1. Member, ASCE
2. Extension Advisor, Univ. of California Cooperative Extension, 1050 E. Holton Rd., Holtville, CA 92250.
3. Prof., Dept. of Hydro. and Biol. and Agric. Engrg., Univ. of California, Davis, CA 95616 (corresponding author).
4. Int. Consultant, Cambridge, U.K.