Abstract
The building of large dams in the Upper Paraná River basin altered the discharge regime at the Porto São José River section. The discharge regime has been altered since 1972, but the changes intensified after the Porto Primavera damming, in late 1998. Considering that discharge control affects the relationship between channel and floodplain, this work aimed to evaluate the intensity of the discharge control that resulted from the operation of the Porto Primavera Dam. To achieve this objective, statistical analyses were carried out based on the Porto São José Fluviometric Station historical series of river level readings and discharge, between 1964 and 2007. Results showed that the average discharge increased from 1964 to 1981 and diminished after river damming. The increase of average discharge rates was followed by an increase of the duration of higher discharges at different levels of geomorphologic and limnological importance, and the reduction of average discharge during the last observed period was followed by a disproportionate decrease in the duration of the abovementioned discharges. Moreover, it is clear that the relationship between fluviometric level and fluvial discharge changed, which implies that a certain river level reading represents a higher discharge than necessary before river damming.
Highlights
The historical series of the Porto São José River Fluviometric Station shows that the Paraná River discharge regime changed after the operation of other dams upstream from this area
Assuming that the disturbing source is the discharge regime, this paper aimed to evaluate the intensity of the outflow controlled by the Porto Primavera Dam, based on the Porto São José Station fluviometric data
Before 1972, the annual average of the daily average discharge levels recorded at Porto São José Station was 2.34 m (6,501 m3/s), and between 1972 and 1998, it increased to 3.48 m (9,150 m3/s) (Rocha et al, 1998)
Summary
The historical series of the Porto São José River Fluviometric Station shows that the Paraná River discharge regime changed after the operation of other dams upstream from this area. Discharge regime changes occurred as other reservoirs were built, regulating the Paraná River fluviometric level (Rocha et al, 1998; 2001; Rocha, 2002). Geomorphologic changes occur because of river discharge regulation. The relationship between channels and the fluvial plain changes, either by magnitude, duration (number of days above a given reading level), periodicity, frequency, water flow rate (Rocha, 2002), sediment transport (Souza Filho, 1999; Rocha, 2002; Crispin, 2001; Martins and Stevaux, 2005; Hayakawa, 2007), or by river channel alterations
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