Wildfires aren’t just polluting air but also waterways, study finds

Wildfires are occurring more frequently, leading to more pollutants found in surrounding waterways, according to researchers of a new report.

The paper, published in Water Resources Research, investigated trends in water after wildfires through an analysis of 184 scientific papers since 1980.

Scientists found stream flow often increases for a few years following a wildfire, as well as sediments and water temperature.

Nutrients, toxic metals and organic chemicals sometimes reached 10 to 100 times higher concentrations than pre-fire levels.

‘Fire frequency is increasing in places like in the western U.S. due in part to climate change, and there is potential for areas burned by fire to become longer-term stressors to water quality if the previous vegetation is slow to recover or fails altogether, said Stephen LeDuc of the U.S. Environmental Protection Agency’s Center for Public Health and Environmental Assessment. ‘[But] burned areas could be targeted for restoration efforts, such as erosion control or plantings.’

Some chemicals left in water post-wildfire, such as arsenic, could exceed regulatory limits, even in drinking water when it’s been processed.

In Paradise, California where houses and vehicles burnt down, the researchers also discovered reports of elevated levels of carcinogen benzene in tap water.

Reviews mentioned higher concentrations of metals in the ash from these fires too, which could potentially affect runoff.

Little research has been conducted on pollutants following urban wildfires, leaving water managers and planners at a disadvantage when recovering from fire.

‘In my view, the main reason for the knowledge gap is the challenge of setting up an urban water quality monitoring program on short notice, like after a fire,” said Dennis Hallema, a hydrologist at Desert Research Institute in Las Vegas who was not involved in the study. ‘There’s plenty of interest, but at the end of the day, successful water quality monitoring efforts come out of projects that were approved in time.’

It’s hoped the research will help water quality managers and communities to recover better from the impacts of wildfires.

Photo by Cecilio Ricardo/ USDA Forest Service