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. In 2021, the jurisdictions renewed the agreement, which included a target for in-lake phosphorus concentration in the bay.
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’s target phosphorus concentrations are also consistent with target concentrations that are the basis of the 2016 Phosphorus Total Maximum Daily Loads (TMDLs) for Vermont Segments of Lake Champlain. 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.