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Alberta loses access to Milk River irrigation water following U.S. canal failure

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Milk River watershed
Water shortages are not uncommon in the Milk River watershed. However, as a result of the recent incident, no more water is expected to be transferred from the St. Mary Basin to the Milk River Basin this year, affecting some 40 water license holders who rely on the water for irrigation. Credit: Milk River Watershed Council Canada

Following a U.S. infrastructure failure in northern Montana, water levels in Alberta’s Milk River will likely be too low this summer for activities like canoeing or kayaking. Water license holders in Alberta should be prepared for only natural flows on the Milk River throughout the summer.

The May 17 failure occurred when a 22 metre tall crumbling concrete portion of a ditch system known as the St. Mary Canal collapsed. This failed concrete drop structure was the last of five drop structures relying on gravity and siphons to convey water through the 46-kilometre long, century-old St. Mary Canal, to the North Fork of the Milk River. Water is diverted into the canal from the St. Mary River, near Glacier National Park and supplies irrigation and municipal water to irrigators and communities along the Hi-line.

St. Mary and Milk River Watersheds Map
St. Mary and Milk River Watersheds Map. Credit: Alberta Environment and Parks

During the irrigation season, from April 1 to Oct. 31, Canada is entitled to 25 per cent of the natural flow of the Milk River, up to a natural flow of 18.9 cubic metres per second, and 50 per cent of natural flows above this threshold.

Water shortages are not uncommon in the Milk River watershed. However, as a result of the recent incident, no more water is expected to be transferred from the St. Mary Basin to the Milk River Basin in 2020, affecting some 40 water license holders who rely on the water for irrigation. There should, however, be enough water already stored to carry them through the dry season, officials estimated.

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While no impacts to drinking water or household use are expected, the province has provided the Town of Milk River with funding to increase water storage. The town’s current stored water supply would support four months of water use in the event the town was unable to draw any more water from the river.

Permanent repairs to the canal have already begun, with completion scheduled for September. Repairs, including a complete replacement of Drop 2 and Drop 5 structures. According to a report in The New York Times, repairs to St. Mary’s Canal may approach $200 million.

“We recognize the severity of the situation and the importance of the Milk River basin to surrounding communities and the local economy,” Jason Nixon, Alberta Minister of Environment and Parks, announced in a statement. “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,” added Nixon.

Following an engineering site inspection by the State of Montana’s Department of Natural Resources and Conservation on May 27, officials concluded that the “complexities and costs associated with providing an interim solution to run water this irrigation season could not be justified considering the anticipated costs and minimal gains in water supply,” according to a statement issued through the U.S. Bureau of Reclamation.

The Milk River previously ran dry in 2001.

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