Ingénierie des systèmes d’irrigation et de drainage

Comparative Evaluation of Small Scale Irrigation Schemes at Adami Tulu Jido Kombolcha Woreda, Central Rift Valley of Ethiopia

Abstract

Shiberu E, Hailu HK and Kibret K

Evaluating the performance of irrigation systems will assist to distinguish whether the targets and objectives of the irrigation projects are met or not. In this study, a comparative performance evaluation was made on two small scale irrigation schemes in Adami Tulu Jido Kombolcha district Oromia Regional State Central Rift Valley of Ethiopia. The irrigation schemes were Haleku scheme with a command area of 42 ha and 96 beneficiaries, and Dodicha scheme with 75 ha irrigable lands and 150 beneficiaries. Primary and secondary data were collected for the study. The primary data include discharge at diversion point, moisture contents of the soils before and after irrigation, measurement of depth of water applied to the fields. The secondary data include total yields, farm gate prices of irrigated crops, area irrigated per crop per season, crop types, incomes generated by the irrigation associations, investment costs and cost of production and metrological data. The two-irrigation schemes were compared using the IWMI (International Water Management Institute) minimum sets of comparative indicators. The comparative indicators used were Agricultural performance, water use performance, Physical performance and Economic performance. From the analysis of Agricultural outputs, the outputs per cropped area were found to be 2,852.77 US$/ha and 2,179.41 US$/ha for Haleku and Dodicha irrigation schemes respectively, but the values of the output per command area of the schemes in the same order were 2,852.77 US$/ha and 1,278.59 US$/ha. The output per unit irrigation supply of Haleku was 0.18 US$/m³ and of Dodicha was 0.13 US$/m³. Output per water consumed was 0.53 US$/m³ and 0.43 US$/m³ for Haleku and Dodicha irrigation schemes, respectively. With regard to the water use performance, water supply and relative irrigation supply were found to be equal which amount 2.89 and 3.34 for Haleku and Dodicha schemes respectively since all the water is supplied through irrigation; there was no rain fall during the study period. The irrigation ratio of Haleku is 1.00 which means 100% of command area was under irrigation and that of Dodicha was 0.59 which means about 41% of command area was not under irrigation during study period. The gross return on investment was 2.33 and 4.66 by ratio for Haleku and Dodicha irrigation schemes respectively. The financial self sufficiency of both schemes show that 5.29 for Dodicha scheme and 27.76 for Haleku scheme. In general, based on the assessment carried out, it can be concluded that the Haleku irrigation project performs better than Dodicha scheme. For improved performance of the schemes, farmers should share operational experience to one another, and get water management training. Further, it is good to provide simple hydraulic flow metering structures on the canals to monitor water supply and utilization.