Canada: Water deficits in Ontario and Quebec

October 26, 2016

The Big Picture
The outlook for Canada through June 2017 (below) indicates exceptional water deficits (greater than 40 years) across central Quebec, and pockets of exceptional deficits in eastern Ontario, northern Manitoba, central Alberta, and northern British Columbia. Deficits of lesser severity are forecast across the Prairie Provinces.

Impacts
Parts of Nova Scotia and Newfoundland received record rainfall in mid-October, due to remnants of Tropical Storm Matthew. Sydney, NS recorded 228.2 mm ( nearly 9 inches) of rain in 24 hours, well above the entire monthly October average of 146 mm (5.7 inches). Streets were flooded or blocked by debris and 1,000 homes were damaged in Sydney; 170,000 homes across the province of Cape Breton lost power due to downed lines. The Nova Scotia government announced CAD$500,000 (USD$373,873) in emergency aid, and requested federal assistance under the national disaster relief program with a preliminary estimate of damages at CAD$10 million (~USD$7.5 million). Nova Scotia has been in a severe drought, and with the dry conditions much of the deluge could be lost to surface runoff and is not expected to significantly benefit the water table.

The summer drought in Ontario has had one surprising effect this fall - apple orchards are producing incredibly sweet, if small apples this season. The hot, dry summer in the Ottawa Valley resulted in significantly higher sugar content in the fruit, and "weird, wonderful" new flavors in the cider.

Forecast Breakdown
The 3-month maps (below) show the evolving conditions in more detail. As seen in the October through December map, areas of exceptional deficits are expected to shrink in the next three months as compared to prior months though a vast area will persist in central Quebec and across the border into eastern Ontario. Mostly moderate (5 to 10 years) deficits are forecast to persist in Southern Ontario near London, growing severe (10 to 20 years) near Toronto and extreme (20 to 40 years) to exceptional (beyond 40 years) near Ottawa. Severe to exceptional deficits are also forecast from Montreal to Quebec City; between the St. Lawrence River and Sherbrooke, Quebec; and southern Nova Scotia.

Moderate to extreme surpluses are forecast in the southwestern corner of Northern Ontario from Kenora north, which may persist through March. Moderate to exceptional surpluses are expected to emerge from October through December in southern British Columbia; in the Columbia Mountains; farther north along the central border of BC and Alberta near Grande Prairie, Alberta; and in the Williston Lake area of BC. Surpluses in BC are also expected to persist through March.

The forecast for January through March looks much like the forecast for October through December with a few exceptions. From January through March deficits in Southern Ontario and along the St. Lawrence River are expected to diminish considerably in both extent and severity, and conditions in Nova Scotia will return to normal.

By April the extent of exceptional deficits in Quebec is forecast to shrink to a pocket in Nord-du-Québec; conditions in the southwestern corner of Northern Ontario will transition from surplus to nearly normal; and surpluses are expected to emerge in the northern reaches of the Coast Mountains in British Columbia.

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