GIS and AHP-Based Assessment of Land Suitability and Water Availability for Surface Irrigation in Beles Sub-Basin, Ethiopia

Assessing available water resources and identifying suitable land for irrigation at the basin level are crucial for effective planning and decision-making in irrigation development projects. Therefore, this study aims to utilize the Geographic Information System (GIS) and the Analytic Hierarchy Process (AHP) technique to evaluate surface irrigation suitability and surface water availability in the Beles Basin. We analyzed surface water availability by constructing a flow duration curve (FDC) and assessing the 90% available flow of the Beles River. Meanwhile, land surface suitability was determined through a GIS-based multi-criteria evaluation (MCE). This method integrates various factors, including slope, proximity to rivers, soil characteristics (type, texture, depth, drainage), proximity to roads, and land use and land cover. These factors were weighted using pair-wise comparison matrices to determine their relative importance in assessing physical land suitability. The results revealed that approximately 13.84%, 73.05%, and 13.11% of the catchment area were highly, moderately, and marginally suitable for irrigation, respectively. Regarding water availability, the FDC analysis indicated that the Beles River maintains a 90% available flow of 1.6 m<sup>3</sup>/s throughout the year. Consequently, in December, the river can only irrigate 0.25% of the total irrigable land, whereas from May to September, it can irrigate the entire irrigable area. The river's low flow presents opportunities for extensive irrigation during the wet season but limits irrigation during the dry season. Therefore, the implementation of water storage structures is imperative to facilitate irrigation across the entire potential land during periods of low flow.