1. Univ. of Nebraska, Lincoln, NE 68583-0915; presently, USEPA, MC: 5102G,1200 Pennsylvania Ave. NW, Washington, D.C. 20460. E-mail: adam.michael@epa.gov
2. Professor, Univ. of Nebraska, 256 Keim Hall, Lincoln, NE 68583-0915 (corresponding author). E-mail: scomfort@unl.edu
3. Water Sciences Laboratory, Univ. of Nebraska, 103 Natural Resource Hall, Lincoln, NE 68583-0844. E-mail: dsnow1@unl.edu
4. Water Sciences Laboratory, Univ. of Nebraska, 103 Natural Resource Hall, Lincoln, NE 68583-0844. E-mail: dcassada1@unl.edu
5. Dept. of Civil Engineering, Univ. of Nebraska, W348 Nebraska Hall, Lincoln, NE 68583-0531. E-mail: mmorley2@unl.edu