Mapping Groundwater Potential and Land Suitability for Surface Irrigation Using Geo-Spatial Techniques in Keleta Watershed, Awash River Basin, Ethiopia

Abstract

In Ethiopia, surface water is the primary source of agricultural production, although groundwater is rarely used for crop production. Many irrigation systems derive their water from river diversions, which benefit only farmers who own land near the irrigation project, while others depends on rainy season. Using groundwater resources for irrigation could be a viable option for alleviating the food shortages. The broad aim of this study was to delineate the groundwater potential zone and potential land suitability zone for surface irrigation using GIS-based Multi-Criteria Decision Analysis (MCDA) techniques in the Keleta watershed, Awash River Basin, Ethiopia. The main influencing parameters to be considered to identify the groundwater potential zone (GWPZ) include landform, lithology, slope, soil, rainfall, land use/land cover, drainage density, and lineament density, while soil type, slope, soil drainage, soil depth, and land use/cover were considered for potential land suitability zone (PLSZ). The thematic layers of each factor were prepared and their weights were assigned, normalized, and ranked based on their suitability to groundwater occurrence and irrigation land suitability using Fuzzy-Analytic Hieraricy Process (FAHP)through Pair-wise Comparsion Matrix (PCM). The weighted overly analysis tool was used to develop GWPZ and PLSZ by integrating all reclassified thematic maps. The result revealed that the area can be categorized into three different classes such as low potential 59.18km2 (5.04%), moderate potential 722.16km2 (61.51%), and high potential 39.66km2 (33.45%) for GWPZ whereas marginally suitable 139.38km2 (11.87%), moderately suitable 809.37km2 (68.94%) and high suitable 225.25km2 (19.19%) for PLSZ. This indicates the study area has more groundwater potential and irrigation land suitability zone as compared to its total areal coverage. The delineated GWPZ was verified with the existing water invertory point data in which, 88% of the total were matched with its corresponding zones. The sensitivity analysis for each map was done and hence, slope was the most sensitive parameters whith the mean variation index of 1.89% for GWP and 1.58% for PLS. In the northeast and northwest parts of the area, the high GWP and PLS were found in the same area, therefore on-land surface irrigation development will be used in this area with minimum initial cost and the rest area will be irrigated from high GW perspective area through the conveyance system.