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Professeure Geneviève Bordeleau, spécialiste en géochimie des eaux souterraines à l’INRS.
Better groundwater management and long-term protection are essential to ensuring access to safe drinking water for everyone. While 10% of Québec’s territory is covered by fresh water found in thousands of rivers and more than three million lakes and bodies of water, another equally vital source lies hidden beneath our feet: groundwater.
Although groundwater helps supply drinking water across 90% of the province’s inhabited territory, it is far from unlimited. In a changing world shaped in part by climate change, groundwater is becoming central to discussions about access to clean, reliable water.
Protecting and sustainably managing groundwater poses major challenges. As part of Water Month, dedicated to raising awareness about the importance of water resources, INRS professor and groundwater geochemistry specialist Geneviève Bordeleau shares her perspective on this timely issue.
How does groundwater form, and why is it so important?
Groundwater is an integral part of the water cycle and comes mainly from rainfall and snowmelt. Some of this water infiltrates the soil and gradually moves downward through porous spaces — such as gaps between sand grains or fractures in rock — until these spaces become fully saturated. These underground water reserves are known as aquifers.
The first saturated layer encountered below the surface, commonly called the water table, is usually located just a few metres underground. Deeper below, there are often several permeable layers, or aquifers, separated by impermeable materials such as clay. These shallow aquifers are the main source of water used for human consumption.
Across Canada, groundwater supplies drinking water to roughly 30% of the population. In Québec, that proportion is about 25%. About half of those people are connected to municipal water systems, while the other half rely on private wells because no collective network is available. In some remote regions, nearly all residents depend on private wells, sometimes requiring filtration or treatment systems depending on water quality. Groundwater is therefore an essential resource.
Beyond drinking water, groundwater also supports agricultural and industrial activities and plays a major role in ecosystems. It helps feed rivers and wetlands, including peatlands with high ecological value.
What factors threaten groundwater availability and quality?
Several factors come into play. First, groundwater is largely invisible. In some ways, this helps preserve its quality because water circulating through confined porous environments is generally less exposed to contaminants than surface water. But invisibility is also a challenge: because declining groundwater levels are difficult to detect, the risks associated with overuse are less apparent.
Québec faces a particular situation because its population, fertile farmland and industrial activities are concentrated mainly along the St. Lawrence Valley. This concentration increases competition for water resources and places growing pressure on groundwater as development and human activity continue to expand.
Pollution and contamination are another major concern. In rivers and lakes, contamination is often detected quickly because impacts are more visible. Groundwater contamination, however, can go unnoticed for years as contaminants move very slowly underground — sometimes only a few metres to a few hundred metres per year. Without proper remediation, a contaminated aquifer can remain polluted for hundreds or even thousands of years. Even once contamination is identified, cleanup efforts can be lengthy and technically complex because they must account for geological conditions underground.
Climate change is also affecting groundwater supplies. Because aquifers rely on precipitation to recharge, warmer temperatures increase evaporation, biological activity and plant transpiration, leaving less water available to infiltrate into the ground. During drought periods, even heavy rainfall may run off the surface instead of replenishing groundwater reserves. A single unusual weather event can affect conditions for an entire season. While these impacts may go unnoticed by the general population, they can have very real consequences for people who depend on private wells.
Québec is often seen as a water-rich society largely untouched by drinking water access issues. Yet climate change is already affecting both the availability and quality of municipal water sources. In addition, nearly one million Quebecers who rely on private wells are personally responsible for monitoring and maintaining the quality of their drinking water — a significant responsibility.
How can we better protect groundwater for the future?
Responsible water use is one essential step. The effects of overconsumption are not always immediately visible, but they can have significant long-term consequences. This applies both to municipalities approving new development projects and to individuals in their everyday water use.
Private well owners must also pay close attention to their infrastructure. In many cases, households using wells also depend on septic systems to manage wastewater. Both systems must follow strict guidelines. Improper use of septic systems can damage their operation and contaminate nearby groundwater sources, including neighbouring wells. Wells themselves should also be tested regularly for bacteria. Yet research shows that fewer than 1% of owners follow the recommended testing frequency of twice a year. These procedures can seem complex and costly, but support initiatives and shared services have already shown promising results in improving water testing practices.
Competing uses of water resources also represent a growing challenge. Farmers need water and fertilizers to maintain crops, while municipalities continue to expand residential development to meet population growth. At the same time, urban expansion reduces the size of natural areas that help filter and recharge water supplies. Together, these pressures increasingly affect both groundwater quality and availability.
In this context, the scientific community plays a critical role. Researchers help map groundwater resources, monitor environmental conditions, detect contamination early and improve overall knowledge of these systems. Scientific expertise also supports better individual and collective decision-making around water protection.
Groundwater science has become increasingly multidisciplinary, bringing together expertise in geology, chemistry, ecology, microbiology, climatology and agriculture. At INRS, our multidisciplinary team works closely with ministries and municipalities to support the sustainable management of groundwater resources.
As a researcher, I also aim to develop practical solutions that help citizens who are not connected to public water systems. Public awareness, financial support programs and improved governance structures are all part of the discussion. One thing is certain: as climate change and land development continue to reshape our environment, groundwater issues will only become more important in the years ahead.
Because access to clean drinking water should never be seen as a privilege, but as a fundamental human right officially recognized by the United Nations since 2010.
Based at the INRS Eau Terre Environnement Research Centre, Professor Bordeleau was also the 2025 recipient of the INRS prix Planète for Excellence in Partnership, Outreach and Knowledge Mobilization.