ASSESSMENT OF PHYSICAL SURFACE IRRIGATION POTENTIAL OF AWATA WATERSHED; GENALE DAWA RIVER BASIN, ETHIOPIA

Abstract

Assessing available land resources for irrigation is important for planning their use and sustainability of irrigation system. This study was initiated to assess the irrigation suitable areas of the watershed. The assessment of surface irrigation suitability for Awata sub-basin was conducted in Guji Zone, Oromia region. The Watershed covers a total area around 148614.8 ha in Genale Dawa Basin. Gathering of the standards for irrigation suitability corresponding to slope, soil data, land use/cover, distance from outlets and delineation of the study area, estimation of crop and irrigation water requirements were made to identify potential irrigable area. Irrigation suitability assessment was evaluated based on FAO guidelines. Based on the analysis, 3.5 % of slope, 66.08 % of soil, 45.03 % of land use /cover and 40.15 of distance from the water source of the study area were identified to be in the range of highly suitable, 16.18% slope, 33.92% soil,46.67% of the distance from water sources are moderately and 21.53% slope and 25.95% marginally suitable for surface irrigation. Whereas, 58.79% of slope, 29.02% of land use/cover, and 2.99% distance from water supply were classified as not suitable for irrigation using surface methods. It was also found much of the land is not suitable for surface irrigation. The weighted overlay analysis of the factors and the result obtained that, the total surface irrigation suitability potential of the study area is 18098 ha, from this; the potentially irrigable land was obtained by multi-criteria analysis as 11098.03 ha. By comparing gross irrigation demand of irrigable land with the available flow in rivers, a gross irrigation demand of potentially irrigable land of 11098.03 ha are not fulfilled with the present flow, so providing a means of water storage is necessary to irrigate the potential command area