Soft computing technique-based prediction of water quality index

Water quality plays a crucial role in management of water resources. Water quality indexes (WQIs) are frequently used methods to assess water quality for drinking purposes. A WQI can be predicted using chemical analysis which might not, however, be viable for a longer period in all country-scale rivers. Thus, in this investigation, two neural-based soft computing techniques – an artificial neural network (ANN) and a generalized regression neural network (GRNN) – and one hybrid soft computing techniques – an adaptive neuro-fuzzy interference system (ANFIS) with four membership functions – were used to predict WQIs in Khorramabad, Biranshahr and Alashtar sub-watersheds in Iran. Ten distinct physiochemical parameters were used as input variables and WQI as output. Simultaneously, a correlation plot and pairs were used to ascertain the relation of input and output variables. The soft computing techniques were compared using six fitness criteria: Nash-Sutcliffe efficiency (NSE), mean absolute error (MAE), Legates-McCabe Index (LMI), root mean square error (RMSE), mean absolute percentage error (MAPE), and coefficient of correlation (CC). Results indicated that ANN better predicted WQI than did GRNN and ANFIS. Among the different membership functions of ANFIS, ANFIS_trimf was far better than were the others. Thus, it was concluded that ANN was a viable tool for the prediction of a WQI.