Ground Water Awareness Week
Checking in on Canada’s groundwater: a cross-country look at the resource
Experts weigh in on its status
July 5, 2022 By Mike Jiggens
Groundwater is one of Canada’s most important, yet poorly understood resources. Canada is often perceived as a country with a seemingly unlimited supply of freshwater, but that surface water is only the tip of the iceberg among the nation’s freshwater reserves.
A larger reserve lies underground in the form of groundwater – most of which exists as an invisible entity.
“The groundwater reserves have an enormous yet often unrecognized strategic and economic value worldwide, and it’s something that’s becoming even more significant in light of the changing climatic conditions,” David Rudolph, a professor of earth and environmental sciences at the University of Waterloo, remarked on World Water Day in March.
Rudolph led a virtual panel discussion – sponsored by the university – to commemorate World Water Day. The “cross-country checkup on Canada’s groundwater” featured insights from some of the country’s foremost authorities on the subject, who shared their perspectives on the future of one of Canada’s most valuable resources.
Panel members included Dr. Grant Ferguson, professor of civil, environmental and geological engineering at the University of Saskatchewan’s school of environment and sustainability; Magdalena Krol, associate professor in the department of civil engineering at York University; Dr. Andrea Brookfield, assistant professor at the University of Waterloo; Dr. Barret Kurylyk, assistant professor at Dalhousie University’s department of civil and resource engineering; Dr. Jean-Michel Lemieux, professor of geology and geological engineering at Université Laval; and Dr. Tom Gleeson, associate professor at the University of Waterloo’s department of civil engineering.
Rudolph noted Canada’s dependence on groundwater as its primary drinking water resource realized a significant spike between the years 1970 and 2015, with an increase of about 10 per cent to 30 per cent. Today, about 10 million Canadians depend daily on groundwater as their source of freshwater.
“This dependency is expected to grow,” he said.
Canada’s dependency on groundwater varies from province to province. In Ontario, for example, about 40 per cent of the population relies on groundwater while the entire province of Prince Edward Island is dependent on the resource.
Ferguson, whose research is focused on hydrogeology and hydrogeochemistry of deep groundwater systems and the interplay between energy and groundwater resources, said the earth’s store of groundwater is massive compared with other parts of the hydrogeological cycle.
“We have about 48 million cubic kilometres of groundwater beneath our feet on the continents,” he said.
The turnover rate for the resource is slow, however, he noted. Some groundwater is shallow – perhaps only a few metres beneath our feet near the water table that is turning over. It’s snow melt that’s being recharged with some of it entering rivers and wetlands. Much further below the surface is water that melted from glaciers following the last Ice Age.
Ferguson said that although it represents a huge resource, not all of it is accessible because it’s too deep in the ground and some of it is apt to be poor in quality.
There are some places throughout the world where well drilling is getting increasingly deeper to access this older water, but he questioned how it can be renewed if it’s so old.
As we look to the future, he said it will likely mean pumping more groundwater as surface water becomes scarcer due to climate change and increased demand.
“We have a huge resource in groundwater but also a huge challenge in terms of management because we can’t see it, and accessing some of these deeper areas presents a serious challenge.”
The beauty of groundwater, Krol said, is that it connects with subsurfaces, but she questioned what would happen if the top of the surface was contaminated.
“Those pollutants can percolate through the ground and contaminate that groundwater,” she said.
Not only can a river be impacted, but the spread can also reach domestic wells and lead people to ingest contaminated groundwater. Contamination can occur in both rural and urban settings by various means.
Krol cited such scenarios as improper waste disposal sites, gasoline spills, septic tanks, underground storage tanks, sewer pipe leakage and other accidental spills. It presents both a national and global concern. In Ontario, there are close to 4,000 contaminated sites, including about 500 where groundwater is contaminated.
“These sites are typically in urban settings, which are called brownfield sites, but they can also be in rural areas.”
Groundwater can be remediated by various means, including a pump-and-treat system in which contaminated groundwater is extracted, treated and put back into the subsurface or surface water body, by thermal technology or by electrical resistance heating. There are physical ways of cleaning up compounds as well as natural methods such as injecting microbes into the surface to help degrade the compounds at that site.
In more recent years, science has looked at making remediation technology more sustainable and “green.”
Krol said such methods as electrical resistance heating and pump-and-treat strategies use up a lot of energy, prompting the scientific community to explore ways to reduce the amount of energy required.
Solar and thermal energy are two such considerations.
“Overall, what we really want to do is reduce the risk to humans as well as the environment, and we do that by either getting rid of the contaminants by remediating sites and making sure there are no receptors for those contaminants or getting rid of the exposure pathways. By getting rid of one of these things, we’re reducing the risk.”
Brookfield looked at the hydrogeological conditions of an agricultural region where water is scarce due to overuse and mismanagement, and where the economic impact of drought is severe.
Recalling research from her previous tenure at the University of Kansas, she said most of the state’s groundwater is used to irrigate agricultural crops, which is the major economic driver in Kansas. Significant declines in groundwater have been observed over the years, however. In some areas of the state, the groundwater level in the aquifer has dropped almost 100 metres because more water is being pulled out than that going back in. Most of this is attributed to irrigation.
Brookfield said efforts are now being made to manage this condition, assessing what is happening, identifying the trends and working toward the future. Monitoring the groundwater provides a snapshot of what the resource is doing and is being done in January when wells aren’t actively pumping and when aquifers can recover the most from irrigation pumping. Sensors are placed in monitoring wells to access data in real time.
“We see that daily fluctuation in our water levels,” she said.
Groundwater levels had become so depleted over the years to a point where irrigation would begin but couldn’t be sustained over an entire season. Brookfield said farmers might be forced to vary their pump rate or turn to dry land farming.
“There are implications here for the economics of not only the landowner, but the state and country as a whole, because this is a huge agricultural contributor to the country and is quite drastic.”
In Kansas, groundwater has made itself visible in a sense, but not in a good way, she said. Areas in the western and central parts of the state have produced streams that are no longer flowing except during intermittent precipitation events.
Brookfield said a trend is emerging in the U.S. south where a consistent decline in base flow to streams is being realized, and it’s happening during each month of the year and not necessarily during only hotter periods.
“This is troubling.”
What this means for Canada, she said, is that we must assess how much groundwater we have and ensure we don’t find ourselves in Kansas’ situation.
Current studies being conducted in the Maritime provinces show a decline in its base flow in April. Perhaps it’s just a shift in water events and is not a serious issue, Brookfield speculated, but maybe it’s something more. In Canada’s west and north, significant declines are being realized during the summer months.
“Perhaps we’re OK, but we do have to watch and measure and assess these resources to make sure that if we do change how we’re using them, we do it in a way that’s sustainable.”
Planning for Canada’s groundwater future requires gathering information now, she said, adding it must continue and be augmented with an understanding of the resources we have and how they can be managed effectively.
Kurylyk has been studying the impact on coastal aquifers by society and climate change. A transition zone between freshwater and saltwater exists at the mouths of rivers that flow into oceans. The same thing happens in the subsurface with coastal aquifers where there are subterranean estuaries or a mixing zone between freshwater and saltwater.
“One of the most important features of coastal aquifers is this saltwater-freshwater interface,” he said.
Because Canada boasts the world’s largest coastline, Canadians should be interested in what happens to their coastal aquifers, Kurylyk said. What holds the most interest for him is Canada’s Maritime region which is regarded as a national “hot spot” of sea level rise and where the percentage of people relying on groundwater ranges between 50 and 100 per cent.
“Maritimers use more groundwater per capita than the average Canadian,” he said. “So, what happens to our coastal groundwater matters, and most of our communities are along the coast and those who use groundwater are using coastal aquifers for their water supply.”
Nova Scotia has issues with arsenic and manganese as well as groundwater shortages due to drought in the southern part of the province.
On Prince Edward Island, there are issues with nitrate in the agricultural industry and concerns about over pumping.
Saltwater intrusion is driven by sea level rise. There is also downward saltwater intrusion. During coastal storms with high waves, the land surface can be inundated with saltwater which can infiltrate down into the aquifer. Eventually, the infiltrating saltwater will flood the unsaturated zone. Plumes of saltwater can eventually be flushed out with fresh recharge from precipitation and snow melt, but the process can take anywhere from days and weeks to decades, depending on the geology. In some cases, fresh aquifers may never be seen again in the context of a human lifetime, Kurylyk said.
Freshwater ponds on Sable Island – located about 175 kilometres southeast of the Nova Scotia mainland – have been shrinking over the past few years.
Some ponds are disappearing while others are getting smaller or becoming saltier. The ponds support the island’s ecosystem.
One of the reasons Sable Island is threatened, Kurylyk said, is because it is situated on the path of hurricanes. Flooded seawater infiltrates into the underlying aquifer, and groundwater goes up and down, driven by tides, storms and heavy rainfall. Large spikes are caused by hurricanes and nor’easters.
The aquifers are normally flushed out with rainfall over time. Before they are fully flushed out, however, another storm comes in, he said, adding the frequency of these flooding events will likely continue to increase in the coming decades.
What happens in the ocean doesn’t stay in the ocean, he said, nor does it stay in the land surface. Kurylyk said changing ocean conditions, whether it’s sea level rise or coastal flooding, can trigger devastating impacts on critical coastal groundwater resources, posing a challenge for freshwater security in the coming decades.
Lemieux addressed water supply challenges in Canada’s remote northern communities. Nunavik, Quebec’s northernmost region, is home to 14 villages where drinking water is distributed by tanker trucks because keeping water unfrozen in pipes is cost prohibitive.
Additionally, climate change is compromising the quality of surface water in the region as thawing permafrost is creating more erosion, allowing more sediment to enter the water and making water treatment more difficult and more expensive.
He said there have also been more extreme precipitation events in the region that are causing more turbidity and facilitating the transfer of bacteria from fecal matter found on the surface.
Rivers can run dry in winter, prompting the need for other drinking water sources to be found, Lemieux said.
Groundwater isn’t usually considered a source in colder regions for several reasons. The geology makes it difficult to find an aquifer in such environments, and the bedrock is usually composed of crystalline rocks which makes the success of water prospecting about the same as winning the lottery.
Fractured areas need to be found, but they’re not always visible, he said. Most people believe that all groundwater is frozen in areas where there is permafrost, and that it’s not viable for pumping, he noted, but he added there are places where it isn’t frozen and can be used as a source of drinking water.
Drinking water management remains a major issue for northern communities, Lemieux said.
Gleeson, whose work addresses groundwater sustainability and systems, said a “people-centric” approach must be taken toward groundwater sustainability.
He said that if people don’t care enough about social problems, they’re apt not to care about the invisible water in dirt and rocks, either.
“We do a lot of great applied research, but we don’t let community needs and public interest drive our research enough,” Gleeson said. “We deal a lot of with maps and graphs and not enough coming from community needs and interests.”
Researchers should listen to community needs and interests first, allowing them to structure research questions, approaches and outcomes, he said. The focus can then be placed on how groundwater is connected to the social, economic and ecological systems rather than simply on the hydrogeology itself.
Putting people and ecosystems first and aquifers and hydrogeology second is the key, he added.
“These types of community-driven needs and interests can and should drive our work in how we relate to the climate crisis, for example.”
One of Gleeson’s projects involves moving away from just hydrogeology by borrowing frameworks from sustainability science and looking at climate, geology, topography, groundwater and surface water interactions.
A social-economic systems framework is being used to map hot spots of water stress.
He said this approach of connective groundwater systems connects people and ecosystems.
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