Wildfires Are Contaminating Water Supplies

In a healthy forest, there’s a lot of “litter” on the ground—pine needles, dead leaves, debris. “It acts like a sponge,” says Rhoades. “As rainfall comes in, it moves through that layer slowly and can trickle into the soil.” When fires scorch the land, they burn that vegetation and organic matter, leaving behind a bare landscape that’s highly susceptible to erosion. Instead of filtering into the ground, rain will slide right off the surface, moving quickly, picking up soil, and carrying it into streams and rivers. Not only does this cause sediment build-up, but it can disrupt the water chemistry. Rhoades found elevated levels of nutrients, like nitrogen, in rivers almost 15 years after a high-severity fire. These nutrients can lead to harmful algal blooms, although they don’t directly impact drinking water quality. But other sites show increased levels of heavy metals like manganese, iron, and even lead after a major fire, which can complicate water-treatment processes.