High Park wildfire
Trees torching at the High Park wildfire on the Arapaho and Roosevelt National Forests and Pawnee National Grassland on June 17, 2012. Photo credit: U.S. Department of Agriculture.

By July 4th this year, numerous fires were burning in Colorado — the 416 Fire near Durango, and the Spring Creek Fire in the southern part of the state have been the biggest so far.

As everyone knows, fires destroy and reshape ecosystems, but they also affect the freshwater supplies we eventually drink. Water providers, like that in Fort Collins, Colorado, spend a lot of effort making sure that when their customers turn on the tap, clean water comes out. And if there have been fires in the watershed, providers don’t want the water to smell smoky – like you’re drinking out of a canteen near a campfire.

Until recently, says Jill Oropeza, water quality services manager for Fort Collins Utilities, there hasn’t been much research about how wildfires change the chemistry of water and what utilities would have to do to treat it. She said, “The High Park Fire which happened in 2012 was the first time that we had seen some really major and sustained impacts on water quality in the Poudre River, so we were suddenly needing to understand what is our new normal in this watershed.”

The High Park Fire was started by lightning six years ago, about 15 miles west of Ft. Collins, and it destroyed nearly 260 homes, burned more than 85,000 acres, and killed one person. The fire surrounded parts of the Cache la Poudre River – one of the two water sources for Ft. Collins.

The city reached out to the research community to help answer questions about how fires affect what comes down the river afterwards. They turned to Fernando Rosario, an associate professor, in the University of Colorado’s Civil, Environmental, and Architectural Engineering Program, who, with funding by the Water Research Foundation and the National Science Foundation, studied the issue. He began with much fieldwork and then took his research into the lab because, obviously, one can’t go start a new fire in the field to see what happens.

Rosario collected soils and litter from areas where fires occurred in order to simulate wildfire conditions by dissolving them in water. He then created wildfire-impacted water that matched some of the properties that were observed in the High Park Fire.

Next he did studies to see how to effectively treat those waters. One major problem that confronted water utilities was the amount of carbon the water contained. Oropeza with Fort Collins Utilities says they had to develop specific treatment requirements to get rid of as much of the organic carbon as possible.

The reason they have to get rid of the carbon is because it can interact with chlorine they use to treat the water and create disinfection byproducts that are carcinogenic and strictly regulated by the EPA. Ironically, the chemical used to treat water can become a contaminant if there are too many other contaminants in the water.

One finding as a part of Rosario’s research was that different levels of heat on soils factored into the amount of organic carbon that was released.

His team observed that while a high-temperature fire may result in more ash and sediment and might be more damaging to the watershed, the high temperatures caused lower amounts of carbon to be released from the soil than a low- to mid- temperature fire.

A lower temperature wildfire may be less damaging to the watershed, but by releasing more organic carbon, it creates more problems for water treatment professionals – and likely higher utility bills for consumers.

Oropeza says that before the new research no one was looking at how to treat wildfire-affected water. She says that the insights will allow providers to be more prepared, which can help to keep costs down for consumers.

And as far as global warming, she adds that because the number and intensity of fires influenced by climate drivers will likely increase, the requirements for water treatment will likely grow as well.

Reprinted with permission of H2O Radio, a Yale Climate Connections content-sharing partner.