Determinants of Post-fire Water Quality in the Western United States

Abstract:

Large wildfires are becoming increasingly common in the Western United States. Wildfires that consume greater than twenty percent of the watershed impact river water quality. The surface waters of the arid West are limited and in demand by the aquatic ecosystems, irrigated agriculture, and the region’s growing human population. A range of studies, typically focused on individual fires, have observed mobilization of contaminants, nutrients (including nitrates), and sediments into receiving streams. Post-fire metal concentrations have also been observed to increase when fires were located in streams close to urban centers.

The objective of this work was to assemble an extensive historical water quality database through data mining from federal, state and local agencies into a fire-database. Data from previous studies on individual fires by the co-authors was also included. The fire-database includes observations of water quality, discharge, geospatial and land characteristics from over 200 fire-impacted watersheds in the western U.S. since 1985. Water quality data from burn impacted watersheds was examined for trends in water quality response using statistical analysis. Watersheds where there was no change in water quality after fire were also examined to determine characteristics of the watershed that make it more resilient to fire. The ultimate goal is to evaluate trends in post-fire water quality response and identify key drivers of resiliency and post-fire response. The fire-database will eventually be publicly available.Large wildfires are becoming increasingly common in the Western United States. Wildfires that consume greater than twenty percent of the watershed impact river water quality. The surface waters of the arid West are limited and in demand by the aquatic ecosystems, irrigated agriculture, and the region’s growing human population. A range of studies, typically focused on individual fires, have observed mobilization of contaminants, nutrients (including nitrates), and sediments into receiving streams. Post-fire metal concentrations have also been observed to increase when fires were located in streams close to urban centers.

The objective of this work was to assemble an extensive historical water quality database through data mining from federal, state and local agencies into a fire-database. Data from previous studies on individual fires by the co-authors was also included. The fire-database includes observations of water quality, discharge, geospatial and land characteristics from over 200 fire-impacted watersheds in the western U.S. since 1985. Water quality data from burn impacted watersheds was examined for trends in water quality response using statistical analysis. Watersheds where there was no change in water quality after fire were also examined to determine characteristics of the watershed that make it more resilient to fire. The ultimate goal is to evaluate trends in post-fire water quality response and identify key drivers of resiliency and post-fire response. The fire-database will eventually be publicly available.