Delineation of potential groundwater recharge zones using analytic hierarchy process-guided GIS in the semi-arid Motloutse watershed, eastern Botswana

摘要

Study regionThe Motloutse Watershed is located in eastern Botswana.Study FocusThis study investigates the spatial distribution of recharge in the semi-arid watershed using Weighted Overlay Analysis.The overuse of groundwater in the Motloutse catchment to support domestic and industrial expansion has generated the need for the determination of areas where renewable storage to groundwater may occur. A select of parameters known to have influence on recharge were considered for input into the analytic process and included lithology, lineament density, ground slope, soil type, soil thickness, and drainage density. A thematic map for each parameter was prepared, reclassified into high, moderate and low potential for recharge. Analytic Hierarchy Process was applied to rank the importance of each parameter relative to one another concerning groundwater recharge. Potential groundwater recharge sites were delineated using Weighted Overlay tool of ArcGIS software.New Hydrological Insights for the RegionHigh recharge sites cover 8% of the catchment and correspond to places underlain by sandstones and fractured basaltic outcrops as well as areas covered by thick sandy soils. Moderate recharge occurs in 78 % and low recharge in 14 % of the catchment area. The results from this study are useful for selecting areas for more focused studies on recharge and also form a significant decision support tool for sustainable and equitable utilization of groundwater resources within the Motloutse catchment.