HYDROGEOCHEMICAL CONTROLS ON GROUNDWATER QUALITY IN THE WEST MAMPRUSI AREA, NORTHERN GHANA

In the Northern Region of Ghana where groundwater is scarce and borehole success rates are low, not much research has been done in the area of groundwater quality. Generally, groundwater is a safer source of drinking water than surface water, but there are naturally occurring elements such as fluoride and arsenic in groundwater that can pose health risks. A better characterization and understanding of geochemical controls on groundwater quality will help predict areas of poor quality groundwater, leading to higher quality drinking water and lowering costs. This study focuses on the West Mamprusi area of Northern Ghana, where geology varies from coarse- to fine-grained sedimentary rocks to a basement complex consisting of metavolcanics, metasediments, and granitoids. Forty-seven (47) groundwater samples are being analyzed for major ions and trace elements, and 27 samples are being analyzed for carbon-13 isotopes.

Analyses from the water samples, in conjunction with water quality data from 120 other boreholes in the district are being included in statistical analyses. These techniques include Piper diagrams, principal component analysis, and cluster analysis, which are being used to categorize the water chemistry and determine important water-rock interactions within the aquifer that control the chemistry of the groundwater. Geochemical modeling with NETPATH using major ions and carbon-13 shows saturation with respect to minerals, shedding light on geochemical processes observed within the aquifer.

The results of this study will lead to a better characterization and understanding of the geochemistry of the West Mamprusi area. Preliminary results have shown high salinity rates in the Voltaian sedimentary rocks where accessory minerals are common and low salinity rates in the Birimian basement complex. Maps created in GIS will show element concentrations, focusing on potentially harmful elements. Hydrogeologic and geochemical data from this study will ultimately be made available to district assemblies of the West Mamprusi area to be used in making sound groundwater management decisions for the communities.