Read Full Article (file size: 481981 bytes)    Cited by

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, D24101, doi:10.1029/2006JD007292, 2006

Role of turbines in the carbon dioxide emissions from two boreal reservoirs, Québec, Canada

Charlotte Roehm

Department de Sciences Biologiques, Université du Québec, Montréal, Québec, Canada

Alain Tremblay

Unité Environnement, Direction Barrages et Environnement, Hydro-Québec Production, Montréal, Québec, Canada

Abstract

The potential for degassing of carbon dioxide stemming from the passage of water through turbines of hydroelectric reservoirs was studied in two boreal reservoirs (La Grande 2 and La Grande 3) located in the James Bay region of Québec, Canada. Samples of dissolved CO₂ were taken monthly over a period of 1 year from the main reservoirs, within the hydroelectric facilities from the shaft entering the turbine system and from the exits below the facilities. Diffusive fluxes from the reservoir surfaces were calculated using the thin boundary layer equation. The differences between CO₂ concentrations above and below the dams were used to calculate the amount of degassing per unit of water turbined. Diffusive flux calculations indicated that the reservoirs acted as sources of CO₂ to the atmosphere throughout the sampling period, with fluxes ranging between 80 and 1800 mg CO₂ m⁻² d⁻¹ at LG2 and between 400 and 1500 mg CO₂ m⁻² d⁻¹ at LG3. Degassing calculated from turbining ranged between 5–45 and 5–25 t d⁻¹ at LG2 and LG3, respectively, and represented between <1 and 7% and mean weighted values of <1% of the equivalent fluxes across the air-water interface of the main reservoirs. The quantity of degassing is seasonally defined, with highest rates observed in the winter/spring period, a result of lower water temperature effects on the solubility of CO₂, and the buildup of gases over the winter period due to mineralization of organic matter and the influx from watershed sources due to the springtime melt. Depending on the effluxes occurring at the air-water interface of the main reservoir, degassing can represent a maximum equivalent 16%. This study indicates that the main role of turbining lies in the seasonality of release of GHG rather than the absolute amount.

Received 13 March 2006; accepted 24 August 2006; published 16 December 2006.

Keywords: carbon dioxide; turbines; hydroelectric reservoirs.

Index Terms: 1857 Hydrology: Reservoirs (surface); 0426 Biogeosciences: Biosphere/atmosphere interactions (0315); 0490 Biogeosciences: Trace gases; 0414 Biogeosciences: Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912); 1834 Hydrology: Human impacts.

Read Full Article (file size: 481981 bytes)    Cited by

Citation: Roehm, C., and A. Tremblay (2006), Role of turbines in the carbon dioxide emissions from two boreal reservoirs, Québec, Canada, J. Geophys. Res., 111, D24101, doi:10.1029/2006JD007292.

Copyright 2006 by the American Geophysical Union.