Mathematical modeling of GHG balance in a subtropical reservoir in south Brazil.

Michael Mannich, João Furtado Resende, Cristovão Vicente Scapulatempo Fernandes, Julio Werner Yaoshioka Bernardo, Tobias Bleninger

Friday 3 july 2015

12:48 - 12:51h at North America (level 0)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology, Poster pitches

Parallel session: Poster pitches: 15F. Environment - Ecohydraulic

Environmental issues associated with the greenhouse gas emissions (GHG) from reservoirs have been intensively discussed since the first studies published in the 90s. The usual strategy to provide a diagnosis about the greenhouse warming potential (GWP) consist of measurements of the fluxes of methane and carbon dioxide. Constraints are imposed by highly temporal and spatial variabilities which represent a restriction for a long time monitoring. In this context and considering the carbon dynamics, this paper presents a zero-dimensional mathematical model for the carbon balance in reservoirs that considers diffusive and bubbling fluxes of carbon dioxide and methane. The model incorporates the main processes related to organic and inorganic carbon in dissolved and particulate fractions dynamics as well their interactions with the sediment. Meteorological and hydrological forcing mechanisms are the main forcing variables. The model was applied to a small subtropical reservoir in south Brazil (Capivari Reservoir) under a Cfb climate according to Köppen classification, and calibrated based on carbon stock changes in the Capivari Reservoir over a period of 43 years. The model results suggest that the reservoir acts as sink for carbon at a mean rate of 720 mgC/m2d. However, even storing carbon, the reservoir emits methane at a mean rate of 27.4 mgC/m2d which has a higher GWP than carbon dioxide. So, the Capivari Reservoir contributes to greenhouse effects at a mean rate of 174.2 mgCO2eq/m2d. These results corroborate previous researches which found that reservoirs store carbon and highlights the relevance of the compromising methane emissions on GHG balance, that is relevant for the comprehensive impact on its emissions.