Performance Evaluation of Surface Irrigation System in the Case of Dirma Small-Scale Irrigation Scheme at Kalu Woreda, Northern Ethiopia

This study was conducted to evaluate the performance of Dirma small-scale irrigation scheme using selected performance indicators. To achieve these objectives, the primary data collected for this study were discharge measurements in the canals, measurements of water applied to the field, and soil data before and after irrigation. Besides, secondary data collected were also climatic and agronomic data, yields, command, and initial area. CROPWAT 8.0 model and Microsoft Excel were used to analyze the data. The results of internal indicators: conveyance efficiency, application efficiency, storage efficiency, and overall efficiency were 76.64%, 56.05%, 79.40%, and 43.54%, respectively, whereas the results of the external indicators: relative water supply, relative irrigation supply, water delivery capacity, irrigation ratio, the sustainability of an irrigated area, output per unit irrigated area, output per unit command area, output per unit water supply, and output per unit water consumed were 1.0, 0.95, 0.26, 0.41, 1.5, 4881.40 US$/ha, 1896.56 US$/ha, 1.64 US$/m(3), and 1.25 US$/m(3), respectively. There was an unfair distribution of water due to water scarcity and illegal water users as the beneficiaries responded. Those performance external indicator values indicate that there is a low water supply, the actual command area was reduced by 61% from initially designed, and some structures initially installed were becoming nonfunctional. The basis of this conclusion was frequent field observation, sustainability of an irrigated area result, and beneficiary responses about the initial and current condition of the scheme. Generally, the overall performance of the scheme is considered poor. Therefore, a gated division system, regular canal cleaning, and maintenance of broken irrigation infrastructures should be applied to mitigate the water scarcity problem.