Martinus Th. van Genuchten

Universidade Federal do Rio de Janeiro

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JŠ

Jiřı́ Šimůnek

University of California, Riverside

Feike J. Leij

California State University, Long Beach

Diederik Jacques

Belgian Nuclear Research Centre

Elizabeth M. Pontedeiro

Universidade Federal do Rio de Janeiro

Amir Raoof

Utrecht University

Yakov Pachepsky

Agricultural Research Service

Todd H. Skaggs

U.S. Salinity Laboratory

Binayak P. Mohanty

Texas A&M University

Dirk Mallants

Commonwealth Scientific and Industrial Research Organisation

Scott A. Bradford

Agricultural Research Service

Cooperative Institutions

Agricultural Research Service

U.S. Salinity Laboratory

Universidade Federal do Rio de Janeiro

United States Department of Agriculture

University of California, Riverside

Utrecht University

University of California, Davis

University of Arizona

Wageningen University & Research

Weatherford College

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Groundwater Recharge at Five Representative Sites in the Hebei Plain, China

Ground Water (2010)

Xiaohui Lu Menggui Jin Martinus Th. van Genuchten Wang Bing-guo

Accurate estimates of groundwater recharge are essential for effective management of groundwater, especially when supplies are limited such as in many arid and semiarid areas. In the Hebei Plain, China, water shortage is increasingly restricting socioeconomic development, especially for agriculture, which heavily relies on groundwater. Human activities have greatly changed groundwater recharge there during the past several decades. To obtain better estimates of recharge in the plain, five representative sites were selected to investigate the effects of irrigation and water table depth on groundwater recharge. At each site, a one-dimensional unsaturated flow model (Hydrus-1D) was calibrated using field data of climate, soil moisture, and groundwater levels. A sensitivity analysis of evapotranspirative fluxes and various soil hydraulic parameters confirmed that fine-textured surface soils generally generate less recharge. Model calculations showed that recharge on average is about 175 mm/year in the piedmont plain to the west, and 133 mm/year in both the central alluvial and lacustrine plains and the coastal plain to the east. Temporal and spatial variations in the recharge processes were significant in response to rainfall and irrigation. Peak time-lags between infiltration (rainfall plus irrigation) and recharge were 18 to 35 days in the piedmont plain and 3 to 5 days in the central alluvial and lacustrine plains, but only 1 or 2 days in the coastal plain. This implies that different time-lags corresponding to different water table depths must be considered when estimating or modeling groundwater recharge.

Depression-focused recharge

Coastal plain

Alluvial plain

Groundwater model

Infiltration (HVAC)

10.1111/j.1745-6584.2009.00667.x

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Citations (102)

Capillary pressure–saturation curves of thin hydrophilic fibrous layers: effects of overburden pressure, number of layers, and multiple imbibition–drainage cycles

Textile Research Journal (2019)

Amir Hossein Tavangarrad S. Majid Hassanizadeh Rodrigo Rosati Luigi Digirolamo Martinus Th. van Genuchten

Unsaturated fluid flow in thin porous media depends on hydraulic properties, such as the capillary pressure, P c , as a function of saturation, S. We measured this relationship for two different types of compressible thin hydrophilic fibrous layers under varying conditions. Among other factors, we changed the number of layers and the overburden pressure (i.e. the confined solid pressure applied on top of the sample) imposed on one layer or a stack of layers. Applying an overburden pressure drastically affected the [Formula: see text] curves. However, increasing the number of fibrous layers had little impact on the capillary pressure–saturation curves. We also investigated the effect of multiple imbibition–drainage cycles on the [Formula: see text] data. Measured data points were used to find general expressions for the [Formula: see text] relationships of compressible thin porous media. Existing quasi-empirical correlations used in vadose zone hydrology, notably expressions by van Genuchten (Van Genuchten MTh. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci Soc Am J 1980; 44: 892-898) and Durner (Durner W. Hydraulic conductivity estimation for soils with heterogeneous pore structure. Water Resour Res 1994; 32: 211–223) for single- and dual-porosity media, respectively, were employed to fit the measured data points.

Imbibition

Capillary pressure

Saturation (graph theory)

Overburden

Overburden pressure

10.1177/0040517519844209

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Citations (13)

Modeling Virus Transport and Remobilization during Transient Partially Saturated Flow

Vadose Zone Journal (2012)

Qiulan Zhang S. Majid Hassanizadeh Amir Raoof Martinus Th. van Genuchten Saskia M. Roels

Virus transport in porous media is affected by the water flow regime. During transient, variably saturated flow, fluctuating flow regimes can enhance virus detachment from both solid–water interfaces (SWIs) and air–water interfaces (AWIs). The objective of this study was to simulate the influence of drainage and imbibition events on the remobilization of attached viruses. Three different modeling approaches were examined. In the first approach, all attachment and detachment coefficients were assumed to be constant, but the values of the detachment coefficients were increased drastically for the duration of transient, unsaturated flow. The second and third modeling approaches involved extensions of the model of Cheng and Saiers, who assumed enhanced detachment of viruses to be proportional to the time rate of change in the water content. Their model was extended to include separate terms for virus attachment–detachment on SWIs and AWIs. In our second approach, we assumed kinetic sorption onto the AWI, with the desorption rate being described as a function of temporal changes in the air content. This approach did not explicitly account for the specific air–water interfacial area. Thus, in our third approach we explicitly included the presence and variation of air–water interfaces and assumed AWI attachment–detachment to be an equilibrium sorption process. The available air–water interfacial area was assumed to be a function of fluid saturation. The models were used to simulate a series of saturated–unsaturated virus transport experiments reported in the literature for conditions of both drainage and imbibition. The most promising results were obtained with the third approach, which explicitly accounts for adsorption to air–water interfaces and assumes equilibrium sorption on the available air–water interfacial area.

Imbibition

Saturation (graph theory)

Transient (computer programming)

Transient flow

10.2136/vzj2011.0090

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Citations (28)

Scaling Parameter to Predict the Soil Water Characteristic from Particle-Size Distribution Data

Soil Science Society of America Journal (1999)

Lalit Arya Feike J. Leij Martinus Th. van Genuchten Peter J. Shouse

The Arya-Paris model is an indirect method to estimate the soil water characteristic from particle-size data. The scaling parameter, α, in the original model was assumed constant for all soil textures. In this study, α is defined as αi = (log Ni/log ni), where ni is the number of spherical particles in the ith particle-size fraction (determined by the fraction solid mass, wi, and mean particle radius, Ri) and Ni is the number of spherical particles of radius Ri required to trace the pore length generated by the same solid mass in a natural structure soil matrix. An estimate for log Ni was obtained by either relating log Ni to log ni using a logistic growth equation or by relating log Ni linearly to log (wi/R3i) based on the similarity principle. For any given texture, both approaches showed that α was not constant but decreased with increasing particle size, especially for the coarse fractions. In addition, α was also calculated as a single-value average for a given textural class. The three formulations of α were evaluated on 23 soils that represented a range in particle-size distribution, bulk density, and organic matter content. The average α consistently predicted higher pressure heads in the wet range and lower pressure heads in the dry range. The formulation based on the similarity principle resulted in bias similar to that of the constant α approach, whereas no bias was observed for the logistic growth equation. The logistic growth equation implicitly accounted for bias in experimental procedures, because it was fitted to log Ni values computed from experimental soil water characteristic data. The formulation based on the similarity principle is independent of bias that might be inherent in experimental data.

Soil texture

Particle (ecology)

Constant (computer programming)

Mass fraction

10.2136/sssaj1999.03615995006300030013x

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Citations (265)

Prediction of the absolute hydraulic conductivity function from soil water retention data

Hydrology and earth system sciences (2023)

André Peters Tobias L. Hohenbrink Sascha C. Iden Martinus Th. van Genuchten Wolfgang Durner

Abstract. For modeling flow and transport processes in the soil–plant–atmosphere system, knowledge of the unsaturated hydraulic properties in functional form is mandatory. While much data are available for the water retention function, the hydraulic conductivity function often needs to be predicted. The classical approach is to predict the relative conductivity from the retention function and scale it with the measured saturated conductivity, Ks. In this paper we highlight the shortcomings of this approach, namely, that measured Ks values are often highly uncertain and biased, resulting in poor predictions of the unsaturated conductivity function. We propose to reformulate the unsaturated hydraulic conductivity function by replacing the soil-specific Ks as a scaling factor with a generally applicable effective saturated tortuosity parameter τs and predicting total conductivity using only the water retention curve. Using four different unimodal expressions for the water retention curve, a soil-independent general value for τs was derived by fitting the new formulation to 12 data sets containing the relevant information. τs was found to be approximately 0.1. Testing of the new prediction scheme with independent data showed a mean error between the fully predicted conductivity functions and measured data of less than half an order of magnitude. The new scheme can be used when insufficient or no conductivity data are available. The model also helps to predict the saturated conductivity of the soil matrix alone and thus to distinguish between the macropore conductivity and the soil matrix conductivity.

Macropore

Tortuosity

10.5194/hess-27-1565-2023

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Citations (18)

Boundary Conditions for Displacement Experiments through Short Laboratory Soil Columns

Soil Science Society of America Journal (1984)

Martinus Th. van Genuchten Jack Parker

Abstract This paper presents a discussion of the physical and mathematical significance of various boundary conditions applicable to one‐dimensional solute transport through relatively short laboratory soil columns. Based on mass balance considerations, it is shown that a first‐type or concentration‐type condition at the inlet boundary incorrectly predicts the volume‐averaged or resident concentration inside both semi‐infinite and finite systems. A third‐type or flux‐type inlet boundary condition preserves mass in semi‐infinite systems, but underpredicts effluent concentrations from finite columns unless a local transformation is used to convert volume‐averaged concentrations into flux‐averaged concentrations. This transformation leads to an expression for the effluent concentration that is identical to the solution for the semi‐infinite system using a concentration‐type boundary condition. For column Peclet numbers greater than about five, the resulting analytical expression for the effluent curve is shown to be nearly identical to the analytical solution for a finite system based on a flux‐type inlet boundary condition and a zero‐concentration gradient at the exit boundary. Both solutions correctly preserve mass in the system; other solutions of the convective‐dispersive transport equation are shown to be inappropriate for analyzing column effluent data.

Mass flux

Péclet number

10.2136/sssaj1984.03615995004800040002x

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Citations (404)

Parameter Estimation Analysis of the Evaporation Method for Determining Soil Hydraulic Properties

Soil Science Society of America Journal (1998)

Jiřı́ Šimůnek Martinus Th. van Genuchten Ole Wendroth

Abstract Soil hydraulic properties are important parameters affecting water flow in variably saturated soils. We estimated the hydraulic properties from a laboratory evaporation experiment using both a parameter estimation method and the modified Wind method. The parameter estimation method combined a one‐dimensional numerical solution of the Richards equation with the Marquardt‐Levenberg optimization scheme. In our study we used both numerically generated data and data measured in the laboratory. Two experiments were carried out on 10‐cm‐high soil cores containing two different soils. Pressure heads inside the cores were measured with five tensiometers, while evaporative water loss from the top was determined by weighing the soil samples. The objective function for the parameter estimation analysis was defined in terms of the final total water volume in the core and pressure head readings by one or several tensiometers. An analysis of numerically generated data showed that the optimization method was most sensitive to the shape factor ( n ) and the saturated water content (θ s ) and least to the residual water content (θ r ). Pressure heads measured close to the soil surface were found to be more valuable for the parameter estimation technique than those measured at lower locations. The optimized hydraulic parameters corresponded closely with those obtained using Wind's analysis. All optimizations gave similar results for the soil hydraulic properties within the range of measured pressure heads (0 to −700cm). Extrapolation beyond this range involved a high level of uncertainty because of high correlation between parameters θ r and n .

Pressure head

Richards equation

Hydraulic head

Water potential

10.2136/sssaj1998.03615995006200040007x

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Citations (239)

Bacteriophage PRD1 batch experiments to study attachment, detachment and inactivation processes

Journal of Contaminant Hydrology (2013)

Gholamreza Sadeghi Jack Schijven Thilo Behrends S. Majid Hassanizadeh Martinus Th. van Genuchten

Virus inactivation

10.1016/j.jconhyd.2013.06.002

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Citations (17)

Modeling subsurface water flow and solute transport with HYDRUS and related numerical software packages

CRC Press eBooks (2007)

Martinus Th. van Genuchten

HYDRUS and related software packages represent a system of numerical models for simulating variably-saturated water, heat and solute movement in the subsurface. The software packages can simulate flow and transport in one-dimensional (e.g., HYDRUS-1D, HP1, SOILCO2, and UNSATCHEM), two-dimensional (SWMS_2D, CHAIN_2D, or HYDRUS-2D), and three-dimensional (SWMS_3D or HYDRUS (2D/3D)) transport domains. While water flow in all of the models is simulated in a relatively similar manner, different solute transport modules exist in the different codes. Some models can simulate only transport of solutes independent of one another, whereas other models include biogeochemical modules simulating complex interactions between the various solutes. For example, HYDRUS-1D and UNSATCHEM models can also consider the transport of major ions and their mutual reactions, such as dissolution-precipitation, cation exchange, or aqueous complexation. The wetland module in HYDRUS (2D/3D) furthermore considers biochemical processes associated with the flow of wastewater through constructed or natural wetlands. Finally, HP1, a model resulting from coupling HYDRUS-1D and PHREEQC, accounts for a broad range of instantaneous and kinetic chemical and biological reactions, including aqueous complexation, precipitation-dissolution, cation exchange, surface complexation, and redox reactions. In this manuscript we review the various models and provide references to many of their applications.

Subsurface Flow

10.1201/9781482288513-8

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Citations (18)

Revisiting the horizontal redistribution of water in soils: Experiments and numerical modeling

Water Resources Research (2017)

Luwen Zhuang S. Majid Hassanizadeh P. J. Kleingeld Martinus Th. van Genuchten

Abstract A series of experiments and related numerical simulations were carried out to study one‐dimensional water redistribution processes in an unsaturated soil. A long horizontal Plexiglas box was packed as homogenously as possible with sand. The sandbox was divided into two sections using a very thin metal plate, with one section initially fully saturated and the other section only partially saturated. Initial saturation in the dry section was set to 0.2, 0.4, or 0.6 in three different experiments. Redistribution between the wet and dry sections started as soon as the metal plate was removed. Changes in water saturation at various locations along the sandbox were measured as a function of time using a dual‐energy gamma system. Also, air and water pressures were measured using two different kinds of tensiometers at various locations as a function of time. The saturation discontinuity was found to persist during the entire experiments, while observed water pressures were found to become continuous immediately after the experiments started. Two models, the standard Richards equation and an interfacial area model, were used to simulate the experiments. Both models showed some deviations between the simulated water pressures and the measured data at early times during redistribution. The standard model could only simulate the observed saturation distributions reasonably well for the experiment with the lowest initial water saturation in the dry section. The interfacial area model could reproduce observed saturation distributions of all three experiments, albeit by fitting one of the parameters in the surface area production term.

Saturation (graph theory)

Discontinuity (linguistics)

10.1002/2017wr020410

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Citations (12)