Avaliação das alterações da qualidade de águas tropicais decorrentes da instalação de barramentos para fins de geração de energia elétrica: estudo de caso do Rio Pomba

Abstract

Brazil is a country with its energetic resources mainly located on hydroelectric power plants, both small and big sized plants. Although there is already a large number of plants on construction and also operating, Brazil still has an enormous potential to profit by theinstallation of more undertakings of this nature, specially because it is a very rich country regarding water resources. A hydroelectric power plant constitute of a dam constructed through a water course. The consequence, in most cases, is the flooding of the up river areas and the formation of a reservoir, altering the water regime and also other water characteristics. The objective of this study was to evaluate the effects of these dams installation on river water quality, with an individually and cumulative analysis. We adopted a case study of three consecutive hydroelectric power plants constructed in Pomba River, on the Paraíba do Sul Basin, Minas Gerais State. We searched to evaluate the effects resulted from the construction of the dams as well as those resulted from other factors that could also influence water quality, such as weather and climate, the use and occupation of the drainage basin, tributaries contribution, among others. We also assessed the possible implication of water quality alteration from the construction of the dams on the actual and potential water usage, according to the current legislation.Therefore, we used quarterly data from the monitoring of physical-chemical, bacteriological and hydrobiological water quality parameters from seven sampling stations, during the period of June 2001 to October 2005. We proceeded with both numeric and graphic statistic analysis, with the total data grouped in four distinct scenarios: (1) without the construction of any dam, and after the construction of (2) one, (3) two and (3) three consecutive dams. The results obtained allow us to conclude that the water quality parameters that suffered a possible influence from the construction of one or more consecutive dams were the Oxygen Biochemical Demand, soluble phosphorous, sedimentable solids, phytoplankton (density and richness) and zooplankton (density). Significant cumulative effects were not observed for these parameters due to the installation of consecutive dams. We also verified that there werent any implications on the water use resulting from water these water quality alterations.