Stochastic Modeling of Water Flow and Solute Transport in the Vadose Zone, T-C.]. Yeh

It is difficult to predict any natural process. The complexity of natural systems often prohibits our understanding of governing principles of processes in the systems. For some natural processes such as water flow and solute transport in aquifers and the vadose zone (the geological medium, i.e., soils and rocks above the regional groundwater table), we seem to understand the governing principle of the processes (i.e., many laboratory-scale experiments have manifested the validity of Darcy’s law for flow and solute transport through saturated and unsaturated porous media). The principle, however, is often limited to a narrow range of scales. For example, when applying the principle to field-scale problems, we encounter the problem of extrap­ olating the principle to much larger scale systems which involve spatial and temporal variabilities of the system characteristics at many different scales.