1. Hydrologist, U.S. Geological Survey, Office of Surface Water, 1201 W. University Ave., Suite 100, Urbana, IL 61801-2748. E-mail: kaoberg@usgs.gov
2. Hydrologist, U.S. Geological Survey, Office of Surface Water, 9818 Bluegrass Parkway, Louisville, KY 40299. E-mail: dmueller@usgs.gov