Pulse flow curbed in wake of downstream concerns

That fell well below the initially planned release of more than 11,000 cfs in the hopes of effectively flushing downstream areas that provide habitat for polychaete worms — hosts of the C. shasta parasite affecting Coho salmon.

The process was intended to combine high-levels of strong water flow downstream with strong flow already building from tributaries filled by recent rains. By increasing the amount of water, it was hoped to cleanse river beds of parasitic hosts that have affected the already threatened salmon species for several years.

‘Flushing flows’

Last Wednesday U.S. District Court Judge William H. Orrick ordered the bureau to implement “winter-spring flushing flows designed to dislodge and flush out polychaete worms that host C. shasta.”

However, the recent heavy rains have raised flooding concerns, particularly in the wake of evacuations in California following the ongoing Oroville Dam crisis, resulting in precautions taken to reduce the planned initial flow.

“The court order required us to go three days with 6,030 cubic feet per second and we were able to do that, though we were hoping to do an even bigger flush,” said Laura Williams, bureau public affairs specialist.

“Due to the danger looming downstream and terribly high water levels just from the run-off from the river and side hills, we decided to scale back. We were hoping for a great big huge flush, but we still got a good one in there.”

Upper Klamath Lake

The water flush lowered Upper Klamath Lake’s levels by approximately one-third of an inch, according to Williams, which hydrologists hope will be replenished by incoming water to the reservoir from tributaries. Now it is simply a waiting game for fish biologists and hydrologists to see if the water release was enough to effectively reduce the population of polychaete worms by cleaning out their preferred river bed habitats.

Areas of focus for the pulse flow extend along much of the Klamath River in California, especially in the area below Iron Gate Dam.

In the Happy Camp area, where river water levels were reaching the highway, residents were getting nervous, according to Williams, of public safety in the wake of planned pulse flows.

“We were getting phone calls from homeowners with concerns about the safety downstream, so we decided to keep it a lower intensity level,” added Williams. We’re trying to do the best for the irrigators and ecosystem and animals, but our first concern is public safety. We sent a good healthy amount of water down after the heavy run-off waters were past the danger point, but we didn’t go as intensely as expected.”

Williams indicated plans for an eventual complete pulse flow, but noted that such further actions will be “played by ear” based on collected water level data and spring salmon research. She emphasized the importance the bureau places in making sure irrigators will continue to have enough water for their needs during the year.

“It sure is a lot nicer this winter than the droughts we have had for the past four to five years,” said Williams of the recent winter storms. “There’s hope, we’re doing the best that we can. We’ll watch and see what is possible with the hydrology that comes to us through the spring season.”