Measuring GHG Emissions From Reservoirs

EOS, Transactions, American Geophysical Union
by L. Yang, F. Lu, and X. Wang

Hydroelectricity has typically been regarded as a green energy source, but reservoirs created for its generation emit greenhouse gases (GHGs) just as natural lakes and rivers do. The role of reservoirs in GHG emissions has been overlooked. Substantial amounts of methane (CH4) are emitted from reservoir surfaces every year, which account for about 20% of the total CH4 emission from inland waters. GHG emissions (transferred into carbon dioxide equivalents) from some tropical reservoirs even exceed CO2 emissions from thermal power plants if the same amount of electricity is generated.

In the past 5 years, some investigations have focused on GHG emissions from Chinese reservoirs.  However, field measurements of GHGs have been limited to a few Chinese and Laotian reservoirs. Production, transport, and emission are the three main processes in GHG emissions from reservoirs, similar to those from natural rivers or lakes.

GHG emissions from reservoirs are a complex biogeochemistry process, influenced by many  environmental variables such as reservoir conditions (flooded organic carbon and reservoir age),  hydrology and water quality (water level, retention time, acidity, and dissolved oxygen), climate  conditions (wind speed, water temperature, light, and rainfall), and biological conditions (type and biomass of aquatic vegetation). Because of this, a remarkable spatial variation has been observed in GHG emissions from Chinese reservoirs, which results in difficulty in accurately estimating the total GHG emissions from reservoirs.

Based on the available literature, the authors conclude that GHG emissions from Chinese reservoirs should be studied further.

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