TECHNICAL PERFORMANCE EVALUATION AND REDESIGNING OF MADA BATU SMALL SCALE IRRIGATION SCHEME, WEST ARSI ZONE OF OROMIA REGION

Abstract

Irrigation enhances agricultural production, improves the food supply and income of rural population in Ethiopia. From this important viewpoint irrigation projects were widely studied, planned and implemented throughout the country. However, little or no attention was given to the monitoring and evaluation of the performance of already established schemes. This study was done during off season of rain in Gedeb Asasa district, West Arsi Zone on Mada Batu Small Scale Irrigation Scheme to characterize the scheme in terms of capacity, dimensions and functionality of reservoir, main and secondary canal, to evaluate the performance of scheme using performance indices such as conveyance efficiency (Ec), application efficiency (Ea), runoff ratio (ROR), deepercolation fraction (DPF), water storage efficiency (Es), overall efficiency (Eo) and distribution uniformity (DU), along with water productivity and finally identifying problems of the scheme. For this study three farmers’ fields were selected each from the upper, middle and lower stream of the irrigation scheme. The scheme has trapezoidal shape of reservoir with a capacity of 2604 m3 live storage along with trapezoidal shape of main canal with average size of 161, 59, 38.2 cm at the top, bottom and depth respectively and maximum discharge capacity when gate was full opened at off take was 70 l/sec. Most of the secondary canals were not functioning due to some part of canal like water closing gate and division box were damaged. Due to this water being diverted to its own way by farmer from division box reaching to their farms. Parameters like Ec, Ea, ROR, DPF, Es, Eo and DU were determined and their average values of scheme were found to be 64.77%, 64.54%, 12.10%, 23.29%, 82.47%, 41.47%, and 93.10% respectively. Water productivities (in terms of water use efficiency) was 0.74 kg/m3 for the upper and middle and 1.61 kg/m3 for lower irrigation scheme whereas, the productivity (in terms of irrigation use efficiency) had values of 1.34 kg/m3 for the upper and middle and 3.68 kg/m3 for lower stream of the xx irrigation scheme. The redesign of scheme was needed due to discharge of main canal to command area size not compatible.