Features

Area

• The low arch of the Milk River Ridge rises 300 metres above the plain, straddling the Mixed-grass and Foothills Fescue Natural Subregions. Water from melting glacial ice has cut a series of wide channels through the ridge including Whisky Gap, Lonely Valley and Verdigris coulee.
• River valley habitats like those found in this Area of Concern are very important for wildlife on the Great Plains. They provide relatively scarce water and shelter.
  
• Riparian cottonwood forests of the Great Plains need spring flood and silt deposition to create habitats suitable for cottonwood seedlings. Many bird species use these forests for nesting, feeding, or stopovers during migration, and mammals find shelter for rearing their young. It is predicted that, without remedial action, cottonwood habitats may disappear by the end of this century.

Township and Range map: JPG | PDF		Natural Subregions map:  JPG | PDF

Twin River Heritage Rangeland Natural Area

• (190 km²) represents the Mixedgrass subregion and includes much of the diversity of this subregion.
  
• It includes dense nesting bird-of-prey populations including ferruginous hawks, golden eagles and prairie falcons. Rare shorthead (St. Mary River) sculpin, yellow-bellied marmot and northern leopard frogs occur.
  
• Rare plants including prickly milk vetch, tufted hymenopappus, and Carolina whitlowgrass are found in the protected area.
  

Watershed

• Milk River Ridge stands as the divide between water flowing north to the Hudson’s Bay and south to the Gulf of Mexico.
• Milk River Map by AB Environment
  
• The Milk River rises in Western Montana, meanders through 160 km of southernmost Alberta, then loops back into the United States. Eventually, the waters that pass through this dry, rugged basin reach the Missouri River and then the Gulf of Mexico – it is the only Canadian river to do so. It relies largely on spring runoff for its natural flow.
• The St. Mary River arises in the high alpine area of Glacier national Park and is partly fed by glaciers. It flows north into Alberta and into the St. Mary reservoir. It becomes part of the South Saskatchewan River Basin whose water flows into Hudson Bay.
• The flow of the Milk River is shared by Canada and the United States under a 1909 International Boundary Water Treaty. Under the treaty, these rivers are considered as one waterway and their flows divided equally between the two countries.
• Under a 1921 agreement, natural flow is divided equally in the winter. But during irrigation season (April 1 – Oct. 30) the U.S. receives up to three-quarters of the natural flow of the Milk River and Canada three-quarters of the St. Mary River. Montana can divert some of its share of the St. Mary River into the north Milk River via a deteriorating canal. In times of higher flow levels, the water is equally shared. Flow in the Milk River in late summer and fall often relies on diversion from the St. Mary.

Biodiversity

• Numerous priority plant species, including hare-footed locoweed, intermediate hawk’s-beard, Raymond’s sedge, few-flowered rush, western blue flag, Cusick’s paintbrush, tufted hymenopappus and whitlow-grass, can be found in Milk River Ridge.
• Rare plants found in the Twin River Heritage Rangeland Natural Area include prickly milk vetch, tufted hymenopappus, and Carolina whitlowgrass.
  
• Wildlife:
• Large mammals prevalent in Milk River Ridge include pronghorn, white-tailed deer, and mule deer.
• Small mammals include the yellow bellied marmot.
• Birds found in the area include peregrine falcon (COSEWIC special concern), Baird’s sparrow, ferruginous hawk (COSEWIC threatened), golden eagle, and prairie falcon.  This area also forms a part of the sharp-tailed grouse dancing grounds.
• Local Fish species include St. Mary River shorthead sculpin (COSEWIC threatened) and stonecat.

Environmentally Significant Areas

• Approximately 50 percent of the Milk River Ridge has been designated Nationally Significant.
  

Environmentally Significant Areas map:  JPG | PDF