Development of specific water quality index for water supply in Thailand

Abstract

In this study, the specific water quality index for assessing water quality in terms of water supply (WSI) usage has been developed by using Delphi technique and its application in Thai rivers is proposed. The thirteen parameters including turbidity, DO, pH, NO3-N, TDS, FCB, Fe, color, BOD, Mn, NH3-N, hardness, and total PO4-P are employed for the estimation of water quality. The sub-index transformation curves are established for each variable to assess the variation in water quality level. An appropriate function to aggregate overall sub-indices was weighted Solway function that provided reasonableresults for reducing ambiguous and eclipsing effects for high and slightly polluted samples. The developed WSI couldbe applied to measure water quality into 5 levels - very good (85-100); good (80-<85); average (65-<80); poor (40-<65)and very poor (<40). The proposed WSI could be used for evaluating water quality in terms of water supply. In addition, it could be used for analyzing long-term trait analysis and comparing water quality among different reaches of rivers or between different watersheds.

Keywords

• water quality evaluation
• specific water quality index
• water supply
• Delphi technique
• weighted Solway function