1. a Africa Center of Excellence for Water Management, Addis Ababa University, P. O. Box 1176, Addis Ababa, Ethiopia
2. b Chemical Engineering Department, Wachemo University, P. O. Box 667, Hossana, Ethiopia
3. c Addis Ababa institute of Technology, Addis Ababa, Ethiopia
4. d Bahir Dar institute of Technology, Bahir Dar, Ethiopia
5. e Department of Natural Resource Management, Debre Markos University, Debre Markos, Ethiopia