Assessment of Groundwater Quality and Identification of Hydrogeochemical Process in Hard Rock Terrain

Abstract

Environmental geochemical studies are carried out to assess the groundwater quality and identification of hydrogeochemical process in hard rock terrain of Bhongir watershed nearer to the Greater Hyderabad. A total of thirty-eight groundwater samples were collected and analysed for important physicochemical parameters, anions and cations. The analytical data of alkalis (Na⁺ and K⁺) and alkaline earths (Ca²⁺ and Mg²⁺), reveal that high concentration of Na⁺ than others (Na > Ca > Mg > K) is probability due to the loss of Ca²⁺ and Mg²⁺ and gain of Na⁺ by the cation exchange process. Among the anions, bicarbonate is identified in majority of the samples in the following order HCO₃ > Cl > SO₄ which confirms that all carbonate minerals might have been dissolved and leached to the groundwater system. Most of the samples (81%) are exceeding the WHO allowable limits of electrical conductivity for drinking. The data sets further suggest that the water chemistry in the study area is not homogeneous and influenced by complex contamination sources and geochemical processes. Besides, highest concentration of nitrate (565.7 mg/L), sulphate (414 mg/L) and chloride (1444 mg/L) firmly suggests the impact of agricultural activities such as irrigation return flow, fertilizer application on water chemistry. The elevated concentrations of fluoride (i.e. maximum 4.1 mg/L) in most of the water samples (66%) reveal the origin and geochemical mechanisms, i.e. rock–water interaction is driving its enrichment. As majority of the parameters are above the permissible limit, the groundwater is not potable for drinking.