Water quality of Alegre River, Espírito Santo

Abstract

This work was carried out to determine the Alegre River water quality. It was analyzed the following physical-chemistry characteristics of water: temperature, acidity, dissolved oxygen-DO, turbidity, total solids, total nitrogen, total match, biochemical demand of oxygen-BDO) and biological (fecal coliformes).  Water was colected in four sample stationsalong the Alegre River in October, December/2003 and March and July/2004). The Water Quality Index (WQI-CETESB) was used to define the water quality. It was verified that the water quality of Alegre River in downstream of district presents the worst quality with high values of fecal coliforms, BOD and low rates of Dissolved Oxygen due to the domestic sewage without previous treatment. In the rainfall season (December/2003 to March/2004), it was observed a decrease in the Water Quality Index, due to the great increase of turbidity and the  total solids as a result of  the runoff sediment yield. These results point out to the lack of the soil conservation practice  in the Alegre watershed, with consequent increase of soil loss rate. The water quality varied from bad to average at the time of study.