Raz Khaleel

• Washington State University

Soil water retention curve (SWRC) is a key characteristic widely used to study single‐ and multi‐phase flow and transport in porous media. Since its direct measurement is time‐ and labor‐consuming, numerous empirical and theoretical approaches were developed to estimate it from particle‐size distribution (PSD). In this study, we apply concepts of f...

A practical approach for modeling field‐scale moisture flow in a highly heterogeneous unsaturated medium is described in this study. The validity of this approach is demonstrated through comparison of the numerical simulations with field observations at a semiarid site located in southcentral Washington State. The methodology is based on upscaling...

Variable, moisture‐dependent anisotropy in unsaturated media is an effective, large‐scale (macroscopic) flow property that results from media heterogeneities at a smaller scale. This technical note documents the variable moisture‐dependent anisotropy calculations using a script for the power‐averaging tensorial connectivity–tortuosity model. The ac...

Vadose zone hydrology plays a key role on moisture flow and contaminant migration through the vadose zone to the underlying aquifer. In particular, vadose zone residence times are significantly impacted by the geologic media heterogeneities, physical and hydraulic properties of sediments, and the moisture content of sediments. This is especially tr...

This textbook integrates classic principles of flow through porous media with recently developed stochastic analyses to provide new insight on subsurface hydrology. Importantly, each of the authors has extensive experience in both academia and the world of applied groundwater hydrology. The book not only presents theories but also emphasizes their...

Scaling considerations relevant to porous media flow are reviewed. An analysis approach is presented for determining the sizing requirements of a large-scale, hydrology physical model. The physical model will be used to validate performance assessment codes that evaluate the long-term behavior of the repository isolation system. Numerical simulatio...

Accurate simulation of flow and contaminant transport in deep vadose zone (DVZ) is often hampered by difficulty in characterizing medium heterogeneity, in particular, heterogeneity in the lateral direction such as horizontal variability of sediment layering structure that is prevalent in sedimentary environments. The transition probability (TP) bas...

We present a predictive model for unsaturated hydraulic conductivity (K) which makes use of the interrelationship among capillary pressure (Pc), wetting phase saturation (Sw), and nonwetting-wetting phase interfacial area. The newly developed model is general so that any closed form Pc-Sw equation can be incorporated. In particular, we formulate Ko...

Various methods have been developed over the past 3 decades to estimate effective unsaturated hydraulic properties. We developed an alternative practical approach to estimate three-dimensional effective unsaturated hydraulic conductivity via a combined power-averaging and tensorial connectivity-tortuosity (PA-TCT) model. An application of the PA-TC...

While pedotransfer functions (PTFs) have long been applied to estimate soil hydraulic parameters for unsaturated flow and solute transport modeling, the uncertainty associated with the estimates is often ignored. The objective of this study is to evaluate uncertainty of the PTF-estimated soil hydraulic parameters and its effect on numerical simulat...

CH2M Hill Plateau Remediation Company (CHPRC) requested the services of the Pacific Northwest National Laboratory (PNNL) to provide technical support for the Remediation Decision Support (RDS) activity within the Soil & Groundwater Remediation Project. A portion of the support provided in FY2009, was to extend the soil unsaturated hydraulic conduct...

Accurate simulation of flow and contaminant transport in heterogeneous media is often hampered by difficulty in characterizing media heterogeneity due to lack of data. Based on the availability of "soft" data (i.e., initial moisture content), three methods were developed for characterizing soil hydraulic parameters for a vadose zone field experimen...

By leveraging use of “soft” data (e.g., initial moisture content, $\theta$i), this study applies the transition probability (TP) based Markov chain (MC) model to sediment textural classes for characterizing the medium heterogeneity and sediment layering structure. The TP/MC method is evaluated by simulating the vadose zone moisture movement at a fi...

The tortuosity and/or pore connectivity factor, τ, in unsaturated media is typically represented by Se$\varepsilon$, where Se = effective saturation. The exponent $\varepsilon$ is treated as an optimized parameter with typical values of 0.5 and 2, respectively, for Mualem and Burdine-type models. In this study, the tortuosity and/or connectivity te...

Characterization of media heterogeneity in unsaturated media is always hampered by lack of site-specific soil samples. In particular, geologic heterogeneity, which controls unsaturated flow and solute transport, cannot be identified based on samples from one or multiple boreholes. This study develops a geologically based Markov chain model to chara...

To characterize heterogeneity of soil hydraulic parameters, we developed a method to incorporate measurements of soil texture, bulk density, soil hydraulic parameter, and moisture content. The method first uses cokriging to estimate heterogeneous soil texture and bulk density (pedotransfer variables) using the moisture content as secondary variable...

The USDOE has initiated an impact assessment of existing vadose zone contamination at the Hanford Site SX tank farm in southeastern Washington State. The assessment followed the Resource Conservation and Recovery Act (RCRA) Corrective Action process to address the impacts of past tank waste releases to the vadose zone at the single-shell tank farm....

Simulations of moisture flow in heterogeneous soils are often hampered by lack of measurements of soil hydraulic parameters, making it necessary to rely on other sources of information. In this paper, we develop a methodology to integrate data that can be easily obtained (for example, initial moisture content, $\theta$i, bulk density, and soil text...

Kriging utilizes a statistically based procedure of spatial interpolation that incorporates the spatial correlation structure of the phenomenon, and provides an error estimate. Kriging was applied to a total of 141 transmissivity values in an attempt to quantify the transmissivity distribution of the Santa Fe aquifer in Mesilla Bolson. New Mexico....

Multi-scale spatial and temporal variability of inflow and outflow of groundwater basins are well-known facts. Multi- scale aquifer heterogeneity is a reality. Traditional in-situ borehole characterization and monitoring methods can cover only a fraction of a groundwater basin. Consequently, our knowledge of a groundwater basin is limited and uncer...

Based on Kozeny-Carman equation for saturated media permeability, a new model is developed for the prediction of unsaturated hydraulic conductivity, K as a function of moisture content, ?. The K(???) estimates are obtained using laboratory measurements of moisture retention and saturated hydraulic conductivity, and a saturation-dependent tortuosity...

Characterization of the heterogeneity of hydraulic parameters that control transport processes in the vadose zone is always difficult due to prohibitive investments involved with direct parameter measurements (so-called `hard' data). `Soft' data such as moisture content (theta) and results derived from geophysical measurements, however, carry signi...

1] Knowledge of unsaturated zone hydraulic properties is critical for many environmental and engineering applications. Various stochastic methods have been developed during the past 2 decades to estimate the effective unsaturated hydraulic properties. Independent of these stochastic methods, we develop in this paper a practical approach to estimate...

1] A vadose zone field injection experiment was conducted in the summer of 2000 at the Hanford Site, Washington. The unique moisture content (q) database is used to identify the lithology at the field site and to interpret, visualize, and quantify the spatiotemporal evolution of the three-dimensional (3-D) moisture plume created by the injection ex...

We have developed a new approach that uses spatial moments of three-dimensional snapshots of a moisture plume under transient flow conditions to estimate the three-dimensional effective unsaturated hydraulic conductivity tensor. The evolution of the spatial first moment in the vertical (z) direction of a moisture plume is used to determine the vert...

A modified steady state head control method was used to obtain, on identical samples, direct measurements of soil moisture retention (volumetric water content θ versus matric potential ψ) and unsaturated hydraulic conductivity (K) as a function of both θ and ψ. The minimum ψ values for the undisturbed coarse-textured samples were as low as −400 cm,...

Tortuosity is the single most important characteristic of flow through porous media that determines several flow and transport phenomena. Currently available definitions of tortuosity are empirical, and do not lend themselves to direct and independent measurement. We present a new definition for the tortuosity factor of saturated media as the ratio...

At the U. S. Department of Energy Hanford Site in Washington state, spatial and temporal distribution of volumetric water contents were measured by neutron probe in 32 wells arranged in a concentric pattern extending to a depth of 16 m [Gee, G. W. and A. L. Ward, ``Vadose Zone Transport Field Study,'' PNNL-13679, Pacific Northwest National Laborato...

To predict contaminant release to the groundwater, it is necessary to understand the hydraulic properties of the material between the release point and the water table. Measurements of the hydraulic properties of the Hanford unsaturated sediments that buffer the water table are available from many areas of the site; however, the documentation is no...

1] To represent a heterogeneous unsaturated medium by its homogeneous equivalent, stochastic theory-based analytical formulas and numerical Monte Carlo simulations are used to obtain upscaled (effective) flow and transport properties. The Monte Carlo experiments simulate steady state flow and transient transport of nonreactive solute in two-dimensi...

Vadose zone soils in arid regions often contain a high gravel fraction (>2 mm size). This paper examines, for coarse-textured soils, variability of the slope alpha of Gardner's [1958] unsaturated hydraulic conductivity K versus matric potential psi relation, K=Ksealphapsi. The steady state head control method was used to obtain unsaturated K for te...

Vadose zone soils in desert environments often contain a high gravel fraction (>2 mm size). Laboratory measurements of moisture retention are typically made on the fine fraction ∥<2 mm size); the measurements are then corrected for field conditions by accounting for the gravel fraction in the sample. A frequently used correction procedure for grave...

Predicting contaminant migration within the vadose zone, for performance or risk assessment, requires estimates of unsaturated hydraulic conductivity for field soils. Hydraulic conductivities, K, were experimentally determined as a function of volumetric moisture content, θ, for Hanford sediments. The steady state head control method and an ultrac...

Over the years, data have been obtained on soil hydraulic properties at the Hanford Site. Much of these data have been obtained as part of recent site characterization activities for the Environmental Restoration Program. The existing data on vadose zone soil properties are, however, fragmented and documented in reports that have not been formally...

This document reports the findings of a performance assessment (PA) analysis for the disposal of solid low-level radioactive waste (LLW) in the 200 West Area Low-Level Waste Burial Grounds (LLBG) in the northwest corner of the 200 West Area of the Hanford Site. This PA analysis is required by US Department of Energy (DOE) Order 5820.2A (DOE 1988a)...

Macrodispersion in discrete colonnade network models is investigated using a series of Monte Carlo type numerical experiments. The numerical simulations consider fluid flow and advective transport through a square flow region of a two-dimensional network of hexagonal colonnades. Macrodispersivities are calculated as a function of the scale and orie...

At the Hanford Site, the record of decision for remediation of CERCLA sites is largely based on results of the baseline risk and performance assessment of the remedial action alternatives. These assessments require the ability to predict the fate and transport of contaminants along appropriate exposure pathways which, in case of the Hanford Site, i...

This study evaluates hydraulic retrieval (sluicing) of the waste in single-shell tank 241-C-106 with respect to the likelihood of tank leaks, gross volumes of potential leaks, and their consequences. A description of hydraulic retrieval is developed to establish a baseline for the study. Leak models are developed based on postulated leak mechanisms...

Using a particle-tracking procedure, numerical simulations are performed to evaluate the asymptotic limits and the length scale requirements for equivalent porosity estimates of discrete colonnade networks. The simulation results are used to determine differences between the scale requirements for equivalent hydraulic conductivities and porosities....

Analytical solutions for computing drawdowns and streamflow depletion rates often neglect conditions that exist in typical stream-aquifer systems. These conditions can include (1) partial penetration of the aquifer by the stream, (2) presence of a streambed clogging layer, (3) aquifer storage available to the pumping well from areas beyond the stre...

Numerical simulations were conducted to model flow and transport from a low-level solid waste burial site at the Hanford Site in southeastern Washington. Solid waste burial trenches are located in the 200 Areas near the soil surface, above the water table. A heterogeneous, layered soil profile representative of the 200 Area soils was used in the si...

Numerical simulations are carried out to determine the scale above which an equivalent porous medium (EPM) model can be used to represent flow through the dense interiors of fractured basalts. Steady laminar flow is assumed to occur through the interconnected network of conduits formed by the intersecting column-defining fracture patterns of the ba...

The method of characteristics is used to solve the one- and two-dimensional convective-dispersion equations in steady, uniform flow fields. Fully documented listings of the FORTRAN programs are presented. Comparison of numerical results with existing analytical solutions show excellent agreement.

The method of characteristics (MOC) was revised to solve convective- dispersion equations in a two-dimensional, integrated saturated-unsaturated porous medium. Instead of usual bilinear interpolation schemes, the revised procedure utilizes a three-way linear interpolation scheme to assign seepage velocities to moving points in a two-dimensional gri...

A fully documented Galerkin finite-element FORTRAN program is presented for solving the one-dimensional, transient flow equation in unsaturated porous media. Material balance error summaries are presented to demonstrate accuracy of the numerical scheme. Comparison of our simulated results with other existing numerical solutions using the Galerkin s...

In a critical review of pathogen and indicator‐organism transformations and transport from land areas receiving organic wastes, microbial die‐off was described assuming first‐order kinetics. First‐order die‐off rate constants ( k ) were calculated from the literature data for various pathogens and indicator organisms. For indicator organisms averag...

Land application of organic wastes such as animal manure, munici-pal wastes, and sewage sludge could alter the soil physical properties. Repeated substantial applications of waste increase the soil organic matter percentage. The available data on effects of waste applications on soil physical properties such as bulk density, water holding capaci-ty...

A state-of-the-art review is presented concerning the transport of nutrients (N and P), oxygen demanding compounds (BOD and COD), indicator organisms and pathogens in runoff from land areas receiving animal wastes. Three different land areas are considered: pastures and rangelands, land application sites, and feedlots. For land application sites, r...

A laboratory study was conducted to evaluate nitrogen, phosphorus and carbon transformations in a coastal plain soil (Norfolk sandy loam) treated with animal manures. Three types of manure—beef, poultry and swine—were either surface applied or incorporated into the soil. The results indicate that losses of ammonia N through volatilisation were high...

A simple conceptual model based on current literature data was developed to describe organic carbon (C) loss from land areas receiving organic wastes. The model considers the decomposition of substrate C as represented by the evolution of CO 2 . Decomposition of wastes was described in two or three phases, assuming first‐order kinetics at each phas...

The purpose of this study was to determine the effect of animal waste loading rates on P adsorption‐desorption characteristics of two soils. In a laboratory incubation study, Norfolk soil was treated with beef, poultry, or swine wastes; and allowed to decompose under optimum moisture conditions for a period of 30 days. Phosphorus adsorption‐desorpt...

A simple model based on current state-of-the-art was developed to describe the nitrate accumulation in land areas receiving animal wastes or plant residues. Earlier models using decay series were useful in predicting long term mineralization, but are less precise in determining the actual rate of mineralization or are less useful in transferring to...

Some chemical pollutants are adsorbed to soil particles and transported with the sediment load. Sediments contain a mixture of particles of varying sizes and densities that have differing transport characteristics and affinities for chemical pollutants. In addition, manure particles are detached and transported by erosion processes during runoff ev...

A simple conceptual model was developed, based on a state-of-the-art approach, to describe NH3 volatilization losses from land areas receiving animal manures. Environmental and soil factors influencing NH3 volatilization were also included in the model. Rate constants for first order relationship were estimated from the existing literature data. Th...

A mathematical model describing transport of sediment and manure during unsteady overland flow from land areas receiving animal wastes was presented in a previous paper. Results of a comprehensive literature survey characterizing model inputs due to manure presence are presented in this paper. Inputs are: manure cover on the watershed, manure erodi...

A 3-dimensional model describing the 2-phase (air-water) fluid flow equations in an integrated saturated-unsaturated porous medium was developed. Also, a 3-dimensional convective-dispersion equation describing the movement of a conservative, noninteracting tracer into a nonhomogeneous, anistropic porous medium was developed. Finite difference forms...

River flow data are often recorded at the site of water resource projects for a short period of time, while records are available for longer periods at other gauging stations. The purpose of this study is to find a mathematical model to represent a time series of monthly river flows at the project site including the statistical parameters of flow a...

A three-dimensional model describing the two-phase (air-water) fluid flow equations in an integrated saturated-unsaturated porous medium was developed. Also, a three-dimensional convective-dispersion equation describing the movement of a conservative, non-interacting tracer in a nonhomogeneous, anisotropic porous medium was developed. Finite differ...