G IS BBAASSED IIRRRRIIGGAATTIION SSUUIITTAABBIILLIITY AANNAALLYYSSIS A CASE STUDY IN ABAYA - CHAMO BASIN, SOUTHERN RIFT VALLEY OF ETHIOPIA

Abstract

Existing data on topography, climate, soil, land use pattern, water availability, agricultural practices, investment costs and socioeconomic practices are investigated and the irrigation suitability criteria is defined based on these variables. Digital Elevation Models (DEMs) is developed to investigate the terrain feature of the basin from the digitized Contour map of the basin and the variation in elevation as well as slope is evaluated. Stream net work characterization, mapping soil and land use units using GIS environment and defining their suitability for irrigation as well as crop development with respect to the prevailing conditions has been made. Super-imposing all these attributes in the GIS environment and identifying potentially suitable areas for crop development , suggesting appropriate method of irrigation, compiling georeferenced suitability data base(slope, soil, land use, water) for irrigation are among the main treatments undertaken during the study. Large portion of Gelana and the lower delta of Hare, Kulifo and Bilate are characterized with suitable soil units having good inherent fertility and high moisture holding capacity. Besides, these areas are with very flat land slope as observed from the DEMs which falls below 10 % and are suitable for surface irrigation. The capacity of low flow as well as 80%, 90% and 95 percentage time of exceedence flow of the available surface water in the respective sub basins