Changes in the flood regime of S?o Francisco River (Brazil) from 1940 to 2006 |
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Authors: | Hersília de Andrade e Santos Paulo dos Santos Pompeu Danilo Okuma Lessa Kenji |
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Institution: | 1. Departamento de Engenharia Civil, Centro Federal de Educa??o Tecnol??gica de Minas Gerais, Av. Amazonas 7675, Belo Horizonte, Minas Gerais, CEP 30510-000, Brazil 2. Departamento de Biologia, Universidade Federal de Lavras, Campus Universit??rio Caixa, Postal 3037, Lavras, Minas Gerais, CEP 37200-000, Brazil
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Abstract: | Flow regulation causes various environmental impacts in the downstream reaches of impounded rivers. The S?o Francisco River
(SF) basin is Brazil’s third most important watershed. Several dams have been built in its course in the last four decades,
mostly for flow regulation and hydropower generation. This paper presents an evaluation of historical changes in the flood
regime. Three regions of the SF River basin, which are under the influence of different levels of regulation, were studied:
the lower, middle, and upper SF River. The components of magnitude, frequency, and duration of floods were quantified for
each region from 1940 to 1960 (prior to the construction of the first dam) and from 1986 to 2006 (after the last dam). The
results have shown the inexistence of big floods in the downstream areas, decreasing durations of small floods as well as
significant changes in the annual seasonality of floods. Reductions in the flood frequency were verified in all stretches,
even in non-regulated systems, such as the lower Velhas River. The climate variation, which occurred in both period, was not
able to explain the changes in the flood regime of S?o Francisco River; therefore, dams and other anthropogenic activity are
the main factors promoting the temporal variability of streamflows in the S?o Francisco basin. |
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