Researchers from the Benton Conservation District,
Yakama Nation, and U.S. Geological Survey are profiling cooler areas in the lower
100 miles of the Yakima River that may serve as safe havens for fish during
Funded by Washington Department of Ecology,
the survey will help protect these sites and meet environmental enhancement
objectives of the Yakima River Basin Integrated Plan https://ecology.wa.gov/Water-Shorelines/Water-supply/Water-supply-projects-EW/Yakima-River-Basin-projects/Yakima-integrated-plan
For 12 days this July, average daily river
temperatures at Prosser were above 80 degrees. Historically, the monthly mean
temperature for July at Prosser is 69.3 degrees.
Over the last four years, the rise in river
temperatures is notable. In fact, 20 of the 30 warmest river temperatures
recorded since 1990 at Prosser were from the years 2015 to 2018, says WDOE.
These “thermal blocks” are stalling the
migration of sockeye salmon. Recently reintroduced to the river by the Yakama
Nation, the sockeye are pausing their migration, waiting at the mouth for
conditions to improve.
Temperatures above 73-77 degrees are
considered lethal to salmon. Survival of late spring smolts is also influenced
by rapid water warming, especially in drought years.
Fish are able to detect water temperature
differences within a half a degree. They move to areas that are cooler and more
favorable in an activity called "behavioral thermoregulation." Of all
Pacific salmon, sockeye prefer the coldest water.
Enhancing thermal refuge locations on the
lower Yakima may support late spring and summer migration of anadromous species
when water temperatures are otherwise too warm for fish passage.
Benton Conservation's water resources
specialist Marcella Appel is leading the multi-agency project to map the
thermal profile of the river from Wapato to Richland. Data will be used to
identify areas where cool water is introduced to the river, be it from shallow
groundwater or subsurface flows influenced by irrigation.
“We want to learn where these temperature
refuges exist because they are so important to salmon,” Appel explained. “The
information will provide one more piece of the puzzle as partners of the
integrated plan seek to restore water conditions on the Yakima River for people
It’s also believed these refuges provide
beneficial warmer water for out-migration of juvenile smolts during the winter
and spring months.
The conservation district, Nation, with
Ecology staff and local community volunteers, have completed eight of nine
floats, already covering 80-plus river miles. The study team has one more float
to log information, planned in early September.
With anticipated climate change impacts in the
basin resulting in higher river temperatures and lower springtime flows,
thermal refuge locations will become increasingly important for migratory
species, says WDOE.
“The support and collaboration for this project
have been amazing,” Appel said. “We could not have completed the rigorous
summer float schedule without the help of our partners and local citizens.
“It is satisfying to see everyone working
together on solutions for the lower Yakima River. I look forward to the next
phase as we analyze the data. We anticipate the efforts of this two-year study
will lead to future projects aimed at helping cool water species navigate an
otherwise hot river,” Appel concluded.
For more information see https://ecologywa.blogspot.com/2018/08/floating-yakima-river-with-purpose.html