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)