Lower Snake Dams are a Major Source of Greenhouse Gas Emissions - New Study Finds
Photo of Lower Granite dam on the Snake River. Photo credit: EcoFlight
The Lower Snake River dams (LSRDs) emit the equivalent in greenhouse gasses each year as burning 2 billion pounds of coal, according to a new report from the Patagonia-backed nonprofit Tell the Dam Truth. The impact of the Columbia-Snake River hydrosystem on wild Snake River salmon has made it clear that these projects are far from “clean energy.” This report now puts an estimate on the major greenhouse gas emissions associated with the four LSRDs, at a time when hydropower is often referenced as critical in transitioning to a carbon-free power grid regionally and nationally.
The scientists with Tell the Dam Truth calculate the total carbon footprint of the four dam and reservoir projects in the report via the All-Res modeling tool. This model is an advancement over conventional carbon accounting for hydropower in that it represents a true “cradle to grave” analysis, including every peer-reviewed greenhouse gas emission source category associated with the lifecycle of a dam - from dam construction/decommissioning to emissions released from a reservoir’s surface or water spilling through the power generating turbines.
While methane, carbon dioxide, and nitrous oxide are all emitted from hydropower systems worldwide, methane accounts for the overwhelming majority of these emissions over the long-term. It is an extremely potent climate pollutant that forms from the decomposition of organic matter trapped beneath the flooded reservoir environment behind a dam.
Both carbon dioxide and methane escape into the atmosphere from this process, but methane emissions persist long after the inundated vegetation and sediment decomposes. This is due to the fact that methane is also produced by bacteria that accumulate over years in the degraded reservoir environment and thrive in oxygen-less waters that are increasingly common due to the widespread algal blooms on the LSRDs’ reservoirs in the summer months.
Key Takeaways
The All-Res analysis is the most comprehensive accounting to date of the true emissions associated with the LSRDs, and those emissions are significant.
The LSRDs are estimated to emit 1.8 million metric tons of greenhouse gasses per year, adding important context to the effort to replace their services and restore the Lower Snake River.
Methane emissions, a potent greenhouse gas, occur throughout a dam’s lifecycle and in fact continue to increase long after hydropower projects are built - as other recent studies have found.
Quantifying the emissions of hydropower projects using the All-Res analysis is critical in accounting for their contributions to climate change, particularly during the transition away from fossil fuels to a clean, renewable power grid.
The path forward for the region, as outlined in the Six Sovereigns Columbia Basin Restoration Initiative document and the commitments the federal government agreed to with the 6S group can ensure that the regional power grid transitions to renewable and affordable energy generation and meets the projected increases in demand, while wild salmon populations are recovered. Accounting for the true emissions impact of hydropower generation is a key part of this process.
We do not have to choose between salmon recovery or the services provided by the Lower Snake River Dams. With planning and engagement by federal agencies in the region, we can have a diverse, reliable, and clean energy grid alongside abundant runs of Idaho’s salmon, while meeting federal Treaty and trust requirements to Tribes – all to the benefit of our communities and local economies in Idaho and the Northwest.