Influence of watershed land use on water quality in the state of Santa Catarina, Brazil

Abstract

The inappropriate use of water resources by human actions compromises the balance between natural and anthropogenic factors. In this study, exploratory and field research were conducted with a scope of quantifying, based on satellite imaging, the use and occupation of land on the banks of the Itajaí-Açu River, the largest watercourse in the Itajaí River Basin, located in the State of Santa Catarina, Brazil. Five sampling points were allocated along the river at different times of the year to analyze water quality using chemical and biological indicators. The characterization of land use and occupation was carried out with Sentinel-2B satellite images at 10m resolution and QGIS software. Version 3.6.3 of the R Software was used to consolidate the data. The land use was categorized into several classes, the most representative of which was vegetation, which presented coverage of 34.42%, followed by the pastures and open fields class, with 27.83%, agriculture, with 18.18%, and urban areas, with 16.59% coverage. Our study showed that 62.6% of the river’s base was affected by anthropogenic influence, characterizing an environment severely altered from its normal state. The results obtained in the statistical analysis revealed a directional correlation between land use and water quality, thus indicating that cities on the banks of watercourses are major sources of potential contaminants. Among the classes of land use, the presence of vegetation along the riverside territory attenuated part of the load of pollutants launched into the Itajaí-Açu River. This finding highlights the importance of conserving the vegetation alongside the river to maintain water quality and, consequently, preserve the ecosystem’s biota.