2 Materials and
Methods
2.1 Site
description
In 2002, the Hayman Fire burned more than 554 km2 of
ponderosa pine (Pinus ponderosa ) and Douglas-Fir
(Pseudotsuga menziesii ) forest in the Pike San Isabel National
Forest (Graham, 2003) (Figure 1). This was one of the largest wildfires
in Colorado’s recorded history and 35% of the fire burned at high
severity (Robichaud et al., 2003). The fire burned the contributing area
of Cheesman Reservoir, a primary drinking water supply to the city of
Denver (Graham, 2003). In combination, the 2002 Hayman and 1996 Buffalo
Creek fires cost Denver’s public water utility tens of millions of
dollars on water quality treatment, sediment and debris removal, and
reclamation (Hall, 2017). Watersheds within the Hayman Fire burn
perimeter receive an annual average of 40 cm of precipitation (WRCC,
2021) and 60-75% of that comes from summer monsoonal rains (Wilson et
al., 2018). Mean elevation within the fire perimeter is 2462 m which is
within the intermittent snow zone that does not maintain snow cover
throughout the winter (Richer et al., 2013). The parent material
underlying our study area is dominated by Pike’s Peak Formation granite
(Ruleman et al., 2011) which weathers to form coarse, sandy loam soils
(Cipra et al., 2003). Ambient Na+ concentrations are
relatively low in granitic basins in our study area. There were no
reported post-fire increases in stream Na+ and
measured post-fire increases in other geochemical ions (i.e., calcium,
acid neutralizing capacity, and conductivity) recovered to pre-fire
levels 2 years after the Hayman Fire (Rhoades et al., 2011).