The collapse of water diversion infrastructure in the United States puts the river at risk of drying up this summer
Alberta’s environment and parks department says it is working to address impacts on water users in the Milk River watershed now that water diversion from the St. Mary River system has been halted.
A concrete drop structure on the St. Mary canal in Montana failed on May 17 and repairs will eliminate any ability to divert water this summer into the Milk River before it flows into Canada.
That means any water in the Milk will be a result of natural flow, which is typically low and possibly non-existent if the summer is hot and dry.
“We recognize the severity of the situation and the importance of the Milk River basin to surrounding communities and the local economy,” said Environment and Parks Minister Jason Nixon in a June 22 news release.
“Environment and Parks is supporting Alberta water users and working with our federal and U.S. counterparts to keep water users informed as work to repair the canal progresses.”
Nixon said the department will provide updates to water users on the water supply outlook and infrastructure repairs. It will also give details on water use and support any necessary water conservation plans.
“With no canal in place, water licence holders in Alberta should be prepared for only natural flows on the Milk River throughout the summer and should proactively explore options for water conservation,” the news release said.
Unlike many other Alberta rivers, the Milk River does not rely on runoff from the mountains but rather on rain and groundwater.
About 8,200 acres on the Canadian side of the international border are irrigated from the Milk River and 93,000 acres of farmland are reliant upon it on the U.S. side.
The Milk River also supplies water to the Town of Milk River and the villages of Coutts, Alta., and Sweetgrass, Montana. However, there are three to four months worth of water storage available for municipal use.
The Boundary Waters Treaty of 1909 governs water use on the St. Mary and Milk rivers. Details of the water sharing arrangement:
- During the irrigation season (April 1 to Oct. 31), Canada is entitled to 25 percent of the natural flow of the Milk River, up to a natural flow of 18.9 cubic metres per second, and 50 percent of natural flows above this threshold.
- On the St. Mary River, from which the St. Mary Canal diverts water, Canada is entitled to 75 percent of natural flows up to 18.9 cubic metres per second during the irrigation season and 50 percent of natural flows above this threshold. Natural flows are shared equally with the United States from Nov. 1 to March 31.
- The United States may accumulate a deficit on the St. Mary River from March 1 to May 31, which would be equalized through a Canadian entitlement to water on the Milk River transferred via the St. Mary Canal.
Diversion infrastructure on the Montana side was built in the early 1900s and has since been repaired only as needed. Funding for major upgrades has been an issue in the U.S. and has prevented major improvements to the system.