results show that small scale soil variabilities are not relevant when the integrated hydrological responses are considered e.g., simulated streamflow or average soil moisture over sub-catchments. On the contrary, these small scale soil variabilities strongly affect locally simulated states and fluxes i.e., soil moisture and evapotranspiration simulated at the grid resolution. A clear trade-off is also detected by aggregating the model output by spatial and temporal scales. Despite the scale at which the soil variabilities are (or are not) relevant is not universal, the RES concept provides a simple and effective framework to quantify the predictive capability of distributed models and to identify the need for further model improvements e

  2. Modeling spatial and temporal change of soil erosion based on multi-temporal remotely sensed data

    Institute of Scientific and Technical Information of China (English)

    Pei Liu; PeiJun Du; RuiMei Han; Chao Ma; YouFeng Zou

    2015-01-01

    In order to monitor the pattern, distribution, and trend of land use/cover change (LUCC) and its impacts on soil erosion, it is highly appropriate to adopt Remote Sensing (RS) data and Geographic Information System (GIS) to analyze, assess, simulate, and predict the spatial and temporal evolution dynamics. In this paper, multi-temporal Landsat TM/ETM+ re-motely sensed data are used to generate land cover maps by image classification, and the Cellular Automata Markov (CA_Markov) model is employed to simulate the evolution and trend of landscape pattern change. Furthermore, the Re-vised Universal Soil Loss Equation (RUSLE) is used to evaluate the situation of soil erosion in the case study mining area. The trend of soil erosion is analyzed according to total/average amount of soil erosion, and the rainfall (R), cover man-agement (C), and support practice (P) factors in RUSLE relevant to soil erosion are determined. The change trends of soil erosion and the relationship between land cover types and soil erosion amount are analyzed. The results demonstrate that the CA_Markov model is suitable to simulate and predict LUCC trends with good efficiency and accuracy, and RUSLE can calculate the total soil erosion effectively. In the study area, there was minimal erosion grade and this is expected to con-tinue to decline in the next few years, according to our prediction results.

  3. Simulating maize yield and bomass with spatial variability of soil field capacity

    Science.gov (United States)

    Ma, Liwang; Ahuja, Lajpat; Trout, Thomas; Nolan, Bernard T.; Malone, Robert W.

    2015-01-01

    Spatial variability in field soil properties is a challenge for system modelers who use single representative values, such as means, for model inputs, rather than their distributions. In this study, the root zone water quality model (RZWQM2) was first calibrated for 4 yr of maize (Zea mays L.) data at six irrigation levels in northern Colorado and then used to study spatial variability of soil field capacity (FC) estimated in 96 plots on maize yield and biomass. The best results were obtained when the crop parameters were fitted along with FCs, with a root mean squared error (RMSE) of 354 kg ha–1 for yield and 1202 kg ha–1 for biomass. When running the model using each of the 96 sets of field-estimated FC values, instead of calibrating FCs, the average simulated yield and biomass from the 96 runs were close to measured values with a RMSE of 376 kg ha–1 for yield and 1504 kg ha–1 for biomass. When an average of the 96 FC values for each soil layer was used, simulated yield and biomass were also acceptable with a RMSE of 438 kg ha–1 for yield and 1627 kg ha–1 for biomass. Therefore, when there are large numbers of FC measurements, an average value might be sufficient for model inputs. However, when the ranges of FC measurements were known for each soil layer, a sampled distribution of FCs using the Latin hypercube sampling (LHS) might be used for model inputs.

  4. Estimation of soil salinity by using Markov Chain Monte Carlo simulation for multi-configuration electromagnetic induction measurements

    Science.gov (United States)

    Jadoon, K. Z.; Altaf, M. U.; McCabe, M. F.; Hoteit, I.; Moghadas, D.

    2014-12-01

    In arid and semi-arid regions, soil salinity has a major impact on agro-ecosystems, agricultural productivity, environment and sustainability. High levels of soil salinity adversely affect plant growth and productivity, soil and water quality, and may eventually result in soil erosion and land degradation. Being essentially a hazard, it's important to monitor and map soil salinity at an early stage to effectively use soil resources and maintain soil salinity level below the salt tolerance of crops. In this respect, low frequency electromagnetic induction (EMI) systems can be used as a noninvasive method to map the distribution of soil salinity at the field scale and at a high spatial resolution. In this contribution, an EMI system (the CMD Mini-Explorer) is used to estimate soil salinity using a Bayesian approach implemented via a Markov chain Monte Carlo (MCMC) sampling for inversion of multi-configuration EMI measurements. In-situ and EMI measurements were conducted across a farm where Acacia trees are irrigated with brackish water using a drip irrigation system. The electromagnetic forward model is based on the full solution of Maxwell's equation, and the subsurface is considered as a three-layer problem. In total, five parameters (electrical conductivity of three layers and thickness of top two layers) were inverted and modeled electrical conductivities were converted into the universal standard of soil salinity measurement (i.e. using the method of electrical conductivity of a saturated soil paste extract). Simulation results demonstrate that the proposed scheme successfully recovers soil salinity and reduces the uncertainties in the prior estimate. Analysis of the resulting posterior distribution of parameters indicates that electrical conductivity of the top two layers and the thickness of the first layer are well constrained by the EMI measurements. The proposed approach allows for quantitative mapping and monitoring of the spatial electrical conductivity

  5. Toward a general evaluation model for soil respiration (GEMSR)

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Soil respiration is an important component of terrestrial carbon budget. Its accurate evaluation is es- sential to the study of terrestrial carbon source/sink. Studies on soil respiration at present mostly focus on the temporal variations and the controlling factors of soil respiration, but its spatial variations and controlling factors draw less attention. Moreover, the evaluation models for soil respiration at present include only the effects of water and heat factors, while the biological and soil factors controlling soil respiration and their interactions with water and heat factors have not been considered yet. These models are not able to accurately evaluate soil respiration in different vegetation/terrestrial ecosystems at different temporal and spatial scales. Thus, a general evaluation model for soil respiration (GEMSR) including the interacting meteorological (water and heat factors), soil nutrient and biological factors is suggested in this paper, and the basic procedure developing GEMSR and the research tasks of soil respiration in the future are also discussed.

  6. Toward a general evaluation model for soil respiration (GEMSR)

    Institute of Scientific and Technical Information of China (English)

    ZHOU GuangSheng; JIA BingRui; HAN GuangXuan; ZHOU Li

    2008-01-01

    Soil respiration is an important component of terrestrial carbon budget. Its accurate evaluation is essential to the study of terrestrial carbon source/sink. Studies on soil respiration at present mostly focus on the temporal variations and the controlling factors of soil respiration, but its spatial variations and controlling factors draw less attention. Moreover, the evaluation models for soil respiration at present include only the effects of water and heat factors, while the biological and soil factors controlling soil respiration and their interactions with water and heat factors have not been considered yet. These models are not able to accurately evaluate soil respiration in different vegetation/terrestrial ecosystems at different temporal and spatial scales. Thus, a general evaluation model for soil respiration (GEMSR)including the interacting meteorological (water and heat factors), soil nutrient and biological factors is suggested in this paper, and the basic procedure developing GEMSR and the research tasks of soil respiration in the future are also discussed.

  7. Towards a model-based inventory of soil organic carbon in agricultural soils for the Swiss greenhouse gas reporting

    Science.gov (United States)

    Staudt, K.; Leifeld, J.; Bretscher, D.; Fuhrer, J.

    2012-04-01

    The Swiss inventory submission under the United Nations Framework Convention on Climate Change (UNFCCC) reports on changes in soil organic carbon stocks under different land-uses and land-use changes. The approach currently employed for cropland and grassland soils combines Tier 1 and Tier 2 methods and is considered overly simplistic. As the UNFCC encourages countries to develop Tier 3 methods for national greenhouse gas reporting, we aim to build up a model-based inventory of soil organic carbon in agricultural soils in Switzerland. We conducted a literature research on currently employed higher-tier methods using process-based models in four countries: Denmark, Sweden, Finland and the USA. The applied models stem from two major groups differing in complexity - those belonging to the group of general ecosystem models that include a plant-growth submodel, e.g. Century, and those that simulate soil organic matter turnover but not plant-growth, e.g. ICBM. For the latter group, carbon inputs to the soil from plant residues and roots have to be determined separately. We will present some aspects of the development of a model-based inventory of soil organic carbon in agricultural soils in Switzerland. Criteria for model evaluation are, among others, modeled land-use classes and land-use changes, spatial and temporal resolution, and coverage of relevant processes. For model parameterization and model evaluation at the field scale, data from several long-term agricultural experiments and monitoring sites in Switzerland is available. A subsequent regional application of a model requires the preparation of regional input data for the whole country - among others spatio-temporal meteorological data, agricultural and soil data. Following the evaluation of possible models and of available data, preference for application in the Swiss inventory will be given to simpler model structures, i.e. models without a plant-growth module. Thus, we compared different allometric relations

  8. SOMPROF: A vertically explicit soil organic matter model

    NARCIS (Netherlands)

    Braakhekke, M.C.; Beer, M.; Hoosbeek, M.R.; Kruijt, B.; Kabat, P.

    2011-01-01

    Most current soil organic matter (SOM) models represent the soil as a bulk without specification of the vertical distribution of SOM in the soil profile. However, the vertical SOM profile may be of great importance for soil carbon cycling, both on short (hours to years) time scale, due to

  9. [Simulated responses of winter wheat yield and soil moisture to different conservation tiliage practices in Weibei Highlands, Northwest China].

    Science.gov (United States)

    Zhang, Yu-Jiao; Li, Jun; Guo, Zheng; Yue, Zhi-fang

    2015-03-01

    Based on the verified precision results by simulation, the WinEPIC (EPIC, environmental/policy integrated climate model) was employed to quantitatively simulate effects of three conservation tillage practices adopted during the period of summer fallow, i.e. sub-soiling, no-tillage and conventional tillage, on wheat yield and soil moisture in Weibei Highlands during 1980-2009. The results showed that during the study period, the yield and annual water consumption of winter wheat under the different tillage practices tended to decrease with fluctuation in the growing period. The yield and water use efficiency of winter wheat under sub-soiling were the highest, averaging 3.33 t . hm-2 and 8.50 kg . hm-2 . mm-1 over the thirty years, respectively, and that of no tillage was the lowest. The annual water consumption of winter wheat was .slightly higher under sub-soiling than under no tillage and conventional tillage. In 0-3 m soil layer, the available soil water content tended to decline in a strongly and seasonally fluctuating manner. No tillage performed best in soil moisture conservation, with the average available soil water content being 89.5 mm, and that of conventional tillage was the lowest. The soil water moisture fluctuated with the seasonal rainfalls in 0-1 m soil layer and kept stable in 1-3 m with no great difference among the tillage practices. Under long-term continuous cropping, sub-soiling showed the best effects on the yield of winter wheat and the most comprehensive effect on soil moisture, and was the best practice of conservation tillage for wheat lands on Weibei Highlands.

  10. Local and Nonlocal Impacts of Soil Moisture Initialization on AGCM Seasonal Forecasts: A Model Sensitivity Study.

    Science.gov (United States)

    Zhang, H.; Frederiksen, C. S.

    2003-07-01

    Using a version of the Australian Bureau of Meteorology Research Centre (BMRC) atmospheric general circulation model, this study investigates the model's sensitivity to different soil moisture initial conditions in its dynamically extended seasonal forecasts of June-August 1998 climate anomalies, with focus on the south and northeast China regions where severe floods occurred. The authors' primary aim is to understand the model's responses to different soil moisture initial conditions in terms of the physical and dynamical processes involved. Due to a lack of observed global soil moisture data, the efficacy of using soil moisture anomalies derived from the NCEP-NCAR reanalysis is assessed. Results show that by imposing soil moisture percentile anomalies derived from the reanalysis data into the BMRC model initial condition, the regional features of the model's simulation of seasonal precipitation and temperature anomalies are modulated. Further analyses reveal that the impacts of soil moisture conditions on the model's surface temperature forecasts are mainly from localized interactions between land surface and the overlying atmosphere. In contrast, the model's sensitivity in its forecasts of rainfall anomalies is mainly due to the nonlocal impacts of the soil moisture conditions. Over the monsoon-dominated east Asian region, the contribution from local water recycling, through surface evaporation, to the model simulation of precipitation is limited. Rather, it is the horizontal moisture transport by the regional atmospheric circulation that is the dominant factor in controlling the model rainfall. The influence of different soil moisture conditions on the model forecasts of rainfall anomalies is the result of the response of regional circulation to the anomalous soil moisture condition imposed. Results from the BMRC model sensitivity study support similar findings from other model studies that have appeared in recent years and emphasize the importance of improving

  11. Heat and Water Transport in Soils and Across the Soil-Atmosphere Interface: Comparison of Model Concepts

    DEFF Research Database (Denmark)

    Vanderborght, Jan; Smits, Kathleen; Mosthaf, Klaus

    Evaporation from the soil surface represents a water flow and transport process in a porous medium that is coupled with free air flow and with heat fluxes in the system. We give an overview of different model concepts that are used to describe this process. These range from non-isothermal two...... lateral and up and downward air flow in the porous medium and vapor diffusion in the pore space play an important role were identified using simulations for a set of scenarios. When comparing cumulative evaporation fluxes from initially wet soil profiles, only small differences between the different...... models were found. The effect of vapor flow in the porous medium on cumulative evaporation could be evaluated using the desorptivity, Sevap, which represents a weighted average of liquid and vapor diffusivity over the range of soil water contents between the soil surface water content and the initial...

  12. A constitutive model for unsaturated cemented soils under cyclic loading

    OpenAIRE

    2008-01-01

    International audience; On the basis of plastic bounding surface model, the damage theory for structured soils and unsaturated soil mechanics, an elastoplastic model for unsaturated loessic soils under cyclic loading has been elaborated. Firstly, the description of bond degradation in a damage framework is given, linking the damage of soil's structure to the accumulated strain. The Barcelona Basic Model (BBM) was considered for the suction effects. The elastoplastic model is then integrated i...

  13. Optimization routine for identification of model parameters in soil plasticity

    Science.gov (United States)

    Mattsson, Hans; Klisinski, Marek; Axelsson, Kennet

    2001-04-01

    The paper presents an optimization routine especially developed for the identification of model parameters in soil plasticity on the basis of different soil tests. Main focus is put on the mathematical aspects and the experience from application of this optimization routine. Mathematically, for the optimization, an objective function and a search strategy are needed. Some alternative expressions for the objective function are formulated. They capture the overall soil behaviour and can be used in a simultaneous optimization against several laboratory tests. Two different search strategies, Rosenbrock's method and the Simplex method, both belonging to the category of direct search methods, are utilized in the routine. Direct search methods have generally proved to be reliable and their relative simplicity make them quite easy to program into workable codes. The Rosenbrock and simplex methods are modified to make the search strategies as efficient and user-friendly as possible for the type of optimization problem addressed here. Since these search strategies are of a heuristic nature, which makes it difficult (or even impossible) to analyse their performance in a theoretical way, representative optimization examples against both simulated experimental results as well as performed triaxial tests are presented to show the efficiency of the optimization routine. From these examples, it has been concluded that the optimization routine is able to locate a minimum with a good accuracy, fast enough to be a very useful tool for identification of model parameters in soil plasticity.

  14. Constitutive Laws for Dynamic Modelling of Soils,

    Science.gov (United States)

    1980-01-01

    shear history progresses. This is the type of approach followed in the endochronic models used by Bazant and co-workers ( Bazant and Krizeck, 1976...h. The plastic strain increments can be derived, according to~ Hill (1950) as: d 1P~ zh 7r(-, df (4 13.4.1 Prevost’s Model 1 Jean Prevost, presently...this improved model to soils (1978). Mean- while, Bazant and his co-workers have continued using the older model for 1describing concrete ( Bazant and

  15. Impact of improved soil climatology and intialization on WRF-chem dust simulations over West Asia

    Science.gov (United States)

    Omid Nabavi, Seyed; Haimberger, Leopold; Samimi, Cyrus

    2016-04-01

    Meteorological forecast models such as WRF-chem are designed to forecast not only standard atmospheric parameters but also aerosol, particularly mineral dust concentrations. It has therefore become an important tool for the prediction of dust storms in West Asia where dust storms have the considerable impact on living conditions. However, verification of forecasts against satellite data indicates only moderate skill in prediction of such events. Earlier studies have already indicated that the erosion factor, land use classification, soil moisture, and temperature initializations play a critical role in the accuracy of WRF-chem dust simulations. In the standard setting the erosion factor and land use classification are based on topographic variations and post-processed images of the advanced very high-resolution radiometer (AVHRR) during the period April 1992-March 1993. Furthermore, WRF-chem is normally initialized by the soil moisture and temperature of Final Analysis (FNL) model on 1.0x1.0 degree grids. In this study, we have changed boundary initial conditions so that they better represent current changing environmental conditions. To do so, land use (only bare soil class) and the erosion factor were both modified using information from MODIS deep blue AOD (Aerosol Optical Depth). In this method, bare soils are where the relative frequency of dust occurrence (deep blue AOD > 0.5) is more than one-third of a given month. Subsequently, the erosion factor, limited within the bare soil class, is determined by the monthly frequency of dust occurrence ranging from 0.3 to 1. It is worth to mention, that 50 percent of calculated erosion factor is afterward assigned to sand class while silt and clay classes each gain 25 percent of it. Soil moisture and temperature from the Global Land Data Assimilation System (GLDAS) were utilized to provide these initializations in higher resolution of 0.25 degree than in the standard setting. Modified and control simulations were

  16. Can simulations of flux exchanges between the land surface and the atmosphere be improved by a more complex description of soil and plant processes?

    Science.gov (United States)

    Klein, Christian

    2013-04-01

    Can simulations of flux exchanges between the land surface and the atmosphere be improved by a more complex description of soil and plant processes? Christian Klein, Christian Biernath, Peter Hoffmann and Eckart Priesack Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Soil Ecology, Oberschleissheim, Germany christian.klein@helmholtz-muenchen.de, ++ 49 89 3187 3015 Recent studies show, that uncertainties in regional and global climate simulations are partly caused by inadequate descriptions of soil-plant-atmosphere. Therefore, we coupled the soil-plant model system Expert-N to the regional climate and weather forecast model WRF. Key features of the Expert-N model system are the simulation of water flow, heat transfer and solute transport in soils and the transpiration of grassland and forest stands. Particularly relevant for the improvement of regional weather forecast are simulations of the feedback between the land surface and atmosphere, which influences surface temperature, surface pressure and precipitation. The WRF model was modified to optionally select either the land surface model Expert-N or NOAH to simulate the exchange of water and energy fluxes between the land surface and the atmosphere for every single grid cell within the simulation domain. Where the standard land surface model NOAH interpolates monthly LAI input values to simulate interactions between plant and atmosphere Expert-N simulates a dynamic plant growth with respect to water and nutrient availability in the soil. In this way Expert-N can be applied to study the effect of dynamic vegetation growth simulation on regional climate simulation results. For model testing Expert-N was used with two different soil parameterizations. The first parametrization used the USGS soil texture classification and simplifies the soil profile to one horizon (similar to the NOAH model). The second parameterization is based on the German soil texture classification

  17. Global modeling of soil evaporation efficiency for a chosen soil type

    Science.gov (United States)

    Georgiana Stefan, Vivien; Mangiarotti, Sylvain; Merlin, Olivier; Chanzy, André

    2016-04-01

    , it is the very first time that a chaotic model is obtained for the SEE. It also shows that the SEE dynamics can be approximated by a low-dimensional autonomous model. From a theoretical point of view, it is also interesting to note that only very few low-dimensional models could be directly obtained for environmental dynamics, and that four-dimensional models are even rarer. Since a model could be obtained for the SEE, it can be expected, now, to adapt the global modeling technique and to apply it to a range of different soil conditions in order to get a global model that would account