Proposing the minimum and maximum probable water quality indices for better water quality management in poor and underdeveloped countries (case study: Bilghan intake)

Increasing measurements costs for surface water quality assessment besides the need for continuous measurements will cause a dilemma in poor countries. Therefore, a new method is proposed to identify and predict minimum probable water quality index (MIP-WQI) and maximum probable WQI (MAP-WQI) values instead of the traditional ones by combining available WQI data and Taguchi method. The water quality data of Bilghan station on Karaj River was used for prediction and comparison of the MIP-WQI and the MAP-WQI. According to the surveys and based on proposed method, the MIP-WQI and the MAP-WQI values based on 2008's data were estimated to be 61.6 and 87.4, respectively. Whereas from 2008 to 2010, actual minimum WQI values were 65.9, 69.8 and 69.3, respectively. In addition, actual maximum WQI values were 83.1, 77.2 and 75.6, respectively. Moreover, these probable indices could be more suitable to be used for water management especially in poor and underdeveloped countries.