PERFORMANCE EVALUATION OF BORKENA SMALL SCALE IRRIGATION SCHEME, NORTHERN ETHIOPIA

Abstract

Performance evaluation of irrigation scheme is mandatory to evaluate the impacts of irrigation practices, to identify performance gaps and to improve system performances. Currently, Borkena irrigation scheme's has problem of unequal water distribution between upstream and downstream users, siltation issue, and growth of weeds. Technical performance indicators were used in this study to evaluate Borkena Irrigation Scheme's effectiveness. This study was carried out for one irrigation season starting from December to April. Secondary data sources were collected from National Meteorological Institution, design document, related journals, FAO documents & other useful written materials and primary data sources were collected by using direct field measurements, household surveys, key informant interviews, focus group discussions and research questions. The collected data’s were analyzed with ArcGIS10.4, CROPWAT8.0 and Microsoft excels soft-wares. The discharge in the irrigation canals were measured by using float method. The minimum and the maximum reference evapotranspiration in the study area were 2.75mm/day and 3.99mm/day, respectively. The average monthly maximum and minimum effective rainfall was 160.5mm and 0mm, respectively. The conveyance efficiency of the main canal, secondary canal and tertiary canal were estimated as 61.3%, 55.4% and 54.2%, respectively. The average relative water supply and relative irrigation water supply of the study area were calculated as 0.86 and 1, respectively. The water delivery performance indicators were estimated to be 0.9 for adequacy, 0.18 for dependability, 0.76 for efficiency, and 0.15 for equity. For better performance and long service of the year; this irrigation scheme highly required regular inspection and maintenance. Lining of the earthen canals with impermeable materials to prevent excessive seepage and growth of weeds. Creating the awareness for the users on how to setting rules, implementing it and well organized water management plan to improve the poor irrigation water management. Applying proper water distribution plan in the system and applying a gated division system to improve irrigation water supply and irrigation water demand. Crop water requirement varies from stage to stage. This means crops having less water requirement at initial stage than developmental stage. Therefore, delivering and scheduling irrigation water based on the crop demand is very essential to fulfill the crop water requirement.