Late Spring runoff causing concerns for fish migrations

With juvenile chinook and sockeye salmon, as well as juvenile steelhead, beginning their migration from the Northwest tributaries and hatcheries, but with very low water in the river due to a late spring runoff, salmon managers have asked for augmentation flows.

The managers asked hydro operators at the April 21st, interagency Technical Management Team meeting to raise flows from Chief Joseph Dam, just downstream of Grand Coulee, to 90,000 cubic feet per second beginning Monday, April 26th, through Saturday, May 2nd, to ensure the speedy outmigration for the smolts.

Jonathan Ebel of the Idaho Department of Fish and Wildlife called on TMT to look at a bigger picture of fish passage – both juvenile and later adults – not only in the mid-Columbia, but also in the Snake River basin where conditions are extremely dry and water could be in short supply as summer approaches.

The bottom line is that Snake River projects may not provide as much augmentation water as expected.

“Everything is really dried up this year,” said the Bureau of Reclamation’s Joel Fenolio. “At least three sub-basins in the upper Snake River (upstream of Idaho Power’s Hells Canyon Complex of dams) have water supplies that are 75 to 85 percent of average.”

Idaho Power’s Brownlee Reservoir is low and is in the process of refilling. Since the power company is not a part of the federal hydroelectric system, there is some uncertainty whether it would pass water from the upper BOR dams as it is refilling its own reservoir, Ebel said.

“Considering the low water forecasts, wouldn’t it be valuable to save mid-Columbia water for the long term?” he asked.

Part of the issue is that cool spring temperatures have delayed the normal runoff, but that could be changing with showers over the region last weekend and more melt should occur by mid-May that could increase river flows to a more natural level, Fenolio said.

The reality is that, according to the Northwest River Forecast Center’s 120 day forecast out to August, much of Western Montana, Idaho and Eastern Washington and Oregon streamflows are expected to be at 75 to 90 percent of average, and many of the streams in southeastern Idaho could be as low as 25 to 50 percent of average.

NOAA’s Claire McGrath expects passage of wild chinook and sockeye to peak the first week of May and supports the proposal for increasing mid-Columbia flows.

Still there is uncertainty when and how much flow will be added over the next few weeks from a later spring runoff from tributaries downstream of Chief Joseph Dam. There is a discrepancy of where people think the water will come from, suggesting that if tributaries downstream of Chief Joseph add water, perhaps Joseph shouldn’t be the control point.

“If you want to control how much augmentation water you use from Coulee, you need the control point to be Coulee,” said Tony Norris of the Bonneville Power Administration. “There would be low certainty of getting the flows needed if we move the control point to Priest Rapids Dam, which is a Grant County PUD-owned dam and not a federally-controlled one.”

Low flows in the Columbia and Snake rivers are also impacting spring spill. The U.S. Army Corps of Engineers in a news release said that cooler temperatures have slowed runoff, leaving river levels too low to reach the high flexible spill levels required by the 2020 Columbia/Snake river biological opinion.

The Corps said that spill for juvenile fish passage helps reduce the proportion of juvenile fish that pass dams through the turbines and helps reduce passage delay at each dam, thereby shortening their travel time through the Snake and Columbia rivers.

Flex spill operations include juvenile fish passage spill at performance standard levels for eight hours each day when energy demand and electricity prices tend to be higher, then spill up to the maximum amount allowed by state water quality standards (TDG) for the other 16 hours a day when electricity prices are lower.

“The continued trial of flex spill will help us assess both short and longer-term benefits to fish while also providing flexibility to balance clean power generation with the needs of fish as we operate the system,” said Tim Dykstra, senior fish program manager for the USACE’s Northwestern Division.

“We need to keep asking the question, ‘How can we do this better,’” said Michael Tehan, Assistant Regional Administrator for the Interior Columbia Basin in NOAA Fisheries West Coast Region. “This is an important opportunity to test the projections for what higher spill may do for fish.”

“The early results have been promising, with the increased generating flexibility in the summer successfully offsetting the negative impacts of reduced flexibility in the spring,” said Kieran Connolly, BPA’s vice president of Generation Asset Management. “Given that water conditions and emerging power markets are very dynamic, we will need to evaluate this innovative approach for multiple years to confirm that these preliminary results hold up over time. Ultimately, flexibility for power generation allows us to keep power costs affordable while also playing a critical role in regional efforts to manage power reliability and carbon emissions.”

While water managers expected 2021 spill to resemble 2020, a slow runoff has left river flows too low to reach those high spill levels. However, flow and spill volumes will increase as snowmelt increases in coming months, federal agencies said.