Water Harvesting for Poverty Reduction and Sustainable Resource Use: Environment and technical issues

This paper investigates environmental and design related issues that can affect the performance of small-scale water harvesting schemes in theTigray region of northern Ethiopia. Results indicate that the impact of evaporation loss during the rainy season on net harvested water is generally small, and depends on the extent of the surface area of the ponds. However, the impact of the seepage loss on the net harvested water is very high unless there is proper lining of the bed and walls of the ponds. The irrigated area can be increased considerably if proper water saving and utilization measures and mechanisms are implemented. The current silt trap structures are ineffective in minimizing the sediment deposition in the ponds. The design, construction and maintenance of the structures need to be improved in order to reduce the sediment deposition and increase the water storage capacity of the ponds. As there is little experience with the extensive use of ponds and hand dug wells for supplementary irrigation in Tigray, the soils of almost all schemes are currently salt free. If the soil salinity and good quality water of the ponds are taken into account, salinity may not be a threat for farmers using ponds for supplementary irrigation. However, the water quality of wells is poor. Besides, since they are continuously recharged by the groundwater, most of the wells irrigate longer period than the ponds. Farmers using wells would have to implement necessary measures indicated earlier to minimize the effect of salinity.