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‘Aggressive’ Deep Drawdown Begins This Week

Greg Taylor, USACE fish biologist, talks about the drawdown during a town hall meeting on Oct. 10. Photos by Sarah Brown

This week anglers and concerned citizens will see the Green Peter Reservoir begin to drop dramatically as a modified deep drawdown begins to take action on Oct. 15 aiming for its target elevation by mid-November.

Questions about dying fish and turbid waters this year will soon be answered, but the U.S. Army Corps of Engineers seems to indicate it won’t be as dramatic as last year. That’s because it’s believed the “aggressive” drawdown will actually reduce turbid conditions and the remaining deep-level fish (Kokanee) are small in number this year.

In fact, after gathering data from last year’s initial deep drawdown at Green Peter Dam, USACE determined the Kokanee fishery in the reservoir is essentially gone.

“We had a lot of Kokanee pass out of this dam,” said Greg Taylor, supervisory fisheries biologist for the USACE Willamette Project, adding that more than one million Kokanee died from barotrauma during last year’s first drawdown.

Initially he hoped enough of the Kokanee would stay in the Green Peter Reservoir to maintain a fishery, but it simply didn’t happen. As such, there’s not much left to pass through the dam this year.

Sandwiched between online informational meetings hosted by USACE in a three-day period, the South Santiam Watershed Council hosted its own town-hall-style meeting at the high school auditorium on Oct. 10 with Taylor.

A resident asks a question during the meeting.

Working for USACE for 23 years, Taylor has been involved with the Green Peter case since at least 2021 when he participated as a panel expert to help determine the plan of action after U.S. District Court Judge Marco Hernandez found for the plaintiffs (Native Fish Society, Northwest Environmental Defense Center, and Wild Earth Guardians). The panel consisted of two experts representing the plaintiffs, two experts from the National Marine Fisheries Service, and two USACE representatives (whose purpose there, Taylor said, was limited to making sure the plan did not damage the safety of the dam).

Taylor reported that a majority of “test” juvenile Chinook had passed through the dam’s spillway last spring, but the percentage of naturally produced Chinook passing through was lower. The number that passed during the drawdown was “really small” (low hundred thousands).

The questions to answer, he suggested, include whether the fish are successfully spawning in the river and passing to the reservoir, how many fish are actually in the reservoir to pass, and are they surviving in the reservoir during the summer.

It will take different methods and monitoring techniques to find what works and what’s needed. This year USACE was allowed to run the deep drawdown in a short, one-month period in an attempt to save fish eggs from overheated water temperatures.

“We need to do this over multiple years,” he said. “Then ultimately you are able to take all that information that you collect, put that all together and make some kind of determination as to whether this is really going to work.”

Background

Green Peter Dam was completed in 1967 with a regulating outlet (RO) near the bottom, a penstock and turbine above that, and a spillway near the top. During the first few decades, there had been different attempts to pass fish through the dam, but none were successful. The penstock cannot be used for pass-through because the turbines increase fish mortality. Chinook successfully pass over the spillway in the spring, but the hiccup is how to pass targeted juvenile Chinook in late fall or winter

In 2008, a Biological Opinion (“BiOp”) from the National Oceanic and Atmospheric Administration Fisheries (NOAA Fisheries) specified 96 actions that the Corps must complete within 15 years (by 2023) to help spring Chinook salmon, which are on the Endangered Species Act list. Taylor explained last year that the Corps accomplished 87 of those actions but, admittedly, did not complete all of them because some needed more time or more funds.

This led to the lawsuit whereby Judge Hernandez agreed USACE violated the ESA, resulting in a set of required actions to ultimately pass more Chinook down the Santiam with a higher survival rate.

“When you do any kind of operation at these dams to try to help a fish, or quite frankly anything else, there’s always a set of impacts and benefits associated with that action we take,” Taylor said at the town hall. “There is not silver bullet stuff out here.”

Other information gleaned from the meeting include:

  • USACE will be taking advantage of the deep drawdown to access and repair a crack on Green Peter Dam.
  • Sediment samples between the Middle and South Santiam rivers indicate no concerning levels of metals.
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