ASSESSMENT OF LAND SUITABILITY FOR IRRIGATION POTENTIAL OF JERJERTU WATERSHED, WABE SHEBELLE RIVER BASIN, ETHIOPIA

Abstract

Irrigation is an important investment for improving rural income through increased agricultural production. The study was to assess the land resources potential and available water of river for surface irrigation development in Jerjertu watershed. To identify the potential irrigable lands with respect to the various irrigation suitability parameters such as slope, soil, LULC and water availability of the catchment then mapped each physical parameter with the use of ArcGIS10.4. The gross irrigation water requirement, crop water requirement, and irrigation requirement of Maize and sorghum estimated as per decade with the use of CROPWAT8.0 model. Soil depth, soil drainage and soil texture to obtain the overall soil suitability and slope suitability was performed using DEM of 30*30-pixel resolution through reclassifying according to FAO guidelines. The overall suitability for surface irrigation potential was done through weighted overlay analysis of the slope, soil, and LULC, with the aid of model builder in the ArcGIS10.4. Accordingly, the overall soil suitability was 66.33%ranging from highly to marginally suitable for the surface irrigation and about 97.5% slope of the catchment was highly to marginally suitable. About 99.17% of LULC was highly to marginally suitable for surface irrigation. The watershed's stream flow data analyzed using the Arc SWAT model with an interface in ArcGIS 10.4 software. The model calibrated and validated using observed stream flow in the watershed the calibration and validation results showed that model performances evaluation statistics. The results of the calibration and the validation were R2, NSE, PBIAS, and RSR were 0.85, 0.81, -7.3%, 0.43 and 0.79, 0.71, -12.27%, 0.36 respectively. This shows a good agreement between the simulated and observed values. The result analysis revealed that 68213.3 ha (99.18%) of the lands in the watershed were in the range of highly suitable to marginally suitable, and 589 ha (0.82 %) unsuitable for surface irrigation. The current study considered only slope, soil physical properties and land use/land cover but other suitability factors like, socioeconomic, environmental issues, method of irrigation system and other relevant parameters should be studied for a detailed assessment of irrigation development in the study area.