Bolt Creek Wildfire Sediment Runoff and Water Quality Active
The Issue: Scientists and water-resource managers recognize the increasing impact of wildfires on water supply in the western U.S. The increasing frequency and severity of wildfires are linked to changes in snowpack, warmer temperatures, and drought. Sedimentation following wildfire can impact aquatic habitat, reservoir storage capacity, water quality, and thus public drinking water supplies. Additionally, communities rely on watersheds for irrigation, drinking water, and fishing.
How USGS will help: In 2021, the Bolt Creek Fire burned in King and Snohomish Counties of Washington State. The fire provides an opportunity to study the impacts of wildfires on water supply in the Cascade Range. We are working to identify water quality constituents of concern, estimate sediment loads, and quantify the concentration of other constituents. Although rivers draining the areas burned in the Bolt Creek Fire are not municipal water supplies, our analysis of water-quality impacts will help managers of municipal water supplies in adjacent basins prepare for potential wildfires in the future.
Problem
Many communities rely on forested watersheds, which are susceptible to burning, for irrigation, drinking water, and fishing. The frequency and severity of fires in the western U.S. is increasing, partially due to changes in snowpack, warmer temperatures, and drought. These changing conditions are motivating research on the impact of wildfires on water supply.
Increased sedimentation following wildfire can impact aquatic habitat, reservoir storage capacity, water quality, and public drinking water supplies. Wildfires often increase sediment yields in nearby rivers, lakes, and reservoirs. A recent study of watersheds draining into Whiskeytown Lake, California, indicated post-wildfire sediment yields as high as 64 times pre-fire yields following the Carr Fire.
In 2021, the Bolt Creek Fire burned in King and Snohomish Counties of Washington State. The fire provides an opportunity to study the impacts of wildfires on water supply in the Cascade Mountain Range. Although rivers draining the Bolt Creek Fire do not impact current municipal water supplies, Seattle Public Utilities (SPU) is interested in an analysis of water-quality impacts that will help prepare managers of municipal water supplies in adjacent basins for potential wildfires. As SPU plans for future wildfire impacts on drinking water supplies in the Tolt and Cedar River basins, they seek data and analysis to help better understand the potential magnitude and temporal impact of surface water draining highly burned basins in the Cascade Range.
Objectives
The primary objective of this work is to identify water-quality constituents of concern. These include:
- suspended sediment
- major cations
- nutrients
- rare trace elements
- organics
In addition to identifying constituents, we will quantify their yields in surface runoff draining the Bolt Creek burn area. Using this data, we will examine the temporal trends and recovery trajectory following the Bolt Creek Fire. This study will provide insight and guidance for potential impacts of future wildfires on drinking water supplies in other basins including the Tolt and Cedar River basins.
Relevance and Benefits
Wildfires often alter watershed hydrology. Variations in water supply and water quality in burned watersheds and downstream areas pose severe potential risks to human and environmental health and water infrastructure. The USGS monitors, models, and assesses water supply and quality throughout the U.S., often in cooperation with other federal, tribal, state, and local agencies, and provides results to the public and water managers through web-based user interfaces. Current research is aimed at better tracking and prediction of water-supply quality responses to wildfires in watersheds throughout the western U.S. and improved understanding of the interactions of wildfire responses with other factors such as land and water use changes, climate change, and drought extent and intensity.
Approach
We are measuring streamflow, quantifying sediment loads, and assessing water quality constituents of potential concern.
We are measuring streamflow and turbidity at two locations.
- A newly installed USGS streamgage 12131300 just upstream of the confluence between Bolt Creek and Beckler River. A web camera also operates at this site to provide real-time imagery to the public.
- The South Fork Skykomish USGS streamgage 12131500 approximately two miles downstream and below the confluence between Beckler Creek and the South Fork Skykomish River.
In addition to traditional streamflow measurements, we are using real-time imagery of Bolt Creek to explore other methods of measuring and transmitting real-time data using a surface velocity radar.
We are also collecting surface water samples during storms at higher streamflow conditions to measure suspended sediment concentrations and contaminants including trace elements. We are pairing measurements of river stage, discharge, and turbidity with depth- and width-integrated surface water samples, and both manual and automated point sampling. These data will be used to estimate concentrations and loads of suspended sediment, trace elements, and organic carbon at the Bolt Creek and South Fork Skykomish gaging stations. Resource managers will use this information to proactively plan for potential contaminants carried by post-fire runoff and determine how long water quality impacts might persist after wildfires.
The Issue: Scientists and water-resource managers recognize the increasing impact of wildfires on water supply in the western U.S. The increasing frequency and severity of wildfires are linked to changes in snowpack, warmer temperatures, and drought. Sedimentation following wildfire can impact aquatic habitat, reservoir storage capacity, water quality, and thus public drinking water supplies. Additionally, communities rely on watersheds for irrigation, drinking water, and fishing.
How USGS will help: In 2021, the Bolt Creek Fire burned in King and Snohomish Counties of Washington State. The fire provides an opportunity to study the impacts of wildfires on water supply in the Cascade Range. We are working to identify water quality constituents of concern, estimate sediment loads, and quantify the concentration of other constituents. Although rivers draining the areas burned in the Bolt Creek Fire are not municipal water supplies, our analysis of water-quality impacts will help managers of municipal water supplies in adjacent basins prepare for potential wildfires in the future.
Problem
Many communities rely on forested watersheds, which are susceptible to burning, for irrigation, drinking water, and fishing. The frequency and severity of fires in the western U.S. is increasing, partially due to changes in snowpack, warmer temperatures, and drought. These changing conditions are motivating research on the impact of wildfires on water supply.
Increased sedimentation following wildfire can impact aquatic habitat, reservoir storage capacity, water quality, and public drinking water supplies. Wildfires often increase sediment yields in nearby rivers, lakes, and reservoirs. A recent study of watersheds draining into Whiskeytown Lake, California, indicated post-wildfire sediment yields as high as 64 times pre-fire yields following the Carr Fire.
In 2021, the Bolt Creek Fire burned in King and Snohomish Counties of Washington State. The fire provides an opportunity to study the impacts of wildfires on water supply in the Cascade Mountain Range. Although rivers draining the Bolt Creek Fire do not impact current municipal water supplies, Seattle Public Utilities (SPU) is interested in an analysis of water-quality impacts that will help prepare managers of municipal water supplies in adjacent basins for potential wildfires. As SPU plans for future wildfire impacts on drinking water supplies in the Tolt and Cedar River basins, they seek data and analysis to help better understand the potential magnitude and temporal impact of surface water draining highly burned basins in the Cascade Range.
Objectives
The primary objective of this work is to identify water-quality constituents of concern. These include:
- suspended sediment
- major cations
- nutrients
- rare trace elements
- organics
In addition to identifying constituents, we will quantify their yields in surface runoff draining the Bolt Creek burn area. Using this data, we will examine the temporal trends and recovery trajectory following the Bolt Creek Fire. This study will provide insight and guidance for potential impacts of future wildfires on drinking water supplies in other basins including the Tolt and Cedar River basins.
Relevance and Benefits
Wildfires often alter watershed hydrology. Variations in water supply and water quality in burned watersheds and downstream areas pose severe potential risks to human and environmental health and water infrastructure. The USGS monitors, models, and assesses water supply and quality throughout the U.S., often in cooperation with other federal, tribal, state, and local agencies, and provides results to the public and water managers through web-based user interfaces. Current research is aimed at better tracking and prediction of water-supply quality responses to wildfires in watersheds throughout the western U.S. and improved understanding of the interactions of wildfire responses with other factors such as land and water use changes, climate change, and drought extent and intensity.
Approach
We are measuring streamflow, quantifying sediment loads, and assessing water quality constituents of potential concern.
We are measuring streamflow and turbidity at two locations.
- A newly installed USGS streamgage 12131300 just upstream of the confluence between Bolt Creek and Beckler River. A web camera also operates at this site to provide real-time imagery to the public.
- The South Fork Skykomish USGS streamgage 12131500 approximately two miles downstream and below the confluence between Beckler Creek and the South Fork Skykomish River.
In addition to traditional streamflow measurements, we are using real-time imagery of Bolt Creek to explore other methods of measuring and transmitting real-time data using a surface velocity radar.
We are also collecting surface water samples during storms at higher streamflow conditions to measure suspended sediment concentrations and contaminants including trace elements. We are pairing measurements of river stage, discharge, and turbidity with depth- and width-integrated surface water samples, and both manual and automated point sampling. These data will be used to estimate concentrations and loads of suspended sediment, trace elements, and organic carbon at the Bolt Creek and South Fork Skykomish gaging stations. Resource managers will use this information to proactively plan for potential contaminants carried by post-fire runoff and determine how long water quality impacts might persist after wildfires.