Surface Irrigation Suitability Analysis of Southern Abbay Basin by Implementing Gis Techniques (A Case Study in Dedessa Sub-Basin)
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Date
2017-02
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Addis Ababa University
Abstract
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.
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Keywords
Digital Elevation Model