Geography Lake Manitoba

1 geography

1.1 tributaries , outflows
1.2 water control dam
1.3 flood in 2011
1.4 historical floods

geography

nasa image of lake manitoba

the irregularly shaped lake, 200 km long, smallest of group of 3 large lakes, other 2 being lake winnipeg (the largest) , lake winnipegosis, found on floor of prehistoric glacial lake agassiz. lake subdivided 2 connected distinctly different basins: small, irregular-shaped north basin , larger south basin. part of watershed of nelson river , hudson bay.

the southern tip of lake, 24 km north of portage la prairie, manitoba, ends in delta marsh, important staging ground migrating birds.

communities on lake include fairford, steep rock, st. laurent, , sandy bay.

tributaries , outflows

the lake fed lake winnipegosis northwest via waterhen river, average annual contribution of 1,900,000 acre feet (2.3 km). whitemud river , local overland flow average 257,000 acre feet (317,000,000 m). precipitation contributes 1,800,000 acre feet (2.2 km). 1970 2003 portage diversion has contributed average annual volume of 246,800 acre feet (304,400,000 m) assiniboine river. lake manitoba drains northeast lake winnipeg through fairford river lake st. martin , dauphin river. average annual river outflow 2,030,000 acre feet (2.50 km). average evaporation 2,020,000 acre feet (2.49 km) per year. of water inflow waterhen river (42% of inflow) , precipitation directly on lake s surface (40%), while 50% of outflow evaporation. explains hyposaline nature.

water control dam

severe flooding around lake led excavation of improved outlet channel between 1899 , 1901. in 1933 following dry years in late 1920s , 1930s, province constructed concrete control dam across fairford river downstream of channel. new dam constructed in 1961. new structure operated try control levels between 810.5 , 812.5 feet (247.0 , 247.7 m) above sea level.

flood in 2011

due above average snowfall on winter of 2010-2011, , above average precipitation in spring on lake manitoba watershed, forecasted water levels on lake manitoba called levels above regulated upper range of 812.5 feet (247.7 m) above sea level , around flood stage of 814 feet (248 m) above sea level. added inflows of portage diversion due high water levels on assiniboine river , tributaries, of 34,000 cu ft/s (960 m/s) of water lake peaked @ 817.2 feet (249.1 m) above sea level on july 21. on may 31, 2011 when lake high, 815.13 feet (248.45 m), strong wind winds north , north-west of 70 km/h gusting 90 km/h caused major damage beaches , communities on south basin of lake including twin lakes beach, st. laurent, st. ambroise, delta beach, lynch point, big point, , large areas of farmland.

historical floods

unlike river can rise , recede relatively quickly, large lakes lake manitoba require months or years lake levels rise , fall. below flood years on record in lake manitoba above flood stage, defined manitoba infrastructure , transportation (mit), of 814 feet asl. however, beginning around level of 813 feet asl, localized flooding of agricultural land around lake can occur.

in 1881-82 lake levels not recorded. however, given topography around lake manitoba, level of 817 feet asl required cause lake drain assiniboine river, occurred in both 1881 , 1882. also, flow of 14,835 cfs recorded on fairford river in 1881, long before significant channel improvements made. based on rating curve flows on fairford river during period, flows correlate lake level high 817.5 feet asl. furthermore, in 1890 study entitled report of exploration of glacial lake agassiz in manitoba , warren upham states lake manitoba rose approximately 8 feet above lowest level, records show around 810 feet asl, suggesting peak of 818 feet asl.


lake levels did not begin recorded until 1914. however, in 1913 flow rate of 11,500 cfs on fairford river recorded, based on rating curve flows during period correspond lake level of greater 816 feet asl.


on may 31, 2011, during major wind event, lake manitoba measured @ 820.37 feet asl @ twin lakes beach. result of high water level wind set-up , wave action, significant damage occurred along south basin of lake manitoba. 2011 peak flood level wind-eliminated peak lake level.




^ volumes provided alf warkentin manitoba water stewardship
^ http://home.cc.umanitoba.ca/~mlast/publications/page1/assets/1988hydrobiol.pdf
^ water survey canada
^ provinical flood control infrastructure review of operating guidelines: report minister of manitoba infrastructure , transportation (pdf). province of manitoba. august 2015. p. 55. retrieved april 24, 2017. 
^ lake manitoba , lake st. martin outlet channels conceptual design preliminary options (pdf). province of manitoba. 2014. p. 17. retrieved april 23, 2017. 
^ 2011 flood: technical review of lake manitoba, lake st. martin , assiniboine river water levels (pdf). province of manitoba. october 2013. p. 40. retrieved april 23, 2017. 
^ 2011 flood: technical review of lake manitoba, lake st. martin , assiniboine river water levels (pdf). province of manitoba. october 2013. p. 25. retrieved april 23, 2017. 
^ provinical flood control infrastructure review of operating guidelines: report minister of manitoba infrastructure , transportation (pdf). province of manitoba. august 2015. p. 52. retrieved april 24, 2017. 
^ provinical flood control infrastructure review of operating guidelines: report minister of manitoba infrastructure , transportation (pdf). province of manitoba. august 2015. p. 23. retrieved april 23, 2017. 
^ lake manitoba , lake st. martin outlet channels conceptual design preliminary options (pdf). province of manitoba. 2014. p. 4. retrieved april 24, 2017. 
^ lake manitoba , lake st. martin outlet channels conceptual design preliminary options (pdf). province of manitoba. 2014. p. 4. retrieved april 23, 2017. 
^ 2011 flood: technical review of lake manitoba, lake st. martin , assiniboine river water levels (pdf). province of manitoba. october 2013. p. 40. retrieved april 23, 2017. 
^ provinical flood control infrastructure review of operating guidelines: report minister of manitoba infrastructure , transportation (pdf). province of manitoba. august 2015. p. 52. retrieved april 24, 2017. 
^ flood bulletin #68 - june 3, 2011 . province of manitoba. june 3, 2011. retrieved april 23, 2017.