Surface fissures have been observed in many desert basins in the western United States. These surface-collapse features are usually discovered after a normally dry surface has been covered with water, either by runoff from intense rainfall, by flooding, or by irrigation.

Field studies and numerical modeling were used to evaluate hydraulic controls on unsaturated flow in the Chihuahuan Desert of Texas. These studies were part of a program to characterize a site for a proposed low-level radioactive waste disposal facility.

Chemical and physical approaches are used to study unsaturated flow; however, few studies include an in-depth analysis of data from both approaches.

Analysis of spatial variability in unsaturated flow is critical to evaluating contaminant transport in areas of focused or preferential flow. This study examined spatial variability at a variety of scales from focused flow through playas to preferential flow in macropores.

Because geomorphic features can readily be mapped, our ability to characterize unsaturated flow over large areas would be greatly enhanced if relationships between geomorphic settings and unsaturated flow could be identified.