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A Talk on the Wild Side.

Idaho: Streamflow Responses to Climate Change - Why Elevation and Geology Matter

A gorgeous view of a flowing, rocky creek surrounded by tall evergreens
Adaptation iconLocation: Pacific Northwest  
Climate Change Impact: Streamflow response changes 


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The Opal Creek Valley, in the Willamette National Forest, contains 50 waterfalls, five lakes, and 36 miles of hiking trails. It forms the largest intact stand of Old growth forest in the western Cascades and 500-1000 year old trees are common. The most abundant trees are Douglas-fir, Western Redcedar, and Western Hemlock. Credit: David Patte/USFWS.

The waterways of the Pacific Northwest run deep. They unify the region that includes Idaho, Oregon and Washington by connecting the glaciers of its high volcanoes to its fertile valleys to the Pacific Ocean. Water coursing through streams and rivers is the lifeblood critical to urban and agricultural uses and to the vitality of aquatic ecosystems. Many iconic fish species in Idaho and the region such as salmon, steelhead, Pacific lamprey, bull trout and other native trout species, depend upon cool and plentiful stream flows to survive. But climate change is causing many stream flows to respond differently than they have in the past.

A changing climate is already bringing warmer air temperatures, an increasing proportion of winter precipitation falling as rain, earlier snowmelt and reduced spring snow pack. These changes all manifest in stream flow responses with decreased base flows, rising summer water temperatures, and more frequent winter flooding from rain-on-snow events.

Several bull trout up close underwater
Bull trout were listed as threatened in June 1998. Critical habitat was designated in 2005. A recovery plan was drafted in 2005 and has not been finalized. In January 2010, the USFWS proposed a revision of critical habitat. Credit: USFWS.

“The complex work of conserving and recovering fish populations in the Pacific Northwest has grown substantially more challenging in light of our changing climate – this has become increasingly clear in the last several years with recent scientific assessments and projections,” said Dan Shively, the U.S. Fish and Wildlife Service’s Regional Fish Passage and Habitat Partnerships Coordinator.  “Robust and diverse fish communities require healthy watersheds and habitat; or more simply put, an abundance of cool, clean water.”


In the Pacific Northwest, both elevation and geology have an important influence on stream flow responses – and therefore not all streams are responding to climate change in the same way. Upcoming published research by a team of hydrologists from the Service, NOAA-Fisheries and the U.S. Geological Survey provides greater understanding of how stream flow responses vary. The research builds on a substantive body of work by the University of Washington’s Climate Impacts Group, among others.

The research concluded that groundwater-dominated river systems of the Pacific Northwest, drawing water from deep beneath the surface, are less vulnerable to some climate change impacts and consequently may serve a greater strategic importance for sustaining aquatic ecosystems and the fish populations they support. These river systems, while vulnerable to the effects of changes in snow pack and winter precipitation, may provide cooler water and greater adaptive capacity to serve as refuges for coldwater-loving fish and other species. 

Shively is using these findings to develop a strategic approach to regional habitat restoration efforts.

Working as an interdisciplinary team with members of the Service’s Regional Water Resources Program and with scientists from other agencies and organizations provides critical understanding of climate change and water resources, Shively said. That understanding, in turn, will provide a foundation for broad landscape-scale strategies that will serve as the “blueprint” for conservation of aquatic habitats and fishery resources in the region.

“Understanding how changing climate is likely to affect stream flow and water temperature decades ahead is paramount when contemplating today’s strategies for investing in both the present and future for healthy aquatic habitats,” he said.  “Our collective interagency and partnership efforts are intended to provide the foundation for supporting self-sustaining populations of salmon, steelhead, trout, Pacific lamprey, and many other native fish species.”

Authors: Tim Mayer, Hydrologist, Water Resources Branch, Pacific Region and Jeff Maslow, Program Assistant, Pacific Region

Contact: Tim Mayer, (503) 231-2395 or Tim_Mayer@fws.gov

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What will likely happen to native, wild fish populations (and their habitat) in places like Harbor Lake in the Frank Church Wilderness? I ask about that particular spot because I once camped backpacking) near its shore.
# Posted By Alan C. Gregory | 6/16/11 1:53 PM

Good question Alan - wilderness areas will feel the effects of climate change along with other places. One would assume that a native fish population in a wilderness area would have few additional stressors and would be fairly resilient. But it just depends on the environmental and hydrologic conditions at Harbor Lake and the particular fish species present.
# Posted By Tim Mayer (USFWS) | 6/16/11 5:34 PM
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