Assessment of many WQI models and development of new WQI model

The water quality index (WQI) is widely used to assess water quality. In all WQI models, selected parameter 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 introduced based on site-specific standards for a particular region and give eclipsing, dichotomous, ambiguity, rigidity, and uncertainty problems. In the present work, an effort is made to test many of the applicable WQI models using many logical conditions. The results showed that no one of the tested models satisfies these conditions. The aim of the present work is to develop a WQI model that can be used universally (regardless of the standard used) and covers different uses of water (drinking, recreational, irrigation, or industrial). Moreover, it can overcome the previously mentioned problem. The suggested new WQI model developed in this work succeeded in achieving these two goals.