The Natural Resources Defense Council (NRDC) on Sept. 29 filed a copy of a new study with the Federal Energy Regulatory Commission that said methane “hot spots” at hydroelectric dams are more of a global warming issue than previously thought.
Methane, a powerful greenhouse gas, is a product of rotting vegetation. The study is entitled “Sediment Trapping by Dams Creates Methane Emission Hot Spots.” The NRDC filed the study with FERC in the record of proceedings for the Susitna-Watana Hydroelectric project. The study, published in June, analyzed greenhouse gas emissions from hydroelectric project impoundments in Europe and found that the dams create “hot spot emission zones” of methane with far greater potential climatic impacts than previously suspected.
“Inclusion of this recent climate change study into the record is consistent with FERC’s ruling on July 18, 2013, denying the requests of the National Marine Fisheries Service (‘NMFS’) and the Center for Water Advocacy to include a comprehensive study of climate change as part of the environmental analysis for the application of the Susitna Dam project,” the NRDC wrote. “In ruling that the comprehensive study of climate change is ‘unlikely to yield reliable data that can be used in the development of license requirements, particularly when balanced against the cost of such assessments,’ FERC nevertheless agreed with NMFS that ‘the effects of climate change on streamflow conditions and any corresponding adverse effects on environmental resources are important issues, and any substantial information regarding these matters will be given due consideration in the Commission’s environmental analysis.’”
This new study was published after the close of the record of the NMFS study dispute and therefore could not have been timely filed within that prior argument, the NRDC added. In the study, measurements were performed over a 93-kilometer section of the River Saar in Germany that includes six small-sized reservoirs and the intermediate riverine reaches between the dams.
“We show that sediment accumulation correlates with methane production and subsequent ebullitive release rates and may therefore be an excellent proxy for estimating methane emissions from small reservoirs,” said the study abstract. “Our results suggest that sedimentation-driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7%.”
The study concluded: “As the number of dams worldwide continues to increase and sediments further accumulate behind already established impoundments, the contribution from CH4 emissions from hot spots to global atmospheric CH4 levels is also likely to increase in the future, especially when coupled with higher average temperatures.”
Arguments already made about needed climate change data
FERC on July 18 had rejected two requests for rehearing related to this 600 MW-800 MW hydroelectric project in Alaska. On May 28, the NMFS and the Center for Water Advocacy filed requests for rehearing of the formal study dispute determination issued by the Director of the Office of Energy Projects on April 26. That decision was on the proposed 600 MW-800 MW (exact project size is not determined yet) Susitna-Watana Hydroelectric Project, to be located on the Susitna River in Matanuska-Susitna Borough, Alaska.
NMFS and the Center sought rehearing of the director’s finding that studies proposed by the potential applicant, the Alaska Energy Authority (AEA), and NMFS related to global climate change are unnecessary to conduct the commission’s environmental analysis and therefore will not be required to be conducted by AEA.
In December 2011, AEA filed a notice of intent to file a license application for the proposed Susitna-Watana project, along with a pre-application document. This submittal initiated the pre-filing stage of the commission’s integrated licensing process (ILP).
In May 2012, NMFS filed a request that AEA perform a climate change study. Among other studies, AEA’s plan included proposed Study 7.7, to analyze the potential effects of climate change on glacier wastage and retreat and the corresponding effects on streamflow entering the proposed reservoir, and to evaluate the effects of glacial surges on sediment delivery to the reservoir.
On April 26, the director issued a formal study dispute determination. The director adopted in part a panel’s modification to RSP 7.7, to require that AEA implement its proposed study component related to a review of existing literature relevant to glacial retreat and summarize the understanding of potential future changes in runoff associated with glacier wastage and retreat.
With respect to the other two disputed study components related to modeling predictions, the director explained that he was not aware of any new information or analysis that was presented in NMFS’ notice of study dispute, at the technical conference, or in the panel’s findings to persuade him that the conclusions in the study plan determination should be changed.
On May 28, NMFS and the Center filed requests for rehearing of the study dispute determination.
The commission said in the July 18 decision that it agrees with NMFS that the effects of climate change on streamflow conditions and any corresponding adverse effects on environmental resources are important issues. However, it does not agree that the climate change studies proposed by AEA and requested by NMFS are likely to yield reliable data, particularly when balanced against the cost of such assessments.