Wildfire Induces Changes in Receiving Waters: A Review With Considerations for Water Quality Management

• Published in: Water resources research 2022-09, Vol.58 (9), p.1-n/a
• Main Authors: Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., Leibowitz, S. G.
• Format: Article
• Language: English
• Subjects: Aquatic organisms; Arsenic; Ash; Benzene; Chemicals; Climate change; Contamination; Drinking water; Fires; Information management; Ions; Managers; metal; Metal concentrations; Metals; nutrient; Nutrients; Organic chemicals; Organic chemistry; Pollutants; Pollution studies; Quality assessment; Quality management; Quality standards; Receiving waters; Restoration; Runoff; Sediment; Sediments; Source programs; Strategic management; Stream discharge; Stream flow; Temperature; Urban areas; Urbanization; water management; Water pollution; Water quality; Water quality management; Water quality standards; Water yield; Watersheds; wildfire; Wildfires; wildland urban interface; WUI
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1029/2021WR030699

Wildfires have increased in frequency in many ecosystems, with implications for human health and the environment, including water quality. Increased fire frequency and urbanization also raise the prospect of fires burning into urban areas, mobilizing pollutants few have considered to date. As a result, water quality managers lack information to anticipate, respond to and potentially mitigate wildfire impacts. Here, we reviewed the scientific literature to assess wildfire effects on response endpoints of a conceptual model linking fire to water quality, quantifying response directionality, magnitude and duration. Physically, water yield, sediments, and temperature all increased post‐fire. Chemically, nutrients, ions, organic chemicals, and metals increased in burned watersheds, sometimes by orders of magnitude over pre‐fire or reference conditions. In select cases, post‐fire concentrations exceeded aquatic life criteria or drinking water standards, at times even in the finished drinking water. Biological assemblages commonly declined after post‐fire runoff events. The duration of effects was less than 5 yr for most endpoints (e.g., metals) on average following fire, although effects did extend 15 yr or more in some individual cases. We found only a few studies on pollutants mobilized from wildfire impacted urban areas with benzene contamination in drinking water and high metal concentrations in ash prominent exceptions. Overall, this review provides a resource for understanding wildfire impacts on water quality endpoints, with the goal of informing the response of managers and other decision makers to this growing problem. Plain Language Summary Wildfires are increasing in frequency due in part to climate change, and the pollutants mobilized during and after fire threaten water quality. Water quality managers should be aware of these threats so they can plan for and respond to them. We reviewed the scientific literature on wildfire effects on water quality. Streamflow typically increases following wildfire, as do sediments and temperature. Nutrients, ions, metals, and certain organic chemicals often increase as well, sometimes 10–100 times or more above reference levels. Some post‐fire chemicals can exceed regulatory limits, even in finished drinking water (e.g., arsenic). Wildfire also commonly affects biological assemblages. Most impacts last less than 5 yr, although they can be much longer. Unfortunately, only a few studies measured pollutants from urban