PERFORMANCE EVALUATION OF DEKEYA SMALL-SCALE IRRIGATION SCHEME IN WOLAITA ZONE, SOUTHERN ETHIOPIA

Abstract

The water delivery performance evaluation of an irrigation system plays a major role in indicating the performance gaps and applying proper mitigation measurements in order to improve the system. Dekeya Small-Scale irrigation scheme was designed to irrigate around 128 hectares but, it does not meet the proposed objective, hence the objective of the study was to evaluate its status using performance indicators such as water delivery performance, maintenance and institutional setup of Dekeya small-scale irrigation scheme. This study was carried out for three consecutive months (one irrigation season) from October to December; 2022. Discharge measurement instruments such as a Partial flume, a Current meter for measuring flow velocity, tape meter for measuring canal length, width and surface elevation ratio, and GPS device for managing control points, were used to collect data from the field. Besides that, software like Arc GIS 10.1 and CROPWAT 8.0 were used for the analysis of collected data. The result revealed that the water delivery performance indicators; such as adequacy, dependability, equity and efficiency were found to be 0.90, 0.57, 0.10 and 0.83 respectively. According to these values, performance of water delivery of the main canal was rated as poor in terms of dependability; however it was fair in relation to efficiency and equity the adequacy value was good. The study also finds that the maintenance indicators such as effectiveness of infrastructure and water surface elevation ratio were found to be and 0.14 for branched canal,70% of installed structure were operative and Water surface elevation ratio values for the head, middle and tail reach of the canal were 0.74, 0.74m and 0.62m respectively. The suitability of irrigation area is 0.78 for main canal. The overall Water surface elevation ratio of the main canal of the irrigation system is 0.70m, which is less than one showing the canal level has raised due to siltation, algae development and weed infestation. Therefore, it is suggested that, effective water management, supplying irrigation water based on crop demand, optimal crop plan, and applying a strong water delivery plan are required to mitigate these problems