1. Research Assistant Professor, V. T. Chow Hydrosystems Laboratory, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign, Urbana, IL 61801 (corresponding author). E-mail: aschmidt@uiuc.edu
2. Deceased December 23, 2001; formerly, Professor, V. T. Chow Hydrosystems Laboratory, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign, Urbana, IL 61801.