IRRIGATION POTENTIAL ASSESSMENT: A CASE STUDY OF GUDER RIVER WATERSHED

Abstract

Spatial and temporal rainfall variability and unsustainable land use practices have always been major hindrances in Ethiopian agriculture. Proper land evaluation for irrigated agriculture is very important to combat such problems. This study was conducted to assess irrigation potential in Guder river catchment, a sub basin of Abay river basin. The study used FAO (1985) guideline: Land evaluation for irrigated agriculture. Five crops (Maize, wheat, teff, sorghum and Barley) and three irrigation methods (surface, center pivot and portable sprinkler irrigation methods) were selected as land utilization types. Soil properties, land slope, land cover and water availability were evaluated against requirements of each land utilization types. Crop water demand was estimated using Penman-Monteith and Hargreaves methods. Surface water potentials of 45 sub watersheds of Guder river catchment were assessed using SCS-CN method. The results show that 54,800ha, 112,000ha and 442,000ha of land are marginally suitable (provisionally irrigable area) for both maize and sorghum under three selected irrigation methods (surface, center pivot and portable sprinkler irrigation systems) respectively. The result for teff is 56,300ha, 116,200ha and 247,200ha under surface, center pivot and portable sprinkler irrigation systems respectively. Whereas 59,500ha, 128300ha and 283,300ha of land is marginally suitable for wheat crop and 59,500ha, 125,500ha and 283,300ha of land is marginally suitable for barley crop under surface, center pivot and portable sprinkler irrigation systems respectively. Major suitability limitation was found to be land slope. Results of surface water potential analysis showed that without considering any artificial water storage structures, surface water potential of Guder river catchment can support 9423 and 15070ha of land for surface and sprinkler irrigation systems respectively. When storage structures are considered surface water potential of the study area can accommodate 532,622 and 798,934ha of land under surface and sprinkler irrigation systems.