Forests form the critical source water areas for downstream drinking water supplies in many parts of the world, including the Rocky Mountain regions of North America. Large scale natural disturbances from wildfire and severe insect infestation are more likely because of warming climate and can significantly impact water quality downstream of forested headwaters regions. To investigate potential implications of changing climate and wildfire on drinking water treatment, the 2003 Lost Creek Wildfire in Alberta, Canada was studied. Four years of comprehensive hydrology and water quality data from seven watersheds were evaluated and synthesized to assess the implications of wildfire and post-fire intervention (salvage-logging) on downstream drinking water treatment. The 95th percentile turbidity and DOC remained low in streams draining unburned watersheds (5.1 NTU, 3.8 mg/L), even during periods of potential treatment challenge (e.g., stormflows, spring freshet); in contrast, they were elevated in streams draining burned (15.3 NTU, 4.6 mg/L) and salvage-logged (18.8 NTU, 9.9 mg/L) watersheds. Persistent increases in these parameters and observed increases in other contaminants such as nutrients, heavy metals, and chlorophyll-a in discharge from burned and salvage-logged watersheds present important economic and operational challenges for water treatment; most notably, a potential increased dependence on solids and DOC removal processes. Many traditional source water protection strategies would fail to adequately identify and evaluate many of the significant wildfire- and post-fire management-associated implications to drinking water “treatability”; accordingly, it is proposed that “source water supply and protection strategies” should be developed to consider a suppliers’ ability to provide adequate quantities of potable water to meet demand by addressing all aspects of drinking water “supply” (i.e., quantity, timing of availability, and quality) and their relationship to “treatability” in response to land disturbance.
Salvage logging. No description of the practice given by the study but salvage logging literally means salvaging the logs from burned forests. Here a large fire burned more than 21 000 ha and research stations were established to sample water quality in unburned watersheds, burned watersheds, and burned + salvage logged watersheds.
|Climate change impacts||Effect of Nbs on CCI||Effect measures|
|Reduced water quality||Negative||Water quality measures – pH, Dissolved organic carbon, stream turbidity, dissolved organic nitrogen, total phosphorus, microbial community analysis, optimal polyaluminum chloride doses needed to treat water, mercury Proportion of time during study period that reference catchment source water exceeded a turbidity threshold (10 NTU)|
Lyons creek east and west catchments in the upper Oldman River Basin, southern Alberta