RESULTS FROM A NATIONAL SCALE SURVEY OF METHANE AND CARBON DIOXIDE EMISSIONS FROM US RESERVOIRS

The US Environmental Protection Agency has included reservoirs in the annual Inventory of US Greenhouse Gas Emissions and Sinks since 2022.  US reservoirs are estimated to emit 30.6 kt of methane per year, making them the seventh largest anthropogenic methane source in the country.  This estimate is based on Intergovernmental Panel on Climate Change default emission factors, however, and it is unclear how well these emission factors represent US systems.  To improve the Inventory estimate, we executed a survey of methane and carbon dioxide emissions from 108 US reservoirs.  The reservoirs were selected using a spatially balanced survey design and were widely distributed across the conterminous US.  Ebullition and diffusion emissions were measured at 15-25 locations in each reservoir during a 48-hour period between June 1 and September 15, 2020-2023.  Approximately 60% of the reservoirs were a carbon dioxide source during the survey.   All reservoirs were a source of methane, with a mean emission rate of 134 mg CH₄ m^-2 d^-1 (Inter Quartile Range (IQR): 18-110 mg CH₄ m^-2 d^-1), which is similar to the average global flux from lakes and reservoirs (156 mg CH₄ m^-2 d^-1), but includes some of the highest diffusive emissions reported in the literature (maximum reservoir-wide average of 2808 mg CH₄ m^-2 d^-1).  On average, diffusion composed 75% of total emissions (IQR: 57–89%), with ebullition constituting the balance. In addition to aiding inventory efforts, this dataset will improve our understanding of both inter and intra-reservoir spatial patterns in greenhouse gas fluxes.

Primary Presenter: Jake Beaulieu, United States Environmental Protection Agency (Beaulieu.Jake@epa.gov)

Authors:

Jake Beaulieu, US Environmental Protection Agency  (beaulieu.jake@epa.gov)

Bridget Deemer, U.S. Geological Society, Grand Canyon Monitoring and Research Center, Southwest Biological Science  (bdeemer@usgs.gov)

Ken Forshay, U.S. Environmental Protection Agency  (Forshay.Ken@epa.gov)

Natalie Griffiths, Oak Ridge National Laboratory  (griffithsna@ornl.gov)

Lilian Herger, U.S. Environmental Protection Agency  (lil.herger@comcast.net)

Jeff Hollister, U.S. Environmental Protection Agency  (Hollister.Jeff@epa.gov)

Scott Jacobs, U.S. Environmental Protection Agency  (Jacobs.Scott@epa.gov)

Peter Leinenbach, U.S. Environmental Protection Agency  (Leinenbach.Peter@epa.gov)

Rachel Pilla, Oak Ridge National Laboratory  (pillarm1@ornl.gov)

Stephen Shivers, U.S. Environmental Protection Agency  (shivers.stephen@epa.gov)

Avery Tatters, U.S. Environmental Protection Agency  (Tatters.Avery@epa.gov)

Katie Buckler, U.S. Environmental Protection Agency  (Buckler.Katherine@epa.gov)

Joseph Corra, U.S. Environmental Protection Agency  (Corra.Joseph@epa.gov)

Payton Goodwin, Pegasus Technical Services  (Goodwin.Payton@epa.gov)

Leah Juilfs, Pegasus Technical Services  (juilfs.leah@epa.gov)

Russell Neill, U.S. Environmental Protection Agency  (Neill.Russell@epa.gov)

Brent Richmond, U.S. Environmental Protection Agency  (Richmond.Brent@epa.gov)

Thomas Sabol, U.S. Geological Survey, Grand Canyon Monitoring and Research Center, Southwest Biological Science Center  (tsabol@usgs.gov)