ASSESSMENT OF LAND SUITABILITY FOR SURFACE IRRIGATION DEVELOPMENT IN WEIYB SUB BASIN, GENALE-DAWA RIVER BASIN, ETHIOPIA

Abstract

Evaluating the suitability of a landscape for irrigation in advance is critical for the sustainability of an irrigation system. The climatic condition of Bale Zone is changing from time to time and crop production through rain-fed agriculture has become uncertain. To overcome such difficulties, irrigation is a sole option. The overarching goal of this work was to evaluate the surface irrigation potential and suitability of Weiyb sub-basin for irrigation development. Collection of the criteria`s for irrigation suitability like soil data, slope and land use/cover and delineating the boundary of the study area, estimation of crop and irrigation water requirements were made to identify potential irrigable area. Geographical information system (GIS) was used to develop irrigation land suitability map of the study area. CropWat was used to compute the crop water requirement (CWR) of four commonly grown crops. The irrigable command area were identified by comparing the irrigation water demand and water potential of the water source in the study area. The analysis of each suitability parameters revealed that 77% of slope, 99% of soil, 96% of land use/ cover of the study area were classified as suitable for irrigation. Whereas 13% of slope, 1% of soil, and 4% of land use/cover were classified as not suitable for irrigation. By using suitability model builder all parameters were weighted through the tool in special analysis on ArcGIS environment, the result reveals that 19.6% of the area was found to be highly suitable whereas about 14.4% of the area currently not suitable for irrigation development. By comparing the monthly required irrigation water and available monthly flow of the river, the total irrigation potential command area was found as 5,010 ha. Lastly, the suitable irrigable area is small; this is mainly due to slope, soil, land use /cover. Alternatively more land could be developed by using irrigation water application methods other than the conventional furrow irrigation methods through further investigation.