Historically, the Snake River was home to almost half of the total Chinook salmon and steelhead in the greater Columbia River watershed. However,current wild-origin returns of salmon to the Snake Basin are 0.1–2% of their historical abundance, with Snake River sockeye salmon listed as “endangered” and Snake River steelhead and Chinook salmon stocks listed as “threatened” under the US federal Endangered Species Act. A 2022 US Department of Commerce study concluded that removing the four lower Snake River dams would be a “centerpiece action” towards these species’ recovery in the Snake River watershed.

A range of organizations, including tribal organizations, local governments and NGOs, are advocating for the removal of the dams and the replacement of their services to restore the species. While the evaporation water loss is just one component of the dam operation trade-offs, it has not been previously studied. This study, supported by Columbia Riverkeeper and The Water Foundation, addresses this research gap.