Because ash and debris from a large fire can wreak havoc on water infrastructure and alter water quality, utilities near the High Park fire have begun to shut off certain water intakes and are already planning to replant the forest.

Photo courtesy of Northern Colorado Water Conservancy District The High Park fire is burning in the hills above Horsetooth Reservoir, which supplies several cities on Colorado’s Front Range.

Brett Walton

Circle of Blue

In the hills that are 24 kilometers (15 miles) to the west of Fort Collins, Colorado, a fast-moving wildfire, which started with a lightning strike on Saturday, has now burned more than 17,000 hectares (43,000 acres), and it continues to grow.

Firefighters are not close to controlling the High Park fire — it is only 10 percent contained as of Tuesday evening — but municipal and regional water officials in northern Colorado are already mulling the risks to their systems. This is because, when combined with the flush of a heavy rainstorm, the ash and debris from a large fire can wreak havoc on water supply infrastructure by clogging reservoirs with sediment, degrading water quality, and fouling the water-treatment process.

“If you get a hard rain on these steep slopes, it’s going to bring all that gunk into your system.” –Brian Werner

Public information officer

Northern Colorado Water Conservancy

The nearby cities of Greeley and Fort Collins have closed their water intakes on the Poudre River, said Brian Werner, a public information officer with the Northern Colorado Water Conservancy District, which provides water to 850,000 people from a Bureau of Reclamation project. The cities are now drawing exclusively from the Bureau’s Horsetooth Reservoir.

Lisa Voytko, water production manager for Fort Collins, told Circle of Blue that the fire has knocked out power at the utility’s Poudre River intake.

“Because we can’t monitor water quality at the source,” Voytko said, “we switched to the reservoir.”

Werner told Circle of Blue that the High Park fire is by far the largest and most extensive ever in the district’s service area.

“There will be impacts,” Werner said. “If you get a hard rain on these steep slopes, it’s going to bring all that gunk into your system.”

History May Repeat Itself

That is what happened a decade ago to Dever’s water utility. In 2002, the Hayman fire — the largest ever in the state — charred 138,000 acres (56,000 hectares), searing the land. When the rains came, the water could not soak into the ground, and it pushed debris into the utility’s reservoirs.

“It creates a water-repellant layer on the soil that increases the chance for flash floods and increases erosion.” –Mage Skordahl

Snow survey specialist

National Resources Conservation Service

“A hot-burning fire can affect infiltration for years to come,” explained Mage Skordahl, a snow survey specialist with the Colorado office of the National Resources Conservation Service. “It creates a water-repellant layer on the soil that increases the chance for flash floods and increases erosion.”

More than three-quarters of a million cubic meters (a million cubic yards) of sediment — enough to cover 155 football fields up to a meter (three feet) deep in muck — filled Denver Water’s Strontia Springs Reservoir. To recover from the Hayman fire and the 1996 Buffalo Creek fire, the utility spent $US 26 million to remove sediment from reservoirs, to repair damaged infrastructure, and to improve water quality.

Furthermore, Denver Water joined the U.S. Forest Service in a $US 33 million program to replant trees in watersheds that supply the city.

Tree planting is already on the minds of those near the High Park fire. Werner said re-vegetation is a top priority.

“We took note of the things that Denver did,” he said.

Water managers in both Fort Collins and Greeley said that the biggest problems will come in the months after the fire stops burning.

“Long-term, as we say, it’s a slow-motion train wreck,” said Jon Monson, Greeley’s water director. He said both summer rains and next spring’s snowmelt could increase sediment in the rivers, block water intakes and add an smoky taste to the water. Like his colleagues in the region, Monson has learned from Denver’s experience.