Modeling Soil Matrix Hydraulic Properties for Variably-Saturated Hydrologic Analysis

Abstract

This article presents a method to estimate soil matrix hydraulic properties to be used for variably-saturated hydrologic analysis, such as rainfall/runoff and stormwater management analyses, among others. The methods are described and verified with the U.S. Department of Agriculture's Unsaturated Soil Database (UNSODA), and the resultant soil hydraulic properties are presented. For conservative estimates of soil infiltration, a filter is recommended to remove soils from the analysis with high-saturated hydraulic conductivity that are likely to be macropore-dominated, and it is confirmed that the removed soils contain substantially more macropore influence than the retained soils. It is shown with the UNSODA database that good estimations of the soil matrix hydraulic conductivity function may be obtained by using the modified van Genuchten-Mualem model normalized to the saturated hydraulic conductivity with an immutable model parameter h e ¼ −0.1 cm if data are not available to calibrate h e ; this allows for the hydraulic conductivity curve to be estimated without laboratory-measured unsaturated data and overcomes some of the limitations of the van Genuchten-Mualem model.

An Approximate Model for Predicting the Specific Yield Under Periodic Water Table Oscillations

“…The second set of data for similar Hydrus‐1D simulations was taken from the study by Lee et al (), which provides a table of soil matrix hydraulic properties for the main soil texture classes, obtained by processing data from the UNsaturated SOil hydraulic Database (UNSODA) (Nemes et al, ). The input soil parameters and simulation results are given in Table .…”

Temporal and spatial variation of infiltration in urban green infrastructure

“…Macropores in the upper soil horizons lower the soil bulk density and promote infiltration in an infiltration‐based GSI system. However, Lee, Welker, and Traver () have argued that macroporosity should not be considered for conservative GSI design. Because the macropore structure of a watershed or GSI site generally cannot be known a priori , widely available estimates of soil hydraulic properties typically fail to distinguish between matrix‐dominated and macropore‐dominated soils.…”

“…When macroporosity data are not available, it is reasonable to assume that soil matrix flow dominates. The natural heterogeneity of soil and soil compaction in GSI limit macropore flow (Lee, Welker, & Traver, ).…”

“…Infiltration rates are a function of several factors, including soil characteristics (e.g., texture, structure, hydraulic conductivity, soil water content, and pore‐size distribution), water properties (e.g., viscosity and surface tension), rainfall‐arrival characteristics (e.g., rainfall intensity), and other soil‐surface factors (e.g., surface slope, surface roughness, and vegetative cover) (Tindall & Kunkel, ). Braga, Horst, and Traver () and Lee et al (Lee, Traver, & Welker, ; Lee, Traver, & Welker, ; Lee, Welker, & Traver, ) reported that hydraulic conductivity plays a critical role in influencing infiltration rates for an infiltration GSI. The field saturated hydraulic conductivity (Ksat) is a critical parameter for the design and post‐construction performance of GSI systems.…”

Evaluation of Soil Class Proxies for Hydrologic Performance of In Situ Bioinfiltration Systems

“…The SHP models are generated from the U.S. Department of Agriculture's UNSODA dataset of soil property measurements (Leij et al 1996;Nemes et al 2001). To obtain the greatest number of soils from this dataset and to ensure that the soil properties are conservatively representative of field-scale properties (i.e., not skewed by high-permeability macropore-dominated samples), the methods from Lee et al (2015) are used to filter the data and estimate parameters for the modified van Genuchten−Mualem SHP model [Eq. (1); Ippisch et al 2006].…”