Abstract:
Groundwater resource development in Ghana contributes substantially to the socio-economic development of Ghana. Utilization of water for domestic, irrigation and industrial purposes for about 80% of the rural – urban population in the Kwabenya Community within the Ga East Municipality are primarily dependent on existing groundwater resources. However, groundwater potential is under serious threat and run a high risk of pollution by agrochemicals, municipal, industrial, and domestic wastes due to population explosion. The indiscriminate sitting of boreholes and hand dug wells in the Kwabenya community without proper planning have raised concerns about potentially adverse effects on human health and the environment.
In this study, the quality of water from private hand dug wells and boreholes within Kwabenya community in Greater Accra region of Ghana were assessed. The physicochemical, bacteriological and nutrient levels, as well as, the seasonal trends in the groundwater were also evaluated. The study also assessed the origin and mixing pattern of the groundwater in the Kwabenya locality using stable isotopes and determines the water quality index of groundwater within the community.
The results of the study revealed that water from boreholes and hand dug wells sampled were slightly acidic to basic with few localized areas showing strong acidic groundwater. Majority of the groundwater samples analyzed (85 %) were found to be fresh since their total dissolved solids (TDS) did not exceed 1000 mgL-1 (WHO, 2011). The total dissolved solids (TDS) of the hand dug wells varied from 256 mg/L to 761 mg/L while that of the borehole varied from 120.50 mg/L to 1003 mg/L. Relatively low concentrations of inorganic constituents were found in water from hand dug wells and boreholes from the study area. Generally, the major anions (chloride [Cl-], nitrate [NO3-], and sulphate [SO42-]) in the groundwater samples were low. The low values suggested minimal anthropogenic influence because of the minimal industrial activity in the Ga East District. The hand dug wells were found to have higher nitrate content than the boreholes. Hand dug wells and boreholes which were closer to septic tanks, soakaway and KVIPs measured nitrate concentration above the WHO limit (2011). The concentration of the major cations were in the order of Na+>Ca2+>K+>Mg2+. The hydrochemical facies identified Na-Cl as the main water type within the locality.
Hand dug wells and boreholes which were less or about 10 m away from septic tanks, soakaway and KVIPs were found to be highly contaminated with total coliform, faecal coliform, E. coli and total heterotrophic bacterial.
Stable isotope composition of δ18O and δ2H of hand dug wells and boreholes showed that recharge is by direct precipitation of -3.5 δ 18O ‰ VSMOW rainfall infiltration and plot of conductivity versus δ18O confirm complete dissolution as precipitation dissolves materials of the aquifer.
The results of the computed water quality index (WQI) indicated that most of the groundwater in the study area (63.64% hand dug wells and 68.42% boreholes) showed ‘excellent water’ quality and 32.25% were found to be of poor quality and unsuitable for drinking without treatment.