Lake Memphremagog covers an area of 97 km2, of which three quarters is in Quebec and one quarter in Vermont. Lake Memphremagog is a source of drinking water for approximate 175,000 Canadians and is used for a variety of human activities, including swimming, boating, and fishing that attract a large number of tourists and locals. These uses are limited by elevated nutrient levels in the lake and resulting cyanobacteria blooms, 156 of which have been reported between 2006 and 2018. The Lake Memphremagog watershed along with the Coaticook and Tomifobia Rivers make up the St. Francais River watershed in Vermont, also called Basin 17. Information about Basin 17 planning efforts can be found on the Basin 17 planning webpage.