Aquifer (Hydrogeological) Study of Southern Areas of Prayagraj,India

The physical and chemical characteristics of spring and well water samples were studied for two years to assess the origin of groundwater and determine the factors driving the geochemical composition. The ionic speciation and mineral dissolution/precipitation were calculated. Water wells, characterising groundwater circulation at shallow depths are moderate to high mineralised waters of Na-HCO₃ type. In contrast to the shallow environment, the CO₂-rich, deeper water is of the Ca-HCO₃-SO₄ type and undergoes significant changes in the baseline chemistry along flow lines with increasing residence time. The main factors controlling the groundwater composition and its seasonal variations are the geology, because of the presence of carbonate formations, the elevation and the rate of karst development. In both groups, the carbonate chemistry was a diagnostic approach. The super-saturation with respect to calcite indicates CO₂ degassing, occurring either inside the aquifer in open conduits or at the outlet in reservoirs. Interaction between groundwater and surrounding rocks is believed to be the main process responsible for the observed chemical characteristics of groundwater in the study area. Mathematical equations were also derived involving the hydro geological variables for better prediction of the aquifer.