Land, Water, People - Water in the Watershed
Water in the River
The water in the Milk River comes from snowmelt in the headwaters, inflows from tributaries and precipitation runoff throughout the watershed. Snowmelt in the headwaters accounts for between 50% and 80% of the water in the river. Precipitation runoff accounts for the remaining 50% to 20% of the water in the river. In addition to the natural flows, the water in the Milk River is augmented by an inter-basin transfer of water from the St. Mary River. 
The St. Mary Canal, completed in 1917, carries water from the St. Mary River to the North Milk River, just before it flows into Canada. This inter-basin transfer allows the U.S.A. to use its share of the water in the St. Mary River system, which also originates in the U.S.A., but flows into the South Saskatchewan River Basin. The canal usually operates from April to October, transferring from 17 to 21 cubic meters of water per second.
Boundary Waters Treaty
Where rivers cross international boundaries, there needs to be agreement on how the water will be shared. The apportionment of water between Alberta and Montana was formalized in the Boundary Waters Treaty of 1909. The Treaty established the International Joint Commission, made up of members from both countries, for the purpose of resolving disputes. In 1921, the International Joint Commission created an Order that set out the rules for the apportionment and measurement of water in the St Mary River and Milk River. The 1921 Order outlines how the water in the St. Mary and Milk Rivers is to be divided. In the irrigation season, the U.S.A. is entitled to three-quarters of the water in the Milk River and Canada is entitled to one-quarter of the flow. The U.S.A. is entitled to one-quarter of the flow in the St. Mary River and Canada is entitled to three-quarters of the flow. In the non-irrigation season, flows are divided equally for both rivers.
Water Underground
Although we can’t usually see it, water stored in underground aquifers is an important source of water for people living in the watershed. The Milk River Aquifer and the Whiskey Valley Aquifer are two examples of important aquifers. The water in aquifers originates from snowmelt and precipitation which slowly percolates through the soil and is stored in sandstone or gravel formations.
The Milk River Aquifer covers an area of approximately 11,300 km2 and is the primary source of water for over 800 farms and ranches and the communities of Skiff, Foremost, Orion and Grassy Lake. The water in the aquifer generally flows in northeasterly direction. Flow is perhaps not the right word, creeping is a better description, as it is estimated as moving at a rate of 0.15 to 1.5 meters/year! The aquifer is recharged by areas of higher elevation, such as the Sweetgrass Hills, Milk River Ridge and Cypress Hills. There is also some recharge by the Milk River itself, where the water-holding sandstone formation comes into contact with the river.
Lakes & Wetlands
Shanks Lake, just north of Del Bonita, is the only large natural lake in the Alberta portion of the watershed. It is a shallow (3.1 m) lake with high levels of dissolved solids and alkalinity. Temporary ponds and shallow wetlands are also important parts of the watershed. They help to recharge groundwater and provide habitat for many wildlife species. The plains spadefoot relies on temporary ponds for their survival. They remain underground until heavy spring and summer rains create temporary ponds. In this dry climate, sometimes this means that spadefoots must hide out underground for five years or more!
Groundwater & Surface Water are Closely Linked
All water in a watershed is connected in one way or another. For example, water from the Milk River helps to recharge the Milk River Aquifer where the sandstone formation touches the River. Under some environmental conditions the water may actually be flowing the other way, from the aquifer in to the river. Red Creek, a tributary of the Milk River is fed by a spring that originates from the Milk River Aquifer. Individual aquifers are also connected. For example, it is thought that the Milk River Aquifer may recharge the Whisky River Aquifer.
Back to Land - Through Foothills and Under Hoodoos