Geographical information system based surface irrigation potential analysis (case study of keto catchment, western Ethiopia)

Abstract

Although Ethiopia has a large potential to develop irrigation, only 7.84% of the 3.7 million hectares of land potentially available has been developed. To examine the underlying causes, this study evaluates the suitability of surface water irrigation in Keto River catchment. The study area covers an area of about 1058.592 square kilometers. This study was initiated with the objective of analyzing the water and land resources potential of river catchments in this River basin for irrigation development by using Geographic Information System. The hydrological, meteorological, Digital elevation model, soil, Land use, land cover map data were gathered from different organization of government and other concerned sectors. First elevation data of the study area were delineated as 30m resolution, then, characteristics of flow direction, contours and radius of elevation noticed. The potential irrigable land was identified by using slope, land use/cover and soil in arc GIS software, spatial analysis tool to analyze their suitability individually, then application of the weighted overlay tool was provided to condense overall suitability factors as specific outcome, and suitability was conducted implementing FAO criteria for surface irrigation. Analysis of the water resource potential of the study area was carried out by using hydrological data after filling different gaps observed using techniques like the average mean method and distance power method to screen them for further application. Here, there was, flow duration curve developed, flood frequency tested, low flow analyzed to differentiate between variability existed between time series of the records. The reservoir requirements of the catchment were dealt with dependable flow by mass curve technique. Also crop water requirement of most widely growing crops of the study area viz. Potato and Maize were computed from climatic data as an input depending on the preference of agro climatic condition of the study area using CROPWAT model, version 8. Potential irrigable land was identified out of the total catchment area considering suitability outcomes for river catchments and selected crops agro ecology. The Gross irrigation demand of selected crops for each month is computed for low flow analysis of 80%, 85%, 90%, 95%, and a 100% exceedence. The result suggests that the irrigation potential of the area considering the analysis of possible low flows and crop gross irrigation requirement is 0.014ha.