Climate change could make WA streams too hot for fish, report shows

A new report prepared for the state Department of Ecology suggests climate change will continue to alter Washington’s rivers, potentially making some watersheds uninhabitable for salmon and steelhead by the end of the century.

The report led by Washington State University researcher Jonathan Yoder and University of Washington researcher Crystal Raymond projects widespread increases in river flows in the winter, declines in the summer and rising stream temperatures.

Nothing in the report is revolutionary, said state climatologist Nick Bond, but it’s a substantial contribution to the conversation. “Climate change has emerged in the conditions we’re seeing here in Washington state,” he said.

End-of-winter snowpack is declining. Storm surges are getting more severe. Summers are becoming drier.

Western Washington rivers saw record low flows this fall, forcing some salmon to drop eggs downstream from their usual spawning grounds. 

In 2015, high temperatures devastated the sockeye salmon run in the Snake and Columbia rivers. An estimated 250,000 sockeye died that year, long before reaching their spawning grounds.

Each of these trends will continue to affect the state’s freshwater highways, according to the report. But it’ll look a bit different depending on where you live.

Researchers analyzed existing studies, and used new data sets from the River Management Joint Operating Committee and the NorWeST modeling project to predict future streamflows and temperatures.

As the warming atmosphere turns snow to rain, the biggest changes will likely be in rivers fed by snowmelt. Watersheds that draw from the Olympics, the western slopes of the Cascades and the Blue Mountains in southeastern Washington could take the biggest hit during the dry season. 

By the end of the century, the report suggests, only the upper elevations of the North Cascades might provide reliable snowmelt. 

Rivers in the Olympic Peninsula and Puget Sound regions will likely see higher peak flows, and lower low flows. That could add stress to endangered salmon populations as they continue to navigate choked, warm waters. According to the report, salmon in the Olympic Peninsula are projected to be hurt the most by decreases in low flows.

Historical data from 1993 to 2011 shows most of the mountain-fed streams maintaining temperatures below 54 degrees Fahrenheit in the month of August. With moderate greenhouse gas emissions, some of those streams could warm up to 64 degrees Fahrenheit by the 2080s, according to the report.

In about five decades, the Columbia River and watersheds in the southeast could see August stream temperatures top 69 degrees.

Streams with temperatures greater than 64 degrees Fahrenheit can stress salmon, and no salmon species can survive waters above 77 degrees.

Over the years, the combination of lower flows and warmer air could make rivers hotter across the map. 

These challenges aren’t unique to Washington, the report states. Climate-induced streamflow changes exist throughout the West. Many states have responded with rules to manage water consumption and protect streamflows, but some have fallen short.

Seven Western states committed to storing water in reservoirs to provide additional security to the Colorado River Basin as part of the 2019 Drought Contingency plan. But the state of Colorado paused the program earlier this year to wait for the other three states in the upper basin to catch up. 

The new report “highlights that there’s really no easy solution to climate change impacts on our water,” said Jennifer Hennessey, special assistant to the director of Ecology. 

Some of those solutions, she said, come from addressing the root cause of climate change: greenhouse gas emissions. The state Climate Commitment Act introduced a plan to reduce emissions through putting a price on pollution, among other things. 

Others are more reactionary, adapting to the effects of drought through water storage and reducing groundwater consumption.

The report suggests the state already has programs that can help manage water in response to climate change. For example, the state Instream Flow Rule authority allows for limits to be placed on water consumption to help protect streamflows for wildlife, fish and water quality.

Ecology officials may request funding for drought planning during the upcoming legislative session to begin looking at new solutions. 

“The projected impacts from climate change are very significant,” said Dave Christensen, Ecology water resources program policy manager. “And those changes could negatively impact our natural systems: our ability to maintain wild salmon populations; it could impact our reliability of our water supplies for cities and culture.”