Vermont and Québec share Missisquoi Bay and its 1,200 mi2 (3,100 km2) watershed. The bay’s water quality has deteriorated in recent decades, and it experiences troublesome cyanobacteria blooms nearly every summer. Recognizing the need to reduce pollution entering the bay, the two governments established a formal commitment in 2002 to share responsibility for its cleanup. This commitment was renewed in the spring of 2021.
The agreement states that Vermont will have 60% of the responsibility for reducing phosphorus loads to the Bay, and Québec will assume 40% of the responsibility. Accordingly, the target phosphorus load for Vermont will be 58.3 metric tons per year (mt/yr), and the target load for Québec will be 38.9 mt/yr. The target loads set by the agreement were based on the June 2000 report of the Québec-Vermont Missisquoi Bay Phosphorus Reduction Task Force, and a subsequent addendum dated October 2001.
The signing of this agreement fulfills a high priority action of the Lake Champlain Management Plan, Opportunities for Action, implemented by the Lake Champlain Basin Program and its partners. The Missisquoi Bay Agreement was also incorporated into the 2002 Lake Champlain Phosphorus Total Maximum Daily Load (TMDL) plan which established maximum allowable phosphorus loads from each sub-watershed in Vermont and New York. VT ANR and VAAFM identified a suite of actions necessary to implement in the Vermont portion of the Missisquoi Bay watershed in order to achieve the target phosphorus loads that Vermont committed to achieving and maintaining. These actions include wastewater treatment plant upgrades, best management practices on farms to reduce nutrient runoff, stabilization of stream banks and stream channels, and better stormwater management and erosion control on developed land and roadways.
In Spring 2020 the International Joint Commission completed a binational Water Quality Study on Missisquoi Bay. The IJC published the findings of the study in the report Nutrient Loading and Impacts in Lake Champlain – Missisquoi Bay and Lake Memphremagog. The report includes a review of hydrological conditions and sources and impacts of nutrients in the Missisquoi Basin and provides recommendations to the Canadian and U.S. governments on steps to reduce harmful algal blooms.