1. Graduate Student, Dept. of Civil Engineering and Engineering Mechanics, The Univ. of Arizona, Tucson, AZ 85721-0072.
2. Professor and Head, Dept. of Civil Engineering and Engineering Mechanics, and Center for Sustainability of Semi-Arid Hydrology and Riparian Areas (SAHRA), The Univ. of Arizona, Tucson, AZ 85721-0072.