Abstract
The contribution of artificial reservoirs to greenhouse gas (GHG) emissions has been emphasized in previous studies. In the present study, we collected and updated data on GHG emission rates from reservoirs at the global scale, and applied a new classification method based on the hydrobelt concept. Our results showed that CH4 and CO2 emissions were significantly different in the hydrobelt groups (p < 0.01), while no significant difference was found for N2O emissions, possibly due to their limited measurements. We found that annual GHG emissions (calculated as C or N) from global reservoirs amounted to 12.9 Tg CH4-C, 50.8 Tg CO2-C, and 0.04 Tg N2O-N. Furthermore, GHG emissions (calculated as CO2 equivalents) were also estimated for the 1950–2017 period based on the cumulative number and surface area of global reservoirs in the different hydrobelts. The highest increase rate in both the number of reservoirs and their surface area, which occurred from 1950 to the 1980s, led to an increase in GHG emissions from reservoirs. Since then, the increase rate of reservoir construction, and hence GHG emissions, has slowed down. Moreover, we also examined the potential impact of reservoir eutrophication on GHG emissions and found that GHG emissions from reservoirs could increase by 40% under conditions in which total phosphorus would double. In addition, we showed that the characteristics of reservoirs (e.g., geographical location) and their catchments (e.g., surrounding terrestrial net primary production, and precipitation) may influence GHG emissions. Overall, a major finding of our study was to provide an estimate of the impact of large reservoirs during the 1950–2017 period, in terms of GHG emissions. This should help anticipate future GHG emissions from reservoirs considering all reservoirs being planned worldwide. Besides using the classification per hydrobelt and thus reconnecting reservoirs to their watersheds, our study further emphasized the efforts to be made regarding the measurement of GHG emissions in some hydrobelts and in considering the growing number of reservoirs.
Highlights
Reservoirs are important components of inland water ecosystems and are recognized as significant sources of greenhouse gases (GHG) globally (Demarty and Bastien, 2011; Beaulieu et al, 2015, 2018; Li et al, 2018)
A novel classification method based on the hydrobelt concept was used to estimate GHG emissions from global reservoirs
Based on the dataset gathered from reservoirs at the global scale from the literature and from new data that we have added, we estimated that annual GHG emissions were approximately 12.9 Tg CH4-C, 50.8 Tg CO2-C, and 0.04 Tg N2O-N
Summary
Reservoirs are important components of inland water ecosystems (together with lakes) and are recognized as significant sources of greenhouse gases (GHG) globally (Demarty and Bastien, 2011; Beaulieu et al, 2015, 2018; Li et al, 2018). Previous research showed that there can be substantial GHG emissions downstream of tropical hydroelectric reservoirs (Abril et al, 2005; Kosten et al, 2010). Even without these downstream emissions, it is undeniable that the impact of reservoirs on global GHG emissions is significant (Giles, 2006)
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