Surface Irrigation Suitability Analysis of Southern Abbay Basin by Implementing Gis Techniques (A Case Study in Dedessa Sub-Basin)

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Addis Ababa University


The study aims at evaluating physical suitability (land and water resource) for surface irrigation development using GIS techniques. The Dedessa sub-basin was selected as a case study for this thesis work. The Dedessa sub-basin located at the Southern part of the Abbay River Basin. The study area covers an area of about 1.96 M hectares. The evaluation of land in terms of the suitability classes for surface irrigation was based on the method as described in FAO guideline for land evaluation. The essence of land evaluation is to compare or match the requirement of each potential land use with the characteristics of each kind of land. (FAO, Land Evaluation for Development. Soil bulletin) A land unit is obtained by the overlaying of selected theme layers, which has unique information of land qualities for which the suitability is based on. The selected theme layers for this study include soil types, with their corresponding physical and chemical characteristics that affect irrigation agriculture, land cover, and slope layer, which is derived from the Digital Elevation Model of the study area. As its being the most limiting factor for the realization of, especially for surface irrigation method, the slope layer was used as the base map for the overlaying analysis. The suitable land identified categorized according to the different climatic zones along the Dedessa River in the sub-basin. They are mostly concentrated in the central and Eastern part of the sub-basin along the Dedessa and Wama River valleys. The 95, 90, 85, and 80 percentage time exceedence flow of the available surface water in the respective climatic zones was estimated and the area that can be irrigated with this flow was computed using the selected climatic station data and estimated ETo.



Digital Elevation Model