Which agreement, signed in 1972, began formal U.S.–Canadian cooperation to protect Great Lakes water quality?

The Great Lakes Water Quality Agreement, signed in 1972, began formal modern U.S.–Canadian cooperation on protecting Great Lakes water quality.

The agreement was created in response to severe pollution problems, including industrial discharges, municipal sewage, and nutrient enrichment. Its purpose was to restore and maintain the chemical, physical, and biological integrity of the Great Lakes system.

The United States and Canada later amended the agreement, including major revisions in 1983 and 2012. The modern framework addresses issues such as toxic chemicals, invasive species, habitat, beaches, drinking water, and harmful algal blooms.

The agreement is different from the Great Lakes Compact. The compact is a U.S. regional agreement focused largely on water withdrawals and diversions, whereas the bilateral water-quality agreement involves both countries.