Water Quality
Exploring the impacts of wildfire on water quality
Prepared by Marley VonWerssowetz (she/her/hers)
MPH Candidate, OHSU-PSU School of Public Health
How do Wildfires Affect Water Quality?
Wildfires impact water quality during an active burn and for months and years after the fire has been controlled. The lasting impacts from wildfire damage interact with ecosystem services, the built environment, and human access to usable water (Environmental Protection Agency, n.d.)
Water Sources and Water Quality
The Bull Run watershed, from which many Portlanders receive their water.
Watershed Health Matters
Watersheds are areas where rain and snowmelt drain into a common body of water, like a river, lake, stream, or slough. Healthy watersheds help to provide good water quality, support wildlife, protect areas from climate change by building climate resistance, and can replenish underground sources of water, called groundwater (Portland Water Bureau, n.d.).
Approximately 80% of freshwater resources in the United States originate in forested land, and nearly half the water supply in southwestern states comes from forests (California Water Science Center, 2018). Within the last 30 years, more than 12 million acres of this land, including important forested water-supply watersheds have been burned by wildfire. Wildfires increase vulnerability of watersheds to environmental hazards like erosion and flooding, which can damage water supplies (California Water Science Center, 2018).
The effects wildfires have on watersheds directly impacts the availability and quality of water in an area, as well as the health of the ecosystem overall.
Wildfires and Drinking Water
Regardless of the water source, treatment of drinking water and water quality can be difficult to strategize in the wake of unpredictable wildfires. Potential effects from wildfire on municipal water supplies and aquatic ecosystems include:
Increased sediment in water-supply reservoirs, shortened reservoir lifetime, and increased maintenance needed
Increased levels of nutrients, dissolved organic carbon, metals, and major ions in streams leading to water sources
Erosion and movement of sediment and debris to downstream water treatment plants, ecosystems, and water-supply reservoirs
Changes in source water chemistry, requiring altered treatment for drinking water
(US Geological Study, 2019)
Water Quality Factors
Mechanisms and contaminants that affect water quality
Erosion
When fires sweep through a watershed, they remove the vegetation and root systems that help keep soil in place. Without this underground structure and vegetation to take it up, more water leaves the forested areas and flows into nearby streams and rivers. In areas with heavy rainfall, the lack of vegetation can increase risk of flooding, landslides, and debris flows that carry rocks, mud, and other material downstream (Phillips & Dahl, 2022). Water treatment systems can become overwhelmed with high volumes of water and increased filtration needed for foreign materials.
Volatile Organic Compounds (VOCs)
After a wildfire in Paradise, California in 2018, volatile organic compounds (VOCs) were found within the town’s water supply as a result of plastic service lines being heated in the fire. The service lines in question were smaller pipes near or above ground and are typically made of plastics like polyvinyl chloride (PVC) and high-density polyethylene (HDPE; Meadows, 2022). Researchers found that PVC and HDPE start to degrade and generate VOCs at high temperatures. While some have little health effect, VOCs like benzene have been known to cause cancer. Because these compounds were unexpected in the water source, water systems were not actively testing for them and many may have gone undetected (Meadows, 2022).
Runoff
During high-severity wildfires, high temperatures can change the soil structure and chemistry to make the soil more water hydrophobic, meaning it repels water (Phillips & Dahl, 2022). Soil will become less able to absorb rainfall and water flows more easily, carrying sediment and nutrients like nitrogen and phosphorus which may have harmful effects to certain aquatic ecosystems or organisms. If gone untreated, animals and humans could become sick from large amounts of these nutrients (Phillips & Dahl, 2022).
If fires reach urban areas, they may catch fire to man-made materials like furniture, computers, and cars, leaving behind heavy metals and chemicals. Heavy rainfall can also bring these into products into streams and water systems (Jordan, 2019).
Dissolved Organic Matter (DOM)
Dissolved organic matter (DOM) is formed from loose ash and other biomass byproducts burned within a fire. DOM itself is not a contaminant with direct impact on human health but causes issues within water treatment after a fire (Chow et al., 2021). It causes discoloration and noticeable taste within water and sometimes serves as a substrate for unwanted microbial growth. Treatment for DOM within water systems requires greater use of added chemicals like chlorine and ferric iron for its removal. Water treatment processes for DOM may also introduce toxic disinfection byproducts (DBPs) such as chloroform and haloacetic acid (Chow et al., 2021).
Unequal Impacts
Who is most likely to be impacted?
A vulnerability index (Davies et al., 2018) was created from census data to assess wildfire risk in communities throughout the United States. Developed through a partnership between the University of Washington and The Nature Conservancy, some key findings from this study show that racial and ethnic minorities are at higher risk from wildfires than predominantly white communities. Communities that are mostly Black, Latinx, or Native American experience 50 percent greater vulnerability to wildfires than other communities (Davies et al., 2018). Native Americans in particular were found to be six times more likely than other groups to live in areas prone to wildfires, attributed to historical forced relocation onto reservations (Davies et al., 2018). These environmental factors paired with greater levels of social vulnerability such as socioeconomic barriers make these populations more vulnerable to wildfires and as well as making recovery after a wildfire more difficult (Davies, et al., 2018).
Infrastructure needs like water delivery systems have been historically undeveloped within Native American territories, with water allocations long contested between tribes, states, and localities. Water allocates to tribal lands date back as early as the early 1800s through treaty provisions and are now closely monitored for health reasons and quantity (NCAI, n.d.). The 2007 Indian Health Services Sanitation Deficiency System Summary Report showed that over 13% of tribal homes lack basic access to safe drinking water and sanitation services, much higher than the one percent of homes nationwide (NCAI, n.d.). Funding for water systems has typically benefited areas surrounding tribal lands. It is important to note that water projects on tribal lands authorized through Congress have been typically underfunded and go into disrepair due to a lack of supporting infrastructure, such as tribal members trained to maintain these systems (NCAI, n.d.).
In Oregon, thousands of residents of the Warm Springs reservation were without water due to an electrical fire in March 2022 that knocked out a transformer at the drinking water treatment plant (Cook, 2022), making access to clean drinking water uncertain. The reservation's water infrastructure has caused problems for risking human health and raising environmental concerns for years (Cook, 2022). The Tribes convened with federal and state agencies to find money for needed updates more than two years ago, but talks have yet to yield concrete plans for a new drinking water plant (Cook, 2022).
For populations that already face infrastructure issues and resource constraints regularly, these communities have greater potential to be interrupted and harmed by wildfire. More must be done in the way of building infrastructure and policy to increase support for Native American communities in the short term, as well as long-term investments to build resilience and equity.
What Can Be Done
Erosion Control
Controlling erosion after a fire is a major concern in watersheds. Multiple methods to reduce potential post-fire erosion and floods have been investigated, as well as tools to predict where erosion is most likely to occur and where to direct efforts. Main erosion mitigation efforts include:
Mulch covers the soil to reduce impact of rain drops falling on the soil, reduces ease of water flow, and offsets water-repellent soil.
Barriers can be installed on hill slopes to slow the flow of water and trap sediment. These barriers are made out of logs, sandbags, straw, and more.
Seeding and revegetation grass seeding helps increase the vegetative cover, increasing roots and promoting growth in erosion-prone soil.
(University of California, n.d.)
Prescribed Fire
Unlike wildfires, prescribed fires, also called planned burns, are fires set intentionally to help meet forest management goals. They can be used for a variety of objectives, like maintaining landscapes, restoring natural ecosystems, and reducing risk of future extreme fires by minimizing vegetation that may fuel larger fires (US Dept of Agriculture, n.d.). Some also speculate that prescribed fires can help build resilience within forests to help weather future unplanned fires (Kane et al., 2022).
The video above from the Clemson University Biochemistry and Environmental Quality Research Group explains planned burns as forest management and interaction of DOC with water quality.
Related Pages & Resources
Explores the ways in which ecosystems are affected by wildfires.
How soil quality and nutrients are impacted by wildfire and what it means for food production.
Find more information about the amazing Bull Run and Oregon watersheds.
US Forest Service analysis of watershed health and threats, including fire, insects, and disease.
References
California Water Science Center, U. S. G. S. (2018, March 6). Water quality after a wildfire. Water Quality & Wildfire | USGS California Water Science Center. Retrieved November 14, 2022, from https://ca.water.usgs.gov/wildfires/wildfires-water-quality.html
Chow, A. T. S., Karanfil, T., & Dahlgren, R. A. (2021, August 12). Wildfires are threatening municipal water supplies. Eos. Retrieved December 6, 2022, from https://eos.org/science-updates/wildfires-are-threatening-municipal-water-supplies
Cook, E. C. (2022, March 21). Warm Springs residents prepare for water outage to continue through Root Feast. opb. Retrieved December 9, 2022, from https://www.opb.org/article/2022/03/21/warm-springs-reservation-clean-water-outage-root-feast/
Courter, J. (2022, March 29). Forests to faucets 2.0 story map. ArcGIS StoryMaps. Retrieved December 8, 2022, from https://storymaps.arcgis.com/collections/4e450a6c7ed24f0cbae4abc1c07843b7?item=1
Davies, I. P., Haugo, R. D., Robertson, J. C., & Levin, P. S. (2018). The unequal vulnerability of communities of color to wildfire. PloS One, 13(11), e0205825–e0205825. https://doi.org/10.1371/journal.pone.0205825
Environmental Protection Agency. (n.d.). Wildland Fire Research: Water Supply and Ecosystem Protection. EPA. Retrieved November 14, 2022, from https://www.epa.gov/air-research/wildland-fire-research-water-supply-and-ecosystem-protection
Jordan, R. (2019, December 14). Wildfire's impact on water quality. Stanford News. Retrieved December 8, 2022, from https://news.stanford.edu/2019/12/17/wildfires-impact-water-quality/
Kane, V. R., Van Wagtendonk, L., & Brenner, A. (2022, April 29). A lidar's-eye view of how forests are faring. Eos. Retrieved December 8, 2022, from https://eos.org/features/a-lidars-eye-view-of-how-forests-are-faring
Meadows, R. (2022, June 6). How wildfires can contaminate drinking water. Chemical and Engineering News. Retrieved November 14, 2022, from https://cen.acs.org/environment/water/wildfires-contaminate-drinking-water/100/i20
National Congress of American Indians (NCAI). (n.d.). Water. Land & Natural Resources Policy Issues. Retrieved December 9, 2022, from https://www.ncai.org/policy-issues/land-natural-resources/water
Phillips, C., & Dahl, K. (2022, June 7). Fire and water in the Western United States. Union of Concerned Scientists. Retrieved November 14, 2022, from https://www.ucsusa.org/resources/wildfire-water-western-united-states#top
Portland Water Bureau. (n.d.). Portland's watersheds. Portland.gov. Retrieved December 8, 2022, from https://www.portland.gov/bes/protecting-rivers-streams/portlands-watersheds
University of California. (n.d.). Erosion control. University of California, Agriculture and Natural Resources. Retrieved December 8, 2022, from https://ucanr.edu/sites/fire/Recovery/Revegetation/Erosion/
US Department of Agriculture. (n.d.). Prescribed fire. US Forest Service. Retrieved December 8, 2022, from https://www.fs.usda.gov/managing-land/prescribed-fire
U.S. Department of the Interior. (2020, March 19). Wildland fire: What is a prescribed fire? (U.S. National Park Service). National Parks Service. Retrieved December 8, 2022, from https://www.nps.gov/articles/what-is-a-prescribed-fire.htm
Water Resources. (2019, March 1). Water quality after wildfire active. Water Quality After Wildfire | U.S. Geological Survey. Retrieved November 14, 2022, from https://www.usgs.gov/mission-areas/water-resources/science/water-quality-after-wildfire#overview
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Peltola, C. (2019). After a forest fire burned through the area the summer before, only the grass had come back by the next summer - which in turn had been "burnt out" by the hot summer sun – and the trees stood like burnt matchsticks in the morning fog [Photograph]. Unsplash. https://unsplash.com/photos/Yoqi404MJ8M
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