For two weeks, the Station Fire, Southern California's huge wildfire, has burned while California’s fire fighters have fought the massive fire to contain it. The fire has destroyed 250 square miles (160,000 acres) of the Angeles National Forest and only now is “mostly” contained. To defeat the fire more than 400 firefighters bravely continue to build containment lines on the fire's eastern flank by eliminating all potential fuel for the fire near the fire line to prevent the fire from continuing to spread. Two firefighters have died and eleven were injured in this massive battle. The ecological toll is vast, but more destruction is yet to come. The wildfire has completely consumed all organic layers and roots of the understory plants within this vast area. Without plants to protect the soil, runoff and erosion will increase and create changes to water quality and quantity.
The chief concern now is the impact the 250-square-mile Station Fire is having on the watershed. Countless canyons, ravines and gullies funnel water toward communities at the forest's edge and into the water management system. There is virtually no area in California where the water and flood system is not managed. Los Angeles County maintains 14 major dams, basins to intercept debris laden flows from the canyons, 500 miles of open storm channels and a network of underground storm drains throughout the metropolitan area to the ocean. The biggest concerns after a fire are erosion, landslides and flooding in areas where the vegetation that once stabilized the soil has been destroyed by fire. The primary impacts to fish and wildlife (that were not killed by fire or related heat) will be from runoff entering streams and lakes from areas destroyed by the fire. The runoff may carry extra sediment and ash, which can kill fish by robbing the streams of oxygen.
The firefighting chemicals can have adverse impacts on water quality and ultimately on fish and other aquatic life. The retardants used, though common chemicals found in fertilizers can cause fish kills if applied directly over lakes and streams. This is because ammonia, nitrogen and phosphorus are in many of the retardants. Ammonia is very toxic to fish, and large quantities of nitrogen and phosphorus which if flushed into a stream or lake can use up all the oxygen in the water body. Even if the retardant has not been sprayed directly over lakes and streams, there is the possibility that runoff will carry the chemicals into the surface water depending largely on the amount of rainfall, the steepness of the terrain. Phosphorus readily binds to soil particles and will increase the levels of phosphorus flowing into surface waters throughout the rainy season. Nitrates are mobile in soil and readily move into ground and surface water. Cyanide can be of special concern after wildfires because it is a byproduct of the red fire retardant slurry I thought I saw picture of. In cells of all animals cyanide inhibits the release of oxygen for hemoglobin to individual cells, starving the animal of oxygen.
Fires also release pollutants that are normally found in soil and in living and decaying plants that are washed into streams and lakes either through runoff or transported through the air. After a fire there are concerns about streams flooding when burned areas receive heavy rainfall. Vegetation and forest litter that once slowed runoff are gone. This means an increased amount of sediment and ash will end up in the water where it can remain suspended or become part of the materials in the steam beds. Suspended solids can make treatment and filtering more difficult downstream possibly impacting the drinking water quality. After the rains come there will be much higher risks for landslides and flooding in the areas once stabilized by the now destroyed vegetation. Hillsides will become unstable and mudslides are expected.
The final tally of the destructive impact from this wildfire will be massive, far beyond the direct costs to fight the fire and the limited number of homes lost. The water quality impacts are cumulative as a result of pollutants mobilized by the fire, chemicals released to fight the fire, and the post fire erosion, mudslides and flooding.