Delineation of Groundwater Potential Zone Using Geographical Information System Based Analytic Hierarchy Process Technique: Case of Chiro River Watershed, Oromiya, Ethiopia

Abstract

Groundwater has greater significance in major portion of world as fresh water resource. It is one of the major components of the entire water supply for drinking and irrigation purposes. Groundwater is the only water sources for the community of study area. So, a thoughtful and proper evaluation groundwater potential area zoning is required for the utilization and management of groundwater. The general objective of this study was to delineate groundwater potential zones of Chiro river watershed using Geographical Information Systems and Analytical Hierarchy Process (AHP) techniques. The thematic layers considered in this study are extracted from existing maps lithology, geomorphology, lineament density, soil and land use/ land cover and pre-processed data which derive from SRTM DEM used for extraction of elevation, slope and drainage density map of the study area, prepared using ArcGIS software, its extension tool and Global-mapper software. The assigned weightage of influence of the various thematic layers using, the AHP method, used to allocate weightage, according to their relative importance and contribution to the availability of groundwater potential zone and finally to generate a combined map of groundwater potential in study area. GIS has ability such as users to store, document, and analyze the spatial and temporal groundwater data sets, provides decision support for groundwater management, saves much time of collecting large number of geographical data, can handle large datasets through integration with Database Management System The final result map was classified into five groundwater potential zones by integrating GIS weighted overlay analysis with AHP methods. Weighted overlay sub module from ArcGIS environment was used to integrate all thematic layers to prepare the groundwater discharge potential zones of the study area. The classifications are very high, high, moderate, and low and very low groundwater potential zone. The results show 10, 8, 42, 21.5 and 18.5 per cent of the watershed classified as very high, high, moderate, low and very low respectively The study concludes that majority of the area covered by very high potential zones as it is shown the new generated predicted groundwater potential map. The study concludes that majority of the area 42% of the area (57 Km2 ) covered by Moderate groundwater potential zones. The study suggested that, generated groundwater potential zone map will serve as useful guidelines for planners, engineers and decision makers providing quick decision- making in the management of groundwater resources.