Fuzzy environmental monitoring for the quality assessment: Detailed feasibility study for the Karun River basin, Iran

Nowadays, fuzzy logic has been successfully employed to handle the environmental issues. Due to inflexible classifications and interpretative difficulties of crisp data involved in the classic water quality index (WQI), employment of fuzzy logic in water resources problems has been repeatedly recommended for decision support in ecological assessment. As a mixed-ability method, it can both provide balance in suitable and unsuitable observations, which results in incompatible outcomes and can interpret social, economic, and biological effects as membership functions of linguistic terms. Accordingly, this study aims at evaluating the Karun River water quality, based on Mamdani fuzzy approach using developing a fuzzy water quality index (FWQI), a hierarchical approach was conducted to avoid curse of dimensionality in fuzzy rules and to take the relationships between parameters in to account as well 21 parameters in the form of physicochemical, chemical, biological and heavy metal fuzzy groups were processed based on trapezoidal membership functions and the rulesets for considering the relationships between parameters. A global FWQI of 36.78 ± 2.17 has been estimated based on 2010 to 2015 data, while the assessment with NSFWQI and CCMEWQI indices scored 41.8 ± 1.33 and 33.65 ± 2.87, respectively. Based on ANOVA test, changes in global FWQI were not significant in sampling stations. Moreover, results show degradation of the water quality from upstream to downstream of the Karun watershed. These results put forward an argument in necessity of regeneration of the Karun water quality to improve ecological conditions in the region. © 2019 Elsevier B.V.