Yesterday’s Provincial Flood Forecast

The province released its first spring flood update yesterday (February 27). Little direct information was provided about Lake Manitoba other than noting that the current level of Lake Manitoba is above its operating range sitting at 813.1 feet.

But useful information was provided for lake residents. For Lake Manitobans and everyone downstream, the key information is in the forecast for the Assiniboine River. Even with unfavourable weather, the forecast looks reasonably good.

MIT anticipates that under unfavourable weather, we will experience Assiniboine river flows comparable to 2005. In that year, flows exceeded the bank capacity on the lower Assiniboine of roughly 17,000 cfs for only a few days on two separate occasions.

Yesterday, the province did not provide a forecast for Lake Manitoba levels in 2015. However, it is not too difficult to use the information they provided to look at what the spring and summer holds for Lake Manitobans. What happens on Lake Manitoba will be driven by whether the Portage Diversion opens for an extended period or not. If we do experience Assiniboine flows similar to 2005, we can use that as a guide to what to expect this summer.

In 2005, the Portage Diversion opened twice. It first opened in April for 19 days with a peak flow of 17,600 cfs (most days were well below this); and it was opened for a second time in June and July for 46 days, with lower flows peaking at about 10,600 cfs. Most days were well below this.

Most importantly, in 2005 the total flow through the Portage Diversion into Lake Manitoba was roughly 780,000 acre feet. That is enough water to raise the level of Lake Manitoba about 8 inches. Thus, even if we get the unfavourable 2005 conditions, Lake Manitobans are still in relatively good shape: the lake will be unlikely to reach flood level this summer, although it will remain high and above its operating range for an extended period.

The province forecasts that under normal weather conditions, Assiniboine flows will be comparable to 2002. The Portage Diversion did not open that year. And with average or favorable weather conditions, the level of the lake should fall steadily over the summer of 2015. It is too early to make firm projections about lake levels but if the diversion is not opened, or opened only briefly to clear ice on the lower Assiniboine, the level of the lake will be headed down, not up, which is better news than we have had in some time.

For the moment, Lake Manitobans should be cautiously optimistic about 2015, with the proviso always that Mother Nature is capricious and does not always play fair.

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Flood update: February 22, 2015

The level of Lake Manitoba continues to fall slowly, and is now sitting at 813.11 feet, 0.04 feet below last week’s level. Last year on this day, the level of Lake Manitoba was 812.04 feet, more than a foot below its current level. On Feb. 22, 2011, the level of Lake Manitoba was 812.92 feet, or about 2/10ths of a foot below its current level.

Flows at Waterhen and especially Fairford have fallen from last week. The level of Lake St. Martin is slightly higher than last week, sitting at 802.03 feet. Last year it was slightly higher on this day, at 802.11 feet.

I am now using the gauge at Headingly to estimate Assiniboine flow. It has changed little from last week, sitting at 2,227 cfs. Last year on this day, the Assiniboine flow was 1,024 cfs. In 2011, the Assiniboine flow on Feb. 22 was 2,750 cfs, above its level today.

A brief bit of history – in 2011, Assiniboine flows began to rise sharply at the end of the first week of April, which was when the Portage Diversion was opened. By April 16th 2011, flows in the Portage Diversion reached nearly 25,000 cfs. In the following week with flows in the Portage Diversion ranging from 18,000 to 25,000 cfs, Lake Manitoba rose more than 0.05 feet per day (see above: Lake Manitoba fell just 0.04 feet over the last week).

We have roughly six weeks until the beginning of flood season depending on late winter weather. Assiniboine flows are currently high, but upstream conditions are more favourable than in 2011, as winter precipitation has been average to below average in the Assiniboine basin. Going forward, we now have to hope for dry late winter and early spring conditions: Lake Manitoba has no capacity to absorb high inflows from the Portage Diversion without flooding the lake in 2015.

River update
Time: 9:00 AM Feb 22
Portage Diversion: closed
Assiniboine at Headingly: 2,227 cfs
Waterhen: 3,106 cfs
Whitemud: 42 cfs
Fairford: 9,072 cfs
 
Lake update
Time: 9:00 AM Feb 22
Steep Rock: 813.15 ft
Westbourne: 813.07 ft
Mean level: 813.11 ft
Lake St. Martin: 802.03 ft

Flood update: February 15, 2015

The level of Lake Manitoba continues to fall slowly and now sits at 813.15 feet. That is 0.05 feet below last week’s level. One year ago, Lake Manitoba sat more than a foot lower at 812.02 feet. The lake is also higher right now than it was in February of 2011. On Feb 15 2011, Lake Manitoba sat at 812.84 feet, or about 4/10ths of a foot below the current level.

Flows at Waterhen and Fairford have changed little from last week. The level of Lake St. Martin is unchanged from last week, sitting at just over 802 feet. I am now using the gauge at Headingly to estimate Assiniboine flows. They are little changed from last week.

River update
Time: 9:00 AM Feb 15
Portage Diversion: closed
Assiniboine at Headingly: 2,259 cfs
Waterhen: 3,258 cfs
Whitemud: 49 cfs
Fairford: 9,319 cfs  

Lake update
Time: 9:00 AM Feb 15
Steep Rock: 813.20 ft
Westbourne: 813.11 ft
Mean level: 813.15 ft
Lake St. Martin: 802.01 ft

New ALMS Executive

At the last ALMS general meeting, a new executive were elected. They are:

President Jack King
Vice President Scott Greenlay
Past President Don Clarkson
Treasurer Alice Dent
Secretary Destiny Watt
Directors at Large Harry Frederick
Jean Allard
Roger Gillis
Science Advisor Scott Forbes

Flood update: February 8, 2015

This has been a week of very little change. The level of Lake Manitoba continues to inch downward, and is now sitting at 813.20 feet, 0.03 feet below last week’s level. Flows at both Waterhen and Fairford have declined slightly over the last week. Lake St. Martin has risen slightly and is sitting at 802.01 feet.

The gauge on the Assiniboine at Holland stopped reporting flows in early January, so I have switched to the Assiniboine gauge at Headingly to get an estimate of the water coming down the river. The current flow is 2,312 cfs well below flows in late November that exceeded 5,000 cfs. However, 2,300 cfs is still six times the median flow for this time of the year, indicating that there is still a great deal of water in the system.

River update
Time: 10:00 AM Feb 8
Portage Diversion: closed
Assiniboine at Holland: no data
Assiniboine at Headingly: 2,312 cfs
Waterhen: 3,346 cfs
Whitemud: 69 cfs
Fairford: 9,266 cfs
 
Lake update
Time: 10:00 AM Feb 8
Steep Rock: 813.23 ft
Westbourne: 813.17 ft
Mean level: 813.20 ft
Lake St. Martin: 802.01 ft

Flood update: Feb. 1, 2015

The level of Lake Manitoba continues to fall, and is now sitting at 813.23 feet, 0.05 feet below last week’s level. Flows at both Waterhen and Fairford have declined slightly over the last week. Lake St. Martin is now sitting at 801.99 feet.

The gauge on the Assiniboine at Holland is not reporting flows right now.

River update
Time: 10:30 AM Feb 1
Portage Diversion: closed
Assiniboine at Holland: no data
Waterhen: 3,509 cfs
Whitemud: 71 cfs
Fairford: 9,337 cfs
 
Lake update
Time: 10:30 AM Feb 1
Steep Rock: 813.28 ft
Westbourne: 813.17 ft
Mean level: 813.23 ft
Lake St. Martin: 801.99 ft