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#           Water Quality after a Wildfire      

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      By California Water Science Center      June 5, 2018    

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About half of the water supply in the southwestern United States is supplied by water from forests, which generally yield higher quality water than any other source. Approximately 80 percent of the freshwater resources in the U.S. originate on forested land, and more than 3,400 public drinking-water systems are located in watersheds containing national forest lands (USDA, 2006). More than 12 million acres of land, including important forested water-supply watersheds, have burned in the southwestern U.S. in the past 30 years. Wildfires increase susceptibility of watersheds to both flooding and erosion, and thus can impair water supplies.

Wildfires can compromise water quality both during active burning, and for months and years after the fire has been contained. During active burning, ash can settle on lakes and reservoirs used for drinking water supplies, like during the 2013 Rim Fire.

Storms following wildfires are known to impair drinking water supplies in the southwestern U.S., as burn areas are prone to greater rates of erosion, increasing the downstream accumulation of sediment in streams, rivers, and reservoirs. Thus, the potential impacts from past, current, and future wildfires on the quantity and quality of runoff are considerable, and may greatly impact water used for domestic, agricultural, and ecological water supplies.

The USGS works with local, state, and federal agencies and resource managers to identify and evaluate issues related to wildfires. Decision makers rely on USGS data to assess and manage the effects of wildfire on California's water and ecosystems. Near-real-time maps and satellite imagery help fire managers monitor current wildfire extent and behavior. Water quality, flow, and sediment data from USGS studies may help managers evaluate the cumulative effects of fire and potential water-quality impacts on drinking-water supplies. Climate and hydrologic modeling can aid in fire forecasting and help inform fire management strategy.

**Watershed Effects**

Wildfires increase susceptibility of watersheds to flooding and erosion and can have both short- and long-term impacts on water supplies, such as increased treatment costs, need for alternative supplies, and diminished reservoir capacity (Smith et al 2011).

The degree to which wildfire degrades water quality and supply depends on multiple factors. These include the extent and intensity of the wildfire, post-wildfire precipitation, watershed topography, and local ecology.

**Implications for Drinking-Water Treatment**

Drinking-water utilities strive to provide safe drinking water for their communities. Unfortunately, the unpredictable nature of wildfire makes it challenging to develop treatment-plant-specific strategies for treating source water degraded by the effects of wildfire. High-intensity rainfall events in steep, burned watersheds are likely to move large amounts of suspended and dissolved material into downstream water supplies.

Potential effects of wildfire on municipal water supplies and downstream aquatic ecosystems include the following:
                                - Changes in the magnitude and timing of snowmelt runoff, which influence filling of water-supply reservoirs
                                - Increased sediment loading of water-supply reservoirs, shortened reservoir lifetime, and increased maintenance costs
                                - Increased loading of streams with nutrients, dissolved organic carbon, major ions, and metals
                                - Post-fire erosion and transport of sediment and debris to downstream water-treatment plants, water-supply reservoirs, and aquatic ecosystems
                                - Increased turbidity (cloudiness caused by suspended material), or heightened iron and manganese concentrations, which may increase chemical treatment requirements and produce larger volumes of sludge, both of which would raise operating costs
                                - Changes in source-water chemistry that can alter drinking-water treatment

The USGS monitors water quality and sediment characteristics in rivers and reservoirs affected by fires. This data helps scientists and water managers evaluate the cumulative effects of fire, and potential water-quality impacts on drinking-water supplies.

High-intensity storms can affect water quality years after a wildfire, Monitoring source water downstream of burned watersheds allow water managers to minimize adverse water-quality effects, such as by temporarily diverting compromised water or changing source water.

**Ecosystems**

Post-fire runoff can also harm ecosystems and aquatic life such as fish and frogs that live in affected watersheds, some of which are critically endangered. Understanding the effects that wildfires have on local water quality helps resource managers plan for and manage contaminants, conservation, and treatment processes.

View Media Details

Urban fires, more than forest fires, result in an increase in chemicals and contaminants. When rains come, contaminants from urban ash and debris can be mobilized by the rainfall runoff and associated wind. These contaminents have the potential to seriously affect the quality of water supplies and sensitive habitat areas or ecosystems.

In a study published in May 2016, USGS scientists noted the presence of multiple trace metals in post-fire storm water. Scientists discovered elevated levels of iron, lead, nickel, and zinc in the streams near Los Angeles, and traced the contaminants back to the 2009 Station Fire in the nearby Angeles National Forest. The study examined the effect of the fire on trace metal contamination in nearby streams, comparing post-fire stormwater quality to criteria for aquatic life. Studies like these help USGS and its cooperators understand how contamination from fires could harm local ecosystems.

Below are other science projects associated with this project.

link

October 25, 2023

####                 Wildfires in California              

California Water Science Center, Wildland Fire Science

link

October 25, 2023

####   Wildfires in California

Learn More

link

June 5, 2018

####                 Post-Fire Flooding and Debris Flow              

California Water Science Center, Wildland Fire Science

link

June 5, 2018

####   Post-Fire Flooding and Debris Flow

Learn More

link

March 28, 2018

####                 Wildfire Effect on Mercury Levels in Putah and Cache Creek Watersheds              

California Water Science Center

link

March 28, 2018

####   Wildfire Effect on Mercury Levels in Putah and Cache Creek Watersheds

Learn More

Below are multimedia items associated with this project.

October 24, 2012

#### Living with Fire: The USGS Southern California Wildfire Risk Project

link

Southern California's fire ecology is unlike that of anywhere else in the United States. Fire control strategies developed for mountain forests don't have the same results here. So can science help uncover new answers to help Southern California communities manage and live with wildfires?

Western Ecological Research Center (WERC), Communications and Publishing

October 24, 2012

#### Living with Fire: The USGS Southern California Wildfire Risk Project

link

#### Living with Fire: The USGS Southern California Wildfire Risk Project

link

Southern California's fire ecology is unlike that of anywhere else in the United States. Fire control strategies developed for mountain forests don't have the same results here. So can science help uncover new answers to help Southern California communities manage and live with wildfires?

Western Ecological Research Center (WERC), Communications and Publishing

Below are publications associated with this project.

May 4, 2016

####                 Trace elements in stormflow, ash, and burned soil following the 2009 station fire in southern California              

Water Resources Mission Area, Mineral Resources Program, California Water Science Center, Geology, Geophysics, and Geochemistry Science Center, Spectroscopy Lab

August 7, 2015

####                 The role of precipitation type, intensity, and spatial distribution in source water quality after wildfire              

Climate Research and Development Program, Land Change Science Program

July 26, 2013

####                 Climatic stress increases forest fire severity across the western United States              

Water Resources Mission Area, Ecosystems Mission Area, Western Ecological Research Center (WERC), California Water Science Center

December 1, 2010

####                 Water-quality data from storm runoff after the 2007 fires, San Diego County, California              

Water Resources Mission Area, California Water Science Center

February 27, 2009

####                 Sample collection of ash and burned soils from the October 2007 southern California Wildfires              

Mineral Resources Program, Geology, Geophysics, and Geochemistry Science Center, Spectroscopy Lab

January 1, 2006

####                 Wildfire hazards—A national threat              

January 1, 1976

####                 A reconnaissance of the effects of a forest fire on water quality in Kings Canyon National Park, California              

Below are news stories associated with this project.

USGS Hydrologist Interviewed about Fire Effects on Water Quality, and on Debris Flow

October 2, 2018

####   USGS Hydrologist Interviewed about Fire Effects on Water Quality, and on Debris Flow

As part of an article on the effects of wildfires on the health of infants, Santa Rosa Press Democrat reporter, Guy Kovner, interviewed Scott Wright...

Read Article

Wildfires, Water, and CAWSC Science

October 19, 2017

####   Wildfires, Water, and CAWSC Science

California's landscape is prone to drought and warmer climates. The recent drought lasted five years (2011 – early 2017), bringing with it many...

Read Article

About half of the water supply in the southwestern United States is supplied by water from forests, which generally yield higher quality water than any other source. Approximately 80 percent of the freshwater resources in the U.S. originate on forested land, and more than 3,400 public drinking-water systems are located in watersheds containing national forest lands (USDA, 2006). More than 12 million acres of land, including important forested water-supply watersheds, have burned in the southwestern U.S. in the past 30 years. Wildfires increase susceptibility of watersheds to both flooding and erosion, and thus can impair water supplies.

Wildfires can compromise water quality both during active burning, and for months and years after the fire has been contained. During active burning, ash can settle on lakes and reservoirs used for drinking water supplies, like during the 2013 Rim Fire.

Storms following wildfires are known to impair drinking water supplies in the southwestern U.S., as burn areas are prone to greater rates of erosion, increasing the downstream accumulation of sediment in streams, rivers, and reservoirs. Thus, the potential impacts from past, current, and future wildfires on the quantity and quality of runoff are considerable, and may greatly impact water used for domestic, agricultural, and ecological water supplies.

The USGS works with local, state, and federal agencies and resource managers to identify and evaluate issues related to wildfires. Decision makers rely on USGS data to assess and manage the effects of wildfire on California's water and ecosystems. Near-real-time maps and satellite imagery help fire managers monitor current wildfire extent and behavior. Water quality, flow, and sediment data from USGS studies may help managers evaluate the cumulative effects of fire and potential water-quality impacts on drinking-water supplies. Climate and hydrologic modeling can aid in fire forecasting and help inform fire management strategy.

**Watershed Effects**

Wildfires increase susceptibility of watersheds to flooding and erosion and can have both short- and long-term impacts on water supplies, such as increased treatment costs, need for alternative supplies, and diminished reservoir capacity (Smith et al 2011).

The degree to which wildfire degrades water quality and supply depends on multiple factors. These include the extent and intensity of the wildfire, post-wildfire precipitation, watershed topography, and local ecology.

**Implications for Drinking-Water Treatment**

Drinking-water utilities strive to provide safe drinking water for their communities. Unfortunately, the unpredictable nature of wildfire makes it challenging to develop treatment-plant-specific strategies for treating source water degraded by the effects of wildfire. High-intensity rainfall events in steep, burned watersheds are likely to move large amounts of suspended and dissolved material into downstream water supplies.

Potential effects of wildfire on municipal water supplies and downstream aquatic ecosystems include the following:
                                - Changes in the magnitude and timing of snowmelt runoff, which influence filling of water-supply reservoirs
                                - Increased sediment loading of water-supply reservoirs, shortened reservoir lifetime, and increased maintenance costs
                                - Increased loading of streams with nutrients, dissolved organic carbon, major ions, and metals
                                - Post-fire erosion and transport of sediment and debris to downstream water-treatment plants, water-supply reservoirs, and aquatic ecosystems
                                - Increased turbidity (cloudiness caused by suspended material), or heightened iron and manganese concentrations, which may increase chemical treatment requirements and produce larger volumes of sludge, both of which would raise operating costs
                                - Changes in source-water chemistry that can alter drinking-water treatment

The USGS monitors water quality and sediment characteristics in rivers and reservoirs affected by fires. This data helps scientists and water managers evaluate the cumulative effects of fire, and potential water-quality impacts on drinking-water supplies.

High-intensity storms can affect water quality years after a wildfire, Monitoring source water downstream of burned watersheds allow water managers to minimize adverse water-quality effects, such as by temporarily diverting compromised water or changing source water.

**Ecosystems**

Post-fire runoff can also harm ecosystems and aquatic life such as fish and frogs that live in affected watersheds, some of which are critically endangered. Understanding the effects that wildfires have on local water quality helps resource managers plan for and manage contaminants, conservation, and treatment processes.

View Media Details

Urban fires, more than forest fires, result in an increase in chemicals and contaminants. When rains come, contaminants from urban ash and debris can be mobilized by the rainfall runoff and associated wind. These contaminents have the potential to seriously affect the quality of water supplies and sensitive habitat areas or ecosystems.

In a study published in May 2016, USGS scientists noted the presence of multiple trace metals in post-fire storm water. Scientists discovered elevated levels of iron, lead, nickel, and zinc in the streams near Los Angeles, and traced the contaminants back to the 2009 Station Fire in the nearby Angeles National Forest. The study examined the effect of the fire on trace metal contamination in nearby streams, comparing post-fire stormwater quality to criteria for aquatic life. Studies like these help USGS and its cooperators understand how contamination from fires could harm local ecosystems.

Below are other science projects associated with this project.

link

October 25, 2023

####                 Wildfires in California              

California Water Science Center, Wildland Fire Science

link

October 25, 2023

####   Wildfires in California

Learn More

link

June 5, 2018

####                 Post-Fire Flooding and Debris Flow              

California Water Science Center, Wildland Fire Science

link

June 5, 2018

####   Post-Fire Flooding and Debris Flow

Learn More

link

March 28, 2018

####                 Wildfire Effect on Mercury Levels in Putah and Cache Creek Watersheds              

California Water Science Center

link

March 28, 2018

####   Wildfire Effect on Mercury Levels in Putah and Cache Creek Watersheds

Learn More

Below are multimedia items associated with this project.

October 24, 2012

#### Living with Fire: The USGS Southern California Wildfire Risk Project

link

Southern California's fire ecology is unlike that of anywhere else in the United States. Fire control strategies developed for mountain forests don't have the same results here. So can science help uncover new answers to help Southern California communities manage and live with wildfires?

Western Ecological Research Center (WERC), Communications and Publishing

October 24, 2012

#### Living with Fire: The USGS Southern California Wildfire Risk Project

link

#### Living with Fire: The USGS Southern California Wildfire Risk Project

link

Southern California's fire ecology is unlike that of anywhere else in the United States. Fire control strategies developed for mountain forests don't have the same results here. So can science help uncover new answers to help Southern California communities manage and live with wildfires?

Western Ecological Research Center (WERC), Communications and Publishing

Below are publications associated with this project.

May 4, 2016

####                 Trace elements in stormflow, ash, and burned soil following the 2009 station fire in southern California              

Water Resources Mission Area, Mineral Resources Program, California Water Science Center, Geology, Geophysics, and Geochemistry Science Center, Spectroscopy Lab

August 7, 2015

####                 The role of precipitation type, intensity, and spatial distribution in source water quality after wildfire              

Climate Research and Development Program, Land Change Science Program

July 26, 2013

####                 Climatic stress increases forest fire severity across the western United States              

Water Resources Mission Area, Ecosystems Mission Area, Western Ecological Research Center (WERC), California Water Science Center

December 1, 2010

####                 Water-quality data from storm runoff after the 2007 fires, San Diego County, California              

Water Resources Mission Area, California Water Science Center

February 27, 2009

####                 Sample collection of ash and burned soils from the October 2007 southern California Wildfires              

Mineral Resources Program, Geology, Geophysics, and Geochemistry Science Center, Spectroscopy Lab

January 1, 2006

####                 Wildfire hazards—A national threat              

January 1, 1976

####                 A reconnaissance of the effects of a forest fire on water quality in Kings Canyon National Park, California              

Below are news stories associated with this project.

USGS Hydrologist Interviewed about Fire Effects on Water Quality, and on Debris Flow

October 2, 2018

####   USGS Hydrologist Interviewed about Fire Effects on Water Quality, and on Debris Flow

As part of an article on the effects of wildfires on the health of infants, Santa Rosa Press Democrat reporter, Guy Kovner, interviewed Scott Wright...

Read Article

Wildfires, Water, and CAWSC Science

October 19, 2017

####   Wildfires, Water, and CAWSC Science

California's landscape is prone to drought and warmer climates. The recent drought lasted five years (2011 – early 2017), bringing with it many...

Read Article