Photo courtesy of the Milk River Project Facebook Page, Click on it to englarge.
Above: The first St. Mary Siphon (aka The Big Pipe) was built between 1912 and 1915. A second, parallel siphon was added later, becoming operational in 1926 - both were part of an intricate 29-mile system of dams, canals, siphons, and drop structures designed to carry water from the St. Mary River to the Milk River valley for irrigation.
Lifeline of the Hi-line . . .
The Milk River is a major tributary of the Missouri River, famous for its distinctive milky color. It got its name from Meriwether Lewis during the expedition in 1805, who described its water as being "the colour of a cup of tea with the admixture of a tablespoonfull of milk" due to the fine, white silt suspended in the river - most of it from badlands in Canada. The Milk River starts in Glacier Park, flows into Canada, and then back into Montana near Havre. It is the longest triburary of the Missouri River, emptying ino the big river just east the Ft. Peck Dam (Nashua area). Communities along the Hi-Line from Havre to the Glasgow (about 18,000 people) rely on it for drinking water, and farmers depend on it for irrigation. The river and its reservoirs also provide recreational opportunities for Hi-Liners, and essential riparian and wetland habitats for diverse wildlife. However, if it were up to mother nature the Milk River would run dry about six out of every ten years, especially in late summer as snowpack in its headwaters area disappears.
The confluence of the Milk and Missouri Rivers near Nashua - Photo credit: Jim Wark, Airphoto. Click on it to enlarge.
Critical infrastructure . . .
History is filled with instances of societies manipulating water resources to meet their needs, and the Milk River Project is a great example of this. The project involved the St. Mary River, which also starts in Glacier Park not far from the headwaters of the Milk River, but eventually flows into the Hudson Bay. In the early 1900's the federal government built a system to divert water from the St. Mary River near Glacier Park and siphon it over a divide into the North Fork of the Milk River. The goal was to make the Milk River a stable water supply that would sustain irrigation and municipal water needs.
How it works? . . .
Beginning with Lake Sherburne Reservoir in Glacier Park (dam constructed 1914-1921), water stored there is released into the St. Mary River before being diverted into the 29-mile long St. Mary Canal and then discharged into the North Fork of the Milk River. The water continues to flow northward into Alberta, Canada before reentering the United States, traveling more than 200 miles where it is stored in Fresno Reservoir until it is needed by farmers. The project also includes storage at Nelson Reservoir, several diversion dams, 200 miles of canals, and over 200 miles of irrigation ditches that deliver water to farms and other entities that have rights to it.
And then it happened . . .
The most interesting part of the Milk River Project is the 29-mile St. Mary Canal System (map below), which includes a diversion dam, miles of canals, two major siphons, and five drop structures. It's been known for years that the many of the century-old components needed to be replaced. Then in May of 2020 one of the drop structures failed, shutting down the system and leaving ~700 Hi-Line irrigators without water for much of the summer. It was quickly rebuilt over the next 22 weeks, but then in June 2024 the St. Mary Siphon ruptured, shutting down the system and prompting a major reconstruction project to replace most of the aging infrastructure, including the siphons shown atop this page. At the time of this writing (12/20/25), construction was going well. For updates and photos of this major construction project, check out the links below.
Term: infrastructure
CLICK HERE to learn more about how the original Milk River Project got started in the early 1900's.
CLICK HERE to go the Milk River Project website for more information and updates on the construction, or CLICK HERE to go their Facebook page (lots of photos).
CLICK HERE to access a photo album that includes maps and photos of the 29-mile portion of the Milk River Project known as the St. Mary Canal.
Below: The divide that the canal system crosses is not the Continental Divide, but rather the divide between water that flows to the Hudson Bay and water that flows to the Gulf of Mexico.
