Influence of environmental variables on diffusive greenhouse gas fluxes at hydroelectric reservoirs in Brazil

Abstract

For almost two decades, studies have been under way in Brazil, showing how hydroelectric reservoirs produce biogenic gases, mainly methane (CH4) and carbon dioxide (CO2), through the organic decomposition of flooded biomass. This somewhat complex phenomenon is due to a set of variables with differing levels of interdependence that directly or indirectly affect greenhouse gas (GHG) emissions. The purpose of this paper is to determine, through a statistical data analysis, the relation between CO2, CH4 diffusive fluxes and environmental variables at the Furnas, Itumbiara and Serra da Mesa hydroelectric reservoirs, located in the Cerrado biome on Brazil's high central plateau. The choice of this region was prompted by its importance in the national context, covering an area of some two million square kilometers, encompassing two major river basins (Paraná and Tocantins-Araguaia), with the largest installed power generation capacity in Brazil, together accounting for around 23% of Brazilian territory. This study shows that CH4 presented a moderate negative correlation between CO2 and depth. Additionally, a moderate positive correlation was noted for pH, water temperature and wind. The CO2 presented a moderate negative correlation for pH, wind speed, water temperature and air temperature. Additionally, a moderate positive correlation was noted for CO2 and water temperature. The complexity of the emission phenomenon is unlikely to occur through a simultaneous understanding of all the factors, due to difficulties in accessing and analyzing all the variables that have real, direct effects on GHG production and emission.

Emissions from tropical hydropower and the IPCC

“…Além dos processos mencionados acima, existe também a influência de outros fatores e parâmetros ambientais que causam efeitos diretos na produção e emissão de GEE em reservatórios hidrelétricos (COLE & CARACO, 1998;KEMENES, 2006;ESTEVES, 2011;ROGERIO et al, 2013).…”

“…O panorama atual sobre emissões líquidas é impreciso e, de fato, existe razoável incerteza sobre a quantificação das emissões de GEE de reservatórios artificiais, que por se tratarem de ambientes naturais são afetados por fatores como: variabilidade climática anual, emissões pré-enchimento e captação de carbono -estudos recentes têm mostrado que reservatórios podem atuar como sumidouros de carbono (SIKAR et al, 2009;CHANUDET et al, 2011;OMETTO et al, 2011;ROGERIO et al, 2013;BRASIL, 2014) captando CO 2 na fase de sedimentação.…”

Reservoir management: an opinion to how the scientific community can contribute

“…(xi) b a c t e r i o p l a n k t o n m e t a b o l i s m a n d p h o t o m i n e r a l i z a t i o n i n v e n t o r i e s (Soumis et al, 2007;Roland et al, 2011), and greenhouse gas emissions in reservoirs of hydroelectric power plants (from pre-filling to operating phases); Santos & Rosa (2005); Rogerio et al (2013); Brasil (2014).…”

Impacto de hidrelétricas brasileiras nas mudanças climáticas: micro-organismos associados à emissão de metano em reservatórios.

“…hydrologic regime, temperature, wind, depth, oxygen concentration, dam closing time, and carbon input (Rogério et al, 2013). Funil also present great influence of human activities such as agriculture and livestock in points near the lake (MME, 2014).…”