Rising temperatures and decreasing flows in area rivers could be deadly for the Pacific Northwest’s most treasured fish.

Daily monitoring of habitat for salmon and steelhead populations will be vital this summer because of dry conditions and a below-average snowpack. Local officials hope new tools put in place through the Yakima Basin integrated water management plan can help prevent anything like the massive fish die-offs of 2015.

Fish aren’t in nearly as much danger yet from this summer’s drought, according to Perry Harvester, the Yakima-based regional habitat program manager for the Washington Department of Fish and Wildlife. Stream flows of Yakima River Basin tributaries have been measured at levels typically not seen until late July, but cooler weather recently has kept water temperatures from rising to dangerous levels.

“Right now I think everyone’s in a wait-and-see mode,” Harvester said. “We know there’s going to be concerns within stream flow, but so much of what ultimately will occur will be determined by the weather between now and fall.”

The National Oceanic and Atmospheric Administration predicted with high confidence the Pacific Northwest will see warmer-than-average temperatures from June through August. Harvester said some of the high temperatures responsible for quickly melting snowpack in April and May likely already caused some fish to die, and it would take less than a week of 100-degree days to cause serious concerns.

Since 2015, numerous actions have been taken by water managers such as the Kittitas Reclamation District to protect fish from drought. KRD manager Urban Eberhart said the district is putting 20 cubic feet of water per second into Manastash Creek to keep it flowing above the surface along a 3.5-mile stretch that previously went dry for four to five months.

The same thing is happening at Taneum, Little and Tucker creeks, using water from the canal system. Other projects include connecting floodplains and adding vegetation, both of which create more cool spots for steelhead and salmon.

“In each of those creeks we’ve been able to show that there are multiple species that are using those streams now that they have water in them,” Eberhart said. “It gives them an opportunity to have a place of refuge out of the main high-flowing Yakima River.”

Harvester said temperatures rose above 70 degrees in the Lower Yakima earlier this year, high enough to impair fish. They struggle to breathe with less oxygen in the water and become easy targets for predators such as birds and bigger fish more comfortable in warm water.

That turned out to be a problem for more than salmon and steelhead in 2015, when several hundred old, large sturgeon ate too many dead salmon and died due to increased metabolisms paired with a lower oxygen supply. Those smolts — juvenile salmon — would have been coming back from the ocean in recent months, so the die-off is a big reason why Harvester said current returns are the lowest seen in 20 to 30 years.

This summer’s biggest concerns will be the steelhead, sockeye and summer chinook migrating back upstream. Harvester said warm water can create “thermal blocks” that cause fish to stack up at mouths of tributaries such as the Klickitat and Deschutes rivers.

If needed, officials can offer aid by creating “pulse flows” — releasing stored water to either push fish through warm sections quicker or give them cool spots to use on their way upstream. Another more drastic option would be to relocate stranded fish. Harvester noted it’s also critical to remove small, informal dams sometimes built by children for fun that block the way.

In 2018, the Department of Ecology began a grant program as part of the 2018 Streamflow Restoration Act to allocate $300 million to help fish and stream flows over the next 15 years. KRD is slated to receive $2 million for a project designed to conserve water and increase flows in Yakima River tributaries with important salmonid habitat.

The Yakama Nation plays a key role as well, staying in close contact with the wildlife department, KRD and other diverse groups all working toward the same goals. Eberhart stressed the importance of finding solutions good for both farmers and fish conservationists, groups that were often opposed not so long ago.

“We’re doing everything we can right now and we’re continuing to find ways to improve things for fish up and down the Yakima Basin,” Eberhart said. “It’s really a collaborative approach to doing things.”

Editor's note: This story has been updated to correct the amount of money going to KRD for a streamflow project.

Reach Luke Thompson at luthompson@yakimaherald.com on Twitter: @luketscribe