Groundwater Evaluation and Borehole Failure in West Gonja District, Ghana: Insight from Geophysical and Lithological Analyses

Abstract

Ellen Benyarku* and Kristine Walraevens

The Voltaian Basin faces a persistent issue with borehole yields and unsuccessful boreholes due to its complex geological settings which affects groundwater accessibility in the areas that are underlain by this geological setting. West Gonja District, the study area faces issues of unsuccessful boreholes and low yields due to the poorly understood geology and the complexity of the Voltaian Basin. Recharge studies indicate sufficient replenishment, prompting a need to understand the causes of borehole failure. From the VES data, the results indicate that the geoelectric sections of the area is underlain by 3–5 layers: for Damongo Formation the topsoil/laterite (42.8–20704 Ωm), for the moist saprolite/mudrock/shale intercalated with sandstone (4.19– 824 Ωm), clay/intercalated sandstone (9.66–11087 Ωm) and the fresh basement (0.31–21000 Ωm). For Anyaboni Sandstone Formation and other formations, the topsoil/laterite (27.3-13002 Ωm), for the saprolite/shale/sandstone (8.03-12943 Ωm), shale/weathered sandstone (2.81–15791 Ωm), sandstone (0.825–51529 Ωm) and the fresh basement clay (0.669-16.5 Ωm). These results indicate that the Anyaboni Sandstone Formation and the other formation which are underlain predominantly by sandstone are more productive for groundwater exploration as against the Damongo Formation due to the presence of the intercalation in the sandstone which are poor and thin fractured. Deeper wells into the subsurface are not recommended in this area, especially within the Damongo Formation. During VES interpretation, layers should be increased up to 10 layers for better delineation of aquifer units and intercalations present, especially in the Damongo Formation. Unsuccessfully drilled boreholes and low yields identified within the Voltaian Sedimentary Basin are primarily caused by the complex geology as well as the interpretation of VES data during analysis.

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