T. H. Skaggs

Agricultural Research Service, ERV, Texas, United States

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Publications (53)88.73 Total impact

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    Elia Scudiero, Dennis L Corwin, Todd H Skaggs
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    ABSTRACT: Despite decades of research in soil mapping, characterizing the spatial variability of soil salinity across broad regions remains a crucial challenge. This work explores the potential benefits of employing reflectance data from the six spectral bands (blue, 450-520 nm; green, 520-600 nm; red, 630-690 nm; near-infrared, 770-900 nm; infrared-1; 1550-1750 nm, and infrared-2, 2090-2350 nm) of the Landsat 7 (L7) satellite sensor (30x30 m resolution) for salinity assessment. Acquisitions of L7 throughout the western San Joaquin Valley, California (ca.15000 km2) were investigated over a seven-year period. Two salinity ground truth datasets were evaluated, across 23 fields farmed with various crops: 226 direct measurements (ca. 2x2 m resolution), from the 0-1.2 m soil profile; and ca. 6000 block-kriged estimations (30x30 m resolution), derived from geospatial electromagnetic induction measurements. The multi-year average of L7 data generally provided stronger correlations (up to R2=0.41), than those observed for each single year. Slightly stronger correlations (up to R2=0.43) were observed between salinity and the multi-year temporal variability of L7 reflectance (i.e., standard deviation at each map-cell over time). The strength of the correlations between L7 data and soil salinity varied according to changing meteorological conditions through the seven-year period and according to soil texture at a field by field basis. Additionally, selected salinity ranges (i.e., 0-2, 2-4, 4-8, 8-16, and >16 dS m-1) were characterized by significantly different values of the blue, green, red, and near-infrared bands. The results suggest that data fusion of the L7 multi-year reflectance with information on meteorological conditions, crop type, and soil texture could lead to a reliable salinity prediction model for the entire western San Joaquin Valley. Land resource managers, producers, agriculture consultants, extension specialists, and Natural Resource Conservation Service field staff are the beneficiaries of regional scale maps of soil salinity.
    ASA, CSSA and SSSA International Annual Meeting, Long Beach, California, USA; 11/2014
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    ABSTRACT: Due to the diminishing availability of good quality water for irrigation, it is increasingly important that irrigation and salinity management tools be able to target submaximal crop yields and support the use of marginal quality waters. In this work, we present a steady-state irrigated systems modeling framework that accounts for reduced plant water uptake due to root zone salinity. Two explicit, closed-form analytical solutions for the root zone solute concentration profile are obtained, corresponding to two alternative functional forms of the uptake reduction function. The solutions express a general relationship between irrigation water salinity, irrigation rate, crop salt tolerance, crop transpiration, and (using standard approximations) crop yield. Example applications are illustrated, including the calculation of irrigation requirements for obtaining targeted submaximal yields, and the generation of crop-water production functions for varying irrigation waters, irrigation rates, and crops. Model predictions are shown to be mostly consistent with existing models and available experimental data. Yet the new solutions possess advantages over available alternatives, including: (i) the solutions were derived from a complete physical-mathematical description of the system, rather than based on an ad hoc formulation; (ii) the analytical solutions are explicit and can be evaluated without iterative techniques; (iii) the solutions permit consideration of two common functional forms of salinity induced reductions in crop water uptake, rather than being tied to one particular representation; and (iv) the utilized modeling framework is compatible with leading transient-state numerical models. This article is protected by copyright. All rights reserved.
    11/2014; DOI:10.1002/2014WR016058
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    Elia Scudiero, Todd H. Skaggs, Dennis L. Corwin
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    ABSTRACT: Despite decades of research in soil mapping, characterizing the spatial variability of soil salinity across large regions remains a crucial challenge. This work explores the potential use of Landsat 7 (L7) satellite reflectance data (30 × 30 m resolution) to facilitate salinity mapping. Reflectance data spanning a seven-year period (2007-2013) were obtained for western San Joaquin Valley, California (ca.1.5 × 106 ha), over five soil Orders (Entisols, Inceptisols, Mollisols, and Vertisols). Two ground-truth datasets were considered: 267 direct measurements of salinity (one per L7 pixel) from soil samples (ECe), and 4891 indirect salinity values ( ) estimated from the relationships of ECe with geospatial (on average 16 per L7 pixel) electromagnetic induction measurements. The ground-truth dataset was characterized by stronger relationship with the L7 reflectance, with the multi-year averages of the L7 data showing R2 up to 0.43. The correlations between L7 data and were significantly influenced by rainfall (stronger in dry years than in rainy years), soil properties (weaker in finer soils), and crop type (stronger when soil salinity was over crop stress tolerance threshold).The results suggest that a fusion of the L7 multi-year reflectance data with information on meteorological conditions, crop type, and soil texture could lead to a reliable salinity prediction model for the entire western San Joaquin Valley. Land resource managers, producers, agriculture consultants, extension specialists, and Natural Resource Conservation Service field staff are the beneficiaries of regional-scale maps of soil salinity.
    10/2014; 2-3:82-90. DOI:10.1016/j.geodrs.2014.10.004
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    T. H. Skaggs, D. L. Suarez, D. L. Corwin
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    ABSTRACT: One strategy for maintaining irrigated agricultural productivity in the face of diminishing resource availability is to make greater use of marginal quality waters and lands. A key to sustaining systems using degraded irrigation waters is salinity management. Advanced simulation models and decision support tools can aid in the design and management of water reuse systems, but at present model predictions and related management recommendations contain significant uncertainty. Sensitivity analyses can help characterize and reduce uncertainties by revealing which parameter variations or uncertainties have the greatest impact on model outputs. In this work, the elementary effects method was used to obtain global sensitivity analyses of UNSATCHEM seasonal simulations of forage corn (Zea mays L.) production with differing irrigation rates and water compositions. Sensitivities were determined with respect to four model outcomes: crop yield, average root zone salinity, water leaching fraction, and salt leaching fraction. For a multiple-season, quasi-steady scenario, the sensitivity analysis found that overall the most important model parameters were the plant salt tolerance parameters, followed by the solute dispersivity. For a single-season scenario with irrigation scheduling based on soil water deficit, soil hydraulic parameters were the most important; the computed salt leaching fraction was also strongly affected by the initial ionic composition of the exchange phase because of its impact on mineral precipitation. In general, parameter sensitivities depend of the specifics of a given modeling scenario, and procedures for routine use of models for site-specific degraded irrigation water management should include site-specific uncertainty and sensitivity analyses. The elementary effects method used in this work is a useful approach for obtaining parameter sensitivity information at relatively low computational cost.
    Vadose Zone Journal 06/2014; 13(6). DOI:10.2136/vzj2013.09.0171 · 2.41 Impact Factor
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    ABSTRACT: Subsurface porous clay pipe irrigation is widely considered to be a very promising method for small-scale irrigation in arid regions. Unfortunately, salt accumulation at and near the soil surface using this method may affect germination of direct-seeded crops. Predicting salt movement and accumulation with clay pipe irrigation will allow producers to anticipate the need for leaching to control salinity in the soil root zone. The HYDRUS-2D model was used to simulate the accumulation of salt from a subsurface clay pipe irrigation system, installed at 30 cm depth, during the growing season of okra (Abelmoschus esculentus) irrigated with water having a salinity of 1.1 dS m−1. The loamy soil profile had an initial salinity of 2.3 dS m−1. Predicted electrical conductivity (ECe) values at the end of the growing season correlated significantly (R2 = 0.952) with measured saturated paste ECe data obtained at the end of the field experiments. Salinity was found to be relatively low around the pipes, but increased with distance away from the pipes. Measured and predicted soil salinity levels were especially higher above the clay pipes. Our results indicate that proper management of salt accumulation is vital for sustainable crop production whenever subsurface irrigation systems are being implemented.
    Agricultural Water Management 10/2013; 121:73–80. DOI:10.1016/j.agwat.2013.01.005 · 2.33 Impact Factor
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    ABSTRACT: Analytical solutions of the advection–dispersion solute transport equation remain useful for a large number of applications in science and engineering. In this paper we extend the Duhamel theorem, originally established for diffusion type problems, to the case of advective–dispersive transport subject to transient (time-dependent) boundary conditions. Generalized analytical formulas are established which relate the exact solutions to corresponding time-independent auxiliary solutions. Explicit analytical expressions were developed for the instantaneous pulse problem formulated from the generalized Dirac delta function for situations with first-type or third-type inlet boundary conditions of both finite and semi-infinite domains. The developed generalized equations were evaluated computationally against other specific solutions available from the literature. Results showed the consistency of our expressions.
    Chemical Engineering Journal 04/2013; 221:487–491. DOI:10.1016/j.cej.2013.01.095 · 4.06 Impact Factor
  • T. H. Skaggs, D. L. Suarez, S. Goldberg
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    ABSTRACT: Advanced numerical simulation models can potentially help improve guidelines for irrigation and salinity management. Many simulation model parameters have considerable uncertainty, and ideally that uncertainty should be reflected in model predictions and recommendations. In this work, we investigate solute transport predication intervals that can be generated by propagating model parameter uncertainty using Monte Carlo techniques. Flow and transport is simulated with a standard numerical model, while soil parameters and their uncertainty are estimated with pedotransfer functions. Generalized global sensitivity coefficients are computed to determine the parameters having the greatest impact on transport prediction and uncertainty. Simulations are compared with Br transport measured under unsaturated conditions in large lysimeters packed with clayey soil materials. In a 48 cm tall, homogeneous soil profile, model prediction intervals provided a reasonably good description of a single, relatively "noisy" breakthrough curve. In replicated 180 cm tall, layered soil profiles, model structural errors limited the accuracy of the prediction intervals under one irrigation water treatment, whereas under another treatment the predictions tracked the time course of the data reasonably well but tended to overestimate solute concentrations. The width of the prediction intervals tended to be small relative to the range of transport variability that existed across replicated lysimeters, particularly at shallow depths. Additional work aimed at operational field testing of model prediction uncertainty is needed if advanced water management models are to reach their full potential.
    Vadose Zone Journal 02/2013; 12(1). DOI:10.2136/vzj2012.0143 · 2.41 Impact Factor
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    ABSTRACT: The advection–dispersion transport equation with first-order decay was solved analytically for multi-layered media using the classic integral transform technique (CITT). The solution procedure used an associated non-self-adjoint advection–diffusion eigenvalue problem that had the same form and coefficients as the original problem. The generalized solution of the eigenvalue problem for any numbers of layers was developed using mathematical induction, establishing recurrence formulas and a transcendental equation for determining the eigenvalues. The orthogonality property of the eigenfunctions was found using an integrating factor that transformed the non-self-adjoint advection–diffusion eigenvalue problem into a purely diffusive, self-adjoint problem. The performance of the closed-form analytical solution was evaluated by solving the advection–dispersion transport equation for two- and five-layer media test cases which have been previously reported in the literature. Additionally, a solution featuring first-order decay was developed. The analytical solution reproduced results from the literature, and it was found that the rate of convergence for the current solution was superior to that of previously published solutions.
    International Journal of Heat and Mass Transfer 01/2013; 56(s 1–2):274–282. DOI:10.1016/j.ijheatmasstransfer.2012.09.011 · 2.52 Impact Factor
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    ABSTRACT: Contaminant transport processes in streams, rivers, and other surface water bodies can be analyzed or predict-ed using the advection-dispersion equation and related transport models. In part 1 of this two-part series we presented a large number of one-and multi-dimensional analytical solutions of the standard equilibrium advection-dispersion equa-tion (ADE) with and without terms accounting for zero-order production and first-order decay. The solutions are extend-ed in the current part 2 to advective-dispersive transport with simultaneous first-order mass exchange between the stream or river and zones with dead water (transient storage models), and to problems involving longitudinal advective-dispersive transport with simultaneous diffusion in fluvial sediments or near-stream subsurface regions comprising a hyporheic zone. Part 2 also provides solutions for one-dimensional advective-dispersive transport of contaminants sub-ject to consecutive decay chain reactions.
    Journal of Hydrology and Hydromechanics 01/2013; 61(3):250-259. DOI:10.2478/johh-2013-0032 · 1.23 Impact Factor
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    ABSTRACT: Analytical solutions of the advection-dispersion equation and related models are indispensable for predicting or analyzing contaminant transport processes in streams and rivers, as well as in other surface water bodies. Many useful analytical solutions originated in disciplines other than surface-water hydrology, are scattered across the literature, and not always well known. In this two-part series we provide a discussion of the advection-dispersion equation and related models for predicting concentration distributions as a function of time and distance, and compile in one place a large number of analytical solutions. In the current part 1 we present a series of one-and multi-dimensional solutions of the standard equilibrium advection-dispersion equation with and without terms accounting for zero-order production and first-order decay. The solutions may prove useful for simplified analyses of contaminant transport in surface water, and for mathematical verification of more comprehensive numerical transport models. Part 2 provides solutions for advec-tive-dispersive transport with mass exchange into dead zones, diffusion in hyporheic zones, and consecutive decay chain reactions.
    Journal of Hydrology and Hydromechanics 01/2013; 61:146-160. DOI:10.2478/johh-2013-0020 · 1.23 Impact Factor
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    ABSTRACT: Recent studies suggest that standard guidelines for managing salinity in irrigated agriculture overestimate the leaching requirement. Transient-state, process-based model analyses offer the possibility of more efficient water and salinity management, but data are needed to evaluate the accuracy of various subcomponents of the models. In this study, tracer (Br) transport in twelve lysimeters identically packed with clayey soil materials was monitored at eight soil depths and in drainage waters. In the first phase of the experiment (the salinization phase), six of the lysimeters were irrigated with high EC waters (8.1 dS m(-1)) and six with low EC waters (0.4 dS m(-1)). In the second phase, all lysimeters were leached with low EC waters (0.4 dS m(-1)). Tracer transport was very different in the high and low EC irrigation treatments, with the high EC treatment exhibiting significant tailing in the breakthrough curves. Due to the replicated experimental design, it was possible to confirm that the differences between the experimental treatments were significant and not due to random deviation. Future research aimed at placing realistic confidence levels on model predictions will allow transient-state models to reach their full potential as water and salinity management tools. Published by Elsevier B.V.
    Agricultural Water Management 07/2012; 110. DOI:10.1016/j.agwat.2012.04.003 · 2.33 Impact Factor
  • Todd H. Skaggs
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    ABSTRACT: Critical path analysis (CPA) is a method for estimating macroscopic transport coefficients of heterogeneous materials that are highly disordered at the micro-scale. Developed originally to model conduction in semiconductors, numerous researchers have noted that CPA might also have relevance to flow and transport processes in porous media. However, the results of several numerical investigations of critical path analysis on pore network models raise questions about the applicability of CPA to porous media. Among other things, these studies found that (i) in well-connected 3D networks, CPA predictions were inaccurate and became worse when heterogeneity was increased; and (ii) CPA could not fully explain the transport properties of 2D networks. To better understand the applicability of CPA to porous media, we made numerical computations of permeability and electrical conductivity on 2D and 3D networks with differing pore-size distributions and geometries. A new CPA model for the relationship between the permeability and electrical conductivity was found to be in good agreement with numerical data, and to be a significant improvement over a classical CPA model. In sufficiently disordered 3D networks, the new CPA prediction was within ±20% of the true value, and was nearly optimal in terms of minimizing the squared prediction errors across differing network configurations. The agreement of CPA predictions with 2D network computations was similarly good, although 2D networks are in general not well-suited for evaluating CPA. Numerical transport coefficients derived for regular 3D networks of slit-shaped pores were found to be in better agreement with experimental data from rock samples than were coefficients derived for networks of cylindrical pores.
    Advances in Water Resources 10/2011; 34(10):1335–1342. DOI:10.1016/j.advwatres.2011.06.010 · 2.78 Impact Factor
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    ABSTRACT: Spatial variability has a profound influence on a variety of landscape-scale agricultural issues including solute transport in the vadose zone, soil quality assessment, and site-specific crop management. Directed soil sampling based on geospatial measurements of apparent soil electrical conductivity (EC a) is a potential means of characterizing the spatial variability of any soil property that influences EC a including soil salinity, water content, texture, bulk density, organic matter, and cation exchange capacity. Arguably the most significant step in the protocols for characterizing spatial variability with EC a -directed soil sampling is the statistical sampling design, which consists of two potential approaches: model-and design-based sampling strategies such as response surface sampling design (RSSD) and stratified random sampling design (SRSD), respectively. The primary objective of this study was to compare model-and design-based sampling strategies to evaluate if one sampling strategy outperformed the other or if both strategies were equal in performance. Using three different model validation tests, the regression equation estimated from the RSSD data produced accurate and unbiased predictions of the natural log salinity levels at the independently chosen SRSD sites. Design optimality scores (i.e., D-, V-, and G-optimality criteria) indicate that the use of the RSSD design should facilitate the estimation of a more accurate regression model, i.e., the RSSD approach should allow for better model discrimination, more precise parameter estimates, and smaller prediction variances. Even though a model-based sampling design, such as RSSD, has been less prevalent in the literature, it is concluded from the comparison that there is no reason to refrain from its use and in fact warrants equal consideration.
    Journal of Environmental & Engineering Geophysics 09/2010; 15(3). DOI:10.2113/JEEG15.3.147 · 0.80 Impact Factor
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    J S Pérez Guerrero, T H Skaggs
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    ABSTRACT: s u m m a r y Mathematical models describing contaminant transport in heterogeneous porous media are often formu-lated as an advection–dispersion transport equation with distance-dependent transport coefficients. In this work, a general analytical solution is presented for the linear, one-dimensional advection–dispersion equation with distance-dependent coefficients. An integrating factor is employed to obtain a transport equation that has a self-adjoint differential operator, and a solution is found using the generalized inte-gral transform technique (GITT). It is demonstrated that an analytical expression for the integrating factor exists for several transport equation formulations of practical importance in groundwater transport mod-eling. Unlike nearly all solutions available in the literature, the current solution is developed for a finite spatial domain. As an illustration, solutions for the particular case of a linearly increasing dispersivity are developed in detail and results are compared with solutions from the literature. Among other applica-tions, the current analytical solution will be particularly useful for testing or benchmarking numerical transport codes because of the incorporation of a finite spatial domain. Published by Elsevier B.V.
    Journal of Hydrology 08/2010; DOI:10.1016/j.jhydrol.2010.06.030 · 2.69 Impact Factor
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    ABSTRACT: In the irrigated western U.S. disposal of drainage water has become a significant economic and environmental liability. Development of irrigation water management practices that reduce drainage water volumes is essential. One strategy combines restricted drainage outflow (by plugging the drains) with deficit irrigation to maximize shallow groundwater consumption by crops, thus reducing drainage that needs disposal. This approach is not without potential pitfalls; upward movement of groundwater in response to crop water uptake may increase salt and sodium concentrations in the root zone. The purposes for this study were: to observe changes in the spatial and temporal distributions of SAR (sodium adsorption ratio) and salt in a field managed to minimize drainage discharge; to determine if in situ drainage reduction strategy affects SAR distribution in the soil profile; and to identify soil or management factors that can help explain field wide variability. We measured SAR, soil salinity (EC1:1) and soil texture over 3 years in a 60-ha irrigated field on the west side of the San Joaquin Valley, California. At the time we started our measurements, the field was beginning to be managed according to a shallow groundwater/drainage reduction strategy. Soil salinity and SAR were found to be highly correlated in the field. The observed spatial and temporal variability in SAR was largely a product of soil textural variations within the field and their associated variations in apparent leaching fraction. During the 3-year study period, the percentage of the field in which the lower profile (90-180cm) depth averaged SAR was above 10, increased from 20 to 40%. Since salinity was increasing concomitantly with SAR, and because the soil contained gypsum, sodium hazard was not expected to become a limiting factor for long term shallow groundwater management by drain control. It is anticipated that the technology will be viable for future seasons.
    Agricultural Water Management 05/2010; 97(5):673-680. DOI:10.1016/j.agwat.2009.12.008 · 2.33 Impact Factor
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    ABSTRACT: A traditional method of reclaiming salt-affected soils involves ponding water on a field and leaching salts from the soil through a subsurfacetile drainage system. Because water and salts move more slowly in areas midway between drain lines than in areas near the drains, achieving a desired level of desalinization across the entire field requires that ponding continue long after areas close to the drains are already free of salts, thus causing an inefficient leaching process that wastes water. A partial ponding method of leaching was recently suggested to improve the leaching efficiency by up to 85%. In this study, we tested the partial ponding method for its potential to save water and time by simulating the leaching of salts from salt-affected profiles with various soil textures, tile-drain depths, and soil depths. Simulations for laboratory sand tanks and field conditions both showed that transport velocities midway between drains are greater under partial ponding than under total ponding because the local hydraulic head gradient is larger under partial ponding conditions. As the ponded area increases toward the drain, water originating from areas near the drain moves faster than water from midway between the drains. By adopting partial ponding, water and time savings of 95 and 91%, respectively, were found possible for a sandy soil. The method also showed water savings of 84% when applied to a loam soil and 99% for a layered sand over loam soil but only 13% when applied to a layered loam over sand soil.
    Vadose Zone Journal 05/2010; 9(2). DOI:10.2136/vzj2009.0129 · 2.41 Impact Factor
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    ABSTRACT: Most analytical solutions available for the equations governing the advective–dispersive transport of multiple solutes undergoing sequential first-order decay reactions have been developed for infinite or semi-infinite spatial domains and steady-state boundary conditions. In this study, we present an analytical solution for a finite domain and a time-varying boundary condition. The solution was found using the Classic Integral Transform Technique (CITT) in combination with a filter function having separable space and time dependencies, implementation of the superposition principle, and using an algebraic transformation that changes the advection–dispersion equation for each species into a diffusion equation. The analytical solution was evaluated using a test case from the literature involving a four radionuclide decay chain. Results show that convergence is slower for advection-dominated transport problems. In all cases, the converged results were identical to those obtained with the previous solution for a semi-infinite domain, except near the exit boundary where differences were expected. Among other applications, the new solution should be useful for benchmarking numerical solutions because of the adoption of a finite spatial domain. KeywordsMulti-species transport-Finite domain-Analytical solution-Integral transform
    Transport in Porous Media 04/2010; 85(1):171-188. DOI:10.1007/s11242-010-9553-4 · 1.55 Impact Factor
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    ABSTRACT: The Ejina Basin is an extremely arid subwatershed in Northwest China. The predominant natural tree species in the area, Populus euphratica, depends on groundwater for sustenance. In recent decades, groundwater overdraft and increased water diversions from the Heihe River caused water table elevations to decline, such that large areas of P. euphratica have withered, creating a highly visible symbol of ecological change and desertification in the Ejina Basin. Ecological restoration efforts aimed at saving existing woodlands and cultivating new stands of P. euphratica are underway. To provide a better scientific basis for ecological restoration plans, it is necessary to understand the effect of water table elevation on P. euphratica water uptake. In this work, we used the HYDRUS-1D software package to study groundwater movement into the root zone and the uptake of groundwater in a 10-year-old P. euphratica woodland. Additionally, we examined the changes in uptake that would occur for different water table elevations. The model calibration was confirmed by comparing predicted soil moisture contents during the P. euphratica growing season with field measured values. The results indicate that in 2000, with an average water table depth of 2·64 m, P. euphratica at the study site obtained about 53% of its water from groundwater during the middle part of the growing season (day of year 160–290). Simulations made with constant water table depths found that increasing the water table depth from 2 to 3 metres resulted in a 74% reduction in transpiration. Many factors can influence the optimal water table depth at a given site. An advantage of the modelling approach is that these factors can be systematically varied, creating a site-specific impact assessment of water management options that may alter water table depths, thus aiding ecological restoration efforts. Copyright © 2009 John Wiley & Sons, Ltd.
    Hydrological Processes 08/2009; 23(17):2460 - 2469. DOI:10.1002/hyp.7353 · 2.50 Impact Factor
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    A.A. Siyal, T. H. Skaggs
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    ABSTRACT: Sub-surface irrigation with porous clay pipe can be an efficient, water saving method of irrigation for many less developed arid and semi-arid regions. Maximizing the efficiency of clay pipe irrigation requires guidelines and criteria for system design and operation. In this study, experimental and simulated (with HYDRUS (2D/3D)) soil wetting patterns were investigated for sub-surface pipe systems operating at different water pressures. Predictions of the soil water content made with HYDRUS were found to be in good agreement (R2 = 0.98) with the observed data. Additional simulations with HYDRUS were used to study the effects of various design parameters on soil wetting. Increasing the system pressure increased the size of the wetted zone. The installation depth affects the recommended lateral spacing as well as the amount of evaporative water loss. For a given water application, the potential rate of surface evaporation affected the shape of the wetted region only minimally. Soil texture, due to its connection to soil hydraulic conductivity and water retention, has a larger impact on the wetting geometry. In general, greater horizontal spreading occurs in fine texture soils, or in the case of layered soils, in the finer textured layers.
    Agricultural Water Management 06/2009; 96(6-96):893-904. DOI:10.1016/j.agwat.2008.11.013 · 2.33 Impact Factor
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    ABSTRACT: Transport equations governing the movement of multiple solutes undergoing sequential first-order decay reactions have relevance in analyzing a variety of subsurface contaminant transport problems. In this study, a one-dimensional analytical solution for multi-species transport is obtained for finite porous media and constant boundary conditions. The solution permits different retardation factors for the various species. The solution procedure involves a classic algebraic substitution that transforms the advection-dispersion partial differential equation for each species into an equation that is purely diffusive. The new system of partial differential equations is solved analytically using the Classic Integral Transform Technique (CITT). Results for a classic test case involving a three-species nitrification chain are shown to agree with previously reported literature values. Because the new solution was obtained for a finite domain, it should be especially useful for testing numerical solution procedures.
    Transport in Porous Media 04/2009; 80(2):373-387. DOI:10.1007/s11242-009-9368-3 · 1.55 Impact Factor

Publication Stats

853 Citations
88.73 Total Impact Points

Institutions

  • 2006–2014
    • Agricultural Research Service
      ERV, Texas, United States
  • 2009
    • Sindh Agriculture University
      • Department of Land and Water Management
      Tando Jām, Sindh, Pakistan
  • 2000
    • University of California, Riverside
      Riverside, California, United States