On the River: Information Used for a Broad Array of Applications
COWLITZ RIVER — About a quarter of a mile below the Lewis County Public Utility District’s Cowlitz Falls Dam, three workers from the U.S. Geological Survey slowly comb from one side of Riffe Lake to the other, blanketing the water with sound.
The sound waves aren’t audible, but like sonar, they give the researchers a picture of what’s happening beneath them.
The red, white and blue acoustic Doppler current profiler (ADCP) is a little bigger than a coffee can and hangs vertically off the side of the boat and into the water.
It shoots sound waves about 13 feet down to the bottom of the lake. The waves interact with the particles floating in the water before bouncing back to the ADCP.
Ken Frasl, USGS field office chief for Western Washington, cruises the boat from one bank to the other several times so the machine can get a good reading.
USGS stream gauger Dan Restivo watches the measurements on a burly, waterproof laptop computer as they come onto the screen.
A thin smile of periwinkle and royal blue comes across the screen as it mimics the shape of the lake bed and informs the researchers where the particle flows are the most dense.
There are 10 sites along the Cowlitz River from just outside of Packwood down to Castle Rock. USGS visits the location just below the Cowlitz Falls Dam twice a year to verify the flows the dam operators believe they’re producing.
The Cowlitz is just one of roughly 400 gauging sites around Washington state where USGS measures streamflows.
When all the data is compiled, it creates a linear picture of how a river’s flow changes through the year.
The information is then used for a wide range of studies by the National Weather Service, the Army Corps of Engineers, private companies and many counties. It helps everything from flood warning systems to road and bridge construction.
The measurements are done around the state throughout the year, but USGS does them more often during extreme flows.
“It’s really important for us to get those extremes, otherwise we’re just guessing,” Restivo said.
For operators at Cowlitz Falls, the readings help ensure turbines are working properly, which ultimately helps them ensure a balance between the need for energy production and the health of fish populations into the year.
The delicate balance is made even trickier by drought.
“We had no snowpack this year,” Frasl said. “The lakes are full right now, but less water means less for power, for fish and for recreation, the whole thing.”
The dam operators estimated their water release to be 2,000 cubic feet per second, but the USGS machine read just over 2,300. The reading was higher, but not high enough to be of a concern.
“If we’re within a certain percentage, we go with what they have,” Frasl said. “More is typical, but it’s within reason.”
By Dameon Pesanti / firstname.lastname@example.org