Wildfires bring ashy sludge to beleaguered Western U.S.

Officials in Las Vegas, New Mexico, had barely finished battling the massive Calf Canyon-Hermits Peak wildfire earlier this month before they had to point their defenses toward another threat: the ashfilled erosion that could pollute their water.

The fire-scarred land along the banks of the Gallinas River is on the forefront of Mayor Louie Trujillo's mind these days. As much as the parched West needs rain, Trujillo and other officials are racing the weather to divert precious river water into a downstream lake before downpour comes and washes the burnt topsoil and ash into the river.

“There are large portions of the watershed you can see that are completely burned. It looks like burnt toothpicks sticking out of the ground for acres and acres,” Trujillo told CNN. “With the soil instability, during a heavy rain event it would be like putting water on a bunch of baby powder where it doesn't absorb at all; it just falls. We hope to beat the monsoon season, doing some of the interventions we're going to have to do along the watershed.”

Megafires aren't just burning down homes, trees and wildlife in the West. They're also destabilizing the soil. When it rains, thousands of tons of charred sediment flow into rivers and reservoirs used for drinking water. The Gallinas River, for example, supplies about 90 percent of the water for Las Vegas.

“It's literally like tasting dirt,” said Andy Fecko, general manager at the Placer County Water Agency in Auburn, California, a city that sits between Sacramento and Lake Tahoe.

“It adds a tremendous amount of treatment costs,” Fecko told CNN. “You're trying to filter out water that's 10 to 20 times dirtier.”

Even if they can filter out the taste of dirt and ash, water treatment managers also worry about the lingering impacts of charred organic compounds mixing with the chlorine used to purify the water so it's drinkable. The Environmental Protection Agency has warned about the health impacts of mixing the two.

All of this is adding more stress to water resources that are already depleting in the West's megadrought. Conservationists and officials are sounding the alarm about yet another impact of a warming climate, massive wildfires and fragile water resources.

“This is not our first megadrought, so we have to make really good use of every drop of water that we store,” said Dan Porter, forest program director for the Nature Conservancy. “These megafires are making that very difficult to do.”

In September 2014, California's King Fire ripped through over 100,000 acres in El Dorado County. That fire was relatively small by the standards of other megafires, but it burned very hot.

It was “a blast furnace of an event that obliterated everything in its path,” Fecko told CNN. “It was nuclear winter up there after that event.”

The fire was just the first problem. The following rainy season, more than 300,000 tons of ashy, topsoil sludge ended up in the Rubicon River -- normally pristine water that flows out of the Sierra Nevada mountains.

The huge sediment dump caused headaches for Fecko's water agency on two fronts, he said. First was the impact to their hydroelectric power operations, which clogged up with dirt that made it tough to run the water through to generate electricity. The second was drinking water.