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.
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
Time: 10:00 AM March 29
Steep Rock: 813.05 ft
Westbourne: 812.84 ft
Mean level: 812.95 ft