Analysis of time series of flow and precipitation in some basins of the São Paulo State with different degrees of human impact

Abstract

Aiming a better understanding of hydrological behavior and its interactions with anthropogenic activities, time series analysis of flow and precipitation were carried out in some basins with different degrees of human impact in the State of São Paulo. The main goals of this project were to define dry and wet periods and perform an exploratory study through the analysis of trends and abrupt changes in the average of those parameters. This hydrological diagnosis is useful as a reference for environmental and biogeochemistry studies being realized within the Biota SP Project (FAPESP), that it has been accomplished in the same basins. The statistical analysis was performed with annual data from 1947 to 1997 or from 1970 to 1997, depending on the data availability for each basin. The results show that in most basins of the project a positive trend in the precipitation exists when the considered time series is from 1947 to 1997. In this period, the flow follows the positive trend of the precipitation in the non-impacted basins, meanwhile negative trends where observed in some more impacted rivers