1. Research Scientist, Dept. of Systems Analysis, Integrated Assessment, and Modelling (SIAM), Swiss Federal Institute for Environmental Science and Technology (EAWAG), P.O. Box 611, 8600 Dübendorf, Switzerland (corresponding author).
2. Associate Professor, Dept. of Environmental Health Science, Arnold School of Public Health, Univ. of South Carolina, Columbia, SC 29208.
3. Professor of Water Resources, Nicholas School of the Environment and Earth Sciences, Duke Univ., P.O. Box 90328, Durham, North Carolina 27708-0328.