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The Milk River Ridge is a 1,663 km2 area in the southern part of Alberta along the Alberta – Montana border comprising extensive foothills grasslands, wetlands, glacial spillways, and deeply incised ravines with intervening ridges.

The Milk River Ridge is an internationally significant grassland, home to several species of rare or endangered fish, amphibians, birds, and plants, an provides important habitat for deer and pronghorn, nesting areas for several birds of prey, including the peregrine falcon, as well as the sharp-tailed grouse. It is one of six large blocks of grasslands left on the glaciated plains of North America.

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    The Milk River Ridge is a 1,663 km2 area in the southern part of Alberta along the Alberta – Montana border comprising extensive foothills grasslands, wetlands, glacial spillways, and deeply incised ravines with intervening ridges. The Milk River Ridge is an internationally significant grassland, home to several species of rare or endangered fish, amphibians, birds, and plants, an provides important habitat for deer and pronghorn, nesting areas for several birds of prey, including the peregrine falcon, as well as the sharp-tailed grouse. It is one of six large blocks of grasslands left on the glaciated plains of North America. The Milk River Ridge area of concern is under threat because of a proposed dam on the Milk River.


    The Milk River Ridge Area of Concern includes two protected areas:

    • Twin River Heritage Rangeland Natural Area (190 km2)
    • Ross Lake Natural Area (19.5 km2)



    • 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.


    • 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.


    • 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


    An expansion of Twin River and Onefour Heritage Rangelands has still not been designated. With local ranchers on board and industry possibly willing to engage in compensation with the Crown, protecting these areas is a clear win-win. However, the process remains stalled and is an example of how conservation is a low priority.

    November 2014

    Minister Kyle Fawcett responds to AWA’s concern about the expansion of Twin River and Onefour Heritage Rangeland, writing, “while it is encouraging to have support from the grazing leaseholder and the Alberta Wilderness Association to extend Milk River Ridge as a conservation area, our government must test these ideas with a broader community of local Albertans.”

    The World Wildlife Fund (WWF) writes a letter in support of moving forward on conservation objectives for the Twin River and Onefour Heritage Rangeland under the SSRP.

    DeeThree Oil is now operating as Granite Oil.

    October 2014

    Under the SSRP, an addition to the Twin River Heritage Rangeland Natural Area is proposed. Petroleum exploration and development by DeeThree threats to undermine this addition. AWA asks for this lease to be surrendered to the Crown and paid compensation.


    The Draft South Saskatchewan Regional Plan is officially unveiled. The draft does not address conservation in native grasslands in any specific way; no legislated protection is proposed for grassland areas despite the large number of species at risk in southeast Alberta. AWA argues that Milk River Ridge, Wild Horse Plains and key stretches of wild rivers in the south should be legislatively designated as Heritage Rangelands.

    September 2013

    AWA learns that sensitive rough fescue and mixed grasslands on the Milk River Ridge are being opened up to exploration activity in the Alberta Bakken oil play. At the same time, efforts to secure legal designation for these lands are being delayed until the Government of Alberta releases its South Saskatchewan Region Plan (SSRP). This comes despite the fact that, in February 2011, the South Saskatchewan Regional Advisory Council (RAC) recommended the Milk River Ridge west of the town of Milk River, adjacent to the Twin River Heritage Rangeland, as a “Candidate Conservation Management Area”. AWA urges the Alberta government to place a moratorium on new surface development in the Milk River Ridge until the SSRP is released.

    February 2009

    Alberta Environment informs AWA that the report had been shelved for approximately five years but would be released to the public within the next few months.

    April 2006

    The International St. Mary and Milk Rivers Administrative Measures Task Force releases its final draft report. The International Joint Commission (IJC) task force was established in 2004 to determine whether water from the two rivers was being apportioned equitably and what administrative improvements could be made to help each country optimize the use of their apportioned waters. The task force found that based on 55 years of records, the U.S. has historically received 4 percent less than the combined flows to which it is entitled, and Canada has received 4 percent more. The task force found that improvements to the St. Mary storage and conveyance facilities in Montana and additional storage on the Milk River in Alberta may allow diversion of full entitlement by both countries; however, environmental impacts and instream flow needs would have to be considered.

    January 2004

    AWA is informed that former Environment Minister, Lorne Taylor, has locked the Milk River Feasibility Study in a cabinet until the IJC finishes its deliberations on Montana’s challenge of the international agreement regarding sharing of water of the St. Mary and Milk Rivers. AWA writes to the new environment minister, Guy Boutillier, to ask about the status of this report and for a copy.

    December 2004

    A new international task force was set up to examine the 1921 agreement and will make recommendations to improve it.

    July 2004

    The IJC, which includes three Canadians and three Americans, holds four public meetings in Montana, Alberta and Saskatchewan to seek public comment on the 1921 agreement. At the meeting in Lethbridge, attended by 300, people were against revising the agreement.

    In letters to the IJC both the Southern Alberta Environmental Group and AWA note that the aquatic and riparian environments of the two rivers are stressed and degraded by current water management. SAEG writes: “Healthy rivers reflect healthy societies. IJC is responsible for making decisions regarding the use and quality of boundary waters. If the test of common good is to be met, decisions by IJC need to consider instream flows to protect and restore the health of the aquatic environments in these shared rivers.”

    April 2004

    Montana Governor Judy Martz asks the International Joint Commission (IJC) to re-open the 1921 agreement arguing that Montana has been prevented from receiving its full 50% share of water under the treaty. In dry years, it calculated that Montana receives around 40%. Alberta argues that the agreement is fair, that it takes only the amount of water it is entitled to, and it needs all the water it currently uses to maintain the irrigation economy of the area.

    It is likely that the 2002 meeting between Alberta’s Milk River Water Management Committee with members of the international group regarding the Milk River Water Study was the catalyst for the Montana challenge.

    February 2004

    The Minister of Environment studies the feasibility study.

    December 2003

    The feasibility study for dams and diversions on the Milk River is completed.


    A water moratorium is imposed on new applications for water allocations from rivers in the Oldman Basin. “That we have reached an environmental limit with respect to water withdrawals is a hard truth that all residents of the Oldman River basin must finally face…,” writes Cheryl Bradley in response to an article in the Lethbridge Herald. “If the old cry of “more storage” sounds again, it will indicate we have not yet come to terms with living in a dry land with limited water resources.”

    January 2003

    Environment Minister quietly launches feasibility study for Milk River Ridge Dam in provincially protected area, the Twin River Heritage Rangeland.

    December 2002

    The Milk River Water Management Committee meets with members of the international group regarding the Milk River Water Study. Mr. T. Gilchrist represents the Committee. Mr. Alan Pentney of Alberta Environment is directing the study.

    November 2002

    Ryan Davison of PFRA speaks at a Warner County Council meeting on the Milk River aquifer study, designed to measure the quantity and quality of the water in the aquifer. The Milk River Water Management Committee is to meet with Minister Lorne Taylor and the Lieutenant Governor of Montana to discuss mutual interests.

    October 2002

    The Milk River Water Management Committee is working with Alberta Environment and their U.S. counterparts in promoting the need for the Milk River project, emphasizing the need for a safe water supply and attends the Premier’s Dinner making many contacts with Ministers and MLAs.

    August 2002

    PFRA announces a National Water Supply Expansion Program, a cost share program to help fund certain water supply projects in drought affected areas in Alberta and Saskatchewan (such as a dam??)

    July 2002

    R. Takaguchi of Warner County Council moves to forward a letter to Alberta Environment asking them to investigate the possible rebuilding of the Monson Dam in the S 1/2 of 3-6-19-4 to ensure that any possible future flooding and irrigation issues can be mitigated.

    G. Peterson moves to forward a letter to Alberta Environment Minister Lorne Taylor requesting the department to consider funding a study on the Whiskey Valley Aquifer through the PFRA.

    R. Jones moves to allocate a maximum of $10 per capita for 802 county residents that are affected by the proposed Milk River Basin Water Management project to the Milk River Basin Water Management Committee.

    June 2002

    Communities of Coutts, Milk River and Warner hold tri-council meetings and continue their efforts to have the province consider a water storage project on the Milk River which will allow the municipalities a better water source.

    May 7, 2002

    The Milk River Basin Water Management Committee continues to keep in contact with key people in Alberta Environment, PFRA and Environment Minister Lorne Taylor


    The St. Mary, Chin, Milk River Ridge, 40 Mile Coulee and Waterton reservoirs are almost empty in March, and the Oldman reservoir is much below normal. A severe drought has affected southern Alberta for two to three years. The Milk River Water Management Committee, concerned about uneven supply of water, wants to explore options to even out the levels.


    The Twin River Heritage Rangeland Natural Area is protected as part of Special Places. It encompasses the confluence of the north and south Milk Rivers. This site “marks a milestone in conserving Alberta’s wilderness and natural heritage…,” says Environment Minister Gary Mar. “[This site contains] important plant and wildlife habitat that bring greater diversity and ecological integrity to our growing network of protected areas.”

    Ron Hierath, MLA for Cardston Taber-Warner says, “The new Twin River protected area is a win-win situation for all Albertans. Ranchers who have used the area for years will maintain their livelihood, while responsible grazing and land-use practices will preserve the grasslands for generations to come.”

    The Order in Council for the Heritage Rangeland was approved without the removal of a Water Resources reservation/notation on the Land Status Automated System (LSAS), the Public lands land registry system. Technically this reservation/notation, which would allow the building of a dam, should have been removed as LSAS designations do not apply to areas under Community Development’s legislation. The local committee, assuming the prospect of a dam was very unlikely, indicated to Environment Minister Ty Lund that the reservation/notation was not a major issue.


    A South Country Protected Areas Report states that “the proposed Milk River Dam and reservoir, if constructed, would flood significant portions of riparian range in the valleys of the north and south forks.” The Milk River Basin Studies estimates that flooding would extend about 30 km upstream from the confluence of the north and south Milk Rivers.


    The Milk River dam is postponed indefinitely because of a withdrawal of federal monetary support.


    Drought-affected communities hope for an early announcement of the dam. It is noted that the Milk River almost runs dry during the fall, making it an unreliable source of water for municipalities.


    The PFRA conducts a feasibility study into dam sites on the Milk River.

    An article in the Wild Lands Advocate considers other reasons not to build the dam, including increased erosion of topsoil, inefficient use of water in a dry and windy area (about 30 per cent of total storage of small reservoirs is lost to evaporation and up to 50 per cent of water diverted could be lost in conveyance and on farms. Overall efficiency of existing irrigation systems in Alberta is only 20 to 40 per cent), loss of valuable valley bottom lands, loss of wilderness canoeing opportunities, loss of valuable wildlife habitat. The author concludes: “Isn’t building a dam to secure Canada’s share of the flows for future use, when it is economically and environmentally detrimental, like insisting on eating your share of the candy even though it makes you sick?”

    December 1985

    A 129 acre conservation notation (CNT 860012) for a potential reservoir area is placed by Alberta Environment. “Part or all of the land may be required to the Milk River dam and reservoir.” However, the reservoir would far exceed the 129 acres.


    The Alberta Government approves a 31 m high irrigation dam on the Milk River, about 16 km west of the town of Milk River, with construction to begin in 1987, at a conservative estimated cost of $30 million of taxpayer money to irrigate 8,100 ha of land owned by 40 farmers. There was no public input. Montana also approves the dam. Environmentalists react “with anger and disbelief.”


    In June, still suffering from drought, farmers are cut off from using Milk River water for irrigation because Canada “has used up its share of water this year.” The PFRA says that the project would require no ditches or auxiliary construction.


    The Milk River dries up during the summer drought. Some Milk River seniors describe the drought as the worst one in memory.


    The Milk River Basin Studies Socio-Economic Analysis of Water Supply Alternatives concludes that “all of the proposed projects have a benefit-cost ratio of less than unity, at least suggesting that none of the projects can be justified solely on the basis of the direct agricultural benefits they would generate.” Secondary benefits, which are expected to be large, possibly making the dam more economically viable, would include regional construction spinoffs, revenue generated from irrigation equipment sales, and savings to farmers who will be able to grow their own cattle feed.

    But the analyses are admitted to be inherently subjective with an element of uncertainty. University professor Terry Veeman says, “Economists remain leery about justifying any project on the basis of secondary benefits.” He adds that better soil and water management practices would be more cost-effective than dams.

    The cost-benefit ratio depends in part on crop prices, which are falling, making the proposed dam more expensive. However, the study notes that it makes no allowance for the desirability of developing agriculture rather than some other sector of the economy. It is also impossible to accurately forecast what the value of river flows would be to Canadians in 50 years. “Will the real value of this natural resource climb vis-à-vis other values?”

    The study on soil and geology says that the soils “are not generally economically productive because they form on unstable material that is easily eroded.”


    The Milk River Basin Studies Environmental Overview Study concludes that “any future modification to the river’s regime would have to be assessed not only in terms of impacts upon the local area directly affected by inundation and the application of abstracted water, but also in terms of the whole basin. Thus potential benefits to land use practices generally and economic development as a whole at the west end of the basin must be assessed not only against local cost, but against benefits and cost accruing to the basin as a whole.

    The matter is important because land uses elsewhere in the basin, particularly along the course of the river, may be affected; because the river supports a riparian habitat that is scarce in the basin; and because certain aesthetic attributes of the river, particularly in the eastern portion of the basin, may be affected. There may also be implications for land use practices in the United States.”


    Natural river flow approaches zero on several occasions.

    The Milk River Water Users Association, a group of ranchers and farmers, are concerned about the serious shortage of water for stock and irrigation uses. This group asks Alberta Environment to examine possible alternatives for ensuring adequate water supply, largely for irrigation, along the Milk River.

    The Prairie Farm Rehabilitation Administration (PFRA) undertakes a study of potential water storage sites in the Milk River Basin. Any control of water supply would require a dam and reservoir, or off-stream storage in a tributary valley. Of the five potential reservoir sites identified, Milk River Site 2 would hold the most amount of water for the least cost.


    PFRA conducts further studies.


    A water development committee proposes that the gap near the Milk River Forks (the confluence of the North and South Milk Rivers) would be a good place for a dam. Pursuit of this option is not followed due to such reasons as hilly terrain, lack of local interest and potential international implications.

    February 1941

    Order in Council PC 682 of the Privy Council of Canada ruled in part: “So far as the interests of Canada are concerned, it appears that it would be preferable to have a reservoir on the St. Mary River at Spring Coulee Alberta instead of the recommended reservoir at St. Mary Lakes in Montana, and to have a reservoir at what is known as the Forks Site in Alberta on the Milk River instead of the recommended reservoir at Verdigris Coulee.”

    1923 – 1924

    Subsequent investigations by the Dept. of the Interior indicated that the Forks Site would be would be a much better site than the Verdigris Coulee proposal and more detailed studies were undertaken.

    October 1921

    The International joint Commission makes a recommendation: “The Commission finds…that the quantities of land in this international region susceptible of development far exceed the capacity of the rivers in question even under the most exhaustive system of conservation…every effort should be made to obtain the maximum efficiency in irrigation from these  waters…the Canadian Reclamation Service [should proceed] with the proposed Verdigris Coulee Reservoir in Alberta.”

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