Reflections is a monthly blog series by Canadian Water Network’s (CWN) CEO Nicola Crawhall. This series is designed for decision-makers navigating complex water-related challenges. It helps leaders stay ahead of change and make informed decisions that shape the future of water in Canada.

As wildfires burn across Canada this summer, communities focus on evacuation, emergency response, and rebuilding. Yet another critical part of recovery often receives far less attention: protecting drinking water.

At the time of writing, 883 wildfires were reported burning across every province and territory except Prince Edward Island and Nunavut (which do not report). These wildfires covered three million hectares, or 30,000 square kilometres.

Wildfires disproportionately impact Indigenous communities. Over the last 40 years, Indigenous communities have made up over 40 percent of all wildfire evacuees in Canada. More information about the impact of wildfires on First Nations groups in Canada is available here.

For the people whose lives have been upended, it will be a long road to recovery. Just ask the residents of Jasper. The 2024 fire tore through a third of the town and destroyed 800 housing units. Of those who lost their homes, only 16 families are back a year and a half following the fires.

Beyond temporary housing, the nightmare of navigating insurance claims, and the physical rebuild, there is another layer of recovery that receives less attention: the impact of wildfires on drinking water.

Landscapes and surface water transformed

In rural and remote areas, the immediate effect of wildfires burning forests is the release of particulates and gases into the air. These are then deposited on the land and in surface water that are sources of drinking water. Ash and charred materials degrade water quality by contributing bioavailable phosphorus, which can cause algal blooms.

But ash is only part of the story.

Wildfires also release many other pollutants. Depending on what has burned, these can include heavy metals such as mercury and lead, nitrogen oxides, sulfur oxides, carbon oxides, and polycyclic aromatic hydrocarbons (PAH). The use of fire retardants may also contribute to the potential pollutant mix entering local watersheds.

At the same time, wildfires strip away vegetation that normally stabilizes soil. Rain following fires then washes the loose sediment into lakes, streams, and rivers. This transportation of debris and other disturbances in the watershed, such as altered flow paths and hydrology, all affect surface water quality. Some water sources recover quickly, while others take years to return to pre-fire conditions.

Wildfire impacts on water quality and treatability

These watershed changes create a second challenge: treating water safely and reliably.

Dr. Monica Emelko from the University of Waterloo has studied the impact of wildfires on drinking water for over 20 years. In particular, she has studied the recovery of Fort McMurray drinking water since its 2016 wildfire. Ten years later, the impacts are still being felt.

As a water treatment engineer, Dr. Emelko knows that just about any water can be treated to make it drinkable if you spend enough on sophisticated treatment technology and highly trained treatment operators. However, many rural and remote areas that are vulnerable to wildfires typically lack sophisticated water treatment systems capable of removing all human-made contaminants. Nor do they typically have real-time data to allow for rapid response.

Most water treatment plants target the removal of turbidity, colour, and organic matter to ensure effective disinfection. “Poor water quality is relatively ‘easy’ to treat,” says Dr. Emelko, “But rapid fluctuations are challenging. A big part of treatment is being nimble and responsive to a wide range of water quality changes.”

Wildfires can alter the quality of dissolved organic carbon (DOC) and produce more nitrogen-rich aromatic compounds that affect the formation of disinfection byproducts. Chemical coagulant demand and sludge production can be impacted. Bioavailability of phosphorus can promote the growth of toxin-forming algae. All of these impacts affect a plant’s ability to operate and treat water efficiently.

The long-term implications are significant.

One study of post-fire data showed that pollutant concentrations increased threefold. Data from over 40 post-fire situations showed increases in total suspended solids and nutrients within a year, whereas heavy metals were found to peak in some post-fire environments after one to two years.

In Southern Alberta, turbidity and nutrients have remained elevated post-fire for over a decade. In the case of Fort McMurray, impacts after the ash flushed through included increased sediment loads and nutrient availability. These drove algal growth and episodic toxin formation, which could not be treated by their conventional water treatment. In response, the water utility owner, the Regional Municipality of Wood Buffalo, considered adding ozone treatment. However, the $50-million price tag million proved prohibitively expensive. After extensive research, the utility and researchers identified and implemented different forms of algae growth mitigation in their reservoirs. This proved effective in reducing algae growth and meeting Canadian drinking water guidelines.

Monitoring quality must be part of recovery

These source water and treatment challenges underline the importance of pre- and post-fire source water testing.

Testing sources of water can identify and create a better understanding of risks that can then be addressed through adjustments to the treatment process and/or source water protection. Yet real-time water quality monitoring is an expensive undertaking, particularly for rural, remote, and Indigenous communities. Even so, it should be considered an essential aspect of post-fire recovery. Keeping residents informed and training operators to respond to variations in water quality are critical to protecting the community’s public health.

With the frequency and intensity of wildfires increasing due to climate change, post-wildfire water quality is an aspect of climate adaptation and resiliency that must be considered. This should extend to watershed management and restoration practices, water treatment plant design and processes, operator training, source water protection and monitoring, and the education and involvement of impacted communities.

For the residents returning home after this summer’s wildfires, recovery may not end when the flames are extinguished and their homes are rebuilt. In many communities, the impacts on drinking water systems, and the associated costs to address them, may continue long after the fire is gone. Recognizing and planning for those impacts is essential to building resilience in a changing climate.

For more information on the impact of wildfires on water, view CWN’s webinar on the topic. You can also read my thought leader interview with Dr. Monica Emelko.