Flows in Portage Diversion rising

The Environment Canada gauge at the Portage Diversion is now up and running. Flows in the Diversion have risen sharply over the last day from about 1,225 cfs to 3,150 cfs this afternoon, and appear poised to rise further. If that happens, and the opening is prolonged, we will start to see measurable effects on the lake level.

The combined inflows to the lake from the Waterhen (4,377 cfs), and Whitemud Rivers (525 cfs) and the  Portage Diversion (3,150) now exceed (8,052 cfs) the current outflows at Fairford (7,978 cfs).

The current level of Lake Manitoba is 812.96 feet. Needless to say, there is no room in Lake Manitoba to store Assiniboine River water.

Scott Forbes

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Lake Manitoba flood update: March 29, 2015

The Portage Diversion was opened this week by MIT to restrict flows on the lower Assiniboine to under 5,000 cfs while the ice clears. The gauge on the Diversion is not yet operational so we don’t have exact data on flows, but they are low. With flows on the Assiniboine peaking at around 7,000 cfs, flows in the Diversion should remain below 2,000 cfs. At that rate, it would cause a rise in the level of Lake Manitoba of about 1/3 of an inch in a week.

The level of Lake Manitoba is beginning to rise as the snowmelt reaches the lake. This is as expected as the lake normally rises during the spring freshet. The lake this morning is sitting at 812.95 feet, 0.03 feet above last week’s level. MIT forecasts that the lake will rise to between 813.08 and 813.18 feet this spring, or about 2 to 4 inches above its current level. This is a below average rise in lake level during the spring freshet: the normal rise is 6 to 18 inches. This is good news for us.

Last year on this day, the level of Lake Manitoba was 811.88 feet, more than a foot below its current level. On March 29, 2011, the level of Lake Manitoba was 812.79 feet, or about 0.15 feet below its current level.

Flows at Fairford are now 7,978 cfs. At the current lake level if Fairford were wide open, flows would be about 10,500 cfs.

With restricted outflows at Fairford, the level of Lake St. Martin is now falling quickly currently sitting at 801.49 feet. This is 3/10ths of a foot below last week’s level.

Waterhen flows have risen to 3,848 cfs and will rise to somewhere between 7,000 and 7,500 cfs when the ice is gone, depending on the level of Lake Winnipegosis. Whitemud flows have fallen to 353 cfs.

Spring is early on the Assiniboine. The flow at Holland is now just under 7,000 cfs. It peaked at just over 7,000 cfs on March 26th. If flows remain at or below this level, there will be no need to keep the Portage Diversion open after the ice has cleared on the lower Assiniboine.

Last year on this day, the Assiniboine flow at Holland was 971 cfs; in 2011 it was 2,969 cfs. The median flow for the Assiniboine at Holland on March 29th is 1,200 cfs.

River update
Time: 10:00 AM March 29
Portage Diversion: open – no data on flow
Assiniboine at Holland: 6,989 cfs
Waterhen: 3,848 cfs
Whitemud: 353 cfs
Fairford: 7,978 cfs
 
Lake update
Time: 10:00 AM March 29
Steep Rock: 813.05 ft
Westbourne: 812.84 ft
Mean level: 812.95 ft

Lake Manitoba Spring Outlook

The province published their spring outlook yesterday. And it looks very good. If we get favourable weather from this point forward, we might be looking at the kind of year we really need, something similar to 2012 when the lake dropped steadily over the summer.

Flows on the Assiniboine are relatively low (about 7,000 cfs) which means once the ice clears, there is no need to use the Portage Diversion. While there is ice, MIT has stated they will restrict flows on the lower Assiniboine to 5,000 cfs, with the surplus headed down the Portage Diversion.

The reports that I have are that the Diversion is currently open but the flow really is a trickle, much less than 1,000 cfs. The Environment Canada gauge at the Diversion has not yet reported any data this year. If this current opening of the Diversion is indeed short term, say 7 to 10 days, and Diversion flows remain at or below 2,000 cfs, then the effect on the lake level will be almost undetectable, less than 1/3 of an inch.

In 2012, the lake was at 813.65 feet on April 1. The Diversion wasn’t opened that year, so the only substantial river inflow was from the Waterhen River and that was higher than it is today, about 8,800 cfs. When the ice clears this year, Waterhen flows will rise to about 7,500 cfs.

Over the summer of 2012, the lake fell to 812.3 feet in September. If we avoid any extreme weather events of the type that require a major opening of the Portage Diversion, we should see the lake fall over the summer. Fairford outflows at the current lake level (812.9 feet) will rise to about 10,500 cfs when the ice clears and MIT (as promised) opens up Fairford to maximum capacity. Depending on rainfall, we could / should see the lake below 812 feet by the end of summer.

My outlook for the summer is cautious optimism. What is unpredictable is the summer weather. If we get another big, slow moving, and rain-laden system as we did last year, the lake could easily rise back to flood level. And with the lake at or near 813 feet, we are still vulnerable to strong windstorms that can easily drive up lake levels four feet or more for short periods of time. But if we get average weather conditions, we will see the lake falling over the summer after perhaps a small rise in the next 4-8 weeks. So we are not out of the woods yet, but can now see the edge of the forest.

Scott Forbes

MIT updates its spring flood outlook

MIT published their March Flood Outlook this afternoon. Below is the lake forecast excerpted from the larger forecast. For Lake Manitoba they forecast only a small rise in the lake from its current level of about 812.9 feet to somewhere between 813.08 and 813.18 feet.

The full media release can be found at:

http://news.gov.mb.ca/news/index.html?item=34470&posted=2015-03-27

Scott Forbes

Lakes

Most of the major lakes including Lakes Manitoba, Winnipegosis and St. Martin have not started to see the effect of the spring run-off.

  • Most of the lakes are expected to be below the flood stage after the spring run-off except Whitewater Lake which is already well above the long-term normal level.
  • Lake Manitoba is expected to peak between 813.08 to 813.18 feet.  This is below the flood stage of 814 ft. but above its upper operating range of 812.5 ft.
  • Lake Winnipegosis is expected to peak between 833.01 to 833.40 ft.
  • Lake St. Martin is currently at 801.6 ft.  The flood stage is 801 ft.  Vulnerable communities are adequately protected at this level.  However, there could be flooding of low-lying agricultural lands between now and mid-July.  By the end of the spring run-off, the lake is expected to peak between 801.29 to 801.44 ft.
  • Dauphin Lake is expected to peak between 855.6 to 856.3 ft, which is below the flood stage of 858 ft.
  • Whitewater Lake is near peak level of 1,633 ft., which is five ft. above the long-term average level.
  • Whiteshell lakes are expected to see minimal rise due to the spring run-off as the potential was normal to below normal.
  • Most of the lakes are still frozen and the effect of wind and ice pileup is currently very low.  This could change once lake ice reduces by 30 per cent and high winds develop.

Portage Diversion is Opening

This afternoon the Province announced they are opening the Portage Diversion.
The text of the Press Release follows – Scott Forbes

March 25, 2015
PROVINCE ADVISES PORTAGE DIVERSION TO OPERATE TO LESSEN IMPACT OF ICE JAMS

Manitoba Infrastructure and Transportation will operate the Portage Diversion to lessen the impact of potential ice jams on the Assiniboine River downstream of Portage la Prairie. This is to maintain a river flow of 5,000 cubic feet per second (cfs). The Assiniboine River is currently rising and the operation of the diversion will reduce potential problems with ice.

The operation of the Portage Diversion for ice management on the lower Assiniboine River will be limited in flow and duration, depending on the flows from upstream. The Assiniboine River flow into the Portage Reservoir is anticipated to increase to 7,200 cfs in the next couple of days.

Ice jams could cause rapid increases of the river level and could impact unprotected areas. The operation is intended to benefit downstream communities and municipalities such as St. François Xavier, Cartier, Headingley and the city of Winnipeg.

The level of Lake Manitoba is 812.9 feet. It is expected diverted flows for this short of a period of time will have a negligible effect on the level of Lake Manitoba.

Flood update: March 22, 2015

The last week has seen rapidly changing conditions as the snowmelt is now reaching the rivers. Lake Manitoba is now poised to begin rising with the spring freshet. How quickly will depend on whether the Portage Diversion is opened by MIT. It remains closed right now.

The level of Lake Manitoba is now sitting at 812.92 feet, 0.02 feet below last week’s level. Last year on this day, the level of Lake Manitoba was 811.92 feet, a foot below its current level. On March 22, 2011, the level of Lake Manitoba was 812.81 feet, or about 1/10th of a foot below its current level.

Flows at Fairford were reduced further this week by MIT to now just 7,784 cfs. With this, the level of Lake St. Martin is now falling quickly, currently siting at 801.79 feet.

Waterhen flows have now reached 3,400 cfs and will rise to about 7,000 cfs when the ice is gone. Whitemud flows have risen to 565 cfs.

Spring has arrived early on the Assiniboine. The flow at Holland rose sharply last week and has now reached 6,000 cfs. MIT starting filling the Portage Reservoir on Wednesday, a step that normally precedes the opening of the Portage Diversion.

Last year on this day, the Assiniboine flow at Holland was 988 cfs. In 2011, the flow on March 22 was 2,960 cfs. The median flow for the Assiniboine at Holland on March 22nd is 950 cfs.

River update
Time: 9:00 AM March 22
Portage Diversion: closed
Assiniboine at Holland: 6,001 cfs
Waterhen: 3,424 cfs
Whitemud: 565 cfs
Fairford: 7,784 cfs
 
Lake update
Time: 9:00 AM March 22
Steep Rock: 812.98 ft
Westbourne: 812.86 ft
Mean level: 812.92 ft
Lake St. Martin: 801.79 ft