1. Department of Geological Sciences, John A. and Katherine G. Jackson School of Geosciences; University of Texas at Austin; Austin Texas USA
2. Now at University of California Center for Hydrologic Modeling; Irvine California USA
3. Department of Hydrology and Water Resources; University of Arizona; Tucson Arizona USA
4. Hydrological Sciences Branch; NASA Goddard Space Flight Center; Greenbelt Maryland USA