2.5 Water quality index (WQI)
WQI is the most significant tool to estimate the drinking water quality in rural, urban, and industrial regions. WQI indicates the nature of water in terms of numbers that reveal the present nature of water for any intended use (Adimalla et al., 2019b, Kirubakaran et al., 2015). The index values are calculated followed by (1) selecting and assigned weightage(wi) of each water quality parameter based its importance in the overall quality for drinking uses (2) relative weightage(Wi) is calculated from the Eqn.2 (3) calculating the quality rating(qi) for each parameter from the Eqn.3. (4) calculating the sub-index (SIi) and summation of sub-index value to estimate the overall quality of water.
\(Wi=\frac{w_{i}}{\sum_{i=1}^{n}w_{i}}\) (2)
\(q_{i}=\frac{C_{i}}{S_{i}}\times 100\) (3)
\(\text{SI}_{i}=W_{i}\)×\(q_{i}\) (4)
\(WQI=\sum\text{SI}_{i}\) (5)