In hot water: Warmer lakes might feel nice for some swimmers, but they come at a cost

Come on in, the water’s warm, scummy and full of dangerous bacteria.

That could be the tagline for some Inland Northwest lakes right now. It’s not as if taking a dip at every local lake feels like swimming in bathwater, but extreme heat has raised water temperatures and brought unwelcome side effects.

Hotter temperatures can create better growing conditions for blue-green algae, a harmful bacteria that can make swimmers and their pets sick. Warm waters can stress and kill fish, too.

In the last week, the Panhandle Health District has issued health advisories due to harmful blooms at three popular swimming spots in North Idaho: Fernan Lake, Hayden Lake and Sagle Slough, where the Pend Oreille River meets Lake Pend Oreille.

Blue-green algae – which is actually an algae-like cyanobacteria that can photosynthesize like plants – can show up as thick green mats atop the water or gobs of floating scum. The bacteria can also discolor the water, or look like streaks of oil on the surface.

Harmful blooms are unsightly and not many people enjoy swimming in lukewarm goop, but they aren’t just an aesthetic problem.

People who swim in blue-green algae can develop rashes or hives. They can have diarrhea, throw up, cough or wheeze. Ingesting enough blue-green algae at high concentrations can even affect the liver and nervous system.

Humans can generally use common sense to avoid drinking water teeming with blue-green algae, but sometimes pets don’t know any better.

“We have had reports of animals becoming sick, animals having to go to the veterinarian and some animals have been reported as having passed away – that’s (what we’ve heard) from the owner, we don’t have confirmation,” Panhandle Health District spokeswoman Katherine Hoyer said.

Pets sometimes lick their fur after swimming and become sick, Hoyer said.

“Then they’re ingesting a ton of toxins,” she said.

Hoyer said the health district recommends not swimming in algal blooms. Anyone who does swim in water with algal blooms should shower afterwards. Fishermen who want to eat a fish caught in a lake full of blue-green algae should remove the fat, skin and organs from their catch before cooking it.

Harmful algal blooms are common here, and some lakes experience them annually. Heat isn’t the only driver of algal blooms. Excessive nutrients can cause them, and other weather conditions play a role, too.

But high temperatures can exacerbate the problem.

“You can’t deny that temperature helps fuel algae blooms,” said Colleen Keltz, water quality spokeswoman for the Washington Department of Ecology.

Keltz said the Department of Ecology tested water in the Little Spokane River on Tuesday after hearing a report about three dogs that died shortly after swimming in the river.

“We are pulling a sample to do a test, but we don’t know yet what could have happened,” Keltz said.

Blue-green algae blooms are more common in ponds and lakes – places with calm, stagnant water. Still, Keltz said it’s “totally possible” to have a bloom in a slow-moving section of river, especially now with water levels relatively low.

“Rivers are lower and slower right now,” Keltz said. “You have some pooling areas that are warming up and you might be mimicking the conditions that you would see in a lake even.”

Keltz and Hoyer said they couldn’t say whether the region is seeing more harmful algal blooms this year than normal. There isn’t a robust tracking system, they said.

“It’s hard to say because we totally rely on folks taking samples,” Keltz said. “There’s no constant monitoring of lakes.”

At the same time, Keltz noted that it seems “we’re entering into a new normal of things changing for our water quality.”

It’s difficult to pinpoint how much warmer the Inland Northwest’s lakes and rivers are in this historically hot year. Neither the Department of Ecology nor the Washington Department of Fish and Wildlife has a coordinated water temperature tracking effort.

Still, experts say they’re confident temperatures are warmer, and the existing data back them up.

The U.S. Geological Survey doesn’t have many temperature gauges for far-eastern Washington, but the agency does have a gauge at Boundary Reservoir near Metaline Falls.

That gauge shows the water temperature on Aug. 4, 2020, peaked at 75 degrees. On Aug. 4, 2021, the temperature hit 77 degrees.

Geological Survey gauges also show lower water levels – either “below normal” or “much below normal” – along most creeks and rivers throughout Eastern Washington and North Idaho.

A few rivers, such as the Pend Oreille River near Ione and the Columbia River at the Canadian border, have “normal” flows.

Warmer waters and algal blooms can hurt or kill fish. Warm water can hold less oxygen than cold water and decomposing algal blooms use up available oxygen, too. On top of that, extreme heat melted snowpack earlier this year, which has contributed to lower water flows, and some creeks have dried up.

Staci Lehman, communications manager for the Washington Department of Fish and Wildlife’s Eastern Washington region, said warm waters haven’t hurt Eastern Washington fish too badly so far, but she said her department is asking anglers to restrict their fishing to the early morning and late evening to avoid stressing fish during the hottest parts of the day.

There have been some heat-caused fish die offs – there was one on the Kettle River a couple of weeks ago – but the drought and heat in 2015 killed more fish, Lehman said.

Lehman noted that water temperatures were higher and flows were lower then.

“This year we haven’t seen anything like that,” she said. “We aren’t in panic mode.”