1. a United States Bureau of Reclamation, Denver Federal Center , Bldg. 67, P.O. Box 25007 (D-8540), Denver, CO, 80225-0007
2. b Iowa Institute of Hydraulic Research , University of Iowa , Iowa City, IA, 52242
3. c Iowa Institute of Hydraulic Research , University of Iowa , Iowa City, IA, 52242