Wildfires can lead to immediate and long-term impacts on the social, economic and ecological systems of communities. More specifically, they can affect the quality of drinking water sources, such as rivers, reservoirs and groundwater, and place an added financial burden on municipalities to operate water treatment during and following a major wildfire. Fires can remove vegetation and reduce the ability of soils to absorb water, leading to an increase in runoff that can transport ash, nutrients, sediments, heavy metals and toxins into streams, rivers and downstream reservoirs used for drinking water supplies. These impacts can last months to years after a wildfire has been contained. While the effect of contaminants tends to diminish as the water moves downstream, there have been occurrences in Alberta where water quality impacts resulting from burned areas persisted for over years. This can lead to increased treatment costs. In some cases, emergency response agencies may use firefighting foams to control wildfires. These foams may contain perfluorinated chemicals, which may pose risks to water quality. The ability to anticipate and prepare for potential contamination risks of drinking water from wildfires is an important factor to consider for the successful implementation of preparedness plans and mitigation measures that ensure safe, reliable drinking water supplies is maintained.
One of the lesser-known effects of wildfires is the potential for a fire to contaminate the drinking water sources of downstream communities; the City of Calgary is taking steps to help mitigate those risks to the drinking water supply. Wildfires can lead to an increase in runoff that can transport ash, nutrients, sediments, heavy metals and toxins into rivers, lakes and reservoirs. This problem can be further compounded by firefighting actions if the chemical retardant used to suppress fires is allowed to enter the water supply as well. In an effort to further understand the risks to Calgary’s water supply, the City of Calgary has made efforts to more precisely map vulnerable areas and identified eleven management strategies to help mitigate wildfire potential and impacts. Collaboration with other organizations, both provincial and municipal, is essential as source waters run well beyond the reaches of Calgary’s jurisdiction. The City hopes that the outcomes of these initiatives will benefit not only Calgary, but all of the communities that draw their water from these rivers.