GIS Based Surface Irrigation Potential Assessment of Muger River Sub Basin

Abstract

Irrigation is key role in improving food security by increasing agricultural production. Land suitability assessment is a valuable tool for land use planning. The main problem in this study area, lack of land resource management and suitability of irrigable land were not known. This study was initiated to assess the land suitability, available surface water, crop water demand of the muger river sub basin for surface irrigation and providing geo-referenced map of these resources using Geographic information system. Irrigation suitability of physical land parameters was classified based on the Food Agriculture Organization guideline for land evaluation in to highly suitable, moderately suitable, marginally suitable and not suitable suitability classes independently, where the final existing and potentially irrigable land was identified by over weighting the factors of suitability using geographic information system. The irrigation water demand was estimated using CROPWAT8.0 software from Gohatsion climatic station for selected crops, potato, cabbage, maize and tomato. Depending on the watershed similarities; stream flows at un-gauged station were estimated from the gauged station by applying area ratio method. The suitability analysis of the parameters indicates that slope 82.15%, soil depth 50.83%, and soil drainage 84.96%, soil textures 100% and land use/cover 73.846% of the study areas classified as potentially suitable for irrigation development in the study area. After over weighted these all parameters, 91099.94ha (11.13%) of the study area was found to be highly suitable, 137589.30ha (16.80%) moderately suitable and 3764.37ha (0.46%) marginally suitable whereas about 586346.39 ha (71.61%) not suitable for surface irrigation developments. From total catchment area the suitable land was 232453.61(28.39%). The map suitability study area weighted overlay by assumed value of influence 10%, 30%, 15%, 16%, 14% and 15% for land use, slope, soil drainage, soil depth, soil textures and distance respectively. The result indicate that, if more factors are considered in the evaluation process and weighted, the total irrigable land is expected to reduce more thereby giving accurate estimate of the land potential for surface irrigation. The capacity of low flow as well as 80% time of exceedance flow of the available surface water in the respective sub watersheds was also estimated. Total estimated of minimum flow was 32.47m3/sec. This study considered only slope, land use land cover, and soil physical properties but other suitability factors like, soil chemical characteristics, and irrigation method should be studied.