Análise do impacto do Sistema Cantareira sobre o regime de vazões na bacia do rio Piracicaba

Abstract

FREDERICE, A. Analysis of the Cantareira System impact on the flow regime in Piracicaba River basin. 2014. 110 p. Dissertation (Master in Science) – Escola de Engenharia de Sao Carlos, Universidade de Sao Paulo, Sao Carlos, 2014. The aim in this paper was to characterize the natural flow regime of the main rivers of Piracicaba River basin and identify the alterations in this regime, mainly due to the implementation of Cantareira System reservoirs. The analyzes were based on the average daily flow series from six fluviometric stations in the basin (DAEE prefix: 3D001, 3D-002, 3D-006, 3D-009, 4D-001 and 4D-007). The IHA (Indicators of Hydrologic Alteration) software was used to calculate 33 hydrological parameters ecologically relevant, that characterizes the magnitude, timing, frequency, duration and rate of flow changes, besides spliting the environmental flow into five components: extreme low flows, low flows, high flow pulses, small floods and large floods. The daily flow series were divided into two periods, pre and post impact, and it was considered as the year of the impact the year that corresponding to the breaking of homogeneity date from the flow series, verified by the nonparametric Pettitt test. It was determined by the IHA software, for post impact period, the Hydrological Alteration factors of the 33 hydrologic parameters and the changes in the environmental flow components. For the rivers influenced by Cantareira System, it was observed that in the post impact period (from 1970/80s), overall, there was a decrease in the mean flow, approximately 24% (3D-006 station) in Atibaia River, 50% (3D-009 station) and 34% (4D-001 station) in Jaguari River, and 14% (4D-007 station) in Piracicaba River, mainly in the dry season (April to September). There was also a decrease in the median of the annual seven days minimum flows by 25% (3D006 station), 56% (3D-009 station), 43% (4D-001 station) and 15% (4D-007 station), and an increase in the frequency and duration of the lower flows. It was also found for these stations a decrease in the duration of high flows as well as an increase in the rise rates and the fall rates of these flows. The most significant changes occurred in Jaguari River, followed by the Atibaia River and were less significant in the Piracicaba River, which is the farthest from the reservoirs. For the Camanducaia River (without influence from Cantareira System), after the 1970s, there was no change in the median of the annual seven days minimum flows and it was observed, overall, an increase in the mean flow by 21% (3D-001 station) and 14% (3D-002 station), as well as an increase in the frequency of the maximum flows, however, the changes were not as significant as in the other rivers.