(Wildfires, Water Quality, Pollution – Sediment)
Fire behavior regulates the effects of forest fire on watershed processes. During the 2002 Hayman Fire, high-severity crown fire killed the overstory forest and consumed forest floor on forty percent of the area burned. The extreme fire behavior and its location in watersheds that deliver water to the Denver metropolitan area drew attention to the adverse effects of wildfire on Front Range water quality and supply. A streamwater monitoring network begun prior to the fire allowed pre- and post-fire comparisons of streamwater properties in three burned and three unburned catchments, and post-fire comparisons of ten basins burned to varying extents (0-87 percent). Here we present the response of stream chemistry, temperature and turbidity during the first year following the Hayman Fire. Flow-weighted concentrations of dominant streamwater anions and cations were about 60 percent higher in burned basins during the four months after the fire; within eight to twelve months most chemical attributes were similar between burned and unburned streams. Temperature and nitrate increased immediately after the fire and remained elevated at the end of study period. The proportion of the total area burned and the proportion burned at high severity explained a significant amount of the variation in streamwater nitrate and sediment.
Rhoades, C., Entwistle, D. & Butler, D. (2006).
Interagency Conference on Research in the Watersheds. May 15-18 2006; Coweeta Hydrologic Lab., NC. 89-98.