DRIED UP: Compounding fires and floods in Southwest pose dire threat to drinking water

The American West is experiencing its driest period in human history, a megadrought that threatens health, agriculture and entire ways of life. DRIED UP is examining the dire effects of the drought on the states most affected — as well as the solutions Americans are embracing.

Las Vegas, N.M., was running out of clean water. 

The city — not to be confused with the Nevada metropolis — was the victim of a combination of flame and flood that put its water supply, as well as that of multiple communities in the Southwest, in serious jeopardy. 

A wildfire, in this instance one that started off as a planned burn by the U.S. Forest Service but got out of control, left behind ash and debris. And then there was the flooding. 

“Our water comes off the Gallinas River, and the Gallinas River was contaminated following the fire and then the floods that brought all that sediment and metals and chemicals and everything down into the river, making the water untreatable by our treatment system,” Maria Gilvarry, the city’s utilities director, told The Hill in an August interview.  

At the time, she said the city only had 35 days’ worth of water left.  

In a follow-up interview this month, Gilvarry said that at one point the city got down to only 21 days’ worth of water.  

“Knowing that you’re down to three weeks of water — that if nothing changes in three weeks you’re not going to be able to necessarily produce water to drinking water standards for the community — was concerning and did result in a lot of sleepless nights for a lot of folks,” she said last week, adding that she had remained confident that the city would be able to install a filtration system that would take care of the issue — at least for the time being.  

While the Southwest region has always been defined by a cyclical weather pattern of drought and monsoon, climate change is making each more intense and variable — creating both drier, longer droughts and more intense rains that can ravage landscapes while failing to do much to return greatly needed water to a region.  

Ricardo González-Pinzón, an associate professor at the University of New Mexico, says that the fires change the composition of the soil, making it more likely to repel water. This, in turn, worsens flash floods that can carry detritus and ash into vital drinking sources.   

And the loss of forested landscapes to fire is dangerous in multiple ways, removing everything from canopies that normally trap much of a heavy rainstorm to root systems that help hold the earth in place. 

“The soil around the roots of the trees has been eroding this year because of the rains,” Gilvarry said. “A lot of the trees are going to start coming down next year, resulting in even less stability.” 

She said New Mexico’s Las Vegas now has 160 days’ worth of water. 

Burning hotter and hotter

Burn scars add an additional layer of devastation to wildfire recovery across the Mountain West, as ever-larger fires destroy forests that once filtered upland water headed for municipal faucets. 

These blazes now burn so hot they incinerate even fire-dependent pinecones, which usually require the heat of a fire to open, leaving behind nothing to grow in their aftermath. With trees gone, there is nothing to slow or absorb water from the region’s powerful, if intermittent, monsoons.  

Burns scars are a bitter “gift that keeps on giving,” said Cynthia Campbell, a water manager for the city of Phoenix.

“If a fire occurred in year one, you can experience the impacts of that fire in year three or four,” Campbell said. 

“It flushes water out, and along with it, all the debris that got burned in the fire. And it’s going to keep flushing debris out for a decade.”

New Mexico state forester Laura McCarthy

Like other large cities across the region, Phoenix has had to face the danger that ever-more-powerful forest fires pose to its water supply — and the agonizingly slow pace of recovery. It still sometimes suffers the flooding aftereffects of the Rodeo-Chediski Fire, which occurred nearly 20 years ago. 

These incidents — in which contaminants can turn normally clear mountain streams to the color and consistency of chocolate milk — are a particular concern because nearly two-thirds of Phoenix’s water comes from upland rivers that are siphoned into the canals of the Salt and Verde Water Project. And Campbell said that proportion will likely have to grow as the Colorado River, which provides the rest, dwindles. 

Back in New Mexico, the makeup of water in the Gallinas Creek changed over the summer, becoming more polluted with sediment.

Data from the U.S. Geological Survey shows that on June 19, water at a monitoring location in the creek had a concentration of just 21 milligrams of suspended sediment per liter. By June 23, that rose to 173 milligrams per liter. Sediment concentration measured highest on Aug. 4, at 368 milligrams per liter. 

González-Pinzón said in an email this week that high sediment values are “one of the main concerns of a water treatment facility” which has to work to remove it. 

“Doing that could be prohibitively expensive, and some localities may not even have the technology to do so (the case of Las Vegas, NM, until recently),” he said. 

Making forests ‘critical infrastructure’

Fears of wildfire-induced water contamination have led Western cities including Phoenix, Denver and Albuquerque, N.M., to invest heavily in water treatment plants and backup water sources.  

The investments have allowed Phoenix to respond to periods of toxic runoff by simply “letting the water go by” as the city draws from backup sources, Campbell said. And upgrades have allowed the city to pull from water sources with higher levels of sediment, the kind of flows that once could have damaged their water treatment machines. 

But for water managers such as Campbell, the burn scars have added an additional degree of uncertainty to an already difficult water situation.  

“It’s almost like a dance you’re doing with the water, where you’re saying, OK, I can afford based on my demand to turn off this treatment plan for this amount of time — but no more,” Campbell said. “If I turn it off for more than that, then I’m going to run into problems meeting demand.” 

So in addition to treatment plant upgrades, Albuquerque, Phoenix and Denver have all invested in thinning and prescribed burns in the upland forests that they depend on to filter their water. 

These upland forests are so important that Christina Burri of Denver Water calls them “critical infrastructure.” 

If the city’s Forests to Faucets program, which pays for such forest treatments, can “keep as little as just 5% of the sediment out of the reservoir through proactive watershed management, then Denver Water experiences a return on our investment,” Burri told The Hill. 

After the 2002 Hayman Fire, for example, Denver Water spent $28 million on recovery, including $16.5 million just to dredge out reservoirs clogged with burn scar runoff.  

The city and its public and private partners have invested $66 million in forest maintenance since 2010.  

“It’s just more costly to be reactive,” Burri said. 

But water managers from all three cities say that the scale of these treatments had not kept pace with the overwhelming need amid a new era of overlapping, year-round fires. 

‘I mean, we failed’

In New Mexico, the state and the U.S. Forest Service focused their attention on the overgrown and fire-prone forests of the Rio Grande watershed — on the other side of the Sangre de Cristo Mountains from Las Vegas, N.M., and the Gallinas River. 

With limited resources to deploy, officials “gambled,” New Mexico state forester Laura McCarthy told The Hill. They invested what they had in full-scale chainsaw and controlled-fire treatments to remove small flammable trees from the Rio Grande watershed.  

That was effective in dramatically reducing the severity of this year’s Cerro Pelado Fire, she said, but that success came at the cost of largely neglecting the Gallinas River watershed. 

In that region, “I mean, we failed,” McCarthy said. “We did those little treatments. A lot of them. But they were too small.” 

That failure and the enormous Hermit Creek-Calf Canyon Fire that spread in the untreated landscapes led to a wholesale and potentially permanent change in the hydrology of the region, McCarthy said.  

“I mean, it can’t absorb water. It flushes water out, and along with it, all the debris that got burned in the fire. And it’s going to keep flushing debris out for a decade.” 

The damage highlighted a longstanding problem with the U.S. Forest Service’s recovery attempts, McCarthy added — they are too small, too short-term and too poorly funded. The Forest Service has only one program that tackles the kind of enormous fuel treatment projects that can head off enormous fires — which isn’t enough, she said. 

“If you want to change fire behavior [from] the kind of conditions that favor [burning] 30,000 acres in a day, and you need treatments that are two, three, ten thousand acres.” 

Where treatments happened on that scale — as in the Jemez Mountains that form the bulk of Albuquerque’s watershed — wildfires “were contained,” she said. 

When it comes to large-scale landscape treatments in the forests above Phoenix, “the Forest Service kind of runs hot and cold in terms of their willingness to assist. They can be very slow moving,” Campbell said, adding, “because it’s very expensive.” 

Direct damage to landscapes and the resulting runoff are also just one of the many ways that destructive wildfires can threaten municipal drinking water. 

The Marshall Fire, which ravaged suburbs of Denver over New Year’s 2022 before growing to become the state’s most expensive wildfire, melted plastic piping that connected houses to the municipal water grid, John Kuo, of the Los Angeles Division of Water and Power, told The Hill. 

In doing so, the heat created toxic plastic byproducts — which contaminated local water systems, Purdue University ecological engineer Andrew Whelton found. 

In Flagstaff, Ariz., this summer’s aptly named Pipeline Fire made it hard for the city to access a pipeline that carries some of its water. 

Erosion damaged the pipeline and ultimately cut off the city from that source of water, said Brian Huntzinger, Flagstaff’s water production manager, who added that the city has other water sources it can draw from. 

Preparing for the future

In Las Vegas, N.M., the immediate emergency situation is over, but challenges persist.  

Gilvarry said the new treatment system “takes away some of the emergency” but the city still has to deal with less water clarity, more sediment and evolving changes to the water quality.  

“As the ash and the sediment impact the water, we have to look at changing our processes for treating the water,” she said.  

“We have the solutions, it just depends on what is the need that year. Is it a drought that we’re going to be dealing with? Is it floods that we’re going to be dealing with? Is it heavy debris or sediment? Each one has a different challenge, but we’re prepared for all of them,” she said.  

Gilvarry added, however, that she can’t guarantee the city will never lose access to clean drinking water. 

“I wish I could definitely say that would never happen,” she said. “There’s so many variables. We’re going to do everything we can so that it doesn’t impact the health and safety of the community, but I cannot guarantee that.” 

Previously in this series:

In Utah, drying Great Salt Lake leads to air pollution

Texas cities in fear of running out of water

Texas cattle industry faces existential crisis from historic drought

Lakes Mead and Powell are at the epicenter of the biggest Western drought in history

Seven stats that explain the West’s epic drought

Why Great Plains agriculture is particularly vulnerable to drought

Five reasons extreme weather is bigger in Texas