Pollution from wildfires can contaminate our water for up to 8 years

When forest fires devastated a large strip of Los Angeles last winter, those responsible warned residents of several postal codes so as not to drink the water, or boil it first if they were to. They feared that the soot, the ash and other debris of the flames would not have infiltrated the groundwater, or that the damaged pipes can allow the toxins of the food. The last of these “not drinking” orders was lifted last month.

However, the first large -scale study of post -fertile water quality revealed that pollution created by such a fire can threaten water supply for eight years – much longer than previous studies indicated. Researchers from the Cooperative Institute for Research in Environmental Science, or CIRS, of the University of Colorado Boulder analyzed 100,000 samples of 500 watersheds across the West of the United States. They found “contaminants such as organic carbon, phosphorus, nitrogen and sediments” throughout those who had burned. At their peak, these pollutants can be found at levels up to 103 times higher than before fire. There may also be 9 to 286 times more sediment in water after a fire.

The results have major implications for water systems while they are preparing for a world in which fires like those who have burned in Los Angeles and, more recently, North Carolina and a large band of Canada, become more common. In the United States, one in six people lives in an area of ​​risk of forest fire, and wooded watersheds provide water to almost two-thirds of municipalities in the United States, making water systems vulnerable.

“I had a lot of conversations with different public and water managers in the West, and each of them is concerned about the impacts of forest fires,” said Carli Brucker, principal of the study, published on Tuesday. But, she added, what they do not have is data in the longer term. “I hope that this research provides these concrete numbers which can really support the concerns of water managers and transform these concerns into real funding that they can start to set up climate resilience. Solid evidence can be very useful for obtaining funding. ”

Public Water Services in the Los Angeles region addressed the threat posed by fires that burned in January in the short term by rinking water pipes and pipes. The managers of the Water & Power department of Los Angeles said they were carrying out current tests in the Palisades region and offer free water quality tests to any resident who wishes.

“These urban fires create these unprecedented challenges that the processing factories cannot really face,” said Brucker. “Burning buildings, business and roads and cars, it creates all these contaminants which are simply more dangerous and much more difficult to manage.”

In the locations, the researchers have analyzed, the levels of contamination varied considerably. In general, pollution after fire was worse in highly wooded or strongly urbanized areas. The “most dramatic peaks” in pollutants such as phosphorus, nitrate, organic carbon and sediments have generally occurred during the first years after a fire, according to researcher Ben Livneh.

“We found that the impacts were really persistent,” wrote Livneh in the conversation. “We have seen considerably high levels of nitrogen and sediment for eight years after a fire.” Even years after a fire, major precipitation can trigger a mud flow, find contaminants. Beyond polluting groundwater, which can cause unexpected environmental problems. “Nitrogen and phosphorus act as fertilizers for seaweed. An increase in these nutrients can trigger algae flowers in tanks, which can produce toxins and create foul smells, “said Livneh.

There are several ways to combat these threats to water supply.

“The first line of defense is simply to diversify water sources,” said Brucker. Ideally, a public service would go in several watersheds, so it has a safeguard in the event that one of them is affected by a fire, she said. They can also build additional sedimentation basins to increase their sediment handling capacity.

“But all these things cost much more,” said Brucker. And it is difficult to convince public services stretched in Western states – which already deal with things like water shortages – to spend money on the attenuation of forest fires without figures. Rural communities, in particular, often count on single source water systems and limited funding, which makes the response to emergencies much more difficult.

“Public services generally do not have this kind of process improvement in place, unless they have a good reason,” she said. “I hope this research can indicate – it is a fairly good reason to start planning and try to budget these improvements in resilience.”