Milk River update – July 27, 2020

Water infrastructure in Montana that diverts water from the St. Mary River headwaters to the Milk River suffered a catastrophic failure on May 17, 2020.

The Accredited Officers of the St. Mary and Milk Rivers have informed Alberta Environment and Parks (AEP) that water use has been greater than Canada’s share of the natural flow of the Milk River, and has put Canada in a deficit position.

In order to comply with the Boundary Waters Treaty, AEP notified Milk River irrigators that licensed diversions must cease as of July 24. We will continue to provide updates on this situation, including progress on canal repairs, as new information becomes available.

For answers to frequently asked questions, see:

Updates will be provided directly to water licence holders and this section will be updated as new information becomes available. If you are a licence holder and have questions about water use in the Milk River basin, please contact: waterapprovals.lethbridge@gov.ab.ca


The Boundary Waters Treaty governs the sharing of waters of international streams between Canada and the United States and established an International Joint Commission (IJC) to monitor compliance and resolve disputes.

The 1921 Order of the IJC set the St. Mary River at the international boundary, and the Milk River at the eastern crossing of the international boundary as the points where apportionment occurs.   It also outlined the roles for Accredited Officers (AOs) for the St. Mary and Milk Rivers.  One officer is appointed by each of Canada and the U.S. to measure and apportion the water.

The AOs calculate the natural flow volumes, and the apportioned shares for each country, twice per month.  The AOs signed a Letter of Intent (LOI) in 2001; it is a mutually beneficial agreement allowing each country to use more of its allotted share during seasonal low flow periods.


The following infographic explains the apportionment procedures, including the LOI.

History of the 1921 Order

In April, 2003, the Governor of Montana asked the IJC to review the 1921 Order. The IJC held four public information sessions in 2004, to gather information on the sharing of the Milk and St. Mary Rivers.

Later that year, the commission established the International St. Mary/ Milk Rivers Administrative Measures Task Force, with four members each from Canada and the United States.

The task force released a draft report in April 2006 for public comment, available on the commission's website.

To view a summary of Alberta's perspective on the task force report, and the Government of Alberta's formal submission to the task force, see the following:


The Government of Alberta (August 2004) submission to the IJC consisted of an overall submission as well as submissions from Alberta Agriculture, Food and Rural Development (now Alberta Agriculture and Forestry) and Alberta Environment (now Alberta Environment and Parks).


Connect with the Transboundary Waters Secretariat:
Email: aep.tws@gov.ab.ca