The basic goal of this project is to measure, predict, and understand the flow of water through soil and rock between the land surface and the water table. Large-scale problems of water quality and water availability require knowledge of travel times through the unsaturated zone for water and substances carried with it. Specifically, our work is intended to advance (1) the assessment and quantification of hazards from toxic and radioactive substances near the earth's surface, and (2) knowledge of aquifer recharge rates for improved management of water resources. We develop laboratory and field experiments, as well as theoretical models, many of which are focused on properties such as unsaturated hydraulic conductivity and water retention relations.

We apply this research at diverse locations. Arid and semi-arid sites are often of great interest because they are vulnerable to water scarcity, and are often favored for hazardous waste disposal. At humid sites the unsaturated zone may be relatively thin, and typically is vulnerable to high flow rates and fast-changing conditions.

Current emphases include (1) preferential flow, including the influence of soil structure and rock fractures on flow and contaminant transport; (2) aquifer recharge estimation, (3) flow at low water contents; (4) physically based modeling and mathematical representation of flow properties; (5) collective effects of diverse features of thick (10’s of meters or more) unsaturated zones; and (6) advancement of techniques in terms of range, accuracy, applicability, effectiveness, and ease of use.