Assessing surface water quality under anthropological influences in the Caí River, Rio Grande Do Sul, Brazil

Abstract

ABSTRACT The Caí River plays a fundamental role in the hydrologic systems of Rio Grande do Sul (RS), the southernmost state in Brazil, and significantly contributes to maintaining the environmental quality of the region through which it flows. This study aims to examine the surface water quality of the Caí River basin in its middle section, based on a water quality index calculation, and to apply a qualitative protocol to the environmental conditions of the water resource and its environment. Nine physicochemical and microbiological parameters were monitored at five collection points located upstream, downstream, and in the central area of Feliz City for a year. The results showed water quality index (WQI) values between 51 and 78 during the evaluation period. Of the samples collected and analyzed, 36% were on the ‘good’ quality scale and 64% indicated ‘reasonable’ water quality. The results showed that water quality was considered good in the studied area. However, some parameters, such as biochemical oxygen demand (BOD) and total phosphorus, did not meet standards recommended by current legislation.