Energy & Environment

Wildfires Threaten Water Supplies

More than 60 million people get their water from national forests. But ash and debris from big fires can make the water undrinkable.
by | July 23, 2012

Founded in 1608, Santa Fe has sustained itself for 400 years on close-to-clear snowmelt from the Sangre de Cristo Mountains. Today, the New Mexico state capital's 68,000 residents still get 40 percent of their drinking water from these slopes just above town. But Santa Fe's clean water could be at high risk if a wildfire breaks out in the watershed.

For a century, firefighters had been quick to douse the small natural fires that cleanse forest floors and thin timber to healthy densities. That's left the watershed vulnerable if lightning strikes or a campfire goes astray. The runoff from rainstorms and snowmelt could choke Santa Fe's two reservoirs with thick black ash and debris. "If we had a big fire up there, it's basically a permanent loss of that water supply," says Dale Lyons, Santa Fe's water manager.

To keep clean water flowing, Santa Fe partnered with the U.S. Forest Service 10 years ago to split the cost of rehabilitating the overgrown watershed. The city contributes $200,000 a year for crews to clear out congested Ponderosa stands and light prescribed fires to remove thick underbrush. Now, "when we do get a lightning strike up there, which we will, we can get on top of the fire fast," says Sandy Hurlocker, the district forest ranger.

But Santa Fe is not alone in worrying about the water they draw from high- elevation forests. From coast to coast, at least 3,400 cities and towns in 43 states serve 60 million people with drinking water from rivers and streams that start in national forests. Of those, 70 million acres are considered prone to catastrophic blazes. And in Santa Fe, and quite possibly in communities around the nation, "we're facing a future of a whole lot less water because of [fires]," Lyons says.

Already, fires are burning hotter and spreading faster along the Rocky Mountain chain. Snows are falling later in autumn and melting more rapidly earlier in springtime. Pine beetle infestations released after mild winters are killing extensive swathes of trees, leaving dead, rust-colored stands ripe to burst into flames. Following a 1996 fire, thunderstorms washed enough ash, soil, rocks and burnt logs into Denver's Strontia Springs Reservoir to fill up more than half its water storing capacity.

Just this summer, the Waldo Canyon fire destroyed 350 Colorado Springs homes and scorched forests surrounding two reservoirs that store 60 percent of the city's drinking water. Subsequent rains are washing soil and debris downstream and forcing the city to divert black, sooty water around the principle water treatment plant. Fort Collins, Colo., shut its Poudre River intake a month ago after the High Park fire raged through the river's steep canyon above the city. The city now is installing upstream monitors to gauge when ash and debris have dispersed to levels that make it practical to treat Poudre water and make it fit to drink. Fort Collins Water Production Manager Lisa Voytko hopes "the river will clear up in a year or so."

Once forests have burned, restoring watersheds takes decades and millions of dollars. Denver Water, the municipal utility supplying water to 1.3 million people, so far has spent more than $26 million restoring city-owned watersheds devastated by two severe fires in 1996 and 2002. The city planted a quarter million trees, dammed two creeks, replaced culverts, and installed logs and hay bales to slow runoff into another reservoir in the path of a 2002 fire. To reduce future risks, Denver Water and the Forest Service have partnered to split the $33 million cost of thinning ponderosa stands and cutting beetle-killed lodgepole pines on 38,000 acres that drain to city watersheds. "We can't prevent fires, but we're working to change how fire might run through a stand" so less intense flames create less havoc, says Claire Harper, the Forest Service's Rocky Mountain region water partnership coordinator.

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