[1] In this study we develop a stochastic model for transient unsaturated-saturated flow in randomly heterogeneous media with the method of moment equations. We first derive partial differential equations governing the statistical moments of the flow quantities by perturbation expansions and then implement these equations under general conditions with the method of finite differences. The stoch...

The water flow in unsaturated soils is governed by Richards equation, a nonlinear parabolic partial differential equation. In a layered unsaturated soil, enforcing the continuity of both pressure head and flux across the interface of distinct soil materials leads to a non-linear interface equation. This interface equation may exhibit multiple solutions. Using different averaging methods for cel...

In this study we determine constitutive relations (relations between saturation, hydraulic conductivity and pressure head) for unsaturated fractured rocks using a computational procedure that mimics the laboratory technique of measurement. Isotropic three-dimensional rock samples with random vertical and horizontal fractures are computationally constructed. Each fracture is conceptualized as a ...

In this study, we derive analytical solutions of the first two moments (mean and variance) of pressure head for one-dimensional steady state unsaturated flow in a randomly heterogeneous layered soil column under random boundary conditions. We first linearize the steady state unsaturated flow equations by Kirchhoff transformation and solve the moments of the transformed variable up to second ord...

Early stochastic studies focused on steady-state, gravity-dominated unsaturated flow in unbounded domains In this study, on the basis of the van Genuchten–Mualem constitu(e.g., Yeh et al., 1985a,b; Russo, 1993, 1995a,b; Yang et tive relationship, we develop a general nonstationary stochastic model for transient, variably saturated flow in randomly heterogeneous meal., 1996; Zhang et al., 1998; ...

[1] Prediction of water flow and transport processes in soils susceptible to structural alteration such as compaction of tilled agricultural lands or newly constructed landfills rely on accurate description of changes in soil unsaturated hydraulic conductivity. Recent studies have documented the critical impact of aggregate contact characteristics on water flow rates and pathways in unsaturated...