Surface water quality assessment with a fuzzy inference system

Abstract

Freshwater is a water resource that has been deteriorating due to natural causes and anthropogenic activities, requiring the evaluation of water quality, comparing the values of physical, chemical and biological parameters with a Water Quality Index. In this study, the surface water quality of the Huaura River Basin (2019-2021) was evaluated, with a fuzzy inference system (FIS), based on the Environmental Quality Standards (ECA), and the categorization of water use according to the National Water Authority (ANA), category 3: Irrigation of vegetables and animal beverages. The theoretical underpinnings of the ICARHF fuzzy index were designed in four steps: define fuzzy sets and membership function; fuzzy set operations; fuzzy logic and inference rules. The Technical Reports of two surface water quality monitoring points in the Huaura River Basin (2019-2021) were analyzed. FIS logic (ICARHF) was implemented with Matlab R2022a. The fuzzy index is correlated with the Surface Water Resources Environmental Quality Index (ICARHS) (r=0.92), accepting that there is no statistically significant difference between the two indices. The results prove that it is possible to design a fuzzy inference system to determine surface water quality, depending on the use to which the water is intended, based on the information available from governmental and non-governmental entities, even when there is little accessible information.