Uncertainty analysis of transient unsaturated flow in bounded domain

This paper analyzes the head variance during transient flows in unsaturated porous media. The analysis is based on a first-order Taylor series expansion of the discretized Richards' equation and stochastic conceptualization of hydrologic properties in space. Effects of boundary conditions and flow conditions (drying or wetting) were examined for different soil models. Results of the study indicate that a constant flux boundary condition affected the pressure head variance distribution close to the surface, originating a decrease of the values at early times during wetting scenarios. On the other hand, a constant head boundary condition strongly affected the variance profiles during both transient and steady flows, also far from the boundary.