To investigate impacts of wildfire on treatability, particularly THM formation and its precursors, the 2003 Lost Creek Wildfire in the southern Canadian Rockies has been studied. Ten years of comprehensive hydrometric and water quality data from seven watersheds have established significant impacts on many aspects of streamflow and water quality. The objective of the investigation presented here was to examine long-term effects of the wildfire and post-fire management on THM formation potential 10 years after the fire. Notably, the extensive hydrometric and water quality data set from multiple reference (unburned), burned, and post-fire salvage-logged catchments enables these impacts to be linked to the wildfire.  Hydrophobic and hydrophilic NOM have been shown to have different impacts on forming disinfection by-products. Accordingly, the impacts of wildfire and post-fire salvage logging on the specific characteristics of NOM were evaluated using resin fractionation, LC-OCD, and fluorescence excitation-emission matrices (FEEM). Formation of the total and individual THMs was assessed and the correlations between them and the NOM characteristics are reported.  Turbidity, UV, and DOC remained low in unburned watersheds; however, in contrast, they remain elevated in the burned and salvage-logged watersheds, even 10 years post-disturbance. Shifts in the humic substances and hydrophobic/hydrophilic character of the NOM have been detected. Moreover, significant increases in the formation potential of THMs, in particular chloroform, were observed. THM-FP was found to have positive correlations with, DOC, UV, and the hydrophobic fraction of NOM.  This works demonstrates that wildfire can cause long term shifts in water quality that have direct implications for water treatment and notably, DBP formation potential. While some studies may report anecdotal experiences, to our knowledge, this is the first study to directly link the impacts of large-scale landscape disturbance by wildfire to water treatment challenges (DBP formation potential) and demonstrate these impacts over the long term.

Long-term wildfire impacts on THM formation potential

248th National Meeting (2014)

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