Subsurface Hydrology

Subsurface HydrologySubsurface hydrology examines the movement of water and solutes in soils and in the geologic media of the earth's subsurface. This specialization is appropriate for students who want to study hydrogeology, groundwater hydrology, and vadose zone hydrology. Those entering the program from non-geology programs are encouraged to take, at a minimum, GEL 105 & 105L and GEL 106.

The most pressing problems in subsurface hydrology concern the widespread contamination of groundwater from an array of constituents and sources in both agricultural and urbanized areas and the ever-growing demands on water supplies, often resulting in groundwater overdraft, which threaten water shortages and land subsidence in many parts of the world. The exposure risks of humans and the environment to these contaminated groundwaters are related to the concentrations, the toxicity, and the migration pathways available to the contaminants. Research in subsurface hydrology at UC Davis is developing the theory and investigative techniques needed to predict the transport and fate of contaminants for purposes of groundwater remediation as well as prevention of contamination.

Because the earth's subsurface is relatively inaccessible to direct observation and measurement, much research in this study area has been directed toward developing and applying numerical computer models to predict the transport and transformation of contaminants in subsurface environments, with the aim of developing improved management and remediation schemes. What is the likely fate of a toxic chemical under the influence of complex physical, chemical, and biological processes in soils or geologic media whose structure is only partly known? Answering such questions hinges on accurately characterizing the heterogeneity of that geologic media and on accurately modeling the processes of fluid flow and solute transport.

Of particular importance is the quantity and quality of water as it moves through the vadose zonethe area situated between the atmosphere and the groundwater. State-of-the-art vadose zone hydrology examines how these water attributes are controlled by physical, chemical, and biological processes and interactions. Whereas in the past these processes have been treated individually, current research seeks to combine expertise in these individual areas. Study in this area by UC Davis hydrologic science researchers emphasizes the influence of complexly distributed non-point contaminant sources, spatially varying groundwater recharge, and the influence of zones of immobile groundwater on the configuration and movement of contaminant plumes in groundwater.

Much progress in modeling fluid flow and solute transport has been achieved in the last two decades, and many exciting and important research frontiers remain, particularly in modeling partially saturated and multiphase systems. But improved modeling techniques alone will not substantially advance our ability to predict the behavior of real-world systems. Equally vital is rigorous field observation of hydrologic phenomena and more detailed characterization of subsurface properties to support the computer models. There is a need for development of field measurement techniques that can support hypotheses with regard to flow and transport processes at various spatial scales and that can be extrapolated from the laboratory, and small field plot scales to the field and watershed levels. The disciplines of geology, geophysics, soil science, hydrology, and mathematics must be routinely integrated to characterize the subsurface in detail. Without such effort, many groundwater contamination and quantity problems will remain unmanaged and unresolved.

Faculty: Fogg, G.E.; Ginn, T.R.; Harter, T.H.; Hopmans, J.W.; Mackay, D.M.; Wallender, W.W.