Assessment of suitable land for surface irrigation development in an Ardy watershed, Upper Blue Nile Basin, Ethiopia

Abstract Despite its abundant water and land resources, Ethiopia has not fully harnessed its potential for irrigation development. This study assessed suitable land for surface irrigation in the Ardy watershed, Ethiopia, with the goal of utilizing the country’s abundant yet underexploited water resources to increase agricultural productivity and sustainability. The data used in this study included soil, land use/land cover, meteorological, and streamflow data. The methodology integrates the Food and Agriculture Organization (FAO) land evaluation framework with Geographic Information Systems (GIS) and multicriteria analysis (Analytic Hierarchy Process, AHP) techniques. Land suitability was determined using factors such as slope, soil, land use/land cover, and proximity to water sources, with slope identified as the most influential parameter (47.09% weight). The Soil and Water Assessment Tool (SWAT) model was used to analyze surface water potential and demonstrated strong reliability during calibration (R² = 0.90, NSE = 0.86, PBIAS = -18.9%) and validation (R² = 0.85, NSE = 0.84, PBIAS = -14.9%). The results indicated that 99% (21,509 ha) of the watershed is suitable for surface irrigation, with 53% classified as moderately suitable. However, CROPWAT 8.0 modeling revealed that during peak irrigation demand periods (December, January, and February), the gross irrigation water requirement for the total suitable land exceeds the available river flow. On the basis of minimum available flows, the critical command area that can be reliably irrigated ranges from 918 ha (maize) to 1,057 ha (potato) across the subbasins. These findings provide policymakers with valuable guidance for developing targeted and effective management strategies to ensure sustainable resource use in the Ardy watershed.