In this investigation, the geochemical progression of a total of 31 groundwater samples of pre-monsoon season was assessed with categorization based on entropy weight water quality index and risk assessment on public health in the semi-arid area of Godavari basin, Maharashtra, Central India. Graphically, the major groundwater types identified were Ca-HCO3, mixed Ca-Mg-Cl, and mixed Ca-Na-HCO3. Based on [Mg2+/Na+] with [Ca2+/Na+] and [HCO3-/Na+] with [Ca2+/Na+] plots, carbonate and silicate weathering were identified as a major geochemical process governing groundwater chemistry. The presence of reverse ion exchange process was authenticated by (Ca2+ + Mg2+) vs. (HCO3- + SO42-) and Na+ + K+-Cl- vs. (Ca2+ + Mg2+)-(HCO3- + SO42-) plots. The saturation index values for calcite and dolomite showed that these minerals were in dissolution state. The dissolution of gypsum, dolomite, and anhydrite increased Ca2+ load in groundwater which accelerated the precipitation of calcite. The high toxic level of NO3- (> 45 mg/L) was identified in 64.5% of the 31 groundwater samples, whereas F- concentration exceeded the threshold value in 12.9% of samples. Based on the entropy weight water quality index values, 70% of the samples were found to have moderate quality for drinking. In addition, health risk evaluation showed that the total hazard, due to fluoride and nitrate through oral pathways, was much higher than that through the dermal pathway. Children were found to be at high risk due to the consumption of NO3- and F- contaminated water. The calculated irrigation water quality index (IWQI) diverge from 7.4-89.2, expressing excellent to good quality for irrigation. Based on the irrigation water quality index, 90.3% of samples were found excellent for irrigation and 6.4% of good quality for irrigation. Authors recommend that continuous water quality monitoring programs along with effective management practices should be developed to avoid excessive extraction of groundwater.
Keywords: Entropy weight water quality index; Geochemical processes; Groundwater; Health risks; India; Irrigation indexes; Nitrate pollution.