### Leading Edge Numerical Modeling in Vadose Zone Ground Water Flow and Transport

This site was dedicated to the proposition that there are still advances to be made in the numerical modeling of below-surface unsaturated ground water flow. It demonstrates the research product of a disabled investigator between about October 1998 and February 2003, with the addition of a surface water dam breach study in 2002. It also contains soil physics and finite difference numerical modeling tutorials written while I was a Technical Assistant to Dr. H. Don Scott when he was at the University of Arkansas, Fayetteville.

Note: This is not the web site for Ballard's Frame Distributors. The robots that search the net for filler material in the various free directories aren't that smart.

A website chronology and new material can be found here

The soil physics and finite difference tutorials are consistently the most popular parts of the site. The soil physics tutorials range in difficulty from sophomore to the senior/graduate/postdoctoral level. They begin with the basics and extend to a new (2001) exact solution to Richards' equation for unsaturated horizontal and vertical flow, which reduces it to a numerical solution of an ordinary differential equation under given conditions. It solves both horizontal imbibition and vertical (top down) infiltration with either pressure or flow inflow boundary conditions. This particular solution solves in steps of saturation instead of space, making the wetting front very well defined regardless of sharpness or depth. New fine details and behaviors are visible that numerical models based on space and time cannot resolve.

The finite differences tutorial is a brief and limited tutorial in the use of finite difference methods to solve problems in soil physics. It is meant for students at the graduate and undergraduate level who have at least some understanding of ordinary and partial differential equations. After an explanation of how to use finite differences in cook-book fashion, the equations, computer code and graphic results are given for three examples: heat flow, infiltration and redistribution, and contaminant transport in a steady-state flow field.