1. Water Resources Engineer, Barr Engineering Company, 4700 West 77th St., Minneapolis, MN 55435 (corresponding author). E-mail: mwong@barr.com
2. Professor, Ven Te Chow Hydrosystems Laboratory, Univ. of Illinois, 205 N. Mathews Ave., Urbana, IL 61801. E-mail: parkerg@uiuc.edu