Technical Background - Basin Lake , Lake St Martin, and Lake via Dauphin River

2 Lake Dauphin Winnipeg 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 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 River into Lake Manitoba via the Waterhen River after Waterhen River

Lake passing through 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 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 .

The Waterhen River is the main tributary to Lake Manitoba. It drains about 55,000 km2, or about 70% of the total Lake Manitoba . 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 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 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 3m /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 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. The 2011 runoff volume 4,000,000

3,000,000 eclipsed the 1955 volume by about 20 percent. Runoff volume (dam

2,000,000

1,000,000 The effects of storage in Lake Winnipegosis is evident

0 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 in the cyclic type of response of the Waterhen River Year to wet and dry periods. The period between 1955 and 1964 was dry and subsequently the Waterhen River flows decreased to record low levels. Between 1965 Frequency Curve of Annual Runoff Volume - Waterhen River, 1955-2011 and 1975 there was a 10 year span when outflows 10,000,000 9,000,000 2011 were about average. Flows were more or less in the Measured at Westbourne 8,000,000

) Pearson III distribution 1955 3 3 average range in the mid 1980s, and the late 1990s, 7,000,000 Mean = 2,590,000 dam Standard deviation = 1,480,000 6,000,000 dam3 Skew = 1.31 punctuated by below- average flows in the early 1980s, 5,000,000 2007 early 1990s, and early 2000s. 4,000,000

3,000,000 Annualrunoff volume (dam 2,000,000 In the period leading up to 2011, flows typically were 1,000,000 above average, setting the stage for high antecedent 0 1.05 1.25 2 5 10 20 20010050 1000500 Return period (years) lake levels. In retrospect, the 2011 runoff volume proved to be about a 200-year event. As is evident in the flow pattern after 1955, it is likely that the Waterhen River will continue to contribute above average flows for the next couple of years, even if precipitation is at or below average. Technical Background - Lake Manitoba Basin Lake Manitoba Water Levels

Inflows to Lake Manitoba were the highest on record Lake Manitoba Inflows and Outflows - 2011 1200 for both the Waterhen River and Portage Diversion. Whitemud River inflow Inflow minus outflow over the year amounts 3 1000 Waterhen River inflow to a net water level increase of 0.46 m, Inflows peaked in early June at about 1450 m /s. Portage Diversion inflow assuming evaporation and precipitation Fairford River outflow offset each other /s)

3 800 Outflows through the Fairford Control Structure peaked at 646 m3/s in late July, coincident with peak lake 600 levels, and continued to recede well into 2012. In 2011

Daily discharge (m 400 ambient levels on Lake Manitoba peaked at 249.1 m in 200 late July. Instantaneous peaks due to wind effects were

0 Jan-01 Jan-31 Mar-03 Apr-02 May-03 Jun-02 Jul-03 Aug-02 Sep-02 Oct-02 Nov-02 Dec-02 Jan-02 typically about 0.25 to 0.50 m above the ambient lake Date, 2011 level, and these occurred virtually in every month.

Between January and early April, lake levels were

Lake Manitoba Water Levels - 2011 relatively steady as outflows at Fairford kept pace with 250.00 the winter inflows derived primarily from the Waterhen

249.50 River. In the second week of April, levels began

249.00 to increase rapidly due to rising inflows from the

248.50 Waterhen River, the Whitemud River, and the

Lake level (m) Lake level Portage Diversion. 248.00

Mean daily at Westbourne 247.50 Mean daily at Steeprock Instantaneous peaks at Westbourne Because of persistent high inflows (mostly from the

247.00 Waterhen River) the Fairford Control Structure has Jan-01 Jan-31 Mar-03 Apr-02 May-03 Jun-02 Jul-03 Aug-02 Sep-02 Oct-02 Nov-02 Dec-02 Jan-02 Date, 2011 been kept effectively open from August 2005 until the present. The only exceptions were the winter flow reductions to 140 m3/s to prevent ice-related flooding along the Dauphin River – invoked from November 12, 2007 until February 4, 2008, and again from October 14, 2008 until February 6, 2009. In the fall of 2010 Fairford flows were above 200 3m /s, but Lake Manitoba levels were high, and indications pointed to the potential for flooding in 2011. A decision was made to cut back Fairford flows because if frazil ice blocked the Dauphin River high spring flows would cause extensive flooding on Lake St. Martin. Therefore the flows were cut back in the period from November 15, 2010 to February 11, 2011. Technical Background - Lake Manitoba Basin Effects of Wind: The May 31 Storm

Given the predominantly northwesterly winds that are experienced in the region, there is potential for high wind- related water levels to occur along the southern margins of Lake Manitoba due to both lake setup and wave runup.

Wind and water level data indicates that there is a strong correlation with wind speed in the direction along the lake and water level differences between and Westbourne. Sustained winds of 20 km/hr can produce a water level differential of 0.2 to 0.4 m.

On May 31, severe winds in excess of 100 km/hr from the northwest produced a setup of 0.65 m at Westbourne – Relationship Between Daily Wind Speed and Setup - Lake Manitoba, 2011 raising the lake level there to 249.35 m. The instantaneous 0.60 60.0

0.50 Water level difference 50.0 Wind speed along lake axis peak level at Twin Lakes Beach reached 250.04 m, almost 0.40 40.0 0.30 30.0 1.5 m above the calm lake level. Waves as high as 2.1 m 0.20 20.0

0.10 10.0 were reported against dikes and buildings. Areas around 0.00 0.0 the lake that -0.10 -10.0

-0.20 -20.0 measured at Winnipegmeasured (km/hr) Water level difference level betweenWater Westbourne and Steep Rock (m) Rock Steep and Westbourne Wind speed along axis of lake as as ofWind speed along lake axis were hardest hit -0.30 -30.0 -0.40 -40.0 include the Rural -0.50 -50.0 01-May 01-Jun 02-Jul 02-Aug 02-Sep 03-Oct Date, 2011 Municipalities of St. Laurent, Woodlands, , Lake Manitoba May 31, 2011 Storm Portage La Prairie, 249.40

Maximum wind-related setup is 0.65 m and the 249.20 Steeprock Westbourne First Nation 249.00 communities of 248.80 Lake Manitoba 248.60 Hourly lake level (m) Hourly lake level and Sandy Bay. 248.40

248.20 May 27 May 28 May 29 May 30 May 31 Jun 01 Jun 02 Jun 03 Jun 04 Date, 2011 Technical Background - Lake Manitoba Basin Mitigation Measures: The Emergency Channel

During the summer of 2011 it was recognized that N frazil ice would again become a problem on the Dauphin River over the winter of 2011-12. To alleviate this problem an emergency channel was constructed from the northeast end of Lake St. Martin to the lower Dauphin River (Route L) and put into operation on November 1, 2011. The channel has a capacity of 100 m3/s when Lake St. Martin is at a level of 244.0 m. With the emergency channel in place there was no need for a severe winter flow curtailment at the Fairford Control Structure.

If the emergency channel had not been constructed flows through the Fairford Control Structure would have been reduced over the winter period. Lake level simulation indicate that levels on Lake Manitoba in the summer of 2012 would have been 0.4 metres higher than recorded, and summer levels on Lake St. Martin would have been 0.5 metres higher.

If Fairford had been kept open all winter before the 2011 flood, lake level simulations suggest that the peak level on Lake Manitoba would have been 0.03 m (three centimetres) lower. The emergency channel would have lowered the 2011 Lake St. Martin peak level by 0.5 m. It is apparent that the capacity of the emergency channel is insufficient to provide significant relief in the short term during events like 2011. However, it Ice conditions on the Dauphin River limit winter outflows from may have some positive effects for less severe floods. Lake St. Martin and increase the probability of winter flooding at Analysis to confirm these effects is still ongoing. It the community. may be that in its present configuration the emergency channel can prove to be valuable over the long term if it is used in combination with a relaxed Lake Manitoba water level regime.