Application of the Entropy Weighted Water Quality Index (EWQI) and the Pollution Index of Groundwater (PIG) to Assess Groundwater Quality for Drinking Purposes: A Case Study in a Rural Area of Telangana State, India.

In this study, the quality of groundwater was assessed in a semi-arid region of India by using an entropy weighted water quality index (EWQI) and a pollution index of groundwater (PIG). The EWQI and PIG methods were used to evaluate data on physicochemical parameters in relation to drinking water quality standards. Groundwater samples were collected from the Dubbak region, Telangana state, India, and were analyzed for pH, total hardness, electrical conductivity, total dissolved solids, bicarbonate (HCO ₃ ^- ), chloride (Cl ^- ), sulfate (SO ₄ ^2- ), nitrate (NO ₃ ^- ), fluoride (F ^- ), calcium (Ca ²⁺ ), magnesium (Mg ²⁺ ), sodium (Na ⁺ ), and potassium (K ⁺ ). The groundwater of the study region is alkaline in nature. The abundance of cations and anions based on their mean values is in the following order: Na ⁺  > Ca ²⁺  > Mg ²⁺  > K ⁺ and Cl ^-  > HCO ₃ ^-  > NO ₃ ^-  > SO ₄ ^2-  > F ^- , respectively. The calculated EWQI values ranged from 49.0 to 174.6, with an average of 93.3. Overall, EWQI data showed that only 60% of groundwater samples were of suitable quality for drinking, although only marginally, whereas the remaining 40% of samples were unsuitable for drinking purposes and would therefore require treatment. The values of PIG varied from 0.5 to 1.8, with an average of 1.0, which showed that only 63% of groundwater samples from the study area were suitable for drinking purposes.