Caracterização da qualidade da água na represa Dr. João Penido (Juiz de Fora, MG)

Abstract

“Dr. João Penido” dam is the main drinking water supply in Juiz de Fora (MG). Despite its importance, no studies have been reported on its water quality, being unknown data for the scientific community. The use and occupation of the land have caused negative impact on the aquatic ecosystems. The sides of the dam are damaged and without riparian forests. There is abundance of macrophytes in various sites of the water mirror and in the regions of the tributaries, indicating that there are processes of eutrophyzation. In this dissertation, it was carried out the water quality monitoring of the surface of the reservoir and of two main tributaries: "ribeirão dos Burros" and "córrego da Grama" (Burros brook and Grama stream). The samplings were performed monthly, during one year. Sixteen parameters were analyzed in five sample sites: three at the dam and one in each tributary. The main objective was to characterize the water quality of the water supply. The parameters analyzed were compared with the CONAMA Resolution 357/2005 (BRAZIL, 2005), which refers to freshwater, class 1. It was observed that the dissolved oxygen, pH, turbidity, BOD and total phosphorus were in disagreement with that resolution. The Water Quality Index (WQI) was calculated for the sample sites, with the use of nine parameters. It was noticed predominance of the “medium” level in the fluvial and lacustrine zones in the dam. The intermediate zone showed “good” level in all samples analyzed. The tributaries showed results which varied from “bad” to “good”, mainly with “medium” level. It was also calculated the Trophic State Index (TSI) for the sample sites, with the use of the parameters total phosphorus and chlorophyll a. It was noticed predominance of “mesotrophic” state for all sites, and there was a register of “supereutrophic” for tributary and “eutrophic” for the dam, in July of 2009 (dry season). Hopefully, the studies demonstrated in this work may contribute with the integrated management of Dr. João Penido dam, in order to ensure good quality water supplies for people now and for future generations. Water quality monitoring is an essential tool, which helps to make the right decisions in relation to preservation of the water supply.