Characterizing off-channel habitats in the Willamette River: Fish need to cool off too!

During the summer, when the mercury clears triple digits on the Fahrenheit scale, people seek out cooler spaces. Shaded parks, air conditioned ice cream parlors, and community pools are often top places to beat the heat. If you’re a resident of Corvallis, Oregon, you may head downtown to dip your toes in the Willamette River. Yet while the river offers a break from the hot temperatures for us, it is much too warm for the cold water fishes that call it home.

Where do fish go to cool off?

As a master’s student in the Water Resources Graduate Program at Oregon State University, Carolyn Gombert is working to understand where cold water habitat is located along the Willamette River. More importantly, she is seeking to understand the riverine and geomorphic processes responsible for creating the fishes’ version of our air conditioned ice cream parlors. By placing waterproof temperature loggers along sites in the upper Willamette, she hopes to shed light both on the temporal and spatial distribution of cold water patches, as well as the creation mechanisms behind such habitats.

 

The cart before the horse: seeking to reconcile science and policy

Because the Willamette Basin is home to Cutthroat trout and Chinook salmon, the river is subject to the temperature standard adopted by the state of Oregon in 2003. Between May through October, Cutthroat and Chinook require water cooler than 18 degrees Celsius (64.4 degrees Fahrenheit). Currently, the main channel of the Willamette regularly exceeds this threshold. The coolest water during this time is found in side channels or alcoves off the main stem. While Oregon law recognizes the benefits these “cold water refuges” can provide, our scientific understanding of how these features change over time is still in its early stages.

Emerging stories

Data collection for Carolyn’s project is slated to wrap up during September of 2017. However, preliminary results from temperature monitoring efforts suggest the subsurface flow of river water through gravel and sediment plays a critical role in determining water temperature. By pairing results from summer field work with historical data such as air photos and laser-based mapping techniques (LiDAR) like in the image below, it will be possible to link geomorphic change on the Willamette to its current temperature distributions.

Between 1994 and 2000, the Willamette River near Harrisburg, Oregon shifted from a path along the left bank to one along the right bank. This avulsion would have happened during a high flow event, likely the 1996 flood.

No stranger to narratives

Prior to beginning her work in hydrology at OSU, Carolyn earned a bachelor’s in English and taught reading at the middle school level. Her undergraduate work in creative writing neither taught her how to convert temperature units from Fahrenheit to Celsius nor how to maneuver in a canoe. But the time she spent crafting stories did show her that characters are not to be forced into a plot, much like data is not to be forced into a pre-meditated conclusion. Being fortunate enough to work with Stephen Lancaster as a primary advisor, Carolyn looks forward to exploring the subtleties that surface from the summer’s data.

If you’d like to hear more about the results from Carolyn’s work, she will be at the OSU Hydrophiles’ Pacific Northwest Water Research Symposium, April 23-24, 2018. Feel free to check out past Symposiums here. Additionally, to hear more about Carolyn’s journey through graduate school, you can listen to her interview on the Happie Heads podcast.

Carolyn conducting field work on the Willamette.

Carolyn Gombert wrote the bulk of this post, with a few edits contributed by ID hosts.

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