Hydrochemistry of groundwater in the Savelugu–Nanton District, Northern Ghana

Calcite (CaCO₃), dolomite [CaMg(CO₃)₂], silicate dissolution, ion-exchange and reverse ion-exchange reactions are the predominant processes influencing groundwater quality in the Savelugu–Nanton District. The main objective of this study is to characterize groundwater and delineate water–rock interactions responsible for the chemical evolution of groundwater in the District. Eighty-one (81) boreholes were sampled for quality assessment. Results showed that, the pH of the boreholes are slightly acidic to basic ranging from 6.1–8.3 pH units. Conductivity values are low to high ranging from 147–23,200 μS/cm with, 23.5 % of groundwater within the study area being either brackish (1,500–5,000 μS/cm) or saline (>5,000 μS/cm) and therefore, unsuitable for potable purposes. TDS values in groundwater varied widely, ranging from 62–11,900 mg/L. 61.7 % of groundwater within the study area are fresh (TDS < 500 mg/L). The chemical constituents generally, have low concentrations and are within the WHO (Guidelines for drinking water quality. Revision of the 1993 Guidelines. Final Task Group Meeting. Geneva, 2004) Guideline values. The relative abundance of cations and anions in the groundwater are in the order: Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ and HCO₃ ⁻ > Cl⁻ > SO₄ ²⁻ > NO₃ ⁻ respectively. Multivariate statistical analysis showed expected process-based relationship derived mainly from the geochemical and biochemical processes within the aquifer. Hydrochemical facies using piper plot of major ions showed one major hydrochemical water type. The Ca–Mg–HCO₃ water type. Due to the high cost of drilling of boreholes coupled with the high percentage (×1 %) of people without access to potable water in the Northern Region, it is recommended that the Government of Ghana and other stakeholders within the Water Sector take immediate measures to reduce (to recommended limits for potable uses) the levels of dissolved solids either by installing Reverse Osmosis equipments on such boreholes or employ other relatively known cheaper methods to reduce the dissolved solids to recommended limits. High yielding boreholes with hydrochemical parameters within WHO guideline limits in the Savelugu–Nanton District could also be mechanized to serve a wider area.