Assessing groundwater quality in peri-urban Accra, Ghana: Implications for drinking and irrigation purposes

In many developing countries, cities are faced with rising water demand due to rapidly increasing population, inadequate municipal water supply and growing sanitation pressure. Consequently, groundwater resources are being heavily relied on to meet the demand. However, the long-term supply and quality of groundwater are threatened by multiple anthropogenic pressures. This study assessed the quality and suitability of groundwater available to more than 600,000 inhabitants in several peri-urban communities in Accra, the capital city of Ghana. Thirty-six (36) borehole samples were analysed for their suitability for domestic and irrigation purposes based on relevant physicochemical parameters. In addition, water quality index (WQI), sodium absorption ratio, and relevant statistical plots were employed to assess the groundwater's quality and suitability for domestic and irrigation purposes. The results indicate that almost all parameters measured were within the WHO recommended limits for drinking water for most samples. This is reflected in the classification of 92% of water samples as good or excellent quality for domestic purposes using WQI. The abundance of ions in groundwater followed the trend: Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ for cations, and Cl⁻ > SO₄²⁻ > HCO₃⁻ > F⁻ > NO₃⁻ for anions. By using principal component and hierarchical cluster analyses, the study identified mineral dissolution and anthropogenic activities as the main factors influencing groundwater chemistry in the study area. These factors resulted in mixed water types, viz: Na–Ca–Mg–Cl and Na–Ca–Mg–SO₄, and Na–Cl as the dominant water type. Classifications based on the Wilcox and USSL diagrams suggest that groundwater in the study area is generally suitable for irrigation. Given that these boreholes are new, the results from this study represent background levels and have important implications for groundwater development and management in the rapidly developing capital of Ghana.