Wildfires’ impact on watersheds will linger for years | Wildfires

0
48

TAOS — A fire manager stands at the edge of a mountain highway and looks out at a panorama of once-lush hillsides now blackened by the largest fire in New Mexico’s recorded history.

These and other charred hills, bereft of live trees and other vegetation, have nothing to catch the runoff that will carry ashy sediment down slopes into waterways and drainage areas during rainstorms.

This soot will end up in watersheds, contaminating rivers, streams, lakes, acequias and municipal water systems.

“When you think of a fire, you can’t think just in terms of when you put it out,” says Ralph Lucas, an operations section chief for an incident management team deployed to fight the monstrous Hermits Peak/Calf Canyon Fire, which has burned over 490 square miles of the Sangre de Cristo mountain range. “Sometimes that’s just the beginning. The post-fire effects are tremendous.”

A robust monsoon this year would be a true mixed blessing. It’s the best hope for enabling crews to finally quell the blaze but also will wreak havoc on burned hillsides that have become spillways, increasing water pollution and the risk of flash floods.

Lucas notes this area off N.M. 518 outside Taos is a small corner of the gigantic fire zone. The aftereffects of the fire, including in the watersheds, will be felt for a long time.

“I would measure it certainly in years,” Lucas says.

Ash pollution unavoidable

The U.S. Forest Service is sending in teams to conduct a Burned Area Emergency Response — or BAER for short — at this and other major wildfire sites. The BAER teams assess the fire damage and its impacts on watersheds and infrastructure on Forest Service lands, with priority given to anything that threatens human life, property and critical resources.

The teams compile reports and generate maps illustrating the severity of burned soil in various spots.

Other federal agencies study the fire’s effects on different types of lands. For instance, the National Resources Conservation Service and U.S. Army Corps of Engineers can survey damage on private lands. One BAER team has made some early sobering findings in the Hermits Peak/Calf Canyon Fire, which has burned more than 314,000 acres and at least several hundred homes.

The burn area is so enormous the team has broken up its investigation into several phases, with the first one covering 115,000 acres in the Gallinas Canyon and Tecolote Creek watersheds, said Micah Kiesow, soil and watershed manager and BAER coordinator for the Santa Fe National Forest.

“What we’re finding out there is very concerning,” Kiesow said.

About half the soil has sustained moderate to high burning, which increases the level of erosion and sedimentation that will occur — and ultimately the amount of ash that will end up in waters, he said.

“The issue with ash in water is it’s so buoyant that it stays in suspension for a long, long time,” Kiesow said. “So it does not settle out, say, like your sands and your rocks. And the ash will move a long way downstream.”

By traveling a great distance, the ash is likely to infiltrate municipal water systems, such as the one in Las Vegas, N.M., he said, adding the city’s water treatment system isn’t equipped to remove the ash from water intended for drinking.

This is worrisome because researchers have identified ash-laden water having increased nitrates, phosphorus, metals, dissolved organic carbon and suspended solids, all of which make it much harder to treat, he said.

“Anything they would do to treat that water becomes more expensive with these increases in those substances,” Kiesow said, noting Colorado has had problems with ash contaminating water on the front range of the Rocky Mountains.

In an email, Maria Gilvarry, the Las Vegas utilities director, wrote that ash can cause problems with treatment systems, and that generally the solution is to let the water go downstream until it clears up.

“I am looking at improving the pre-treatment system and currently do not have a cost estimate,” Gilvarry wrote.

Ash flowing into waterways also can harm or kill fish, Kiesow said. It lowers the dissolved oxygen the fish need to breathe, clogs their gills and raises the water temperature higher than what they can survive in.

As Kiesow described it, any measures to deal with ash will have to be done by downstream users such as ranchers, farmers and cities.

“There is no way to prevent ash from moving downhill into water,” he said. “What we say is, ‘Ash happens.’ If you have a fire, you’re going to have runoff, and you’re going to have ash in your water.”

The most urgent priority will be to help protect property owners in the fire zone from flooding. Kiesow envisions the agency setting up an early warning system — in which a hilltop gauge alerts people when rainfall gets heavy — so they can evacuate in plenty of time.

Lucas said firefighting teams will take some immediate actions, such as installing larger culverts to handle a higher volume of runoff and placing sandbags in some areas where homeowners might be imperiled.

Kiesow expects to see more watershed impacts as the team surveys scorched lands in subsequent phases.

“If you have a fire in a watershed or above the watershed, those waterways, those creeks, those streams will be affected,” he said. “As we move further north in this assessment, there will be more waters that are going to be impacted.”

Closer to Santa Fe, another team has begun probing the impacts from the smaller Cerro Pelado Fire, which has charred almost 46,000 acres in the Jemez Springs region and was 95 percent contained Saturday. A BAER spokeswoman said the team hasn’t had a chance to report this fire’s effects beyond the extent of the burned soil.

The team issued a map Friday indicating the soil damage isn’t nearly as severe, with 67 percent either unburned or mildly burned. About 32 percent is moderately burned and only 1 percent sustained high burning.

This means there’s much less chance of ash contaminating waterways.

Acequias could be hard hit

The Hermits Peak/Calf Canyon Fire is predicted to have adverse impacts on acequia communities when rainstorms wash ash into waterways already reduced to a near trickle in the drought and, at the same time, cause flooding.

“For the acequias, this fire is devastating,” said Paula Garcia, executive director of the New Mexico Acequia Association. “These watersheds are the headwaters of our acequias and our rivers. So we feel very much impacted.”

Garcia said her association has begun mapping fire-affected acequias to share with federal agencies, partly for information sharing and also so farmers and ranchers can qualify for emergency relief and insurance.

So far, they’ve tallied 68 acequias that will be harmed by the fire, and that’s just in the Mora area, Garcia said. She estimates at least 100 farms will suffer hardship as a result.

With the help of local soil and conservation districts, the group will survey the impacts that the Cerro Pelado Fire, the Cooks Peak Fire northwest of Hermits Peak/Calf Canyon and the McBride Fire in Ruidoso have had on acequias, she said.

Garcia said she is concerned about the risk of flooding for those who live at the foot of scorched hills. The charred soil doesn’t absorb water, and the trees and vegetation have been burned away, leaving nothing to slow torrential runoff.

Her group will instruct people to comply with evacuation orders when there’s a flooding threat, she said.

The fire has created a very uncertain future for those in agriculture, she added.

Water flow in the acequias was expected to be low this summer, and now what little they get will be tainted with ash.

Some hard lessons were learned in the 2012 Little Bear Fire in south-central New Mexico, Garcia said. Those who irrigated their pastures with ashy water saw their grasses die.

It took several years for acequia communities to recover from that fire, and it might take even longer for this fire, she said, adding some farms will make it and some probably will be wiped out.

There are techniques such as building containment ponds to catch ashy runoff, but it seems almost impossible to cover the nearly 500-square-mile burn area, she said.

“The scale of it is so big, it’s hard to imagine being able to get beyond scratching the surface,” Garcia said. “We can’t heal all of these watersheds all at once. For me, it will be the rest of my life.”

Source