Performance Evaluation of the Erer Irrigation Scheme: A Case Study of the Irsha Limat Irrigation Project, Somali Region, Ethiopia

Irrigation plays a critical role in enhancing agricultural productivity and food security particularly in arid and semiarid regions where rainfall is unreliable and the Erer Irrigation Scheme one of the oldest surface irrigation schemes in the Somali Region of Ethiopia has experienced declining performance associated with structural deterioration sedimentation and conveyance losses. This study evaluated the technical, operational and maintenance performance of the scheme during a citrus irrigation season from October 2023 to January 2024 using standardized irrigation performance indicators and field measurements were conducted along the main and secondary canals to determine discharge, flow velocity, water levels and conveyance losses. Crop water requirements were estimated using CROPWAT 8.0 with climatic data obtained from Jigjiga Meteorological Station. The assessed indicators included adequacy, equity, dependability, efficiency, conveyance efficiency, water surface elevation ratio, infrastructure effectiveness and water delivery ratio. Main canal conveyance efficiency ranged from 85.71% to 93.33%, with an average of 89.52%. Mean conveyance efficiency was 67.11% in secondary canal one, 66.15% in secondary canal two and 63.85% in secondary canal three. Mean adequacy values for the three secondary canals were 0.86, 0.76, and 0.79 respectively. Only 19 of 29 originally installed control structures were functional giving an infrastructure effectiveness of 65.5%. Water delivery ratios at the monitored secondary canal offtakes ranged from 0.56 to 0.84. The results indicate that performance deteriorates in several middle and tail reaches and that structural and maintenance constraints are important contributors to water delivery losses and rehabilitation of canal infrastructure improved sediment and vegetation management, improved water scheduling and systematic maintenance are recommended to improve scheme performance and sustainability.