A vulnerability assessment of wildland fire impacts to public drinking water in the western and southeastern United States
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Wildland fires in the United States (U.S.) have increased in frequency and area burned since the mid-1980s. This trend is most pronounced in the western United States, and to a lesser extent in the nation’s southeastern region. Historic fire suppression policies have resulted in accumulation of forest fire fuels with the risks of burning heightened by increased temperatures and dry conditions driven in part by climate change. With increased burn area, burn severity, and frequency of these events, wildland fire (WF) can negatively impact water quality (WQ) immediately following the fires and in the long-term dependent on landscape recovery rates.
When WFs occur, they can negatively affect freshwater resources through release of a variety of pollutants that include sediment, dissolved organic compounds, and metals. Nutrients released from WFs can also contribute to downstream eutrophication and harmful algal blooms that can adversely affect drinking WQ. Economic devaluation has resulted from cyanobacterial metabolites producing taste and odor problems that often elude conventional drinking water treatment.
The impact of WFs on drinking WQ is an area of increasing concern, with approximately 66% of the U.S freshwater supply originating from forested watersheds. The impact of WFs on community drinking water supplies is apparent through many past incidents, such as the 2013 Rim Fire that threatened the San Francisco, CA water supply and the Hewlett Gulch and High Park fires that impacted the Fort Collins, CO water supply. These fires impacted the drinking water of 2.6 million people and 300,000 people, respectively. While the role of forests in source water protection and water security is widely acknowledged, WFs are usually absent in global reports and mapping initiatives focused on water security and management. A mapping effort of the risks posed to drinking water supplies across the U.S. would provide communities with guidance on their potential exposure to degraded drinking water in the event of a wildfire, as well as potential locations for prioritizing potential management interventions. In this presentation we identify and rank WF vulnerability and impacts on 361 freshwater systems (lakes, rivers, streams) that provision drinking water to communities within the continental U.S. Using historical WF data, in concert with other landscape, climate, and anthropogenic factors we identify and rank these vulnerable water bodies. This vulnerability assessment will assist in locating watersheds for modelling nutrient and chemical mobilization and movement following fires of differing intensities.