4/13/2024
Tell The Dam Truth
Response to statements by the U.S. Army Corps of Engineers about our estimate of GHGs, using the All-Res Tool, for the four Lower Snake River Dams.
On March 18, 2024, Tell The Dam Truth released a new report titled, “Estimate of Greenhouse Gas Emissions for the Lower Snake River Dams and Reservoirs using the All-Res Modeling Tool.” The report is posted here. On April 5, 2024, the Columbia River Bulletin posted a story containing statements attributed to the U.S. Army Corps of Engineers (Corps) that responded to our report. The Columbia River Bulletin story is posted here (it’s paywalled).
Below is our response to the Army Corps of Engineers’ statements.
- Corps statement:
“We’re aware of the reported analysis of the lower Snake River dams carbon emissions,” wrote Tom Conning, Public Affairs Specialist, Northwestern Division of the Corps. “While we have not seen the actual analysis, it is important to note that this study did not specifically measure emissions at these four federal dams. Instead, it uses pre-existing literature from the Columbia River System Operations (CRSO) Environmental Impact Statement (EIS) to make a generalized claim.”
Our response:
- We did use measurements from Miller et al (2017) taken at Lower Granite Reservoir, and used the measurements to estimate emissions from littoral areas in the four LSR dams (Miller, BL, EV Arntzen, AE Goldman, and MC Richmond. “Methane Ebullition in Temperate Hydropower Reservoirs and Implications for US Policy on Greenhouse Gas Emissions.” ENVIRONMENTAL MANAGEMENT 60, no. 4 (October 2017): 615–29. https://doi.org/10.1007/s00267-017-0909-1)
- Corps makes a common mistake when it comes to estimating GHGs from ecosystems by insisting that estimates must be made from local measurements. That argument has been thoroughly discredited in the scientific literature, most authoritatively by the International Panel on Climate Change (IPCC). Models, combined with measurements (as the US Environmental Protection Agency is doing in its national greenhouse gas inventory), are the preferred method to estimate biogenic greenhouse gas emissions. Unfortunately, insisting on local measurements, saying one cannot be sure until they measure it locally, means the very expensive measurements will never be taken, and action on preventing further emissions gets delayed indefinitely.
- Delaying action with the argument that one cannot be certain about emissions until one has local measurements puts the financial and institutional risk of the agency and economic interests ahead of the climate risk. It frequently means that new projects with severe climate risk go forward because the agency insists the impacts are uncertain.
2. Corps statement:
“The U.S. Army Corps of Engineers advocates for transparency and public discourse; however, this evaluation and conclusion could be misleading without more context.”
Our response:
The All-Res Tool uses emissions models for each source category available in public peer-reviewed scientific literature, and then we combine those models together into the Tool. While each of the models have been peer-reviewed, our Tool has not yet. We are in the process of reaching out to scientists working in the subject, presenting our Tool to them, and collecting their feedback. We are also in the process of working to place the Tool’s methods into a peer-reviewed journal. Additionally, we would be happy to meet with the Corps to answer any questions and discuss the models and Tool at length.
3. Corps statement:
“A review of the existing available scientific literature on GHG from reservoirs performed for the CRSO EIS concluded that methane gas is generally not an issue for the relatively clean reservoirs in the Federal Columbia River Power System; reservoirs with a higher concentration of decomposing debris see more methane.”
Our response:
- The CRSO EIS review ignores findings that eutrophication and even moderate chlorophyll a concentrations, as have been observed in all four LSR reservoirs, reported in the media, and reported in the EIS, are associated with high methane emissions from reservoir surface and downstream from turbines.
- The paper by Miller (2017) explicitly states that the surface emissions measurements are not representative samples, and should not be extrapolated to the entire reservoir.
- Recent studies (Rosentreter 2022) note that methane surface emissions from temperature reservoirs like the LSR dams are major sources of greenhouse gas emissions.
- The CRSO EIS review only focused on carbon dioxide and methane from surface and turbines, and did not address the other six emissions source categories included in the All-Res Tool.
4. Corps statement:
“It is also important to note studies attributing some level of GHG to reservoirs have largely been conducted in tropical climates with environments vastly different from the Pacific Northwest. Even recent work by the Department of Energy’s Oak Ridge National Laboratory to improve the accuracy of GHG measurements in reservoirs relies on a sampling pool of reservoirs in a cluster of southern states that do not reflect the environmental and temperature characteristics common to the FCRPS.”
Our response:
- The sample size from temperate reservoirs in the U.S. is smaller than tropical regions. We are aware of ongoing sampling in the Pacific Northwest that may provide more data in the near future. We are also aware of additional sampling, and published papers, from other temperate regions outside of North America that challenge the Corps statement. We are also aware of the work ongoing at the Oak Ridge Lab. The Oak Ridge Lab studies are pointing to uncertainty in the measurements and claiming it is a reason for inaction. We agree that uncertainty exists, and our Tool actively embraces that uncertainty with a robust technique to estimate margins of error. In addition, uncertainty is not a valid reason for delay in addressing the risk of climate change. See our note about climate risk above.
5. Corps Statement:
Appendix G, Sec. 5 of the Columbia River System Operation final environmental impact statement, discusses GHG emissions in the Columbia/Snake rivers, as well as the differences in those emissions between rivers in the Northwest and those elsewhere, particularly in warmer climates. That information can be found at Columbia River System Operation Final EIS.
In Appendix G’s methane (CH4) emissions summary, the EIS says:
“The available data presented in this report on surface fluxes of CH4 emissions from diffusion for the Columbia River hydroelectric project reservoirs, particularly those located on the mainstem or in more arid terrain, demonstrate that the basin’s overall contributions to global CH4 emissions are very small compared to other studies of comparable systems, although they can be quite high locally,” Appendix G says. “The Columbia basin reservoirs produce CH4 in the range of one or two orders of magnitude less than current global estimates of surface emissions from reservoirs, even when only including hydroelectric reservoirs.”
Our response:
- Appendix G’s findings were based on a narrow review that did not examine the evidence that eutrophication, algal blooms, and significant chlorophyll a concentrations in the four LSR reservoirs indicate the reservoirs are likely to be high methane emissions.
6. Corps statement:
The EIS’s Appendix G concludes that differences that contribute to the lower levels of methane emissions are the relatively cold water temperatures, the well-oxygenated conditions in most of the river and the “low water residence times prevalent throughout the basin” (the flow), according to the EIS.
Our response:
- The Corps statement is incorrect. The scientific papers the Corps cites, including Deemer (2016) and others, show that water temperatures cannot be relied upon alone to accurately estimate surface methane emissions. Chlorophyll a concentrations and nutrient loading that drives eutrophication are statistically much stronger indicators.
7. Corps statement:
The EIS says the Columbia and Snake river systems of dams and reservoirs are just a “modest” source of CH4 and worldwide a small source of GHG.
“Indeed, CH4 emissions from reservoirs compared to total global sources are quite small. In mean estimates of data from the 2000s, global reservoirs, including tropical locations, contributed about 4–5% of CH4 from anthropogenic sources, and of these, hydroelectric reservoirs contributed about 3–6% of CH4 emissions,” the EIS concludes. “However, nontropical reservoirs have been shown to emit far less CH4 due to local regional features such as geology, climate, type of flooded soils and vegetation, and hydrologic regime.” The EIS goes on to say that methane emissions from hydroelectric reservoirs in the Western U.S. “were reported to be the lowest of those on the continent, compared to eastern Canada and Central/South America.”
Our response:
- This statement is not based on the most recent research, and it is a narrow interpretation of the Corps narrowly-defined review, within which they excluded much of the body of evidence that points to emissions from the basin. The Corps is basically saying “the problem is worse in the tropics than it is here.” This weakens the Corps position.
8. Corps statement:
Still, climate change may alter these findings, according to Appendix G: “Additionally, since increased GHG emissions is positively correlated with warmer temperatures, there will be an ongoing need to study the impacts of climate change on CH4 processes within temperate hydroelectric reservoirs,” according to an International Panel on Climate Change study.
In a 2006 study, the IPCC noted that temperature is the main driver affecting reservoirs as a result of climate change and, among other impacts, will change oxygenation levels, lake stratification mixing rates and growth of biota.
Our response:
- The science is rapidly advancing. The Corps is conflating “increased temperatures mean higher emissions” with “water temperatures are good indicators of methane emissions.” A reservoir with water temperatures of 60 degrees will not necessarily have lower emissions than a reservoir of 70 degrees, however if nutrient loading remains unchanged in the two and climate change increases the water temperature in both by 5 degrees, both will likely see increased emissions.
Again, we are pleased that the Corps has commented on our report. We would be happy to have a conversation with the Corps to present our Tool and findings so that a broader dialogue can occur. We welcome input from all scientific colleagues.
Mark Easter, Chief Scientist
Gary Wockner, Director