The 2012 Great Lakes Water Quality Agreement states that “the Waters of the Great Lakes should be a source of safe, high quality drinking water”.
Assessment highlights
The overall status of treated drinking water sourced from the Great Lakes is Good and the 10-year trend is Unchanging. The Great Lakes continue to be a good source for producing high-quality drinking water. As with all source waters, water from the Great Lakes must be treated to ensure it is safe to consume.
Ontario and U.S. state agencies assess the quality of treated drinking water for microbial, radiological, and chemical parameters in comparison to health standards. Monitoring protocols and reporting requirements regarding treated drinking water quality vary by country. Health-based violations of treated drinking water occur infrequently in both Canada and the U.S.
In Ontario, it is estimated that 65% of the population is supplied with treated drinking water sourced from the Great Lakes. In 2023, over 99.9% of municipal residential treated drinking water quality tests from systems using the Great Lakes as source water met Ontario Drinking Water Quality Standards.
Of the approximately 20 million U.S. residents served by the public water supplies sourced by the Great Lakes in 2023, 97% were serviced with drinking water that met all applicable health-based standards. Water treated at 99% of community water systems that draw from the Great Lakes met health-based standards. This indicator utilizes violations associated with source water that is processed and treated at the plant, such as violations associated with filtration, corrosion control, and/or maximum contaminant levels because they are indicative of source water quality. Violations associated with the distribution system, such as high levels of disinfection byproducts, lead service line replacement and public education were excluded from the report.
Percentage of the U.S. Community Water Systems (CWS) from 2014-2023 meeting all health-based standards associated with processing and treating water in the plant before it leaves to the distribution system. Green and red dashed lines represent the Good-Fair and Fair-Poor status thresholds, respectively. N = number of U.S. water systems evaluated for the assessment.
Sub-indicator supporting the Drinking Water assessment
Sub-Indicator | Lake Superior | Lake Michigan | Lake Huron | Lake Erie | Lake Ontario |
Treated Drinking Water | Good & Deteriorating to Unchanging | Good & Unchanging | Good & Unchanging | Good & Unchanging | Good & Unchanging to Improving |
Status
