TECHNICAL PERFORMANCE EVALUATION AND REDESIGNING OF SMALL SCALE IRRIGATION SCHEME: CASE OF GUDER IRRIGATION SCHEME AWI ZONE, AMHARA REGION

Abstract

The bulk of available land and water resources potential in Ethiopia is still underutilized. Even worse already developed irrigation schemes are not performing as desired. This study was made in an effort to contribute towards the betterment of the performance of irrigation schemes, using Guder small scale irrigation scheme as the case study site. Measurement of canal discharge, soil moisture and its physico-chemical properties were made to investigate the technical performance; and interview using structured questionnaires were made to identify potential social and inistitutional factors in the performance of the irrigation scheme. Internal and external technical performance indicators were used to evaluate the scheme for better performance in terms of water applied and water consumed for future improvements. The irrigation scheme has average conveyance, application, distribution, Christianson’s uniformity coefficient and storage efficiency value of 88%, 49.74%, 82.3%, 90%, and 70% respectively. Absence of WUAs and irrigation expert, low institutional support service, inadequate input and credit supply were the major social and inistitutional factors of the scheme. The irrigation project was over designed. This was due to unmeasured river base flow and diversion weir, main canal, division boxes and drop structures were redesigned. Large amount of water lost was measured from the system before reaching the target fields due to spillage and seepage from unlined main canal. It is also recommended that the pimary section of canal be lined with stone masonry or concrete and the remaining earthen canal should be compacted properly for which the support of institutions may be important.