PERFORMANCE EVALUATION OF IRRIGATION SCHEME - THE CASE OF RATTE LARGE SCALE IRRIGATION SCHEME, DASENCH WOREDA, SOUTH OMO, ETHIOPIA

Abstract

Ratte large-scale irrigation scheme is located in the in Dasench woreda, South Nation Nationality people regional state, Ethiopia, and had a service of five years. However, the performance of the irrigation scheme has not been evaluated yet. In the present study, the performance of the scheme was evaluated by estimating water delivery performance indicators, water conveyance efficiency, water conveyance losses, and satisfaction of irrigation users. The water delivery performance were evaluated by monitoring discharge at nine selected offtakes; three each at the head, middle and tail end of the scheme command area during the crop season from April to June 2022. The water conveyance efficiency of the main and secondary canals and thus the water losses in water conveyance were estimated by measuring irrigation water flow at different locations along the canals. The satisfaction of the irrigation water users from the irrigation service received was evaluated manually at the head, middle and tail end of the irrigation scheme, and for the entire irrigation scheme. Irrigation water flow in the main and secondary canals, as well as at nine tertiaries off takes was measured using float velocity method and 3-inch Parshall flume. The data were analyzed using CROPWAT 8.0, ARC GIS software, and Microsoft Excel. The analysis of internal performance indicators showed that the conveyance, application, storage, and overall irrigation efficiencies, and distribution uniformity were 57.3 %, 63.6 %, 88.17 %, 36.2 %, and 88.6% respectively while the deep percolation ratio is 35.7 %. respectively. The loss in conveyance was unavoidable unless the canal was lined or could be minimized with better canal management activities. Approximately 35.6% of beneficiaries express satisfaction with the irrigation services provided. It was generally found that the irrigation service provided to the user was insufficient, and the program's intended beneficiaries did not receive the benefits. Rearranging WAUs, improving user capacity, and optimizing water delivery scheduling. In summary, in order to optimize irrigation and water management, it is crucial to give careful consideration to converting unlined canals to lined ones and to exchanging water use management best practices from various irrigation projects that enhance the scheme's performance