GIS BASED SURFACE IRRIGATION POTENTIAL ANALYSIS: A CASE STUDY OF UPPER BIRBIR SUB BASIN,WESTERN ETHIOPIA

Abstract

The study is specifically concerned with analysis of Upper Birbir surface irrigation potential using GIS. The study area is found within rural communities, striving to overcome food self insufficiencies utilizing natural resources. However, to date, there is no appropriate surface irrigation potential data, for paramount natural treasures found within the study area to put over practically. For this reason, the writer decided to give away, with application of GIS in line with other relevant nearby data. This thesis, first identify potential irrigable land and characterize its nature of utility for surface irrigation. In a second stage estimate potential surface water resource for irrigation and determine crop water requirement for very common crops of the study area. Finally, recommend the storage volume demands unless the available water resource would meet the demand of the potential area and crops. The hydrological, meteorological, Digital elevation model, soil, Land use, land cover map and etc data were gathered from different organization of government and other concerned sectors. First elevation data of the study area were delineated as 90m 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 8627.8ha. The storage requirements are 700, 105, 35 and 55,55Mm 3 for Birbir, Keto, Iowa, Kuni and Merdafo rivers respectively, so as to endure 432,776.9ha total irrigable potential area. Generally, Site specific studies with latest technologies will be encouraged to provide more substantial outcomes.