1. Lead Scientist, Global Water Initiative, Institute on the Environment, Univ. of Minnesota, 1954 Buford Ave., Suite 325, St Paul, MN 55108 (corresponding author).
2. Associate Professor, Dept. of Civil and Environmental Engineering, Yang and Yamazaki Environment and Energy Building, Stanford Univ., MC 4020, Room 257, 473 Via Ortega, Stanford, CA 94305.
3. Director, Center for Conservation Biology, Dept. of Biology and Woods Institute for the Environment, Stanford Univ., MC 5020, 371 Serra Mall, Stanford, CA 94305.