Effective Soil Hydraulic Parameters for Transient Flows in Heterogeneous Soils

Abstract

This study investigated the use of effective soil hydraulic properties (expressed in terms of hydraulic parameters) applicable to large‐scale transient infiltration problems in a landscape with horizontally heterogeneous soil hydraulic properties. The heterogeneous landscape was conceptualized as an equivalent homogeneous medium with effective hydraulic properties. The main objectives were to investigate: (i) which effective soil hydraulic property schemes are suitable to represent average behavior of large‐scale infiltration processes, (ii) how the effective hydraulic parameters are sensitive to the process time frame, and (iii) how hydraulic parameter variability and correlation impact the effective hydraulic parameters. The heterogeneous landscape was represented by a series of vertically homogeneous stream tubes or parallel columns. Large‐scale average infiltration behavior in the heterogeneous soils was quantified through Monte Carlo simulations of multiple realizations (stream tubes) of local‐scale infiltration. The optimal effective hydraulic parameters were then calculated with an inverse procedure that minimized the difference between average cumulative infiltration and cumulative infiltration based on a single set of effective parameters. Three scenarios were used to optimize either two hydraulic parameters simultaneously or only one hydraulic parameter while using the arithmetic mean for the other parameter. Results indicate that while the effective hydraulic parameters could simulate average infiltration more closely when multiple parameters were optimized together, the effective parameter values were more variable as time evolved. Optimizing only one hydraulic parameter while keeping the arithmetic mean for the other parameter produced more uniform effective hydraulic parameters with time, but this approach did not represent average infiltration behavior of the heterogeneous soils as well as when multiple hydraulic parameters were optimized simultaneously.

A hydropedological approach to quantifying groundwater recharge in various glacial settings of the mid‐continental USA

“…Many other researchers have used HYDRUS 1D to examine both recharge (Jiménez‐Martínez et al , ; Zhu and Sun ; Lu et al , ; Leterme et al , ) as well as solute and contaminant transport (Cheviron and Coquet ; Rozemeijer et al , ; Rieckh et al , ). HYDRUS 1D version 4.16 (Šimůnek et al , ) solves the Richards equation for vertical unsaturated groundwater flow, and the models in this study apply the van Genuchten () and Mualem () equations for soil hydraulic parameters.…”

Unsaturated Hydraulic Conductivity for Evaporation in Heterogeneous Soils

“…The main goal of using effective hydraulic properties is to capture particular flow and transport processes in a heterogeneous soil, through conceptualization of heterogeneous formation as an equivalent homogeneous formation. In this way, the heterogeneous system is replaced by an equivalent homogeneous medium (e.g., Rubin, 2003;Zhu & Mohanty, 2003a,b;Zhu & Mohanty, 2004;Zhu et al, 2007;Zhu, 2008;Zhu & Sun, 2009;Zhu & Sun, 2010). Hydraulic parameters that define the equivalent homogeneous medium are known as effective parameters.…”

“…In a study of effective hydraulic parameters for transient hydrological processes, combined the one-dimensional local process and the Miller-Miller (Miller & Miller, 1956) media concept, thereby illustrating that effective hydraulic parameters depend on the time frame being considered. Zhu & Sun (2009) investigated the use of effective soil hydraulic properties (expressed in terms of hydraulic parameters) applicable to near surface large-scale transient infiltration problems in a landscape with horizontally heterogeneous soil hydraulic properties. These studies show that methods to aggregate and upscale local hydraulic parameters are critical to improve the understanding of near surface large-scale hydrologic processes.…”

“…More recently, Coppola et al (2009) studied the effects of using unimodal and bimodal interpretative models of hydraulic properties on the ensemble hydrological behavior of stream tubes by comparing predictions to mean water contents measured over time at several field scale sites. Zhu & Sun (2009) examined how the effective hydraulic parameters are sensitive to the time frame of hydrologic processes, by using the stream tube concept to study the effective hydraulic parameters for transient infiltration. Ahuja et al (2010) who also used the steam tube approach, explored effective parameter sets to describe field-average infiltration and redistribution under different rainfall conditions and investigated whether an effective field saturated hydraulic conductivity and correlated hydraulic parameters derived from matching early-stage average ponded infiltration could give reasonable results for infiltration under lower rainfall rates as well as for soil water redistribution.…”

Numerical Evaluation of Effective Unsaturated Hydraulic Properties of Fractured Rocks using a Stochastic Continuum Approach

“…Numerous studies have investigated the effective properties for partially saturated porous media, including theoretical work (Yeh et al, 1985; Mantoglou and Gelhar, 1987; Zhu and Sun, 2009, among others), numerical simulations (Wildenschild and Jensen, 1999a; Khaleel et al, 2002), and experimental studies (Wildenschild and Jensen, 1999b). Most of these studies focus on estimating effective hydraulic conductivity under different tension or pressure.…”