MAPPING GROUNDWATER POTENTIAL ZONES IN HARGEISA WATERSHED USING INTEGRATED GIS REMOTE SENSING AND AHP TECHNIQUES

Abstract

Groundwater is a critical resource, especially in arid and semi-arid regions where surface water is scarce or unreliable. In such regions, groundwater often serves as the primary source of water for drinking, agriculture, and industrial activities. It is the only source of water available on the community of the study area. Therefore, considering to this a proper assessment for identifying groundwater potential zones on the study area were required to make suitable management and utilization of groundwater potential zones. The main objective of this study was to delineate a map of groundwater potential zones of Hargeisa watershed coverage using Geographical Information Systems, remote sensing and Analytical Hierarchy Process (AHP) techniques. Seven thematic layers developed in this research are extracted from existing maps geology, rainfall, geomorphology, soil and land use/ land cover which derived from Operational land imager satellite and pre-processed data which is derived from SRTM DEM used for extraction of slope and drainage density map of the study area, prepared using ArcGIS software. In generally, all of these themes and their individual features were given weights based on their relative importance in groundwater occurrence, and the corresponding normalized weights were derived based on the Saaty's analytical hierarchy process (AHP) and a standard weighted overlay analysis were used to evaluate and generate the study's potential zones. A final thematic map was made to identify possible places for groundwater potential zones. The created map was classified into five zones: 'very low', 'low', 'moderate', 'high' and 'very high' of groundwater potential area which is covered by 130 km2(1%), 8970km2(68%), 2785km2(21%), 1305km2(10%) and 6km2(<1%) respectively. Result shows, a combination of high potential zones was found at the southwestern edge, southern and west region of the coverage. Apart from the geology and rainfall the groundwater is closely depended on slope of the area. Based on the results of the very high and high GWP zones are located in areas where the slope is very flat and the poor GWP zone is located in areas where slope class is very high. The produced groundwater potential zones are also validated using potential yield data of 136 available boreholes and dug wells in the region and the validation revealed that 81.7 % agreed the model result. The validation clearly confirms and underlines the efficiency of the combined RS and GIS methodologies used in this work as a valuable current tool for accurate groundwater resource evaluation, offering timely prospective recommendations for groundwater exploration and utilization.