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Wildfires could raise temperatures, cause algae blooms in Oregon watersheds

Salem is one of several Oregon population hubs that rely on water from sources in or near wildfire-affected locations. This photo from before the fires in 2017 shows water flowing west of Detroit Dam. Detroit Lake waters flow downstream into Salem’s drinking water intake.
Bradley W. Parks
Salem is one of several Oregon population hubs that rely on water from sources in or near wildfire-affected locations. This photo from before the fires in 2017 shows water flowing west of Detroit Dam. Detroit Lake waters flow downstream into Salem’s drinking water intake.

Water supply and quality seems to be mostly unharmed in parts of Oregon affected by ongoing wildfires, though some of the hardest hit counties are asking residents to reduce their water use.

Several wildfires are continuing to burn across western Oregon, prompting roughly 500,000 people to be put under evacuation or pre-evacuation orders. By Friday, more than 900,000 acres had burned across the state, with many larger fires still at less than 10% to zero percent containment.

Officials across the state say they expect that this unprecedented amount of fire will inevitably change watersheds, which could lead to higher water temperatures and harmful algae blooms in the future.

Clackamas River Water Providers supplies drinking water to over 300,000 people in Clackamas and Washington counties. The agency’s water resource manager, Kim Swan, said the water is safe to drink, and that operations are fully functioning and capable of providing water. But she said water demands have increased because of the fires.

“Water demands in the areas closest to the fire have increased dramatically and, in an effort to provide the most water to the effort of fire suppression and life safety, we ask residents to curtail any unnecessary use of water,” Swan said.

Officials are asking residents living in Level 1 (“Be Ready”) or Level 2 (“Be Set”) evacuation areas, and those outside of fire-impacted areas, to reduce their water use so the Clackamas River Water Providers can send more water to areas that are more severely impacted by the fires.

Medford, which has been affected by Almeda Fire that originated in Ashland, is asking its residents to reduce their non-essential water usage in order to “preserve water for fire emergencies and necessary domestic use due to fire activity and sustained high demand on the water system.”

The Medford Water Commission said that, with stable reservoir levels and increased flow from the city’s Big Butte Springs water source, these water use restrictions are voluntary.

On Tuesday, Medford issued a boil-water advisory for a specific area of the city due to a pump station losing pressure due to nearby fires. That advisory was lifted Thursday after samples showed no harmful bacteria in the water.

Meanwhile, other populous cities along the Interstate 5 corridor, including Portland, say their water supplies are abundant and safe, although some residents have said their water has a strong taste and odor.

The Bull Run Watershed, which serves Portland, Gresham and Tualatin, has about 6 billion gallons of drinking water. So far there has been no noticeable ash fall in that watershed. Winds have been blowing the smoke and ash west. Midday Friday, the watershed was just outside of the area put under Level 1 evacuation orders. The nearest fire, the Riverside Fire, is near Estacada and is not considered an immediate threat to Bull Run.

In Eugene, drinking water is sourced from the McKenzie River and treated at the Hayden Bridge Water Filtration Plant in Springfield.

Joe Harwood, the public information officer with the Eugene Water & Electric Board, said some customers have been calling in with concerns of “a chlorine odor and even an ashy taste.” That’s due to the Holiday Farm Fire burning east of Springfield, up the river, he said.

“We have had to increase our chlorine to disinfect the water because we are seeing more contaminants than usual,” Harwood said. “So what we’ve been doing is, start to mitigate the turbidity issues that are associated with the fire and we’re hoping those measures essentially take care of the taste and odor.”

Harwood said customers should notice an improvement by Friday or Saturday. In preparation for the fires, the utility also filled 28 water storage reservoirs on Tuesday, but Harwood said there should not be any water shortage and the water is safe to drink.

Salem Public Works Director Peter Fernandez also said the water in that community is safe to drink, noting that the taste of the capital city’s water has not changed due to the fires.

“Our slow sand filters are working just fine,” Fernandez said. “There’s more turbidity [cloudiness] in the water, so the screens have to be cleaned, but the filters, the filtration system, that’s cleaning the water is working just fine. It’s not affecting it at all.”

Salem’s drinking water is processed at the Geren Island Water Treatment Facility on the North Santiam River near Stayton, just west of the Beachie Creek Fire — also referred to as the Santiam Fire — which had burned more than 180,000 acres as of Friday morning.

Stayton and other surrounding cities are currently under a Level 2 “Be Set” evacuation order.

Fernandez said even if workers needed to evacuate the facility, the plant would still be able to produce and filter water on its own for a while.

“We’ve been fortunate that the fires have stalled their westbound movement, so we’re cautiously optimistic that evacuating the water plant will not be an issue for us,” Fernandez said. "But we continue to be watchful.”

Even though most of Oregon’s water supply does not immediately appear to be affected by fires, some officials said there could be longer term health and environmental effects.

“We’re in sort of uncharted territory here. I’ve never seen anything like this,” said James Crammond, director of the U.S. Geological Survey’s Oregon Water Science Center. “I don’t think anyone has ever seen anything like this in Oregon.”

Although USGS and other agencies regularly study data on how wildfires impact landscapes, “nobody really knows what a million acres of contemporaneously burned land will do,” Crammond said.

He said there are general expectations for how watersheds tend to change after being affected by wildfire, usually including an immediate aftermath of more sediments and nutrients in waterways, murkier water and possibly stronger flowing water.

The U.S. Environmental Protection Agency has also said that wildfires can potentially cause erosion and even flooding due to changes in soil.

“You’re going to probably see water at a higher temperature in a lot of these watersheds,” Crammond said. “It’s very possible that fish life and a lot of other life in these streams will be negatively affected, or at least change, in response to the stressors.”

That could also lead to harmful algal bloom, Crammond said.

Fernandez said that’s something he’s worried about in Salem.

“Our theory is that that kind of ash is what leads to feeding the algae that creates a cyanotoxin, which is what we’ve been battling here for the past few years,” Fernandez said. “So, we anticipate that we’ll have turbidity problems in the winter in the source water and then probably more significant algae blooms in the years to come.”

Fernandez said the city is also working with the Oregon Health Authority to discuss other concerns, including the effect of excessive fire retardant on water filtration systems.

Crammond with USGS noted that many people in Oregon get drinking water from wells, and groundwater will likely not be affected, or at least the effects of fire on wells be more delayed than in areas that use large water processing plants.

“All of these things will eventually return to something that kind of looks like our previous normal,” Crammond said. “It’s just going to take a long time.”

Copyright 2020 Oregon Public Broadcasting

Meerah Powell, Monica Samayoa