1. The Aquaya Institute, PO Box 21862, Nairobi, Kenya
2. Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, North Carolina 27695, United States
3. Civil and Environmental Engineering, Tufts University, Medford, Massachusetts 02153, United States
4. Department of Civil and Environmental Engineering, Stanford University, Stanford California 94305-4020, United States