COMPARATIVE EVALUATION OF ELA AND LINTALA SMALL SCALE IRRIGATION SCHEMES, WOLAITA ZONE, SOUTHERN ETHIOPIA

Abstract

Irrigation schemes are usually constructed to deliver service on the assumed efficiency. Due to the schemes’ age and management practice, service rendering status of schemes may be below assumed performance level. Non- operational parts of the irrigation schemes were commonly seen in the study schemes. Therefore these study schemes were evaluated with the help of internal and external performance indicators. Internal performance indicators were conveyance efficiency, application efficiency, irrigation adequacy and uniformity. External performance indicators were water delivery performance and water productivity. Water delivery parameters used were Relative Irrigation Supply, Relative Water Supply, and Water Delivery Capacity. The water productivity of the schemes was also compared with respect to the irrigation water used. Conveyance efficiencies of Ela and Lintala schemes were 86% and 81%, and also Irrigation application of these schemes were 55% and 42%. So that, system efficiencies of Ela and Lintala small scale irrigation schemes were 47% and 34%. So that in Ela irrigation scheme water management in the field was better than Lintala scheme. Also Storage efficiencies in Ela and Lintala plots were 86% and 81%. So, in irrigation time, selected plots acquired the required irrigation depth fairly. And calculated Irrigation uniformity in these plots were 88% and 77%. In Ela irrigation scheme, Relative water supply and Relative irrigation supply was in the interval 0.95-1.96 and 0.94-2.4. In these intervals the lower values 0.95 and 0.94 were obtained in the month February. This revealed the scheme water delivery performance couldn’t answer ETc of the crops in driest month. But its water delivery capacity of main canal was 3.8. So Ela scheme canal capacity was not constraining factor for croping intensity. The Relative water supply and Relative irrigation supply of Lintala was in the intervals 2.53-3.73 and 2.8-4.5. And also its main canal capacity was 2.2. So that this scheme water delivery performance was enough to answer the ETc of the crops. In existing water management, average irrigation water productivity of maize in Ela and Lintala plots was 0.89 and 0.52 kg per m3 of irrigation water reaching the farm.