International Joint Commission Launches Study to Look at Improving Water Apportionment on St. Mary and Milk Rivers


The International Joint Commission’s (IJC) Commissioners approved the formation and membership of the International St. Mary and Milk Rivers Study to explore options to improve access to apportioned waters by each country, in recognition of climate change and challenges to apportionment since the original 1921 Order was issued. The effort includes a desire to achieve long-term resiliency in accessing the shared waters of the St. Mary and Milk Rivers.  

The study will consider different options, including non-structural solutions (such as modified balancing periods and deficit trading) as well as structural options such as new (or improvements to existing) structures. The study is expected to last approximately four years. Recommendations from the Study Board will be presented to the IJC for consideration. The IJC will then report the study findings and its recommendations to governments. 

“The Commission is very excited to launch this study. We are very much looking forward to hearing from all interested public and organizations over the next four years. Receiving input from all who are reliant upon and interested in the St Mary and Milk Rivers is essential to reviewing acceptable structural and nonstructural options that may improve each nation’s ability to receive their apportionments of water” , said Commissioner Rob Sisson. 

“The Commission’s involvement in this basin dates back over 100 years.  Changing climate conditions increases the timeliness and importance of this work. I believe we have established a small and nimble study board able to work binationally and recommend more efficient water apportionment for the future”, said Commissioner Pierre Béland.   

The Study Board is co-chaired by the two Accredited Officers of the St. Mary and Milk Rivers, John Kilpatrick and Dr. Alain Pietroniro. The Accredited Officers are appointed by the United States and Canada to apportion the waters under the guidelines set out by the 1909 Boundary Waters Treaty and the 1921 IJC Order, which specify how the water is measured and apportioned between the two countries during the irrigation season. Additionally, the Board features four other members, two from Canada and two from the United States. These members have been chosen for their expertise and ability to provide unbiased, scientific advice for the basins. 

Experts from government agencies, Indigenous Nations and stakeholder groups will have the opportunity to provide their input through advisory and technical groups. Establishing these groups will be an early task for the study board. 

The St. Mary and Milk Rivers each form in different parts of Montana off the Rocky Mountains, with the St. Mary flowing north into Alberta and the Milk River moving northeastward into Alberta before turning back into Montana. Though hydrologically distinct, these rivers are connected through the St. Mary Canal in Montana. This century-old structure moves water from the St. Mary River, which has a dependable, year-round flow of water originating from mountain streams to the Milk River, which relies heavily on snow and rainfall and can experience significantly reduced flow in the summer months. Under guidelines set out in the 1909 Boundary Waters Treaty and the IJC’s 1921 Order, the water in both rivers is divided up between the two countries, where it is used for irrigation, municipal water supplies and environmental flows based on each country’s own governance. 

The IJC was established by the Boundary Waters Treaty of 1909 to help the governments of Canada and the United States prevent and resolve disputes over use of the waters shared by the two countries. 



Paul Allen (Ottawa)                        613-222-1475

Edward Virden (Washington)         202-372-7990