1. a Division of Hydrologic Sciences , Desert Research Institute , 755 E. Flamingo Road, Las Vegas , NV , 89119 , USA
2. b Department of Civil Engineering , University of New Mexico , MSC01 1070, Albuquerque , NM , 87131 , USA E-mail:
3. c Division of Hydrologic Sciences , Desert Research Institute , 755 E. Flamingo Road, Las Vegas , NV , 89119 , USA E-mail:
4. d Department of Civil Engineering , University of New Mexico , MSC01 1070, Albuquerque , NM , 87131 , USA E-mail: