Canada-US boundary waters treaty

Official title: Treaty Relating to the Boundary Waters and Questions Arising Along the Border between the United States and Canada (The Boundary Waters Treaty)

Subject category:
Type of agreement / instrument:
Canada - United States
Legally-binding treaty
  • Signed January 11, 1909
  • Entry into Force on May 5, 1910
Lead & partner departments:
Global Affairs Canada
Environment and Climate Change Canada
For further information:
Web links:
ECCC Inquiry Centre
Compendium edition:
February 2022
Reference #:

Plain language summary

The Boundary Waters Treaty (BWT) has rules that help keep Canadian waters clean. Many lakes, rivers, and other waters flow between Canada and the United States, so both countries follow the same rules. Canada and the United States agree not to pollute water if it could hurt people or property in the other country. Both countries also need to agree on certain projects that could change the amount of water in lakes and rivers. Canadians and Americans are part of a group called the International Joint Commission. The International Joint Commission helps Canada and the United States agree on how they want to take care of the water that they share.


BWT established the principles and a mechanism for addressing boundary and transboundary water issues and resolving disputes along the Canada-United States boundary primarily concerning water quantity and quality.

Key elements

The BWT stipulates that water levels and flows in boundary waters must not be altered without the approval of the responsible government and the International Joint Commission (IJC).

The BWT also stipulates that boundary and transboundary waters shall not be polluted in either country to the injury of property or health of the other country (Article IV).

The BWT created the IJC to provide a mechanism to resolve and prevent disputes. The IJC is a permanent body composed of six Commissioners (three appointed by each country). Its duties include responding to applications for the use, obstruction, or diversion of certain boundary and transboundary waters affecting levels and flows. Where the IJC has the authority to grant approval, it may impose binding conditions on both countries and appoint an international board of control to oversee compliance with the conditions.

Canada and the United States maintain exclusive jurisdiction and control over the use and diversion of all waters on their own side of the boundary. However, if any injuries occur as a result of the use or diversion of waters covered by the treaty, the injured party shall be entitled to the same rights and remedies as if such injury took place in the country where the diversion or interference occurred (Article II).

Canada and the United States enjoy "equal and similar rights in the use of the waters" on their own side of the boundary, and in the event of a dispute among competing uses, water use priorities will be ranked in the following order: domestic and sanitary; navigation; power (Article VIII).

Under Article X, the IJC has arbitral authority over any subject referred to it, but the governments have not made use of this provision.

Expected results

This agreement provides a mechanism for cooperation and coordination in managing shared waterways and in investigating environmental issues of mutual interest along the border.

Canada’s involvement

Under Article IX, either government may refer to the IJC any question or matter of difference along the common frontier (usually concerning water quantity and water/air quality issues). In practice, such references have been transmitted jointly by the two governments, after consultations on the specific terms. The IJC investigates, reports, and makes recommendations for resolving the issue in question. Implementation of the Commission's recommendations is at the discretion of the governments, and is usually exercised after bilateral consultation.

Environment and Climate Change Canada provides technical support to the IJC and advises  Global Affairs Canada on technical matters relating to the licensing of developments on transboundary waters in accordance with the International Boundary Waters Treaty Act.

Environment and Climate Change Canada supports the IJC, providing secretariat and technical support. Environment and Climate Change Canada also monitors levels, flows, and water quality to ensure compliance with IJC objectives and with the BWT and related agreement requirements, including water apportionment provisions. Environment and Climate Change Canada officials also participate directly on the boards set up under the treaty, providing technical support and advice to the IJC, and provide support to other government departments and provinces in meeting commitments under the BWT. 

Environment and Climate Change Canada also supports the BWT with the International River Improvements Act.

Results / progress


Over the years, more than 100 boundary water issues have been referred to the IJC. In addition, the IJC has created numerous control boards, pollution boards, watershed boards, advisory boards, and study boards. The IJC’s website has more details on past and present boards and task forces.


Relevant reports include the following:

  • IJC Biennial/Triennial Reports on Great Lakes Water Quality
  • Regular reports from boards established under the BWT

IJC Reports and Publications

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