Evaluation of hydraulic performance, physical sustainability and maintenance indicators of the Lasho small scale irrigation scheme in Wolaita Zone, Ethiopia

Water scarcity is a critical global challenge limiting food production, and improving the performance of existing irrigation systems has become a key strategy for enhancing agricultural productivity. In Ethiopia, small-scale irrigation schemes play a vital role in ensuring food security and poverty alleviation; however, many schemes operate below their design capacity due to technical, managerial, and operational deficiencies. The objective of this study was to evaluate the current state of the Lasho small-scale irrigation scheme in Wolaita Zone, Ethiopia using hydraulic performance, physical sustainability, and maintenance indicators. Primary data were collected through field observations, discharge measurements using a 90° V-notch at three locations along the main canal (head, middle, and tail reaches), and water surface elevation measurements at 36 stations. Secondary data on climate, crops, and design specifications were obtained from national government offices and analyzed or extracted using CROPWAT 8.0, ArcGIS 10.3, and New_LocClim10.1 software. The results revealed poor adequacy (0.79), dependability (0.202), and equity (0.253), but fair efficiency (0.70) of the irrigation system. The scheme experienced a 15% water deficiency, with the tail reach showing the highest deficit at 18.8%. Physical sustainability indicators showed that only 48% of the irrigable command area is currently being irrigated, and the sustainability of the irrigated area stands at 60%. The delivery performance ratio of 0.8 indicated that the main canal achieves only 80% of its design discharge. Maintenance indicators revealed a water surface elevation ratio of 0.72, indicating significant sedimentation and weed problems, and only 62.22% of irrigation structures remained functional. The study concluded that the scheme is performing poorly across most hydraulic performance indicators due to a combination of technical problems, managerial issues, and operational constraints. Future research should prioritize long-term monitoring across multiple seasons, along with socio-economic and cost-effectiveness analyses of rehabilitation options. Urgent interventions including routine maintenance, structural rehabilitation, improved water management, and stronger water user associations are essential to enhance scheme performance and ensure sustainable water delivery to all users.