EVALUATION OF WATER DELIVERY PERFORMANCE OF CANALS AND ITS INFRASTRUCTURES OF OMO KURAZ IRRIGATION SCHEME, SOUTHERN, ETHIOPIA

Abstract

Poor irrigation conveyance infrastructure is the major challenges of Omo Kuraz II sugarcane irrigation scheme. This study assesses the performance left bank main canals of the Kuraz Sugarcane Irrigation, focusing on conveyance efficiency, water delivery capacity, effectiveness of infrastructure, and water surface elevation ratios. Soil texture was evaluated through hydrometer test analysis in laboratory where field capacity and permanent wilting point were estimated using pressure plate apparatus. Crop water requirement and irrigation duty were estimated through CropWat model by using soil and climate data as input. Climate data was collected from Kuraz automatic climate station. Canal discharge was measured using floating techniques and actual canal cross section such as depth and width were measured using tap meter. The maximum discharge at two cross drainage structure was estimated using Hydrological HEC-HMS model. The functional and non-functional infrastructure in the scheme were counting through field survey. The results reveled that the representative soil texture was clay and the mean value of soil dry bulk density, field capacity, permeant wilting point of soil were 1.36g/cm³, 40.2% and 26.4%, respectively. The total crop water and irrigation requirement for sugarcane were 1761.9mm and 950.1mm respectively. The irrigation duty of the sugarcane was varied from 0.12 l/s/ha (April) to 0.44 l/s/ha (August). The conveyance efficiency of main canal was varied from 48.7% to 95.1% with average value of 74.7%. The conveyances efficiencies secondary canal 1, secondary canal 2 and secondary canal 3 were 77.8%, 84.4%, and at 83%, respectively. The irrigation water delivery capacity of the left bank main canal was 30.3%. The effectiveness of the infrastructures was 87.5% (secondary Canal 5), 78.6%, (secondary Canal 6), 96.3% (secondary canal 10), and 38.7% (main canal). Additionally, the study reveals a progressive reduction in water surface elevation ratio (WSER) with increasing canal length with mean value of 63.8%. The maximum discharge of catchment at outlets of cross drainage 13 and 14 were 46.1m3/s and 73.4m3/s, respectively. Generally, Kuraz sugarcane irrigation scheme found under poor performance status that shows urging silt removal, and infrastructure maintenance are needed to enhance scheme status