Carbon pathways responding to water moviment in hydropower reservoirs.

Abstract

The physical, chemical and biological processes that occur in lakes and reservoirs are, for the most part, dependent on circulation processes that occur in the water column. The horizontal movement caused by the surface currents induced by wind plays an important role in the transport of nutrients and phytoplankton. Researchers say that the phytoplankton is distributed in patches along a lake, probably due to variability in the hydrodynamic conditions of the habitat. In addition to horizontal transport, vertical mixing can occur and break the natural barrier imposed by stratification. This facilitates, for example, primary production due to the incorporation of nutrient-rich water from the hypolimnion to the superficial layers. Authors show that the tropical primary productivity in reservoir is correlated with the age of the reservoir due to the contribution of the vertical transport of nutrients decomposed from the organic material flooded after the filling. Furthermore, analyzes in Manso reservoir show that vertical transport of gas-rich water, caused by winds, can provide an increase of 12% in CO2 emissions in July and August (Roland et al. in 2010). Authors show that there is spatial heterogeneity in CO2 emissions due to the variability in eater movement in hydroelectric reservoirs. This study aims at determining the influence of circulation patterns in hydroelectric reservoirs on carbon pathways, greenhouse gases (GHGs) emissions, phytoplankton composition, input of allochthonous carbon and nutrient concentration . This work will be done in two tropical hydropower reservoirs: UHE Funil (RJ) and UHE Três Marias (MG). In these reservoirs, the water currents will be determined along the main body of the reservoir and river. The concentrations of carbon forms, nitrogen and phosphorus, and phytoplankton communities will be quantified in order to represent the variation over the body of the reservoir and the water column. This is a pioneering research to tropical ecosystems and will contribute to research on carbon balance and greenhouse gas emissions in tropical reservoirs. This proposal is included within the project "Limnology and Metabolism planktonic controlling transfer rates of greenhouse gases - called strategic 09 - ANEEL, Monitoring GHG emissions" - which involve institutions such as COPPE / Federal University of Rio de Janeiro (UFRJ), Universidade Federal de Juiz de Fora (UFJF), International Ecology Institute (ERI) and the National Institute for Space Research (INPE).