By Amanda Stahl, Washington State University and Karie Boone, The Center for Sustaining Agriculture and Natural Resources, Washington State University

Predicting climate impacts on water availability for agriculture and potential effects on salmon populations requires us to understand natural seasonal changes in streamflow patterns across the Pacific Northwest. The Washington Department of Ecology in collaboration with WSU, UW, the Climate Impacts Group, and the State of Washington Water Research Center recently published updated scientific information highlighting upcoming climate challenges to streams and salmon.

The WSU Team’s report explains that expected changes include lower summer flows that last longer and contribute to warmer water, meaning salmon will have less habitat and more barriers to migration and survival. In the mountains, warmer spring weather will likely cause earlier snowmelt and more common rain-on-snow events. The resulting floods can wash away incubating salmon eggs from mountain streams. Each type of streamflow change will happen in different places, depending on the distance from the coast, elevation, the source of the water, and the characteristics of surrounding areas. Salmon travelling along each length of river or stream will be impacted by a different combination of these changes as described below.

The state is divided into five regions to project combinations of climate impacts on rivers and streams (see map below).

Map of Regions in Washington State defined by climate driven changes to stream flow and temperature, and salmon population characteristics (migration distance and status) (Yoder et al. 2022).
Regions in Washington State defined by climate driven changes to stream flow and temperature, and salmon population characteristics (migration distance and status) (Yoder et al. 2022).


Streams in the Olympic Peninsula and Puget Sound and southwestern Washington will have more flooding in winter-spring and lower low flows in summer-fall. Salmon with summer-fall migrations will have less habitat available and will encounter more significant barriers to spawning and survival.

Sockeye salmon from above. Photo Credit: Daniel Auerbach, WSU Pullman
Sockeye salmon from above. Photo Credit: Daniel Auerbach, WSU Pullman


Streams on the east side of the North Cascades and the Okanagan Mountains are likely to have higher early spring flows with more flooding. Alpine areas will keep snowpack longer and those streams may show less of a change. Winter-run steelhead with springtime egg incubation may be most vulnerable to spring floods. Spring-run Chinook will likely be vulnerable to both spring flooding and the stress of swimming through warmer, lower waters in summer and fall.

Streams on the Columbia Plateau and in the Blue Mountains will have lower flows in summer. Here salmon will experience the stress of higher cumulative exposure to warmer waters while migrating up the Columbia or Snake River and their tributaries.

Are water policies ready for climate adaptations to support salmon populations?

Because each salmon population has different needs that change with time and place, developing more adaptive water policies to help them while protecting water rights is a complex and challenging endeavor. In Washington and more broadly across the West, water management is predicated on the Prior Appropriation Doctrine. Under this doctrine, “first in time first in right” protects user water and rights but doesn’t necessarily help users or ecosystems adjust to changing water availability from year to year. Climate adaptive water policy for water users and salmon would ideally be able to respond to new information more quickly than the current system allows.

Washington water policy does include tools to help ensure flows for fish and address other environmental considerations. Water for the environment and fish were added as a sanctioned water use through Instream Flow Rules, allowing for the maintenance of a minimum streamflow for fisheries by limiting more junior water diversion rights. The Washington Trust Water Right Program allows for water rights to be temporarily or permanently leased, acquired, or donated by water right holders to the Department of Ecology to benefit instream flows or preserve groundwater levels. Together, these policies largely determine how much water stays in the stream, yet they may not be adequate to protect salmon populations.

Timing is a key factor for adaptability. Water availability changes by season and year and is only partly predictable. From the salmon perspective, when low-flow conditions pose a major threat, water use adjustments could be promptly implemented to protect their population. However, this may be difficult or impossible to achieve if instream water rights are junior to out-of-stream rights. The Trust Water Program additionally allows water right holders to withdraw their right from the program at their discretion, making potential contributions to streamflow indefinite.

Many entities are grappling with how best to protect fish populations under a changing climate, including other western states (California, Colorado, Idaho, Montana, Oregon, and Utah) and Tribal Nations. States are developing comprehensive water plans that include water budgets based on climate change information, encouraging flexible use of water rights, when possible, risk sharing, and tradability of water rights. Meanwhile, Tribal Nations also manage Tribal Treaty reserved water rights to support fisheries for cultural value. The act of gathering salmon is often linked to tribal religious practices. Tribes such as the Nez Perce and Yakama recognize their deep-rooted connections to the river and its influence on cultural identities. They believe that they have a duty to protect the river for future generations and that climate change threatens not only the river but their culture (AP 2022). They thus manage water and fisheries from a distinct ethos stemming from the belief that the river itself has a spiritual identity and is sacred.

Policy adaptation may be guided by recognition of the cultural value of salmon and supported by ongoing science. Future modelling efforts may be directed to focus on summer low flows in snow-dominated areas, understanding more about predicted low flows, particularly in southwestern Washington, and including more detail to predict impacts on salmon by species and run timing for watersheds across Washington.

For more information on projected climatic changes on stream flow, see the report:

Yoder, J., et al. (2022). Climate Change and Stream flow: Barriers and Opportunities (Publication 22-11-029). Washington State Department of Ecology. Online Access


The Associated Press. (2022, August 21). Columbia River’s salmon are at the core of ancient religion. Npr. Online Access

Isaak, D., Wenger, S., Peterson, E., Ver Hoef, J., Nagel, D., Luce, C., Hostetler, S., Dunham, J., Roper, B., Wollrab, S., Chandler, G., Horan, D., Parkes-Payne, S., 2017. The NorWeST Summer Stream Temperature Model and Scenarios for the Western US: A Crowd-Sourced Database and New Geospatial Tools Foster a User Community and Predict Broad Climate Warming of Rivers and Streams. Water Resources Research 53, 9181–9205. Online Access

National Atmospheric and Oceanic Administration (NOAA), National Marine Fisheries Service (NMFS). West Coast Region Endangered Species Act Critical Habitat, 2005. URL Online Access.

The work that resulted in this post is jointly funded by Washington State Department of Ecology (Ecology) and the “Technology Trade Project” with support from USDA National Institute of Food and Agriculture, project #1016467.

Article originally published on May 15, 2024, on the AgClimate Network website.