Relentless wildfires threaten supplies of drinking water in western U.S.

A region accustomed to wildfires is facing "unprecedented" destruction.

Potential sediment erosion on a slope from a wildfire over the Los Padres reservoir in California. CREDIT: U.S. Forest Service
Potential sediment erosion on a slope from a wildfire over the Los Padres reservoir in California. CREDIT: U.S. Forest Service

Wildfires fueled by dry weather and scorching temperatures have smothered parts of the western United States in smoky, ashy air, forcing communities to take measures to protect their drinking water supplies.

Earlier this week, at least 81 large fires were raging across 1.5 million acres of the West, from Colorado to California and north to Washington. North of the border in Canada, British Columbia has already had an “unprecedented” fire season.

With much of the nation focused on the Gulf Coast’s recovery from Hurricane Harvey and emergency preparations for incoming Hurricane Irma, officials in the western United States continue to work on bringing wildfires under control. While some thunderstorms formed over southern Oregon on Thursday, the rainfall was insufficient to quench wildfires, AccuWeather meteorologist Faith Eherts reported Friday.

“Very unhealthy air quality is forecast for wide swaths of the Pacific Northwest through the weekend, mainly in eastern Oregon and Washington, Idaho and western Montana where smoke is the most dense,” Eherts said.

In Portland, Oregon, firefighters are battling to protect the city’s drinking water reservoir from the fire burning in the Columbia River Gorge. In the West, communities rely on water from rivers and reservoirs that originate in watersheds where sedimentation is projected to increase, according to a new study by the U.S. Geological Survey (USGS). More than 30,000 acres of the Columbia River Gorge west of Portland have burned since last Saturday.

The Senate approved a bipartisan funding bill on Thursday to help with the cost of fighting the wildfires in western states as part of a disaster and government funding bill that is expected to pass the full Congress. But the funding would not fix the consistent under-funding of fire suppression, a bipartisan group of U.S. senators from the West wrote in a letter Thursday to Senate Majority Leader Mitch McConnell (R-KY).

“The accounts being robbed to fight fires are those that fund wildfire preparedness and mitigation projects in our forests,” the senators said. “Instead of robbing one set of priorities for another, what the nation needs is a consistently funded Forest Service that can address wildfire prevention, as well as emergency wildfire suppression, in the same years.”

The area burned annually by wildfires in the United States is expected to increase due to climate change. Burned areas increase soil erosion rates within watersheds, which can increase sedimentation in downstream rivers and reservoirs. The excess sedimentation causes excess turbidity that increases water-treatment costs and harms aquatic life.

“Does climate change cause wildfires? No. Most fires in the U.S. are due to human ignition. But climate change is making wildfires bigger,” Katharine Hayhoe, director of the Climate Science Center at Texas Tech University tweeted earlier this week.

In the Pacific Northwest, meteorologists say it has been an unusually dry summer. In a region known for rain, it has not rained significantly in Seattle since June. An estimated 35 fires were active across the region earlier this week. Gusty winds helped spread several, sending a layer of smoke and a downpour of ash onto Portland and Seattle.

Anthony LeRoy Westerling, associate professor of environmental engineering at the University of California, Merced, wrote that after 15 years of studying the science of climate and wildfires, he concluded it is a warming climate that is drying out western U.S. forests and leading to more, larger wildfires and a longer wildfire season.

According to experts, climate change has increased the threat of wildfires by influencing the variables that start or fuel fires. Warmer temperatures and drier conditions increase the chances of a fire starting, or help a fire spread. Climate change may also alter storm patterns, directly affecting the number of lightning-caused fires.

Montana’s fire season has devastated a large part of the state, with more than 1 million acres of land burned as of September 6, the third-largest acreage burned by wildfires in the state over the past two decades. The number of acres burned by lightning-caused fires is 922,506; the acres burned by human-caused fires is 110,295.

Fighting the fires has cost the state about $284 million in 2017, with about $53 million coming from the state and the rest from the federal government. Previous wildfires include the Great Fire of 1910 that burned 3,001,600 acres across Montana, Idaho and Washington. The Yellowstone fires of 1988 scorched 1,293,880 acres in and around the national park.

This “supercharged” hurricane and fire season is unleashing a “fire and fury” on the nation, while President Donald Trump ignores or discounts fossil fuels’ contributions to these disasters, according to Food & Water Watch Executive Director Wenonah Hauter.

“Our thoughts are also with the communities fighting to protect their homes and critical infrastructure from blazing wildfires,” Hauter said in a statement Friday. “At some point, our policymakers need to understand that these are not simply natural disasters. Their strength, severity and human toll are intensified by our addiction to fossil fuels.”

Wildfires can burn away ground cover and vegetation across the landscape, leaving soils exposed and easily erodible by precipitation. In other cases, fires can cause soil surfaces to harden. Instead of the rain soaking into the soil, rainwater and melted snow can rush across these hardened surfaces, gaining enough power to erode loose sediments.

USGS scientists studied climate, fire, and erosion models for 471 large watersheds across the West and found that by 2050, the amount of sediment in more than one-third of watersheds could at least double. In nearly nine-tenths of the watersheds, sedimentation is projected to increase by more than 10 percent.

The study’s findings could be used by communities to identify whether their water resources are especially at risk, and whether they have a suitable watershed management and protection plan in place, said Joel Sankey, USGS scientist and lead author of the study.

“At least 65 percent of the water supply in the West originates in watersheds with fire-prone vegetation,” said Sankey. “So, understanding how changing fire frequency, extent and location will affect watersheds, reservoirs and communities is of great societal importance.”