The majority of my career has involved projects in hydrogeology, that is, the study of the movement and quality of water underground. My projects have ranged from working in the field to characterize sites to mathematical analyses using computer models of subsurface flow and contaminant transport.

Water Resources

Most recently, I co-developed a successful proposal for an assessment of the water resources of Kane County, IL, acted as technical lead for groundwater modelling, and co-authored the comprehensive project report. I also presented the study methodology and summarized the results for over 200 policy makers on behalf of the study sponsor (see the 10th and 12th presentations; requires Internet Explorer).

Water resources tend to ignore administrative and disciplinary boundaries, so it is often useful to bring investigators and decision makers across the region of interest. I've organized several such meetings, including:

Straddling the Divide, a conference of over 200 scientists, engineers, lawyers, and policy makers from four states to discuss the water resources of the southern Lake Michigan region (summary).

2009 meeting of the North-Central Section of the Geological Society of America (32 technical sessions, approximately 600 attendees).

Research on Hydraulic Testing

I've maintained an active program of research on hydraulic testing, a field method for characterizing aquifers, funded by the National Science Foundation, the National Center for Super Computing Applications, Sandia National Laboratories, the Illinois Water Resources Center, and the Illinois State Water Survey. My research into the interpretation of these tests in fractured rocks has resulted in a series of peer-reviewed publications, including:

Walker and Roberts, 2003. Flow dimensions corresponding to hydrogeologic conditions, Water Resour. Res. 39:12.

Walker, Cello, Valocchi, and Loftis, 2006. Flow dimensions corresponding to stochastic models of heterogeneous transmissivity, Geophys Res. Lett. 33.

Cello, Walker, Valocchi, and Loftis, 2009. Flow dimension and anomalous diffusion of aquifer tests in fracture networks, Vadose Zone J. 8:1.

Contaminant Transport

I've had a number of projects characterizing and predicting the fate of contamination in groundwater, leading to several reports and publications:

Walker and White, 2001. Analytical solutions for transport in porous media from Gaussian source terms, Water Resour. Res. 37:3.

McKenna, Walker, and Arnold, 2003. Modeling dispersion in three-dimensional heterogeneous fractured media at Yucca Mountain, J. Contam. Hydrol. 62-63.