Characterization of the quality of groundwater from the major aquifers in Ghana

In Ghana, groundwater plays a very crucial role in the overall water delivery system, especially in the rural areas. This resource is being assessed for possible exploitation for irrigation projects since the over reliance on rain-fed agriculture does not auger well for national development in the face of dwindling and equally erratic rainfall patterns in the country. In this study, Q-mode hierarchical cluster analysis (HCA) and R-mode factor analysis were used jointly with Geographic Information Systems (GIS) to determine the spatial groundwater quality types in Ghana, and the spatial variation of the major sources of variation in the hydrochemistry of groundwater in the country. In addition to assisting in the understanding of the different groundwater types in the country, the study demonstrates the applicability of multivariate statistical methods in groundwater quality classification in Ghana. This study finds that two major groundwater types exist in the country: the Na-Cl groundwater types which dominate the coastal aquifers where groundwater salinity is high and attributed partly to seawater intrusion and Na-K-HCO3 groundwater types which dominate aquifers farther inland. It has also been determined that the effects of seawater intrusion on groundwater quality in Ghana is significant along the coast where over extraction of the resource has led to seawater up-coning. Farther inland, groundwater hydrochemistry is controlled principally be mineral weathering processes, among which silicate mineral weathering has been noted to be the predominant. The effects of chemical fertilizers, organic manure, and domestic sewage are significant in areas where the aquifers are relatively unconfined and shallow or where the well head is poorly protected and where agricultural activities are high. High nitrate concentrations have been noted in groundwater sample from the northern parts of the country, some parts of the forested areas and the Keta strip of the Volta region of Ghana. The oxidation of organic carbon is a minor factor because its effects are relatively insignificant when compared to mineral weathering and anthropogenic contamination. Interpolation maps have been generated to highlight the intensity of each of the major processes in the country. Groundwater quality for irrigation purposes is discussed in relation to the major hydrogeological basins in the country.