Permeability – the ease of fluid flow through porous media – varies about 17 orders of magnitude in geologic media. My research concerns fluid and solute transport in the low part of the of the range (~ 10-19 – 10-25 m2), where measurements are difficult, standard relations such as Darcy’s law are unverified, and unfamiliar phenomena that include osmosis and ultrafiltration affect movement of water and solutes. Testing can sample only small volumes of low-permeability formations, and finding ways to characterize them on regional scales – and thereby detect leakage through fractures and faults - is especially important for problems such as repository siting, CO2 and other waste injection, and protection of aquifers. Understanding of how confining layers not only protect aquifers but also control their long-term productivity is needed to meet increasing water demands. Finally, low-permeability groundwater systems are of fundamental scientific interest because they record information about the processes of geological change.
The hydrogeology of low-permeability environments was historically bypassed and data are sparse, so fundamental aspects remain uncertain. For example, the roles of chemically-driven water flow and filtration of solutes continue to be debated. Measuring formation properties and groundwater pressure, and sampling groundwater itself still present serious technical challenges. My research focuses on (1) devising and improving testing and sampling techniques, (2) clarifying the nature and importance of various flow and solute transport processes, and (3) analyzing low-permeability flow systems to characterize how they control aquifer behavior, how they behave as barriers, and to understand their roles in groundwater flow systems and Earth processes.
