The net carbon footprint of a newly created boreal hydroelectric reservoir

Abstract

[1] We present here the first comprehensive assessment of the carbon (C) footprint associated with the creation of a boreal hydroelectric reservoir (Eastmain-1 in northern Québec, Canada). This is the result of a large-scale, interdisciplinary study that spanned over a 7-years period (2003)(2004)(2005)(2006)(2007)(2008)(2009)), where we quantified the major C gas (CO 2 and CH 4 ) sources and sinks of the terrestrial and aquatic components of the pre-flood landscape, and also for the reservoir following the impoundment in 2006. The pre-flood landscape was roughly neutral in terms of C, and the balance between pre-and post-flood C sources/sinks indicates that the reservoir was initially (first year post-flood in 2006) a large net source of CO 2 (2270 mg C m À2 d À1) but a much smaller source of CH 4 (0.2 mg C m À2 d À1). While net CO 2 emissions declined steeply in subsequent years (down to 835 mg C m À2 d À1 in 2009), net CH 4 emissions remained constant or increased slightly relative to pre-flood emissions. Our results also suggest that the reservoir will continue to emit carbon gas over the long-term at rates exceeding the carbon footprint of the pre-flood landscape, although the sources of C supporting these emissions have yet to be determined. Extrapolation of these empirical trends over the projected life span (100 years) of the reservoir yields integrated long-term net C emissions per energy generation well below the range of the natural-gas combined-cycle, which is considered the current industry standard.

Low methane (CH<sub>4</sub>) emissions downstream of a monomictic subtropical hydroelectric reservoir (Nam Theun 2, Lao PDR)

“…This contribution of downstream emissions to total emissions is low compared to tropical reservoirs located in South America (Abril et al, 2005;Kemenes et al, 2007). Disregarding the first 2 years of monitoring (2009 and 2010) during which the quantification highly depends on the management of the reservoir, the contribution of downstream emissions to total emissions is even lower than in boreal reservoirs (Teodoru et al, 2012). The low downstream emissions arise from the fact that the reservoir is monomictic.…”

“…When all emission pathways from tropical or temperate hydroelectric reservoirs (disregarding the drawdown emissions) are taken into account, downstream emissions could contribute 50 to 90 % of total CH 4 emissions (Abril et al, 2005;Kemenes et al, 2007;Maeck et al, 2013). At two other sites located in Canada and in the Lao People's Democratic Republic (Lao PDR) where this pathway was studied, downstream emissions were found to contribute less than 25 % when it exists (Chanudet et al, 2011;Teodoru et al, 2012). According to the differences from one reservoir to the other, it appears that the factors controlling downstream emissions from reservoirs must be identified in order to propose realistic estimations of the global emissions from reservoirs, including downstream emissions.…”

“…This latter estimate is mostly based on CH 4 diffusion at the reservoir surface and to a lesser extent on CH 4 ebullition, which are the two best documented pathways to the atmosphere. However, emissions from the drawdown area (Chen et al, 2009(Chen et al, , 2011 and emissions downstream of dams (Galy-Lacaux et al, 1997;Abril et al, 2005;Guérin et al, 2006;Kemenes et al, 2007;Chanudet et al, 2011;Teodoru et al, 2012;Maeck et al, 2013) were poorly studied and are not taken into account in the last global estimate (Barros et al, 2011). Some authors attempted to include these two pathways in the global estimation of greenhouse gas emissions from reservoirs (Lima et al, 2008;, and it increased drastically the emission factors of reservoirs.…”

Estimating Carbon Dioxide (CO2) Emissions from Reservoirs Using Artificial Neural Networks

“…Since the problem of greenhouse gases (GHGs) emissions from hydroelectric reservoirs was first addressed in the publication in 1993 [1], it has been the focus of research around the world [2], especially in Canada [3,4], Brazil [5], and the United States [6,7]. Over the past two decades, a growing amount of work has documented reservoirs' roles as GHG sources [8,9], after extensive research was carried out in various reservoirs.…”

Impacts of boreal hydroelectric reservoirs on seasonal climate and precipitation recycling as simulated by the CRCM5: a case study of the La Grande River watershed, Canada

“…Fortunately, radiative and turbulent flux measurements were taken during the period 2008-2012 at three eddy covariance towers in the southwestern portion of the watershed (Fig. 2), as part of a study on greenhouse gas emissions from boreal hydropower reservoirs (Teodoru et al 2012). One of the towers was located over the Eastmain-1 reservoir (52°07′ 30″ N, 75°55′ 51″ W), the second one, over an ombrotrophic bog (52°17′25″ N, 75°50′25″W), and the third one, in a black spruce forest (52°06′ 16″ N, 76°11′ 48″ W).…”