Hydrogeochemical processes and quality assessment of groundwater in Dumka and Jamtara districts, Jharkhand, India

The hydrogeochemical study of groundwater in Dumka and Jamtara districts has been carried out to assess the major ion chemistry, hydrogeochemical processes and groundwater quality for domestic and irrigation uses. Thirty groundwater samples were collected and analyzed for pH, electrical conductivity, total dissolved solids (TDS), total hardness, anions (F⁻, Cl⁻, NO₃ ⁻, HCO₃ ⁻, SO₄ ²⁻) and cations (Ca²⁺, Mg²⁺, Na⁺, K⁺). The analytical results show the faintly alkaline nature of water and dominance of Mg²⁺ and Ca²⁺ in cationic and HCO₃ ⁻ and Cl⁻ in anionic abundance. The concentrations of alkaline earth metals (Ca²⁺ + Mg²⁺) exceed the alkali metals (Na⁺ + K⁺) and HCO₃ ⁻ dominates over SO₄ ²⁻ + Cl⁻ concentrations in the majority of the groundwater samples. Ca–Mg–HCO₃ is the dominant hydrogeochemical facies in 60 % of the groundwater samples, while 33 % samples occur as a mixed chemical character of Ca–Mg–Cl hydrogeochemical facies. The water chemistry is largely controlled by rock weathering and ion exchange processes with secondary contribution from anthropogenic sources. The inter-elemental correlations and factor and cluster analysis of hydro-geochemical database suggest combined influence of carbonate and silicate weathering on solute acquisition processes. For quality assessment, analyzed parameter values were compared with Indian and WHO water quality standards. In majority of the samples, the analyzed parameters are well within the desirable limits and water is potable for drinking purposes. Total hardness and concentrations of TDS, Cl⁻, NO₃ ⁻ _, Ca²⁺ and Mg²⁺ exceed the desirable limits at a few sites, however, except NO₃ ⁻ all these values were below the highest permissible limits. The calculated parameters such as sodium adsorption ratio, percent sodium (%Na) and residual sodium carbonate revealed excellent to good quality of groundwater for agricultural purposes, except at few sites where salinity and magnesium hazard (MH) values exceeds the prescribed limits and demands special management.