Lake Winnipegosis, Lake St Martin, and Lake Winnipeg Via Dauphin River
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Technical Background - Lake Manitoba Basin Lake Winnipegosis, Lake St Martin, and Lake Winnipeg via Dauphin River 2 Lake Dauphin Winnipeg Lake Manitoba has a surface area of 4,740 km . River Dauphin River First Nation Lake Emergency 2 Winnipeg Channel It drains an area of 79,900 km that includes the Lake Pineimuta Lake Lake St. Martin St. Martin First Nation Little Saskatchewan First Nation east side of the Riding Mountains and most of Red Deer River Fairford Pinaymootang Control First Nation Structure the Duck and Porcupine Mountains. Runoff from the Duck and Porcupine Mountains finds its way Swan Waterhen Lake River into Lake Manitoba via the Waterhen River after Waterhen River Lake passing through Lake Winnipegosis and Manitoba Waterhen Lake. Dauphin Lake Manitoba Narrows Lake Manitoba also receives inflow via the Portage Lake Manitoba Diversion when flows are high on the Assiniboine Whitemud River Assiniboine Portage Diversion River and high flood levels are imminent at River Lake Manitoba Basin Winnipeg. Inflows into Lake Manitoba can be well established by considering flows on the Waterhen Lake Manitoba Basin Area Map and Whitemud Rivers and by accounting for flows at the Portage Diversion at Portage la Prairie. The Waterhen River is the main tributary to Lake Manitoba. It drains about 55,000 km2, or about 70% of the total Lake Manitoba drainage basin. However, flows on the Waterhen River are naturally regulated by storage in Lake Winnipegosis. The Fairford River provides the only outflow from Lake Manitoba, and it is regulated by the Fairford Control Structure. It conveys flows into Lake St. Martin (surface area of 345 km2) which connects to Lake Winnipeg via the 50 km long Dauphin River. Outflows on the Fairford River are severely limited by water levels on Lake St. Martin and the winter capacity of the Dauphin River. An emergency channel has been constructed between Lake St. Martin and Lake Winnipeg to augment the capacity of the Dauphin River and there are considerations to construct a channel between Lake Manitoba and Lake St. Martin to add to the capacity of the Fairford River. Technical Background - Lake Manitoba Basin The Portage Diversion The Portage Diversion was completed in 1970. It is one component of the works constructed in the 1960’s to prevent flooding in Winnipeg. The Diversion Portage Diversion consists of two separate control structures: one which Portage Reservoir controls the flows down the Assiniboine River and another which diverts some of the flow of water in Assiniboine River the Assiniboine River into a 29 km long diversion channel that empties into Lake Manitoba near Delta Beach. The diversion was originally designed to carry a maximum flow of 700 m3/s. Portage Diversion on May 11, 2012 when the flow into the Portage Reservoir was 1,412 m3/s and 862 m3/s was being diverted into Lake Manitoba. To prevent the Assiniboine River dikes from breaching and flooding much of the prairie between Portage and Winnipeg, the Manitoba authorities, under a state of Portage Diversions for Selected High Flow Years 1000 emergency, raised the dikes along the diversion 900 channel to accommodate a flow of about 1,000 3m /s. Initial design capacity of 800 diversion = 700 m3/s 3 700 The diversion flow averaged about 710 m /s over a /s) 3 3 600 period of about 15 weeks, peaking at 983 m /s on 1976 Volume = 1,800,000 dam3 500 1995 Volume = 1,400,000 dam3 May 14. The resulting volume diverted to Lake 400 3 Daily discharge (m 2011 Volume = 5,900,000 dam 3 300 Manitoba was 5,900,00 dam or more than three 200 times the next highest volume that occurred in 1976. 100 0 01-Jan 31-Jan 03-Mar 02-Apr 03-May 02-Jun 03-Jul 02-Aug 02-Sep 02-Oct 02-Nov 02-Dec 02-Jan In 2011 the Portage Diversion was operated for a Date period of 130 days. In early May 2011 forecasters predicted a record flood volume with a peak flow of 3 Annual Portage Diversion Flow Volumes over 1,400 m /s on the Assiniboine River at Portage la 7,000,000 7,000,000 Prairie. The expected dike capacity of the Assiniboine 2011 volume = 5,900,000 dam3 6,000,000 6,000,000 ) River downstream of Portage la Prairie was only about 3 5,000,000 5,000,000 500 m3/s due to geotechnical considerations. 4,000,000 4,000,000 3,000,000 3,000,000 2,000,000 2,000,000 Annual volume diversion (dam Average volume prior to 2011 = 325,000 dam3 1,000,000 1,000,000 0 0 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 Year Technical Background - Lake Manitoba Basin Historical Water Levels on Lake Manitoba Although some attempts were made to regulate Lake Manitoba levels as early as the 1880’s they had minimal impact on lake levels until the Fairford Control Structure was constructed in 1960. Before 1960 the lake fluctuated naturally over multi-year cycles. However the Fairford Control Works allowed the operators to maintain Lake Manitoba levels within a narrow range. This operation resulted in wider and more frequent fluctuations on Lake St. Martin a few kilometres downstream. The July 2003 report of the Lake Manitoba Regulation Review Advisory Committee recommended that Lake Manitoba be regulated in a more natural fashion. They recommended that when both lakes are within a “normal” range no adjustments be made to the control structure. When either or both lakes are outside their desirable ranges the lakes should be regulated to balance the impact on both lakes. The government of Manitoba adopted these recommendations. In most years the major source of inflow to Lake Manitoba is the Waterhen River. The Waterhen River Annual Inflows Into Lake Manitoba After Portage Diversion shows multi-year cycles of dry and wet periods that 9,000,000 8,000,000 are evident in the plot of Lake Manitoba levels before Waterhen River 7,000,000 Whitemud River 1960. Waterhen River flows from Lake Winnipegosis ) Portage Diversion 3 6,000,000 were above average every year from 2005 to 2010. 5,000,000 4,000,000 By the fall of 2010 Lake Winnipegosis levels were the Inflow volume (dam 3,000,000 highest levels in 50 years, thereby guaranteeing above 2,000,000 1,000,000 average Waterhen River flows in 2011. The high Lake 0 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 Winnipegosis levels in 2010 coupled with the record Year high inflows to Lake Winnipegosis in 2011 resulted in the highest Waterhen flows on record. Technical Background - Lake Manitoba Basin Whitemud River Natural Flows Comparison of Precipitation and Runoff in the Whitemud River Basin The Whitemud River provides a reasonable analogue 800 160 Snow - Nov-Apr precipitation Total precipitation, snow and rain for the contribution of the ungauged catchments 700 140 Summer runoff, Whitemud River at Westbourne 600 120 around the southern extent of Lake Manitoba. 500 100 Precipitation in the Whitemud River basin in 2011 was 400 80 (mm) about 550 mm - slightly above the long term average Runoff (mm) 300 60 and corresponded to something less than a 5-year 200 40 Total yearly andTotal winter yearly precipitation 100 20 return period. Previous years with the large amounts 0 0 of precipitation were 1956 and 1975. 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 Year The annual runoff volume in 2011 was the largest on record – some 850,000 dam3. This eclipsed the 1970 Historical Runoff Volumes - Whitemud River and 2001 runoff volumes by about 30 percent. The 1,000,000 900,000 wet periods in the early 1970s, the mid 1990s, and Runoff, April to October 800,000 the 2010s (extending into 2011) are evident, along ) 700,000 3 600,000 with the dry periods in the early 1960s and the early 500,000 1980s. 400,000 Runoff volume (dam 300,000 200,000 In 1975 only about 5 percent of the precipitation 100,000 was converted to runoff – in 2011 it was about 23 0 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 percent. In 2011, high antecedent moisture conditions Year resulted in a high percentage of the precipitation being converted to runoff due to a lack of storage in the basin. The 2011 runoff volume from the Whitemud Frequency Curve of Runoff in the Whitemud River Basin, 1958-2011 200 River basin was about a 100-year event. 180 Measured at Westbourne 160 Pearson III distribution 140 Mean = 29.8 mm 2011 Standard deviation = 26.2 mm Frequency Curve of Precipitation in the Whitemud River Basin, 1946-2011 120 Skew = 1.76 900 100 Yearly precipitation 2005 2001 800 80 Pearson III distribution Annual runoff runoff (mm) Annual 700 Mean = 507.0 mm 1956 60 Standard deviation = 93.6 mm Skew = 0.19 1975 40 600 20 500 2011 0 400 1.05 1.25 2 5 10 20 20010050 1000500 Return period (years) 300 Annual precipitation (mm) 200 100 0 1.05 1.25 2 5 10 20 20010050 1000500 Return period (years) Technical Background - Lake Manitoba Basin Waterhen River Natural Flows Historical Runoff Volumes - Waterhen River The Waterhen River is the main contributor to flows into 9,000,000 Lake Manitoba and inflows from the Waterhen reflect 8,000,000 7,000,000 Annual runoff, November to October water levels on Lake Winnipegosis. The Waterhen River Summer runoff, April to October ) 3 6,000,000 flows were the highest on record in 2011 – about 3.2 5,000,000 times the historical mean flow.