Integrated Assessment of Groundwater Influenced by a Confluence River System: Concurrence with Remote Sensing and Geochemical Modelling

There is growing evidence of escalating pollution threats to groundwater owing to change in mineral phase chemistry arose due to high anthropogenic activities. This manuscript primarily deals with the results of physicochemical parameters in relation to the hydro-geochemistry of groundwater influenced by two confluence river systems i.e. Ganga and Yamuna at Allahabad, India. The groundwater samplings was performed in two seasons namely pre-monsoon and post-monsoon respectively to explore the link of seasonality and impact of land use change on mineral phase and quality of groundwater in the region. Computation of saturation index for both the seasons was performed independently by WATEQ4F geochemical model. The analysis indicates that Halite and Brucite solutions showed a very high degree of under-saturation in both seasons indicated that they were largely affected by the dilution. The chemical categorizations of groundwater samples represented through piper diagram suggested a common composition and origin. It has been found that sodium, magnesium and calcium were the most dominant cations present in the groundwater of the study area. Most of the stations, the water facies during the pre-monsoon season was showing a Mg-HCO3 type (70 %) water while in post-monsoon season its dominant nature was Na-HCO3 type (50 %). The investigation of salinity hazard, residual carbonate and magnesium hazard indicates that groundwater during the both pre and post-monsoon for some of the stations were even not fit for irrigation purpose. At some stations high fluoride content were also reported having elevated concentrations of fluoride in the water samples as compared to WHO/BIS standards. The analysis of land use estimated from Landsat TM imagery and seriation analysis based on iterative performances of permutation matrix suggests that the main driving factors for hydro-geochemical changes are governed by the human induced factors followed by the natural processes.