PERFORMANCE EVALUATION OF SILE IRRIGATION SCHEME IN ARBAMINCH, SOUTHERN ETHIOPIA

Abstract

Evaluating the performance of existing irrigation schemes helps to compare the potential of the scheme with that of current service. Direct field data collection and secondary data were used to address the objectives and answer the research questions. The main objective of the study area was to evaluation the performance of Sile irrigation scheme and to know the problems and suggest possible mitigation measures. It was important to study its performance level and introduce the information to government and non-governmental organizations. This study was done to identify and understand the current status of the performance of Sile irrigation scheme. The scheme was evaluated using performance indicators such as conveyance efficiency (Ec), relative water supply (RWS), and relative irrigation supply (RIS). It was also evaluated in terms of water use indicators such as application efficiency (Ea), water storage efficiency (Es), deep percolation (DP), and overall efficiency (Eov). For this study, three farm fields were selected from the upper, middle, and lower streams of the irrigation scheme to account the performance. Discharges were measured using a velocity stage probe and Parshall flume. The primary data, like discharge measurements in the canals, measurement of applied water to the farm fields, determination of soil moisture contents, soil physical properties, and secondary data, were analyzed using CROPWAT, ARC GIS software, and Microsoft Excel. The results obtained for the average conveyance efficiency of the main, secondary, and tertiary canals were 86.67%, 76.32%, and 54.8%, respectively, and the mean value of application efficiency was 60%. The water conveyance efficiency of the canals and the water losses in water conveyance were estimated by measuring irrigation water flow at different locations along the canals. The main canal had high conveyance efficiency due to conceit structure, line canal. The secondary and tertiary canals were poorly maintained, and some of the structures were not functional, which caused water loss in the entire scheme. This result indicates that the values of most of the water delivery and water use indicators were below the attainable values suggested by many researchers. These values were due to illegal water abstraction, sedimentation of canals, and a lack of maintenance. Therefore, regular maintenance and suitable management approaches are required to improve the irrigation scheme's performance