Navegando por Assunto "Water chemistry"

Agora exibindo 1 - 1 de 1

Acesso aberto (Open Access)
Aspectos limnoquímicos do reservatório da Usina Hidrelétrica de Tucuruí (PA): uma avaliação temporal entre 1986 e 2001
(Universidade Federal do Pará, 2003) SANTOS, Márcio José Moura dos; RAMOS, José Francisco da Fonseca; http://lattes.cnpq.br/8189651755374537
The reservoir of the Tucuruí UHE, whose quota is around 72 m, holds a volume of about 50.8 million cubical meters and floods an area of 2.850 of Km2 . It has about 170 km length along its major axis (Main River) and maximum 40 km width. The average time of water residence in the reservoir is approximately 50 days, with a volume of only 3 % of non renewable water. The present work deals with the hydrochemistry of the following water systems: The Tocantins River (up- and downstream the dam) and the reservoir itself. They have been characterized during the year 2001 through horizontal and vertical distribution of the diverse physical, physico-chemical and chemical parameters analyzed, besides time-series evaluation in the period 1986 up to 2001, since the lake formation up to now. The study was carried after analysis of the following parameters: Temperature, Transparency and Total Suspended Solids – TTS, pH, Conductivity, Dissolved Oxygen, free CO2, Ca2+, Mg2+, Na+ , K+ , HCO3 - , Fe-total, P-Total, Ammonia and Nitrate. Studies of the trophic levels of the systems during the year 2001 have also been carried out following the Carlson´s Index of trophic state. It is based on three variables: transparency, a-chlorophyl and P-Total, in order to classify the water body in terms of its trophic level. The data used in this work were gently yielded by Eletronorte Company (Center for Environmental Research - CPA), besides our proper data collected in a fild work in November, 2001. Sampling stations have been established in the reservoir, either in the central body (M1 and M3 – old channel; MJV, MP and MR – outer zone) as in the Caraipé compartment (C1 and C2). In the Tocantins river, samples were collected upstream (M5) and downstream the dam (JT, NP, IT, MJ and cm). The results have shown that the system, as a whole, exhibit quite different hydrochemical characteristics (the central and outer part of the reservoir and up and downstream parts of the Tocantins river. According to studies conducted by Eletronorte, such difference is due to diverse hydrodynamic conditions of the reservoir. For instance, in the central body, the outer parts (MJV, MP and MR) have a hydraulic retention time ned for the rainy and dry seasons. It is also important to notice the role of the Tocantins river as supplier of micronutrients, mainly iron and P-total that will further get into the reservoir. Time-series analysis of the variables Total Suspended Solids, pH, Dissolved Oxygen, free CO2, P-Total and Ammonia did not show significant increasing or decreasing contents. pH and DO have also shown a narrow range of variation while the other parameters exhibited strong variations in the period studied. Finally, in 2001, it is possible to classify the study area a mesotrophic and oligotrophic in the dry and rainny seasons, respectivelly. The results have also shown that inside the reservoir, trophic levels are lower than those found in the Tocantins river (up and downstrean). Regarding only the reservoir, one finds that the Caraipé compartment has a greater trophic level than the central body.