Evaluating the performance of small-scale irrigation schemes in subhumid Ethiopian highlands

This study was conducted to evaluate the performance of two small-scale irrigation (SSI) schemes in the subhumid Ethiopian highlands. Water application at the farm level and flow velocity along the main canal were monitored using a Parshall flume and current meter, respectively. The infiltration was measured at the head, middle and tail of the scheme within the command area using a double-ring infiltrometer. Soil samples were collected using an auger up to 60 cm in depth. Climatic and agronomic data were supplied to the crop water assessment tool (CROPWAT) to determine crop water requirements. The results showed that the average conveyance efficiency for the lined main canal was 90% and 92% for the Mugie and Fesas SSI schemes, respectively. The conveyance efficiency for the unlined main canal was in the order of 86% and 87% for the Mugie and Fesas SSI schemes, respectively. On the other hand, the average application efficiency and overall efficiency were found to be 56% and 51%, respectively, with a storage efficiency of 50% for the Mugie irrigation scheme. Similarly, the overall, application and storage efficiencies were 50%, 54% and 56%, respectively, for the Fesas irrigation scheme. Failure of operating gates, canal siltation and leakage through the main canals were the main causes of poor performance.