Trophic state index for heavily impacted watersheds: modeling the influence of diffuse pollution in water bodies
Laís Carneiro, Anaís Ostroski, Emílio Graciliano Ferreira Mercuri
Abstract
This study aims to understand the response of the trophic state index (TSI) of a reservoir under different watershed land-use scenarios. A novel methodology was applied to the Verde River Basin in the south of Brazil, which is exploited by agricultural activity and has a reservoir for water supply. An ecohydrological model was used to calculate daily nutrient concentrations in the water system, which allowed the determination of the reservoir's TSI. The authors propose a new TSI known as TSImod, considering phosphorus, nitrogen, and chlorophyll in its determination. The results indicate that TSImod may be more appropriate for classifying highly impacted environments when compared to the index currently used in Brazil. The Verde River Reservoir was classified as mesotrophic under the current land-use scenario and eutrophic under the proposed scenarios. The framework developed in this study can be replicated in other watersheds to evaluate the impacts of land-use change on water quality.