Development of water quality index for Godavari River (India) based on fuzzy inference system

Abstract

In view of higher pollution strength of Indian rivers, prevalent water quality indices of the western countries like the National sanitation foundation water quality index (NSFWQI) and indigenous Vedprakash water quality index (VWQI) cannot truly represent the water quality status of Indian rivers. To overcome this limitation, fuzzy modeling has been used in this study for the prediction of water quality of Indian rivers. The fuzzy models have been developed using triangular and trapezoidal membership functions with centroid, bisector and mean of maxima (MOM) methods for defuzzification. It is observed that the fuzzy model with triangular membership function utilizing the bisector method of defuzzification performs better, compared to triangular and trapezoidal membership function utilizing the centroid and MOM method of defuzzification. The values of water quality index based on fuzzy logic have been compared with the NSFWQI and VWQI. It is observed that the values of fuzzy based water quality index are more representative to actual river water quality status of Indian rivers as compared to NSFWQI and VWQI. This is due to the fact that the adopted fuzzy logic approach is equally sensitive to all parameters and can truly represent the minor change in the value of any parameter, especially in case of river stretches having higher pollution.