Abstract

Erratic rainfall in Ethiopia has brought areas under extreme drought is increasing year to year. Assessing land suitability for irrigation has become the key strategies to minimize vulnerability to food insecurity. The main objective of this study was to evaluate the irrigation potential of the Mannissa watershed of Offa Woreda for surface irrigation. The watershed covers an area of 36.3km².The Landsat imagery (2020) with 28.5 m resolution and DEM data from USGS were used for land use land cover classification (LULCC). ArcGIS 10.8, ERDAS Imagine 10.5 and Google Earth software were used for the entire process of land use classification, delineation of the watershed, extraction of the stream network and derivation of the slope map. Metrological data were obtained from the World Climate Data Portal and cross-validated to the National data. In order to identify a suitable potential surface irrigation area, the soil chemical (pH, organic carbon) and physical (soil type, soil drainage, soil depth and texture classes) properties, mean annual temperature and precipitation, LULC, elevation and slope were reclassified using ArcMap 10.8 and categorized according to their suitability classes ranging from ‘very suitable’ (class S1) to ‘not suitable’ (class N2). The multi-criteria assessment of suitability employed using the Weighted Overlay Tool. Based on the model analysis, from 36.3 km² area coverage of the watershed, approximately 55.1% (20km²) is estimated to be suitable ranging from “very suitable” to “slightly suitable” whereas the remaining area of the study area estimated to be not suitable currently. From the area delineated as potentially “suitable” for surface irrigation, about 14.5% land is “very suitable” (S₁), 22.5% is “moderately suitable” (S₂), and 17.65% is “slightly suitable” (S3), respectively. Thus, the study watershed has extensive potential areas for surface irrigation. The local government and other stakeholders should plan irrigation schemes and encourage farmers to engage in surface irrigation in these high and moderately suitable areas to enhance land productivity and reduce food insecurity.

Key Words: GIS, Irrigation, Land requirement, Multi-Criteria Evaluation, Suitability Analysis