Mapping irrigable land potential for surface irrigation through GIS-based multi-criteria analysis in Ethiopia’s Gidabo watershed

Identifying land suitable for surface irrigation is essential for improving agricultural production while ensuring efficient use of land and water resources. However, such assessments are often challenging in data-scarce regions where terrain, soil conditions, land use, and access to water and infrastructure vary widely. This study evaluated land suitability for surface irrigation in the 3180 km 2 Gidabo Watershed in Ethiopia’s Rift Valley Lakes Basin. Seven biophysical and accessibility factors were analyzed: slope, soil depth, soil texture, soil drainage, land use/land cover, and distance to rivers and roads. These factors were standardized using FAO guidelines and local expert knowledge and integrated through the Analytical Hierarchy Process (AHP) and GIS-based weighted overlay analysis. The results indicate that slope was the most influential factor, with a weight of 46.34%, followed by distance to rivers (28.51%) and soil characteristics (14.46%). The AHP consistency ratio of 0.053 indicated acceptable consistency in the expert judgments. Overall, 93.23% of the watershed was physically suitable for surface irrigation to varying degrees (S1–S3). However, only 35.79% (113,831 ha) fell within the highly and moderately suitable classes (S1–S2), representing areas with more favorable conditions for irrigation development. Highly suitable land (S1) accounted for 4.32% of the watershed and was mainly located in valley bottoms and lowland areas along the Gidabo River and its major tributaries. In contrast, steep slopes exceeding 8%, which cover about 62% of the watershed, represent the main physical constraint. The distribution of S1–S2 land also varied considerably among sub-basins, ranging from 471 to 21,486 ha. These findings highlight that while most of the watershed has some level of physical suitability, the area with favorable conditions for practical irrigation development is much more limited. The resulting suitability map provides a useful tool for prioritizing areas for detailed feasibility studies and guiding irrigation investment planning in the Gidabo Watershed and similar data-scarce watersheds in sub-Saharan Africa.