I study fluid flow and transport in permeable media, using field & laboratory experiments and mathematical models. In the past this has included studies of the movement of water, non-aqueous phase liquids, dissolved chemicals, colloids, and bacteria through porous, fractured, and faulted media. Other research work is directed toward well-head protection, estimation methods to find the source of observed groundwater contamination, flow through heterogeneous media, and the geological characterization of aquifers.
The laboratory studies emphasize flow visualization, which I featured as the 1992 Darcy Lecturer for the Association of Groundwater Scientists and Engineers. Recent lab studies have focused on diffusion problems in both porous and fractured systems, with one or two fluid phases. A recent MS student completed the study of diffusion through a single pore throat study, in a successful attempt to understand enhanced vapor diffusion in the vadose zone. The student was awarded a best paper prize at the AGU 1999 Spring Meeting.
Another recent focus is the solution of stochastic or probabilistic flow and transport equations backward in time-and-space, to help identify sources of groundwater contamination using mathematical models. This approach can be used to delineate pumping well capture zones, design aquifer remediation schemes, or to allocate liability or cost.
A third recent focus involves studies of the spatial pattern of permeability and its relationship to natural geologic variability on outcrops and undisturbed rock samples. One of these studies investigates upscaling models for permeability, and is based on over 200,000 automatic laboratory permeability measurements taken at five different spatial sample volumes, spanning several orders of magnitude. These upscaling studies have a bearing on large scale numerical simulation of aquifers, and the assignment of properties to the simulators.