Groundwater Recharge Zone Mapping Using GIS-based Analytical Hierarchy Process and Multi-Criteria Evaluation: Case Study of Greater Banjul Area
Adama Gassama Jallow, Djim M. L. Diongue, Huguette C. Emvoutou, Daouda Mama, Sérigne Faye
Abstract
Remote sensing (RS) and Geographic Information System (GIS) play a crucial role in understanding groundwater potential recharge in semi-arid areas. In this present study, groundwater recharge zone map is delineated for the shallow aquifer in the Greater Banjul Area (GBA) using GIS, RS and Multi-Criteria Evaluation (MCE) technique utilizing seven criteria (geology, land-use/cover, slope, drainage density, soil texture, groundwater fluctuation and aquifer transmissivity). Analytical Hierarchical Process (AHP) is used as MCE technique to normalize the weights of the various criterion. Each class of the different themes was assigned suitable score and normalized using a Fuzzy membership algorithm. Thematic layers were integrated using Weighted Linear Combination (WLC) in a GIS platform to generate groundwater recharge zone maps. The recharge map thus obtained was divided into four classes (poor, moderate, good, and very good) based on their influence to groundwater recharge. Results indicates that about 10.5 % of the total study area falls under âpoorâ and âmoderateâ zone and cover the estuarian portion of GBA, 40% of the total area falls under âvery goodâ zone which is a good indication for future artificial recharge planning and potential drilling of boreholes.