River flows are increasing on the Trinity and Lower Klamath Rivers to help spring-run Chinook salmon survive during this year’s unprecedented drought, according to a Yurok Tribe press release.
“Originating from Lewiston Dam, the 3-day pulse flow is intended to reduce river temperatures in the Lower Trinity River where adult spring-run Chinook salmon are holding in limited thermal refugia (creek mouths),” the Tribe stated. “Lower water temperatures will help fish migrate upriver into more suitable habitat. This action is being taken in response to the extremely high water temperatures in the Trinity River and evidence of widespread Columnaris (gill rot) infections in Spring Chinook. Please use caution when at the river during this time and be aware of changing river conditions as they could impact your personal safety and property.”
Here is the schedule of pulse flows:
• The pulse flow began on August 1, at 1:00 am. Flows will ramp up to 750 cfs immediately from Lewiston Dam and remain at this level for 24 hours.
• On August 2 at 1:00 am, flow will be reduced to 650 cfs and continue for 48 hours.
• On August 4 at 1:00 am, the flow will be reduced to base flow of 450 cfs.
• This pulse flow will reach the lower Trinity and Klamath Rivers sometime on August 2 and last for 3 days.
• Flows in the lower Trinity will increase from 600 cfs to 900 cfs and then ramp back down.
• Flows in the lower Klamath will increase from 2200 cfs to 2500 cfs before ramping back down.
The river releases follow a catastrophic spring on the Klamath River, where nearly all of the downstream migrating juvenile fall-run Chinook salmon perished on the river before reaching the ocean, due to outbreaks of disease in warm and low water conditions.
The flow release also takes place as another run of spring Chinook, the Central Valley spring Chinook, faces disaster due to an outbreak of disease due to low and warm flows.
A record run of over 18,000 wild spring Chinook returned this spring to Butte Creek, a Sacramento River tributary, the second largest since 20,000 fish ascended the creek in 1998, according to the California Department of Fish and Wildlife (CDFW). Allen Harthorn of Friends of Butte Creek estimates the size of this year’s run to be even larger, 25,000 fish.