Irrigation & Drainage Systems Engineering

Performance Evaluation of Sanko Small Scale Irrigation Scheme at Basketo Special Woreda in SNNPR, Ethiopia

Abstract

Markos H, Shemelies A and Sirak T

This study conducted to evaluate the performance of Sanko small-scale irrigation scheme at Basketo Special Woreda, South Nation Nationalities Peoples Regional states. The irrigation scheme includes command area of 120 ha and 600 beneficiaries. The scheme was evaluated using internal and productivity performance indicators. From the analyses of the internal performance indicators, the conveyance efficiency of the main canal was found to be 69.3% and application efficiencies at head (61.6%), middle (63.4%) and tail (46.5%) with average application efficiency of 57.2%. A light soil with high infiltration rates favors deep percolation losses at the top of the fields, resulting in low field application efficiency in tail end part of the scheme. A deep percolation ratio and storage efficiency of the scheme was found to be 42.8% and of 78.5% respectively. Generally overall scheme efficiency of scheme was 39.6%. From the evaluation of productivity indicators, the outputs per cropped area found as at head (84,706 Birr ha-1), middle (220,690 Birr ha-1) and tail (69,686.4 Birr ha-1) and the value of the outputs per command area of scheme was 15,003,276 Birr per command area. The output per unit irrigation supply of irrigation scheme was at head (13.5 Birr m-3), middle (33.95 Birr m-3) and tail (22.12 Birr m-3). Relative water supply and relative irrigation supply; found to be 1.28, which was the same for both since there was no rainfall during study period. From the analysis result, there was lower water use efficiency (WUE) at upper head (23.37 ton/m3) as compared to middle (48.78 ton/m3) and tail (60.22 (ton/ m3) part of the scheme in relation to yield obtained. Based on the evaluation result, highest yield was obtained from at middle part of irrigation scheme and lower yield was obtained from both upper and tail end part of the scheme. The yield reduction in upper and tail part of the scheme was due to over and under irrigation. However, there is still a room for improvement at all system levels. Therefore to reduce over and under irrigate; farmers should get awareness how to use, when to use and how much water used on their fields.