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Greenhouse gas emissions from freshwater reservoirs: what does the atmosphere see?
Citation:
Prairie, Y., J. Alm, J. Beaulieu, N. Barros, T. Battin, J. Cole, P. del Giorgio, T. DelSontro, F. Guérin, A. Harby, J. Harrison, S. Mercier-Blais, D. Serça, S. Sobek, AND D. Vachon. Greenhouse gas emissions from freshwater reservoirs: what does the atmosphere see? ECOSYSTEMS. Springer, New York, NY, 21(5):1058-1071, (2018). https://doi.org/10.1007/s10021-017-0198-9
Impact/Purpose:
Freshwater reservoirs are a known source of greenhouse gas (GHG) to the atmosphere, but their quantitative significance is still only loosely constrained. Although part of this uncertainty can be attributed to the difficulties in measuring highly variable fluxes, it is also the result of a lack of a clear accounting methodology, particularly about what constitutes new emissions and potential new sinks. In this paper, we review the main processes involved in the generation of GHG in reservoir systems and propose a simple approach to quantify the reservoir GHG footprint in terms of the net changes in GHG fluxes to the atmosphere induced by damming, that is, ‘what the atmosphere sees.’ The approach takes into account the pre-impoundment GHG balance of the landscape, the temporal evolution of reservoir GHG emission profile as well as the natural emissions that are displaced to or away from the reservoir site resulting from hydrological and other changes. It also clarifies the portion of the reservoir carbon burial that can potentially be considered an offset to GHG emissions.
Description:
Freshwater impoundments, like all inland aquatic systems, are sites of intense carbon processing and transport. They receive carbon in several forms (coarsely aggregated into dissolved and particulate fractions of both inorganic and organic forms), convert one C species to another, some of which will be emitted to the atmosphere and some of which will be buried more or less permanently in their sediments, and some of which will be transferred to the systems downstream. For natural aquatic systems, research of the past decade has demonstrated that their role is disproportionately larger than their surface area would suggest. Although they cover only about a few percent of the terrestrial surface of the Earth, the latest estimates show that their net contribution to the atmosphere is of the same order of magnitude as the net exchanges that occur between the oceans and the atmosphere (although in the opposite direction) or that between the land and the atmosphere. It is also greater than the delivery of terrestrial carbon to the oceans. Given the global importance of natural systems, it is to be expected that man-made freshwater reservoirs may be questioned as to their own footprint. Published estimates of the global GHG associated with reservoirs vary by more than one order of magnitude and underscore the considerable uncertainty of these assessments, a situation that is likely to continue given the number of ongoing damming projects in various stages of planning or completion.
URLs/Downloads:
DOI: Greenhouse gas emissions from freshwater reservoirs: what does the atmosphere see?
GHG_10312018.DOCX
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