Research snapshot: Fires can significantly accelerate fine sediment transport and alluvial fans can buffer this impact

In the latest research from the forWater Network, scientists have found that fires in forested source water regions can significantly accelerate fine sediment transport from hillslopes to receiving streams. The mobilization of fine sediment and associated nutrients, such as phosphorus (P), into high quality surface waters can substantially increase primary productivity, which can severely degrade water quality, threaten aquatic ecosystem health, and challenge drinking water treatability to the point of service disruptions.

The research snapshot Impact of the Kenow wildfire on the form and mobility of particulate phosphorus in gravel bed rivers at large basin scales: Implications for downstream propagation, examines abiotic controls (e.g., adsorption, precipitation) on particulate phosphorus (PP) in fine suspended and ingressed river sediment in several oligotrophic gravel-bed rivers in Alberta, Canada following the 2017 Kenow wildfire.
 

Specifically, extractions were conducted to assess the immediate influence of severe wildfire on the form and mobility of PP in these systems.

The wildfires, although devastating for the Alberta region, have also been an opportunity for scientists to study how fire affects the composition of fine sediments. In particular, wildfire was shown to alter the composition of fine sediments, typically enriching them in bioavailable P.

Results indicate that all wildfire-impacted sediments had the ability to act as a source of phosphorus to the overlying water column, especially at low flow conditions.

Key takeaways also indicate that ingressed, or entering sediment may act as a legacy (extended) source of bioavailable P in highly dynamic, oligotrophic gravel-bed rivers. Bioavailable P can lead to elevated levels downstream resulting in cyanobacteria blooms, or commonly called algal blooms which can be challenging to water treatment.

Although not currently a common management focus for water treatment, researchers stress that development of strategies for managing fine sediment upstream is critical to maintaining source water quality and treatability in systems with reservoirs, especially in wildfire-prone regions.
 

Download the full research snapshot containing detailed research results,
recommendations and figures from the forWater Network.

For more information on this research please contact:
Mike Stone – mstone@uwaterloo.ca
Monica B. Emelko – mbemelko@uwaterloo.ca