Spate Irrigation Potential Assessment for Ethiopian Watershed

In the low lands of Logia sub basin, Ethiopia, because of shortage of rain to fully grow crops, irrigation is an obligation in general and the presence of seasonal rivers flowing in the region in particular makes flood utilization ideal for spate irrigation. The subjects of the present study were to assess the spate irrigation potential of Logiya watershed that has been brought under irrigation on the basis of flood water availability and land suitability. A GIS based technique combined with analytical hierarchy process (AHP) was applied to access the potential of the watershed for spate irrigation development. Potentially suitable sites for spate irrigation development were assessed for Maize, Sorghum and Tomato crops. Spate irrigation area was evaluated based on land use/cover, slope and soil suitability. CROPWAT software was used to estimate the reference crop evapotranspiration, effective rainfall, net irrigation and gross irrigation water requirement. The suitability model developed shows that only 26.15% of the total area falls under marginally to highly suitable categories for spate irrigation development. The Logiya seasonal river flow from July to October was 301.64 Mm3. However, the annual flood water available from the river was less than the total GIWR by 8.77 Mm3 during growing period. The surplus water available from the river before July might be stored and used for irrigation during water deficit period during growing seasons.