EVALUATION OF LASHO SMALL SCALE IRRIGATION SCHEME HYDRAULIC PERFORMANCE: THE CASE STUDY OF WOLAITA ZONE, ETHIOPIA

Abstract

Hydraulic performance evaluation of irrigation scheme plays a vital role in identifying the gaps and applying mitigation measures, improving the future functionality of the system. This study was conducted to evaluate the water delivery performances using internal indicators and to suggest water management strategies in the scheme for one irrigation season from October-January, 2022 G.C. The primary data were collected from fields by measuring the flows and field observation was conducted in order to get the existing hydraulic structures were identified and recorded. The discharge and water surface level of the canals was measured by 90 degree v-notch and graduated staff gauge respectively. Secondary data were collected from New_LocClim1.10 (climate data) and other data from respective government offices. CROPWAT 8.0 software was used to calculate crop water requirement. The internal hydraulic performance indicators of the irrigation system were evaluated using adequacy, efficiency, dependability, and equity; the computed values were 0.79, 0.70, 0.202 and 0.253 respectively. The result indicates that adequacy, dependability, and equity of the system were poor but the efficiency of the irrigation system was fair. The management and operational indicators; ERHT was found from 1.01 to 1.5 and the overall average value was found to be 1.2.Therefore, it obtained here are poor management and delivery performance ratio and equity ratio for head, middle and tail reaches were found to be 0.89, 0.84 and 0.78, respectively. These values indicate that, the existing performance of the canal was good on head, poor on middle to tail compared to the intended performance. Maintenance and sustainability performance indicators are water surface elevations ratio, delivery duration ratio, effectiveness of infrastructure, irrigation ratio and sustainability of irrigated area were found to be 72%,150%, 62.22%,48% and 60 %, respectively. These values indicate that, actual water level as well as command area was reduced from initially designed, and a number of structures initially installed were become nonfunctional. Based on the results obtained, the recommendation drawn as the water should be fairly distributed spatially and temporally in this scheme. Moreover, capacity building and awareness creation to concerned bodies holds the key to improve water management and also maintenance of the scheme is critical to keep the performance of scheme and to optimize water use efficiency