ASSESSMENT OF LAND SUITABILITY AND IRRIGATION WATER POTENTIAL IN KERSA WATERSHED, WABESHEBELLE RIVER BASIN, ETHIOPIA

Abstract

Ethiopia faces droughts due to population growth, water resource imbalances, and land degradation. Inadequate irrigation technology hinders food security and income. Kersa Watershed's irrigated agriculture lacks sustainability and suitable locations. Assessing feasibility, taking into account land and water resources, and creating maps are all critical. The study was to evaluate the land suitability and irrigation potential for surface irrigation development in the Kersa watershed using the analytic hierarchy process. Multiple factors which affect irrigated agriculture productivity such as elevation, slope, soil, LULC, and distance to source were considered and each physical parameter was mapped with the use of ArcGIS 10.4.1. All factors were measured to obtain the overall suitability and reclassified according to FAO guidelines. The overall suitability for surface irrigation potential was determined through an analytic hierarchy process and weighted overlay analysis with the aid of a model builder in ArcGIS 10.4.1. Accordingly, about 56.83% of the slope of the catchment, 92.56% of elevation, 87.60% of soil depth, 100% of texture, 84% of drainage, 85% of distance to source, 99.92% of LULC was highly to marginally suitable for surface irrigation. The overall weighted overlay of all parameter results revealed that 97.13% (58,481.1 ha) of the potential irrigable lands in the watershed were in the range of highly suitable to marginally suitable, and 2.87% (1725.87 ha) were unsuitable for surface irrigation. The gross irrigation water requirement, crop water requirement, and irrigation requirement of Maize and sorghum are estimated per decade with the use of the CROPWAT8.0 model. The result has shown that irrigation requirements of the identified command area vary according to the nearby climatic stations and the type of crops selected. The discharges at un-gauged sites were estimated from gauged sites by applying the runoff coefficient method and results were obtained monthly. By comparing the gross irrigation demand of irrigable land with the available flow in rivers, a gross irrigation demand of potentially irrigable land of 58,481.1 ha is not fulfilled with the present flow, so providing a means of water storage above the potential command area is necessary. The current study considered only seven factors, but other suitability factors like socioeconomics, environmental issues, method of irrigation, and other relevant parameters should be studied for a detailed assessment of irrigation development in the study area.