Assessment of Irrigation Water Management Performance Indicators and Mitigation Measure in Arba Minch Irrigation Scheme, Ethiopia

Abstract

Irrigated agriculture has been practiced in Ethiopia for several centuries and performance of scheme was poor due to inadequate irrigation water management practices. This study was conducted to evaluate irrigation water management indicators and to suggest possible mitigation measure for Arba Minch irrigation scheme. Primary data such as field and canal flow, soil moisture content, and canal slope were measured on field and soil physical properties were evaluated in the laboratory. Utilizing climate and crop data, the CropWat 8 model was employed to estimate seasonal crop water requirements, while furrow and border irrigation dimensions were designed using SURDEV software. The average field application efficiency (30%), storage efficiency (76%), percolation losses (66%), and overall efficiency (25%). The average relative water and irrigation supply in the scheme were 1.7 and 3.3, respectively. The mean water and land productivity of the wheat, onion, pepper, watermelon, and maize of the Arba Minch irrigation scheme were 0.1 kg/m3 and 0.5 ton/ha, 0.9 kg/m3 and 4.9 ton/ha, 1.5 kg/m3 and 6.2 ton/ha, 0.5 kg/m3 and 0.6 ton/ha, and 0.9 kg/m3 and 4.2 ton/ha, respectively. Watermelon had the highest net returns per hectare ($1,693), followed by onion ($1,829), pepper ($1,221), and wheat ($1,057). In terms of net returns per cubic meter of water, onion led with $0.3, followed by watermelon ($0.2), pepper and wheat with the lowest at $0.1 (top of form). The average value conveyance efficiency, water surface elevation ratio and manning coefficient were 82%, 42%, and 0.06%, respectively. The existing, and corrected length were 843 and 135 m (border irrigation) and 20 and 595 m (furrow irrigation), respectively. In conclusion, the Arba Minch irrigation scheme was very poor performance and low efficiency. To address these issues, farmers and irrigation authorities implement improved irrigation water management practices. Policymakers should promote sustainable water management and explore crops with higher water productivity for overall scheme improvement.