On its path from the North Cascades to Skagit Bay, the Skagit River moves through a series of powerhouses to generate electricity. It is home to protected salmon and steelhead species, and it provides water for Skagit Valley farms and household use.

A group of scientists monitoring the river system have concluded that those functions are at risk because the river “is highly vulnerable to climate change.”

The Skagit Climate Science Consortium says river flow, water temperature and the movement of sediment in the Skagit River will change as rising global temperatures alter precipitation patterns, reduce snowpack and melt glaciers.

The Skagit River delta will be affected by those changes and by a rise in sea level, according to the consortium.

A series of studies by consortium scientists that look at how the region’s water systems will be affected by climate change was published in the winter 2016 issue of Northwest Science, Journal of the Northwest Scientific Association.

The association, a network of scientists that promotes research and education about environment and natural resource issues, published the consortium’s work because of its relevance to the impact of regional climate change.

“Skagit is the largest tributary to Puget Sound and the largest river between the Fraser River in Canada and the Columbia River. The watershed has the characteristics of Pacific Northwest rivers ... that make its response to climate change relevant throughout the region,” Northwest Scientific Association board president Andrea Woodward said.

The consortium is a group of scientists with a variety of backgrounds from such government agencies and universities as the U.S. Geological Survey, Seattle City Light and the University of Washington.

They were tasked with independently researching different aspects of regional climate change.

The group came together in 2009 with support from the Swinomish Indian Tribal Community, with the goal of taking a closer look at the Skagit River and surrounding areas. It aims to provide information to the public and government agencies that may inspire action to protect local communities and resources from the effects of climate change.

In addition to being published in Northwest Science, the consortium’s research was recently featured in an exhibit at the Museum of Northwest Art in La Conner, and is being used to help facilitate a series of climate discussions hosted by the nonprofit Transition Fidalgo & Friends.

“The issue of climate change is complex and the stories we see are usually about average global trends or far away places and issues like (flooding and sea level rise in) New Orleans, polar bears and remote tropical islands,” said consortium member and ecosystem ecologist Roger Fuller. “We want to bring the issue of global warming down to the local scale so that we can understand what it really means to us here and now.”

The U.S. Environmental Protection Agency estimates temperatures have increased about 2 degrees statewide and will continue to increase in coming years, according to a fact sheet released in August.

In response to rising temperatures, glaciers are melting rapidly, snowpack has decreased 20 percent since 1950, and warmer waters are fostering more toxic algae blooms.

Meanwhile, stream flows will become more extreme seasonally, and sea level rise will threaten waterfront infrastructure and habitat, according to the fact sheet.

That doesn’t bode well for hydropower, fish, forests and agriculture.

The consortium is helping to spell out how the natural resources in the Skagit River watershed will be affected.

“If you live here in Skagit County and you drink water, if you eat food, if you own a house or rent, if you enjoy hiking in the mountain forests, if you travel on highways and local roads ... you will be affected by climate change,” Fuller said.

The consortium estimates temperatures in the Skagit River watershed will increase 5.8 degrees by 2080.

Here’s a closer look at some of the potential impacts of climate change, according to the consortium’s recent studies.

GLACIERS

An estimated 12.4 square miles of glacial ice has melted in the Skagit River watershed since the 1950s, and the trend is expected to continue.

Glaciers supply about 12 percent of the Skagit River’s flow during the summer, when rain is sparse and snowpack is diminished.

The amount of glacier ice lost is the equivalent of an estimated 100 years worth of freshwater used in Skagit County.

SNOW AND RAIN

As temperatures increase, the elevation at which water freezes in the North Cascades will also increase, meaning less snow will accumulate in the mountains.

Snowpack helps keep streams full as it melts during the summer, when there is little rain.

Average freezing elevation in the Skagit River watershed has risen nearly 600 feet since 1958.

The snowpack that will accumulate in coming years will melt earlier and faster as temperatures increase, shortening the time during which snowmelt provides water to area streams during the dry season.

And more precipitation will fall as rain rather than snow due to higher winter temperatures.

STREAM FLOW

The Skagit River’s flow is expected to become more extreme with changes in snow and rain patterns. Summer will likely see lower flows, while fall, winter and spring will likely see higher flows.

That will cause more frequent and intense flooding, change the availability of hydropower for area utilities and threaten fish, which don’t do well in warm, shallow water.

Hydropower generated at dams on the Skagit and Baker rivers could increase an estimated 19 percent during winter and spring, and decrease by 28 percent during summer.

SEDIMENT

Higher streamflows and more frequent flooding are also expected to increase the amount of sediment in the Skagit River.

During peak flows in December, the amount of sediment in the river could increase by as much as 335 percent by 2080.

When sediment — sand, stones and other materials — settle in the river channel, it reduces room for floodwater. Murky water also isn’t ideal for fish.

SEA LEVEL

With sea level expected to rise 2 to 3 feet and with more extreme flooding, the area in the Skagit County predicted to be under water during a 100-year flood could increase 74 percent by the 2080s.

Sea level rise could also exacerbate the erosion of marsh habitat in the Skagit River delta.

Marshes provide important habitat for threatened Chinook salmon and other species, and can act as a buffer against storms. Aerial photos documenting the delta since 1937 show marshes are eroding along both the north and south forks of the river.

— Reporter Kimberly Cauvel: 360-416-2199,

kcauvel@skagitpublishing.com

, Twitter:

@Kimberly_SVH

,

Facebook.com/bykimberlycauvel

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