Characterization and performance evaluation of Small scale irrigation scheme; the case ashar Amhara region, ethiopia

Abstract

Irrigation is one means by which agricultural production can be increased to meet the growing demands. The principal objective of evaluating the performance of irrigation scheme is for a variety of reasons: to improve system operations; to assess progress against strategic goals; as an integral part of performance-oriented management, to assess the general functionality of a system; to assess impacts of interventions; to diagnose constraints; to better understand determinants of performance. While conducting this study, initial assessment and field observation, consultation with different stalk holders was made to visualize the study area. The scheme characterization was made by measuring the canals discharge capacity, dimensions, length of flow and functionality of the structures, using selected performance indicators such as conveyance, application, storage, distribution uniformity and overall efficiencies along with the water productivity in terms of water use efficiency. Conveyance efficiency of canals was estimated using area velocity method at different cross section of the canals. For crop water demand, the FAO's computer program CROPWAT8 package was utilized to calculate the crop water requirements. Average conveyance efficiencies were obtained as 61.21%,59.95% and 62.97% in head, middle and tail end location of the scheme respectively. The application efficiencies were 62.67%, 52.58% and 52.32% in head, middle and tail end location of the scheme respectively. The average storage efficiency for all fields was 52.64%. The distribution uniformity was found to be 88.63%, 87.52% and 91.47% for upstream, middle and downstream location of test plots respectively. The losses were only deep percolation as the furrows were close ended. The deep percolation ratio was found in the range of 47.68% in tail location farm to 37.33% in head location’s. The average overall scheme efficiency for all fields was 34.15%. Finally, the economic water use efficiency of test plots in terms of benefit-cost ratio were estimated and found as 1.83, 2.04 and 2.27 for head, middle and tail locations, respectively and found to be efficient