Utilizing Indicator Kriging to Identify Suitable Zones for Manual Drilling in Weathered Crystalline Basement Aquifers
Manual drilling offers a practical and affordable method of increasing access to groundwater supply in regions struggling with economic water scarcity. However, manual techniques are limited to specific hydrogeological contexts and must be sited appropriately. Indicator kriging is proposed as an interpolation method that builds upon previous efforts to identify suitable zones for manual drilling, particularly in weathered crystalline basement aquifers. This approach allows for heterogeneity within weathering profiles and provides probability mapping of success for regional planning. Modeling was conducted in the Upper East Region of Ghana using available borehole-log data, including: transmissivity, static water depth, laterite thickness, depth to hard rock, water quality parameters, and the degree of weathering. Indicator kriging interpolations predicted binary variables with over 90% accuracy. The model predicts that drilling into highly weathered layers will be common, and percussion techniques will be necessary to reach sufficient depths. The results suggest that suitable zones occur near Bolgatanga, Bawku, and Zebila, which coincide with historical drilling efforts in the central and eastern portions of the region. The original dataset was derived from the Hydrogeological Assessment of the Northern Regions of Ghana Project (HAP) implemented by SNC-Lavalin, Institut national de Recherche Scientifique (INRS) and the Water Resources Comission (WRC) of Ghana, and was supported by the Canadian International Development Agency. Hydrogeological data was collected and aggregated for the Voltaian Sedimentary Basin and Precambrian Basement complexes in Ghana from numerous sources. The data was compiled into a GIS databased for further study and analysis of the groundwater resources in Ghana. For this study, the dataset was obtained from the University of Ghana upon request with a focus on manual drilling feasibility. Borehole records were manipulated with various interpolation methods within the Upper East Region in ArcGIS, as described within the journal article.