The metropolitan region of Sao Paulo represents the largest urbanized area agglomeration of the country, leading to a complex management with regard to the supply of water in sufficient quantity and quality to meet the inserted demand. The Biritiba-Mirim reservoir is part of the watershed responsible for providing this feature. Inserted in the Alto Tiete Producer System, the same has been the object of analysis in this Thesis about water quality and the possible changes in biogeochemical cycles under the pressure caused by human activities in the region. Two systems were analyzed, the water and sediments in suspension in which several samples were colleted in two sectors of the lacustrine environment, one in which agricultural activities were close to the body of water and another where there was the protection of riparian vegetation by comparing these areas. It was determined physical and chemical parameters pH, dissolved oxygen, oxidation-reduction potential, electric conductivity and turbidity). The suspended sediments were chemically analyzed qualitatively and semi quantitatively using a scanning electron microscopy (SEM). The mapping of the reservoir as for its current use and occupation, considering the regional, social, hydrological, geological, pedological and geomorphological features were raised through remote sensing images and bibliographical review and update. The results showed statistically significant differences between these two areas as physical and chemical parameters analyzed. Presence of P,