Canada: Exceptional water surpluses to emerge in southeastern BC

28 May 2020

THE BIG PICTURE
The 12-month outlook for Canada through January 2021 indicates a forecast of deficits for many regions of Quebec north of the Gouin Reservoir in the Mauricie region of the province. Vast areas of exceptional deficit are forecast west of Lake Mistassini and in a wide path on Quebec’s eastern border.

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Exceptional deficits are also forecast for western Labrador, a column along Ontario’s northeastern border, the southwest corner of Hudson Bay, a belt across central Manitoba north of Lake Winnipeg reaching into Ontario, central Alberta west of Edmonton and the province’s northwest corner.

A large block of extreme to exceptional surplus is forecast surrounding Churchill Lake in northern Saskatchewan leading north well past Lake Athabasca and west past Fort McMurray, Alberta. Moderate to severe surpluses are expected around Fort St. John in northern British Columbia, and exceptional surpluses in the southern Columbia Mountains.

FORECAST BREAKDOWN
The 3-month maps (below) show the evolving conditions in more detail.

The forecast through July for Canada’s most populated areas indicates nearly normal water conditions for Québec City, Montreal, Ottawa, Edmonton, and Calgary; surpluses near Toronto; intense deficits around Winnipeg; and mild deficits near Regina and Saskatoon. Mild deficits are also forecast for Vancouver though deficits will be more intense on Vancouver Island.

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Deficits will shrink and downgrade somewhat in Newfoundland and New Brunswick, though exceptional anomalies are forecast. Moderate deficits will emerge in Nova Scotia. The extent of exceptional deficits in Quebec (QC) will shrink considerably though vast areas will persist along the eastern border and west of Lake Mistassini. Moderate surpluses are forecast in the Gatineau River Watershed north of Ottawa. Deficits will increase in Southern Ontario (ON) but a pocket of moderate surplus will persist west of Toronto. Deficits will emerge north of Lake Superior and will increase in the western half of the province. Surpluses will shrink but persist in the north on Hudson Bay.

In the Prairie Provinces, exceptional deficits will persist in a wide band north of Lake Winnipeg, Manitoba (MB), in the northeast along Hudson Bay, and a small pocket around Winnipeg. Surpluses in northwestern MB will nearly disappear. In Saskatchewan (SK) exceptional deficits will persist in the Upper Assiniboine River region and mild to moderate deficits will emerge in pockets of southern SK. A vast block of intense surplus will persist in northwestern SK reaching across the border past Fort McMurray, Alberta (AB).

Exceptional deficits are forecast to persist in northwestern AB and the Middle Reaches of the Athabasca River Watershed in the center of the province. Surpluses will increase along the central border of AB and British Columbia (BC) in the Peace River region, reaching Fort St. John, BC. Surpluses will increase in southeastern BC and will be exceptional; deficits will shrink on Vancouver Island.

From August through October, deficits will decrease in eastern Canada though vast pockets of intense deficit will persist in eastern QC and west of Lake Mistassini. Conditions in southern QC will normalize. Surpluses west of Toronto will nearly disappear. Normal conditions will return to southern SK and southern AB. Deficits in central and northern AB will shrink somewhat and downgrade. Widespread surpluses are expected to persist in southeastern BC but the extent of exceptional anomalies will shrink. Conditions in southwestern BC will normalize.

The forecast for the final three months – November through January – indicates that deficits will shrink overall, particularly in QC as normal conditions return to much of the province and surpluses emerge in the far north. Southern Ontario will return to normal as well and near-normal conditions are expected in the southern regions of the Prairie Provinces.

(It should be noted that forecast skill declines with longer lead times.)

IMPACTS
Alberta has committed $147 million (US $106.8 million) for flood recovery in the northern part of the province where Fort McMurray was particularly hard-hit. A late-April ice jam reached 23 kilometers in length (14 miles) on the Athabasca River, pushing floodwaters into much of the city’s downtown area and forcing the evacuation of 13,000 people. One death was reported 55 kilometers (34 miles) north in the community of Fort MacKay at the confluence of the Athabasca and MacKay Rivers.

Heavy rainfall in the upper Mill Creek watershed of southern British Columbia pushed debris into the creek’s lower regions, flooding parts of Kelowna in early May. In response to prior flood events on Mill Creek in 2017 and 2018, $55 million (US $40 million) had been earmarked for flood mitigation work scheduled but not yet begun this year.

Quebec has issued a ban on campfires across the province as 240 fires burn fueled by a dry spring. That number is nearly double the seasonal average.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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