As California’s historic drought continues, every year brings stories of catastrophic wildfires destroying thousands of acres of forestland. Normally, stories discuss how families have to flee their homes and the property damage and loss of life associated with the fires. What isn’t discussed, however, is the long-term effects of these fires, especially in terms of how they affect the state’s water supply.
The drought has resulted in water shortages and increased risk of wildfires. But the wildfires themselves also pose a direct risk to the water supply. The Sierra Nevada and Cascade mountain ranges along California’s eastern edge provide water for more than two-thirds of the state, plus two millions acre of farmland. When fires destroy large tracts of forest ecosystem, they also destroy the role that these ecosystems play in preserving our water supply.
The September 2014 Kings Fire burned almost 100,000 acres in El Dorado National Forest, home to a critical watershed. In a healthy forest, trees shade snowpack and manage its melting rate, keeping water flowing to streams, rivers and lakes year-round. Trees also filter out pollutants and regulate the water’s temperature. The Kings Fire affected 50 percent of the region’s watershed. Without the tree cover, and with dead trees and their root systems rotting away, communities in the watershed face a greater risk of flooding and sedimentation, which increases the water supply’s turbidity and putting stress on the area’s water treatment plants.
Towns in the watershed are anxious that February rains could result in erosion of wildfire-affected land and dump tons of sediment into the region’s drinking water. And since the area is a major source of water across the state, such disasters could can affect the water supply of cities hundreds of miles away.