Over the last decades the acceleration of the industrialization and urbanization processes together with the intensive agricultural
practices have resulted in an impact on the Piracicaba river basin, state of São Paulo, Brazil. The source rivers drain from
an area of low population density, absence of heavy industries, non-significant agriculture, native forest and reforestation,
the opposite is found in the middle part of the basin. Samples of riverbed sediments were collected along the basin for chemical
analysis. Results showed that the source rivers still preserve their natural characteristics, while the Atibaia river in the
middle part shows signs of pollution from the agricultural activity, industrial effluents and urban sewage.