1. a Department of Ecology and Natural Resources Management, Center for Development Research (ZEF), University of Bonn, Genscherallee 3, Bonn 53113, Germany
2. b Department of Water Resources Engineering, Lund University, P.O. Box 118, Lund S-221 00, Sweden
3. c Department of Civil and Environmental Engineering, Universidad de los Andes, Carrera 1E 19A-70, Bogotá 111711, Colombia
4. d International Centre for Water Resources and Global Change, UNESCO Category 2 Centre, German Federal Institute of Hydrology, P.O. Box 200253, Koblenz 56002, Germany