Contribuição da cidade de botucatu - SP com nutrientes (fósforo e nitrogênio) na eutrofização da represa de Barra Bonita

Abstract

It was compared the level content of nutrients (phosphorus and nitrogen) at the Lavapés brook with level content at source and cross-town (domestic sewage discharge) and also with the level/ content at source and mouth the Capivara river. The head-waters of the Capivara river, as well as those of the Lavapés brook, are on the highlands (at the top of the sierra/ mountain-range) and its waters flow into the Barra Bonita dam on the Tietê river (Figure 1). One of its sources is near a Lavapés source and their mouths are close to each other at the Barra Bonita dam. Along the banks of both streams the use of land and the types of soil are alike, which implies in a similar rural pollution; so, what makes the difference in water quality between them is the urban pollution affecting the Lavapés brook in Botucatu. Therefore it was evaluated the contribution of nutrients (phosphorus and nitrogen) to the Barra Bonita dam of the Capivara river and the Lavapés brook. Taking into account the domestic sewage carried into the Lavapés brook in Botucatu, it was estimated the nutrient load of its silt (kept in its silt) and the one discharged into the Barra Bonita dam. The study was conducted during drought, without overflows, which made it possible to measure the near-mouth-flow and to evaluate the nutrient load daily discharged into the dam. It was also evaluated the dissolved oxygen, the chemical oxygen demand and the electrical conductivity. Although the results are estimated and variable in time we can conclude that pollution of the Lavapés brook waters with domestic sewage in Botucatu, besides making the use of its waters not viable and causing other (environmental) damage (financial losses), contributes to aggravating the eutrophication at the Barra Bonita dam.