assessment of many WQI models and development of new models

Water quality index (WQI) is a widely used term to assess water quality. In all WQI models, selected parameters data are transformed into many steps to a single number. Since the work of Horton (1965), a lot of WQI models have been developed. However, all models suffer from many problems such as they are developed based on site-specific standards for a particular region and they give eclipsing, dichotomous, ambiguity, rigidity, and uncertainty.
In the present work, many logical conditions are set to test many applicable WQI models. The results showed that all of the tested models failed to pass the test. There is a need for universal WQI that can be applied universally covering different uses of water and at the same time can pass the above logical conditions. The present work aims to develop such a model. New four WQI models (referred to as M1WQI, M2WQI, M3WQI, and M4WQI) are developed in this work and it is found that it passed all of the set conditions. Moreover, it can be applied universally (regardless of the standard used) and for any purpose of water use (drinking, recreational, irrigation, industrial)