The Souris River - A Glacial Spillway
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This earthcache is the third in a series which focuses on the effects of glaciation on the Saskatchewan landscape.
The Souris River was named as the result of a story. Prior to European settlement, a group of Metis hunters was camped on its southern bank. In late winter their camp was invaded by "great hordes of mice". The river became known as the Mouse River in the U.S.A. but Canadians used the French word for mouse or the "Souris" River. The modern flow of the Souris River begins in the Yellowgrass marshes north of Weyburn. It has a total length of about 700 km and drains 17,600 sq. miles. It flows through communities in Saskatchewan (Weyburn, Estevan, Roche Percee, Oxbow). in North Dakota (Burlington, Minot, Velva), and in Manitoba (Wawanesa, Melita, Souris). It joins the Assiniboia River near Brandon, Manitoba. Most of the annual flow comes from snow melt and spring rains. Annual flow can vary from 3400 acre feet (1937) to 2.1 million acre feet (1976). The Souris River Valley is an excellent example of a wide glacial spillway occupied by a misfit stream that could not have carved its river valley. Geologically, the Souris River formed when the Wisconsinian (10,000 years ago) glaciers melted. The Moose Mountain uplands split the glacial ice into the Weyburn lobe and the Moose Mountain lobe in SE Saskatchewan. Glacial sediments were deposited along the Weyburn lobe forming the Oxbow moraine. The original Souris River was a meltwater channel that used the Riviere des Lacs drainage to the south because the meltwater flow was blocked by the Weyburn ice lobe. Evidence of this flow still exists as 1850 foot terraces scattered along the Souris River between Glen Ewen and Oxbow. At this time, the river valley was broad but relatively shallow. The Souris River Valley, as we know it today, began when the Weyburn ice lobe melted to expose the lower land east of Oxbow. When the river cut through the Oxbow moraine, it changed its course to the northeast and joined the Moose Mountain Creek drainage near Oxbow. Proglacial Lake Regina drained in a rapid release, cutting downward through glacial sediments. It formed a wide, deep glacial spillway with a deeply entrenched river as glacial water flowed to proglacial lakes Hind and Agassiz in Manitoba. Historically, the Souris River acted as a highway for settlement in SE Saskatchewan.The availability of firewood, a water supply, coal at Roche Percee and proximity to the U.S.A, border attracted the Palliser Expedition, N.W.M.P. on their western trek, and Boundary commission surveyors. Its irregular flow limited its value as a transportation corridor. It has had a number of dams built along its course to supply water for the railroad (eg; Oxbow in 1921) and to retain water for livestock (eg, PFRA dams at Souris, Oxbow, Melita in the 1930`s). The Sours has also been a "mighty mouse" with major floods (eg.1904,1916,1920,1948,1969,1976,1979) that have caused widespread damage and loss of life in Canadian and American communities, The damage caused by a flooding Souris River lead to a historic agreement between the Canadian and American governments. Inspite of many protests, the Rafferty Dam on the Souris River near Estevan and the Alameda Dam on Moose Mountain Creek near Oxbow were constructed. The U.S.A. contributed $50 million to ensure flood protection for Minot,N.D. In Canada, the dams provide flood protection and a reliable water supply for municipal,domestic, irrigation, and recreational use, and a water supply for the Shand Power Station. Canada can retain 50% of the water flowing into the Souris River Basin. Water is released to maintain the flow of water to N.D. communities and wildlife refuges in the Upper Souris Basin. To date, the dams have prevented major flooding in the Souris River Basin. The "mighty" mouse appears to have become a "tamed" mouse. To log this earthcache, you will study a portion of the river valley near Glen Ewen, SK. You will access the valley via an all weather gravel road that has a low local traffic volume. Please be aware of local traffc as you do your measurements and observations. (1) Drive to the coordinates N49 11.479 W102 01.729 on the north side of the river valley. Describe the appearance and vegetation of the river valley from this position. Also note the mileage on your odometer. (2) Set your GPS coordinates to N49 10.292 W102 01.720. Drive through the river valley following the grid road until you reach the above coordinates on the south side of the river valley. Record the total distance you have travelled. Also describe the vegetation on south side of the river valley from this view. (3) Return to the bridge ( N49 10.816 W102 01.634) Estimate the width of the river. Is the terminology of a misfit stream an appropriate term for the Souris River from your measurements? (4) To verify your visit to the site, state the name and the location of the company that produced the reflective signs at the ends of the bridge. Email your measurements and answers to the questions to me. Incomplete or incorrect answers will be deleted. Enjoy your visit to the scenic Souris River Valley. REFERENCES: Against the Flow cap.estevan.sk.ca/flow/atf.html Christensen,E.A.,1956, Glacial Geology of the Moose Mountain Area Saskatchewan, Saskatchewan Department of Mineral Resources Encyclopedia of Saskatchewan, Souris River esask.uregina.ca/entry/souris_river.html Oxbow-Glen Ewen History Book Committee, 1984, Furrow to the Future, D.W, Friesen & Sons Ltd. Saskatchewan Water Authority, Water Control- Saskatchewan Dams and Reservoirs, www.swa.ca/WaterManagement/DamsAndReservoirs.asp? Wikipedia, Souris River, en.wikipedia.org/wiki/Souris_River
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