1. Geology Department, State University of New York at Cortland, Cortland, NY 13045, USA
2. Oxford Molecular Biosensors, Centre for Innovation and Enterprise, Begbroke, Oxford OX5 1PF, UK
3. Africa Center of Excellence for Water Management, ACEWM, Addis Ababa University, Addis Ababa P.O. Box 1176, Ethiopia
4. Water and Land Resource Center, WLRC, Addis Ababa University, Addis Ababa P.O. Box 1176, Ethiopia
5. Water Resource Associates, Wallingford OX10 3XA, UK
6. School of Geography and the Environment, University of Oxford, Oxford OX1 3QY, UK