Remote Sensing-Based Estimation of Irrigation Water Use and Supply in the Amibara Irrigation Scheme, Ethiopia: A Multi-Scale Assessment

Accurate estimation of irrigation water use and supply is essential for effective irrigation management, yet most withdrawals remain unmetered and unreported in many irrigation schemes. This study applied a remote sensing–based approach to quantify irrigation water use and supply in the Amibara Irrigation Scheme, Ethiopia. The irrigation component of crop evapotranspiration (Blue ET) was isolated using the Water Accounting Plus (WA+) framework and integrated with irrigation efficiency parameters to derive remote sensing–based irrigation supply (RbIS) estimates across multiple spatial scales. Moreover, we developed crop type maps for 2010 and 2024 and a digitized irrigation layout to evaluate irrigation performance using relative evapotranspiration (RET) and relative irrigation supply (RIS) and to compare changes between the two years.

Crop type mapping revealed a substantial decline in irrigated area, from 9,941 ha in 2010 to 4,532 ha in 2024.  RbIS showed  reasonable agreement with reported supply in 2010 (R² = 0.6) and measured supply in 2024 (R² = 0.8), though it consistently underestimated observed supply in both years. Irrigation distribution was relatively better in 2010, with 46% of blocks experiencing deficits compared to 70% in 2024, while excess irrigation decreased from 50% of blocks in 2010 to 26% in 2024.  RET and RIS estimates were generally consistent across most irrigation blocks, reinforcing the robustness of these performance indicators. However, irrigation performance varied substantially across blocks and canals, with irrigation deficits evident in both years. Key informant interviews and focus group discussions further corroborated these irrigation water deficits, supporting the remote sensing–based assessment. Overall, the methodology of this study is scalable for data-scarce regions and offers strong potential for operational irrigation monitoring to support targeted interventions.