When the 2018 Thanksgiving week rains finally came to help firefighters contain the Camp Fire, the most destructive and deadliest wildfire in California’s history, Butte Creek ran dark brown. Like “over-brewed black tea” with “a strong smoky smell,” said California State University, Chico water-quality chemist Jackson Webster. Webster watched the toxic mix of ash, metals, and chemicals course through one of Central Valley’s last habitats for spring-run salmon. The rain blessed many but may have further cursed Butte Creek’s salmon.
The Camp Fire and the Salmon Life Cycle
Spring-run Chinook salmon are named for when the adults travel from the Pacific Ocean to their fresh-water homes. Butte Creek’s Chinook migrate and spawn at similar times as spring-run in other streams, but they are different in that most of the fry that emerge roughly in December migrate out. The remaining fry linger until the following fall. Once an abundant species, the threatened Butte Creek salmon numbers dipped sharply in 2017. California Department of Fish and Wildlife’s Fisheries Branch Anadromous Assessment reported its 2017 Butte Creek Snorkel count at 982, which was only 22.06 percent of the 2016 count of 4,450.
When the wind-driven Camp Fire swept from Paradise to Butte Creek in November 2018, adult fish had just finished spawning. That meant recently hatched juveniles faced the worst of what wildfires do to creeks and streams. According to the California Department of Fish and Wildlife, increased water temperatures plus higher levels of phosphorous and nitrogen in the water are typical in fires like these and can trigger algal blooms. Wood ash can raise water’s pH, making the water more alkaline. In the long run, these changes may make Butte Creek more inviting to non-native invasive species that might compete with or even eat the spring-run Chinook.
Of particular concern are sediments washed into Butte Creek as well as the tributaries that carry runoff from Paradise. Juvenile salmon are especially vulnerable to excess sediments caused by fire intensity. Hot fires burning a lot of plant fuel actually create a gas that condenses as a slick surface coating on the soil. Denuded hillsides compounded by this waxy coating means more rain will run directly into water systems. That increased runoff erodes creek banks and carries debris down-stream. Silt not only fills pools, but also clogs gills, smothering young salmon.
The Camp Fire created an especially toxic mix of silt and debris. Beyond the chaparral and mixed conifer ecosystem that burned, the fire engulfed urban living spaces. Homes, cars, and businesses packed with asbestos, electronics, chemicals, plastics, paint, and pesticides incinerated in a dangerous fallout that mixed with rains. The short and long-term risks these pose to the area’s water supplies and aquatic ecosystems are complex and not yet understood.
Unfortunately, Butte Creek’s salmon had probably been exposed to toxic runoff prior to the disaster. Mercury, likely from mining tailings, has long “impaired” Butte Creek’s waters. According to a 2010 report conducted by the Regional Water Quality Control Board, “28 of 38 fish tissue samples exceeded the USEPA Fish Tissue Residue Criterion of 0.3 mg/kg.”
Fire retardants are also toxic to salmon. Although fire fighters take great pains to keep ammonia-based fire retardants at least 300 feet from streams, fires create unpredictable drafts, and winds shift. Most Cal Fire planes carry between 1,000 and 3,000 gallons of retardant in one run. When fires blow up, pilots can drop as many as 166,000 gallons in one day. Ammonia is especially toxic to juvenile salmon that have just hatched.
Despite weeks of evacuations and coping with the unimaginable loss of friends, property, and area neighbors, residents of Butte Creek Canyon organized for salmon when the rains came. They laid down 800 long rolls of straw called wattles near burned-out residences and streams to ease runoff and capture debris. That effort is one of many to mitigate the effects of a fire that burned 240 square miles and killed 88 people. We do not yet know if the spring-run Chinook will recover from this disaster. The salmon may be a surface water test case; a harbinger of what’s to come for other species and humans once those heavy metals and toxins seep into the ground water and eventually the aquifer.
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