Canada-US treaty for Skagit River, Ross Lake and Seven Mile Reservoir

Official title: Treaty between Canada and the United States of America relating to the Skagit River and Ross Lake, and the Seven Mile Reservoir on the Pend d’Oreille River

Subject category:
Type of agreement / instrument:
Canada – United States
Legally-binding treaty
  • Signed: April 2, 1984
  • Ratified: December 14, 1984
  • Came into force: December 14, 1984
  • Termination: No sooner than January 1, 2065, with one year’s notice
Lead & partner departments:
Global Affairs Canada
Environment and Climate Change Canada
For further information:
Web links:
GAC Inquiry Centre
Compendium edition:
July 2022
Reference #:

Plain language summary

The Skagit River Treaty requires the United States to limit the size of the reservoir for the Ross Dam’s hydroelectric power generation to the boundary of the Canada-United States Border. The treaty also requires Canada to provide electricity to the United States to offset the loss of electricity generation that could have been realized if the Ross Dam reservoir had extended across the border into Canada.


The treaty sets out Canada’s obligations related to the agreement between British Columbia and the City of Seattle, by which Seattle agreed not to construct the Ross High Dam, which would have the effect of raising the level of Ross Lake and the Skagit River across the international boundary, provided that British Columbia supply it with the electricity approximately anticipated from the construction of the Ross High Dam.

The treaty implicates the Government of Canada in the event British Columbia fails to comply with the BC–Seattle agreement.

Key elements

Under the BC–Seattle agreement, British Columbia is to supply Seattle, for 80 years, with power equivalent to that which would have been generated if the Ross High Dam height had been raised. Seattle will pay British Columbia the equivalent of the cost of building the Ross High Dam. Either party to the agreement may give notice to terminate after 1991. If British Columbia gives notice, it must return the money to Seattle so that the dam can be raised, which will lead to the flooding of the Skagit Valley across the border into British Columbia. As part of the agreement, British Columbia is allowed to raise the operating level of the Seven Mile Dam reservoir on the Pend d’Oreille River at the international border, but must compensate Seattle for reduced electrical generating capacity at the Boundary Dam on the Pend d’Oreille River due to the backwater effect across the border of British Columbia’s Seven Mile Dam. If Seattle terminates the agreement, it loses the right to operate Ross Lake to the agreed-upon full pool elevation at the international boundary. If British Columbia terminates the agreement, Seattle gains the right to operate Ross Lake to a higher full pool elevation at the international boundary, thus flooding more of the Skagit Valley into Canada. Termination of the agreement will not affect British Columbia’s ability to operate the Seven Mile reservoir.

Canada’s involvement

In 1984, Environment Canada (now Environment and Climate Change Canada) co-signed the related agreement between Canada and British Columbia with the Department of External Affairs (now Global Affairs Canada) and maintains a supporting role to DFATD as required from federal action under the treaty.

In the event that British Columbia discontinues its obligations under the agreement or an arbitration panel determines British Columbia to be in breach of the agreement, Canada is required to ensure that British Columbia pays Seattle any amount owing per the agreement or make the payment to the United States on behalf of British Columbia.

Results / progress


Although Environment and Climate Change Canada has no obligations under the treaty, it maintains a water level monitoring station on the Skagit River at the international boundary as part of its overall joint monitoring program with the United States.

The United States Geological Survey monitors Ross Lake levels at the international gauging station near Newhalem, Washington. BC Hydro and Seattle City Light monitor the elevation of the Seven Mile Dam Reservoir on the Pend d’Oreille River.

Effect on the boundary waters treaty

While the treaty is in force, the powers, functions and responsibilities of the International Joint Commission under Articles IV (paragraph I) and Article VIII of the Boundary Waters Treaty shall not apply to the Skagit River and Ross Lake, or to the Pend d’Oreille River and the Seven Mile Reservoir.

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