Great Lakes Water Quality in 2026: Monitoring Data, Emerging Contaminants, and Federal Investment

The Great Lakes hold approximately 21 percent of the world’s surface freshwater, making water quality monitoring across Lakes Superior, Michigan, Huron, Erie, and Ontario one of the most consequential environmental priorities in North America. As 2026 begins, federal agencies on both sides of the border are expanding their monitoring programs in response to emerging contaminants and shifting climate patterns.

Current State of Great Lakes Water Quality

According to Environment and Climate Change Canada’s most recent Great Lakes surveillance data, the overall health of the Great Lakes system shows a mixed picture. Lake Superior continues to maintain the highest water quality among the five lakes, with consistently low phosphorus levels and minimal algal bloom activity. Lake Erie, by contrast, remains the most ecologically stressed, particularly in its western basin where agricultural runoff from Ohio and Ontario continues to drive seasonal harmful algal blooms.

The International Joint Commission (IJC), the binational body responsible for overseeing Great Lakes water quality under the Great Lakes Water Quality Agreement, reported in its 2024 Triennial Assessment that phosphorus loading in Lake Erie exceeded target levels for the seventh consecutive year. The IJC’s recommended target of 6,000 metric tonnes of total phosphorus per year for the western and central basins has not been met since monitoring intensified in 2015.

Emerging Contaminants: PFAS and Microplastics

Per- and polyfluoroalkyl substances (PFAS), commonly referred to as “forever chemicals,” have emerged as a primary concern for Great Lakes water managers. A 2024 study published in Environmental Science and Technology by researchers at the University of Toronto found detectable PFAS concentrations in surface water samples from all five Great Lakes, with the highest concentrations recorded near urban discharge points along the Lake Ontario shoreline.

Health Canada’s drinking water guidelines set a maximum acceptable concentration of 30 nanograms per litre for total PFAS in drinking water. While most Great Lakes surface water samples fall below this threshold, the persistence of these compounds in sediment and aquatic food chains has prompted calls for more aggressive source control measures.

Microplastic contamination presents a parallel challenge. Research conducted by the Rochester Institute of Technology’s Great Lakes microplastics monitoring program has documented an average of 43,000 microplastic particles per square kilometre across the Great Lakes surface, with concentrations highest in Lake Erie and Lake Ontario due to their proximity to dense population centres and industrial facilities.

Nutrient Loading and Algal Blooms

Nutrient pollution, primarily from agricultural sources, remains the most visible water quality challenge in the Great Lakes basin. The National Oceanic and Atmospheric Administration (NOAA) issues an annual harmful algal bloom forecast for Lake Erie each summer. The 2025 forecast predicted a severity index of 6.5 on a scale of 10, indicating a significant bloom event driven by above-average spring rainfall that increased phosphorus runoff from farmland in the Maumee River watershed.

On the Canadian side, the Ontario Ministry of the Environment, Conservation, and Parks has been implementing the Canada-Ontario Agreement on Great Lakes Water Quality, which includes commitments to reduce phosphorus loading by 40 percent from 2008 levels by 2025. Progress toward this target has been slow. The most recent provincial monitoring data indicates a reduction of approximately 18 percent, well short of the stated goal.

Climate Change Impacts on Water Quality

Rising water temperatures are compounding existing water quality challenges. Data from NOAA’s Great Lakes Environmental Research Laboratory shows that surface water temperatures across the Great Lakes have increased by an average of 1.2 degrees Celsius since 1980. Warmer water temperatures extend the growing season for algal blooms, reduce dissolved oxygen levels in deeper waters, and alter the distribution of aquatic species.

Lake Superior, historically the coldest and least productive of the Great Lakes, has warmed faster than any of the other lakes. Research published in the Journal of Great Lakes Research documented a 2.5-degree Celsius increase in Lake Superior’s summer surface temperature since 1979, a rate of warming that exceeds the global average for freshwater lakes.

Monitoring Infrastructure and Investment

Both Canada and the United States have increased investment in Great Lakes monitoring infrastructure. The Canadian federal government allocated 420 million dollars over ten years through the Great Lakes Protection Initiative, renewed in Budget 2024, to support science-based decision making and community-led restoration projects.

On the American side, the Great Lakes Restoration Initiative (GLRI) received 1 billion dollars in the Infrastructure Investment and Jobs Act, supplementing its annual congressional appropriation of approximately 350 million dollars. These funds support over 300 active projects addressing toxic substances, invasive species, nonpoint source pollution, and habitat degradation.

What Residents Can Do

Residents of the Great Lakes basin can contribute to water quality protection through several practical measures. Reducing fertilizer use on residential lawns decreases phosphorus runoff into local waterways. Proper disposal of household chemicals prevents contamination of wastewater systems. Supporting local conservation authorities and participating in community science programs, such as the Lake Ontario Waterkeeper’s swim monitoring program, provides valuable data to supplement government monitoring efforts.

Water quality data for specific Great Lakes beaches and intake points is available through Environment Canada’s Great Lakes Water Quality Monitoring portal and the EPA’s Great Lakes dashboard at greatlakes.epa.gov.