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Wildfire and Drinking Water Sources

Potential impacts to public water systems after wildfires

Wildfires impact public water systems in many ways, directly and indirectly, and ranging from immediate effects to long-term changes within watersheds. Wildfires can directly damage treatment facilities and other infrastructure or impact the streams, rivers, and reservoirs serving as sources of drinking water. These changes may affect the water quality used at drinking water intakes, wells or springs and the effects may change over time.

For information specific to wildfires visit DEQ's Wildfire Response web page.

Planning for the future to reduce risks

Source water protection planning is a way for public water systems to evaluate wildfire risks and develop risk reduction strategies. Implementation measures often require collaboration among drinking water providers, landowners, and restoration/conservation practitioners. While there are upfront costs to protect source water, the long-term costs of inaction or business-as-usual are often higher. The DEQ and OHA Drinking Water Source Protection programs can assist public water systems and communities with developing protection strategies.


Wildfires can cause significant chemical and physical changes in the watersheds, including streams, rivers, and reservoirs. Through erosion and runoff during rain or storm events, these changes can impact water quality by increasing inputs of chemical constituents such as:
  • Total organic carbon
  • Nutrients such as phosphate, nitrate, and nitrite, particularly if fire retardants were widely applied within the watershed during firefighting efforts
  • Heavy metals, including lead and chromium, which may be contained in ash and the remnants of burned homes or other structures
  • Suspended sediment, which can cause elevated turbidity (water cloudiness) and decrease water clarity

These effects of fire also impair or destroy the quality of vital aquatic habitats that support fish, mammals, invertebrates and other species. Ecological impacts may include:

  • Death or injury to aquatic species from the acute toxicity of materials contained in ash, debris or fire retardant
  • The likelihood of more algal blooms in lakes, slow-moving rivers, or reservoirs

Wildfires can cause immediate impacts to water systems through loss of structures or other infrastructure issues like loss of power, damage to treatment systems, and/or impacts to piping that distributes the water. This can result in boil water notices, the need to flush entire systems, or other repairs. Oregon Health Authority's Drinking Water Services Program provides regulatory and technical assistance for evaluating treatment and distribution system issues to ensure water systems are in compliance and providing safe drinking water to communities.

Public water systems that get their source water from streams, rivers and lakes may find that water has more sediment and is murkier. This is because wildfires can burn trees and plants, which makes it easier for the soil to erode, and because there is burnt material on the ground that can easily flow into rivers and streams when it rains. This extra soil and ash in the water can cause an increase in organic carbon, pH, manganese, iron, and nutrients like nitrogen and phosphorus in the water. This can make treatment challenging and possibly lead to algal or cyanobacterial growth. In addition, the watersheds may have increased risk of landslides, flooding, and debris flows that can impact infrastructure. 

DEQ's Drinking Water Protection Program can provide technical assistance to address short-term stormwater and watershed stabilization efforts as well as longer term watershed evaluation, mitigation and restoration.​

Although the source of water for wells and springs is naturally protected from wildfires, water systems may have challenges with short-term impacts due to depressurization or direct impact to infrastructure. These impacts could allow pollution to enter the system or lead to stagnant water lines that may need to be flushed. OHA Drinking Water Services provides guidance for system flushing and subsequent sampling for volatile organic compounds. Oregon Water Resources Department provides information on evaluating and maintaining wells following a fire.​

Firefighting agencies use a variety of materials as fire retardants including both long-term retardants, applied via air tankers or helicopter, and short-term fire suppressants, typically foams and gels. Long-term fire retardants are typically 10% fertilizer, primarily phosphorus. Phosphorous is a key nutrient for plant life so it can be taken up by plants surviving the fire. However, phosphorous that is not taken up by plants on the landscape may make its way to the nearest waterbody when it rains. Excess nutrients in water can affect the water quality and contribute to growth of plants and algae. Some fire retardants have also been known to contain “performance additives" that may contain metals. See DEQ's fact sheet: Cleaning up Fire Retardant and Fire Suppressants.​

​The extent of longer-term impacts, meaning one to 10 years after the fire, for drinking water systems using surface water intakes will depend on burn severity, riparian and watershed conditions and land management practices. Longer term impacts may include the following:

  • Infrastructure damage from sediment and debris.

  • Increased hydrologic and water-quality variability.

  • Ongoing pulses of high turbidity and high pH.

  • Altered seasonality of hydrological and chemical export from burned catchment.

  • Risk of landslides, flooding, and debris flows.

  • Increased sedimentation and debris in reservoirs and loss of storage capacity.

These conditions may increase suspended sediment and turbidity, pH, organic carbon, manganese, iron, and nutrients like nitrogen and phosphorus, all of which can create challenges for treatment and possibly lead to harmful algal blooms.

DEQ and OHA Source Water Assessment reports​ ​can tell the water system operator and community about the watershed or recharge area that supplies the well, spring or intake – what the agencies refer to as the “drinking water source area." These reports also identify potential risks and susceptible areas within the source area. Information in the reports can be used in conjunction with burn severity maps to identify areas for stabilization and restoration. ​​

Mitigation and restoration

Visit our Post-fire Mitigation and Restoration Measures page to learn how assessments drive restoration work.

A lasting impact

The September 2020 wildfires impacted numerous public water systems, with immediate effects to water quality and infrastructure and anticipated long-term changes within watersheds that supply drinking water.

​​​There were 50 public water systems using surface water affected, and 96 public water systems using groundwater have source areas within the wildfire perimeters. ​

Long-term impacts to water systems depend on burn severity, slope gradient, riparian and watershed conditions, and land management practices. DEQ participated on the Erosion Threat Assessment/Reduction Team to evaluate fires that burn on nonfederal land, including private, state, and local jurisdictions. The team assessed post-fire changes on the landscape to identify threats and potential risks to drinking water resources and provide recommendations to protect human life and safety, assets and infrastructure, and important natural and cultural resources. 

​Maps of select river basins with 2020 Wildfire Perimeters and Drinking Water Intakes (including downstream water providers):

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Resources and tools

​​​Oregon Health Authority's Emergency Preparedness and Planning Resources for Wildfire includes guidance to public water systems on post wildfire monitoring, treatment optimization recommendations, advisory tips, and more.

DEQ's main Wildfire Response page includes broad information on affects to air, land, and water across the state for the public.

​There are many partners and resources available to assist public water systems with watershed stabilization and restoration, including:

For questions about regulations, water quality, treatment plants, and testing, contact OHA Drinking Water Services at 971-673-0405 or Info.drinkingwater@odhsoha.oregon.gov. OHA is the agency responsible for implementation of the federal Safe Drinking Water Act.

If you are concerned about your water from a private or domestic well see the following resources:

Oregon's fact sheet on funds and resources for drinking water source protection provides descriptions and contact information for partners, resources and funds available to public water systems and others to assist with drinking water infrastructure and source protection projects including watershed stabilization and restoration

Contact

For more information, email: 
Drinkingwater.Protection@deq.oregon.gov