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

Abstract

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 growing demand. Nonetheless, the long-term sustainability of groundwater supply and its quality is threatened by multiple anthropogenic pressures. This study assessed the quality and suitability of groundwater in peri-urban communities in Accra, the capital city of Ghana for domestic and irrigation purposes. In this regard, thirty-six (36) groundwater samples were analysed for physico-chemical parameters including pH, total dissolved solids, electrical conductivity, and ions including nitrates and chlorides. The water quality index (WQI), sodium absorption ratio and relevant statistical plots were employed in assessing the quality and suitability of the groundwater for domestic and irrigation purposes. The results indicate that for most samples, almost all parameters measured were within the WHO recommended limits for drinking water. This is reflected in the classification of 92% of water samples as good or excellent quality for domestic purposes using WQI. The results show that the abundance of ions in groundwater as: Na+ > Ca2+ > Mg2+ > K+ for cations and Cl– > SO42– > HCO3– > F– > NO3– for anions. Principal component and hierarchical cluster analysis 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 generally reflect background levels and have implications for groundwater development and management in the rapidly developing capital of Ghana.