Canada: Water surpluses continue to emerge in southern British Columbia

28 February 2018

THE BIG PICTURE
The 12-month outlook for Canada through October 2018 (below) indicates exceptional water deficit in: southeastern Newfoundland; eastern New Brunswick; western Labrador around Churchill Falls; eastern Quebec at the mouth of the St. Lawrence River near Sept-Îles; southern Quebec near Sherbrooke; central Quebec; along the central Quebec/Ontario border; and on the southeastern and southwestern shores of Hudson Bay.

Severe to extreme deficits are forecast for the Quebec/Ontario border corridor; northwestern Ontario into central Manitoba; central Alberta west of Edmonton, and northwestern Alberta; and large pockets in British Columbia surrounding Prince George and in the northwest. Moderate deficits are forecast in southern Manitoba.

Surpluses are forecast for central Manitoba west of Lake Winnipeg and into Saskatchewan; northwestern Saskatchewan around Churchill Lake westward to Ft. McMurray, Alberta; and near Kelowna, British Columbia.

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

The near-term forecast, February through April, indicates a distribution of water anomalies persisting in a pattern much the same as observed in the prior three months, though with some overall shrinkage of anomalous conditions in the eastern half of the country. One notable difference is the emergence of widespread intense surplus conditions in southern British Columbia from Kamloops past the US border.

From May through July, much of the eastern half of the country will transition to moderate to severe deficit, with exceptional deficits continuing to emerge in eastern Quebec from Sept-Îles northward, in central Quebec west of Lake Mistassini, and along the Quebec/Ontario border near Lake Abitibi. Intense surplus conditions are forecast near the mouth of the St. Lawrence River. Ontario will transition to nearly province-wide deficit. Moderate deficits will diminish in southern Manitoba and will downgrade to merely mild in southeastern Saskatchewan. Deficits in central and northern Alberta and BC will downgrade to primarily moderate. Intense surpluses are forecast to persist in southern BC from Cariboo Mountains Provincial Park down through Kamloops and Kelowna to the US border, but will transition to conditions of both surplus and deficit in southeastern BC. Moderate surplus will emerge in southern Alberta.

The forecast for the final three months – August through October – indicates mild to extreme deficits throughout much of country.

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

IMPACTS
Heavy rain pounded Canada’s east coast in early February. In Nova Scotia, an ice-clogged brook flooded its banks twice when 60 mm (2.36 inches) of rain fell in 24 hours. Sharp temperature declines following the rain froze 23 cars in place within minutes in a flooded parking lot, requiring bulldozers to free the encased vehicles. In Newfoundland, five residences were evacuated by a volunteer fire department due to rain-induced flooding.

A state of emergency was declared in Chatham-Kent, Ontario as warmer temperatures produced melting snow that combined with heavy rainfall to swell the Thames River. Residents brought out kayaks, and emergency responders towed people to safety in rafts. Officials in Brantford, Ontario ordered the evacuation of 5,000 as the Grand River overflowed. One child was reported missing, swept away in floodwaters, and several area roads and bridges were closed.

In the British Columbia Interior, average February snowfall amounts were surpassed by the end of the first week of the month after a single snowstorm dropped 25 cm (9.8 inches).

Snowpack levels are up 135 percent of normal in some parts of British Columbia. Concerned officials have begun monitoring regional lakes in anticipation of spring flooding. Damaging floods can follow February snowpack levels as low as 79 percent of normal - as they did last year in Okanagan - depending on area lake water levels. Officials hope that drawing down lake levels ahead of time can prevent devastating floods.

Around 27,000 residents of BC's South Coast lost power during a storm that brought snow and high winds to the Fraser Valley and Vancouver areas.

Soil moisture levels remain depleted in Saskatchewan, with low rainfall and a winter snow drought providing no boost. Farmers are anticipating lower yields and contemplating a switch from canola to pulses, which require less moisture.

Climate change is amplifying the highly variable climate of Saskatchewan Province, says a University of Regina professor who spoke at the annual Assiniboine River Basin Initiative conference. The increased variability will cause some years to be exceptionally dry, as was 2017 for some communities, and some to be much wetter. Saskatchewan's Environment Minister emphasized that proper management of the province’s wetlands will be key to buffering the region from inter-annual water anomalies.

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