State, tribal and federal officials have already implemented the few tools at their disposal to mitigate rising water temperatures in the lower Snake River. Earlier this week, they began releasing 42-degree water from the Dworshak Reservoir. It will take three to four days for the water to reach the lower granite dam on the Snake River, where official policy is to keep the water at or below 68 degrees.

Fisheries and dam managers have also activated pumps at the Lower Granite and Little Goose dams that lift cooler water from deeper areas in front of the dams and direct it to the fish ladders. Ladders generally attract warmer surface waters, and during heat waves they can reach levels high enough that migrating salmon are reluctant to use them.

“In my opinion, we really don’t have a lot of options that will make a big difference,” said Charles Merrill of the Washington Department of Fish and Wildlife and a member of the Fish Passage Advisory Committee, a regional fishing and fishing group. ‘water. “We only have a limited amount of water in Dworshak and this heat wave will remove most of the water that would (normally) support cold water temperature management until the end of August. . “

His commentary illustrates that many temperature mitigation actions have advantages and disadvantages. While the early application of Dworshak water may help avert a potential disaster for sockeye salmon, it could also have consequences for chinook and rainbow trout later this summer.

The water releases began on Tuesday while the reservoir was still 3 feet from the fill. In most years, the discharge of fresh water begins after the July 4th vacation and continues until mid-September. Over the course of about 2.5 months, the tank is lowered 80 feet.

Starting before the tank reaches the full pool means there will be less water available for the cooling operation. Starting about 10 days to two weeks earlier means that the available water will be depleted sooner – from early to mid-August, when adult chinook and some rainbow trout move up the river. Without the cooling effect of Dworshak’s water, these runs might stop or the fish might suffer from the river temperatures in the 70s.

Becky Johnson, production manager of the Nez Perce Tribe’s Fisheries Resource Management Department, called him a potential “heartthrob”.

“We’ve worked so hard to increase that population,” she said of the Snake River fall chinook run.

Spring and summer wild chinook salmon biding their time in tributaries of the Snake River before spawning in August and September are also at risk. The current heat wave could cause water temperatures to rise for these fish.

“It’s hot out there and there isn’t much water,” said David Johnson, director of the tribe’s fisheries resource management department. “It doesn’t bode well for these fish and there are very few fish out there.”

Low flows and water temperatures approaching 70 degrees on the South Fork of the Salmon River prompted the Tribe and Idaho Fish and Game to move the hatchery chinook back from a holding facility in Rapid River. Hatchery.

Idaho fisheries officials and the National Oceanic and Atmospheric Administration plan to intercept adult sockeye salmon at the Lower Granite and Ice Harbor dams and truck them upstream to Stanley Basin which will be held in the Sawtooth Hatchery. Sockeye salmon enter the Columbia River and ascend in June and July, exposing them to potentially dangerous temperatures.

“They’re having bad timing in relation to these heat waves,” said Jonathan Ebel, a fisheries biologist with the Idaho Department of Fish and Game in Boise.

Members of the Fish Passage Advisory Committee have even considered hypothetical ‘out of the box’ actions that could help reduce water temperature, but admit that they are unlikely to be implemented without a. long and rigorous review process that would last well beyond the impending emergency. These actions include things like reworking reservoirs on the Snake River to levels that would temporarily halt barge transport; periodic opening of locks to facilitate the passage of returning adult sockeye salmon; operating the Snake River reservoirs at lower levels, known as the minimum operating basin, which would hamper but not stop barge transport; reduce or modify discharge regimes at some dams to reduce mixing of cold water from Dworshak with warmer water from the Snake River; or change their target temperature in the lower Snake River from 69 to 70 degrees for the purpose of stretching the Dworshak water.

Ebel said the ideas were generated more as a brainstorming exercise than as actions that can be implemented quickly.

“It just shows that we need a long term temperature plan, because we see these hot years more often,” he said. “We have to think outside the box for the long term. “