Geochemical assessment of groundwater in a desertic region of India using chemometric analysis and entropy water quality index (EWQI)

Natural processes and anthropogenic activities are the major factors that can deteriorate groundwater quality. This study provides an insight into groundwater quality and its drinking suitability in part of Rajasthan. The physicochemical analysis of parameters (pH, EC, TDS, Ca2+, Mg2+, Na+, K+, F-, HCO3-, Cl-, NO3-, and SO42-) was conducted in the laboratory. High alkalinity and hardness were significant problems in most of the groundwater samples. The maximum concentration observed for F- and NO3- was 3.8 mg/L and 110.70 mg/L, and around 27.66% and 12.76% of samples, respectively, were above the WHO permissible limits. The dominant natural processes affecting groundwater quality were assessed through chemometric analysis, geochemical modeling, and conventional plots. Carbonate dissolution, reverse ion exchange, silicate weathering, evaporite dissolution, and rock-water interaction were the dominant processes responsible for groundwater's chemical characteristics. However, anthropogenic activities like improper drainage of sewage and fertilizer use in agriculture also impact groundwater quality. Cluster analysis resulted in 4 groups representing specific geochemical properties within each group. Entropy-based weights of the water quality parameters were used to calculate the entropy water quality index (EWQI) to assess groundwater suitability for drinking. Nearly 25.53% of samples (EWQI > 100) were unsuitable for drinking. Policymakers can assess groundwater suitability using EWQI to prioritize the interventions for providing suitable quality water for domestic use. This study's findings are relevant from the public health perspective and in understanding water quality parameter's spatial distribution.