USGS study brings new focus to strategic monitoring of wildfire impacts on water sources

After wildfires, canopy vegetation is lost and soil properties change, causing more water to flow over the land when it rains. This can lead to flooding, erosion, and the entry of sediment, ash, pollutants, and debris into surface waters.

The effects of wildfires on water quality can range from no noticeable change to significant increases in the amounts of sediment, nutrients, metals, and other constituents. This can result in reduced water quality, reduced reservoir storage capacity, degradation of stream habitats, and increased treatment costs for drinking water suppliers.

The most severe water quality impacts are often delayed until high-intensity rainstorms occur, which may not occur until months or even years after a fire. This can complicate efforts to collect post-fire water quality data, as funding opportunities for data collection may have waned by the time the worst impacts occur.

To better understand how wildfires affect water sources, U.S. Geological Survey scientists developed A strategy Select water sampling locations and data collection methods to better identify regional insights into wildfire impacts on water quality.

“We currently don’t have enough data to estimate how wildfires affect water quality in different regions,” said Sheila Murphy, a research hydrologist with the U.S. Geological Survey and lead author of the study. “Monitoring water quality after wildfires in a strategic, consistent way will help us assess and predict the impacts of wildfires on surface waters, which is critical to human and ecosystem health.”

Hundreds of wildfires burn in watersheds across the country every year, making it difficult to monitor every stream within or downstream of a burned area. Collecting post-wildfire water quality data from sites with varying climate, land use, geology, and vegetation can provide a foundation for distinguishing regional differences in water impacts.

A key finding of the study is a list of important parameters that need to be measured after a fire. These parameters are critical to understanding how post-fire water quality affects humans, wildlife and the environment.

These parameters are divided into two tiers to help balance the collection of basic data with financial and practical constraints. The first tier parameters include water temperature Turbidity is considered the highest priority for assessing the impact of wildfire on water quality. Second-tier parameters, such as Alkalinitylaying the foundation for the next generation of modeling capabilities, but will also significantly increase monitoring costs.

The USGS study can provide actionable guidance to water suppliers, reservoir operators, land managers and emergency response agencies to prevent and mitigate the impacts of wildfire on water sources.

Learn more about how the USGS is assisting the water resources community in planning for and adapting to water resource impacts following wildfires here.