My research focuses on the hydrology of the vadose zone which comprises the soil and rock masses between the land surface and the groundwater table. The hydrological processes in this zone determine to a large extent the vulnerability of groundwater for contamination and the amount of fresh water available for aquifer recharge.
In recent years, I have been working with Brian Borchers in the Math Department on modeling the effects of soil physical properties on landmine detection sensors.
In many different environments, one-dimensional computer models have predicted a negligible risk of groundwater contamination due to sufficient residence time in the vadose zone. However, it has been found that significant pollution of the groundwater has occurred where these models predicted none. The cause of these cases of groundwater contamination is the occurrence of preferential flow paths in the vadose zone. Such preferential flow paths can be caused by macropores or by the occurrence of unstable wetting fronts. My graduate students and I are conducting research projects which aim at the quantification of fluid and contaminant movement through preferential flow paths. One project deals with the effect of macropores on deep percolation under zero-tillage agriculture in the Eastern Plains of New Mexico. Another project investigates the occurrence of unstable wetting fronts in homogeneous sand dunes during infiltration of rainwater into the soil.
The energy balance of semi-arid regions plays an important role in global climate change. An important parameter for the determination of the energy balance is soil moisture in the vadose zone. Because existing techniques to measure soil moisture over large areas are too time consuming and expensive, my graduate students and I are investigating the application of electromagnetic induction and ground-penetrating radar methods for quick non-invasive measurement of soil moisture over large areas of land. This research is conducted in the Sevilleta, a 100,000-ha national wildlife refuge which is our prime field site for hydrological investigations.