CANADA: WATER SURPLUS IN SOUTHERN BC TO INCREASE

25 April 2018

THE BIG PICTURE
The 12-month outlook for Canada through December 2018 (below) indicates water deficits throughout much of the eastern half of the country.

Deficits are expected to be intense in eastern Newfoundland; eastern New Brunswick; western Labrador around Churchill Falls; a large block in Quebec north of the mouth of the St. Lawrence River; southern Quebec near Sherbrooke; central Quebec surrounding Lake Mistassini; along the Quebec/Ontario border; the southeastern and southwestern shores of Hudson Bay; and, north of Lake Winnipeg in Manitoba.

In the West, significant deficits are forecast for central Alberta west of Edmonton, northwestern Alberta, a large pocket in British Columbia surrounding Prince George, and in northwestern BC.

Surplus conditions are expected in a large block of northwestern Saskatchewan around Churchill Lake westward to Fort McMurray, Alberta; and surrounding Kamloops and Kelowna, BC.

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

Several transitions are immediately apparent in the near-term forecast through June: in the West, the emergence of widespread, intense surplus conditions in southeastern British Columbia, particularly surrounding Kamloops and Kelowna; while, in the East a transition from surplus to deficit in northern Quebec and central Ontario. Significant deficit conditions will continue to emerge during this period along the Ontario/Quebec border corridor, increasing in extent. Deficits in eastern New Brunswick will diminish somewhat, and nearby on the Gaspé Peninsula conditions will transition from deficit to modest surplus, becoming exceptional across the St. Lawrence River.

Moving west, deficits in southern Manitoba will upgrade, becoming primarily severe. A large block of deficit in the Upper Athabasca Watershed of central Alberta is forecast to become more intense, reaching exceptional severity; extreme deficits will emerge in the northwestern part of the province. In British Columbia, intense deficits will continue to emerge surrounding Prince George and also in the northwest.

Along with aforementioned surplus conditions in southern BC, moderate to severe surpluses will emerge across the border in southern Alberta, particularly along branches of the Saskatchewan River. Exceptional surplus conditions will continue to emerge from Fort McMurray, Alberta to Churchill Lake, Saskatchewan, and around Fort St. John in the Peace River Region of northeastern BC.

From July through September, deficits will continue to emerge in much of the eastern half of the country but the extent of exceptional deficits along the Ontario/Quebec border corridor will shrink, and deficits elsewhere in Ontario will become primarily moderate. In Canada’s western half, water anomalies – both deficit and surplus – will generally shrink and downgrade. Primarily mild deficits are forecast across the southern portion of the Prairie Provinces. Surpluses in southern BC will diminish considerably, but will remain exceptional around Kelowna.

The forecast for the final three months – October through December – indicates a significant downgrade in deficits nation-wide, leaving conditions ranging from normal to moderate deficit.

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

IMPACTS
Late-season snowfall in the Canadian Prairies has improved dry conditions but not reversed the long-term precipitation deficit some parts of the region have suffered. Extreme drought persists in southern Saskatchewan, though the area affected has receded, and conditions in southern Manitoba are still moderate to severe. Cool temperatures are delaying spring and slowing the spring melt - not a bad development since this will allow a more measured infiltration - but snow accumulations are below what is typical in many areas.

Farther west, southern Alberta entered winter with dry conditions but picked up precipitation in February, March, and into April, leading to above average snowpack in early April: 120 percent in the Bow River Basin through Calgary, 130 percent in the Athabasca River Basin north of Edmonton, and 144 percent in the Oldman River Basin. Longer winter conditions prompted farmers to delay agricultural supply purchases - spending fell 17 percent in February.

Melting of heavy snowpack has already produced flooding in some communities. Authorities ordered evacuations near the town of Drumheller in Alberta as the Red Deer River rose, and in Okanagan, British Columbia, where $1.5 million (US $1.16 million) in federal and provincial funding will support floodplain mapping.

Though rich in water resources, Western Canada is not immune to the risk of water shortages, says John Pomeroy, the Canada Research Chair in Water Resources and Climate Change. Pomeray has been studying snowpack dynamics in the Canadian Rockies for 15 years and has observed changes in conditions that portend poorly for the future. Global warming is affecting the accumulation of snow in the region as well as its persistence into the spring. The prospect that seasonal drought could become a regular event in one of North America’s prime growing regions is "not impossible" Pomeroy emphasizes.

Bigger floods may also be part of Canada’s future. The head of University of Waterloo’s Intact Centre on Climate Adaptation, Dr. Blair Feltmate, warns that the recent past is just a prelude to bigger floods. Over the past five years, a number of Canadian regions have been hit with catastrophic and expensive flooding: Calgary and Toronto in 2013, Burlington in 2014, Southern Alberta in 2013, and Montreal and Quebec in 2017. As climate change advances, says Feltmate, the future holds prospects for worse.

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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