Here are the places in Canada yes, Canada vulnerable to drought

This story is part of our seriesWaterat Risk,which looks at some of the risks to thewatersupply facing parts of Canada, South Africa and the Middle East.Read morestories in the series.

As conservationists and organizations around the globe markWorld Water Day Thursday, some scientists are warning that Canada is not immune to water shortages and periods of drought.

All regions should prepare for them to some extent, says John Pomeroy, professor of geography and director of the Centre for Hydrology at the University of Saskatchewan.

Predicting drought is difficult because, although we are able to predict changes in temperature relatively well, tracking potential changes in precipitation and weather is more difficult, he said.

Barrie Bonsal, a research scientist with the Water Science and Technology Directorate of Environment Canada, has been working on a Canada-wide study of the likelihood of drought.

The study, which looks at 29 climate change models to the year 2100, forecastshow much moisture different areas of Canada can expect if greenhouse emissions grow unchecked, but alsoif they are successfully reduced.

"Drought is a natural part of our climate. We've had it in the past and will see it in the future," he said.

Faced with global warming, "what we want to know is whether the precipitation changes will be able to offset higher temperatures," he said.

These are the parts of the country most at risk:

Prairie provinces

All three Prairie provinces, stretching from theRocky Mountainsto the shore of Hudson Bay, are vulnerable to drought, says David Price, a scientist for Natural Resources Canada who models climate change outlooks.

Winds over the Pacific Ocean pick up moisture and sweepover British Columbiauntil they hit the Rockies, when the moisturefalls as rain or snow, Price says. A little of the moisture makes it over the mountains, but as summer temperatures rise, the risk of drought across Alberta, Saskatchewan and even Manitoba will grow, he said.

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Southern parts of those provinces are vulnerable to drought, Bonsalagrees, and droughts could become more severe later in the century.Alberta will be particularly vulnerable as glaciers in the Rockiesmelt, ending a formerly reliable source of water.

Pomeroy points to Palliser's Triangle in the southwest Prairies, which stretches from Calgary andRegina to the U.S. border, as a region that could potentially be in trouble.

The name comes from Irish explorer John Palliser, who was tasked in the 1850s with exploring Western Canada for suitable places to settle. He concluded that the region should be avoided because it was too arid.

Pomeroy sayspeople who live in Palliser's Triangle are used to its dryness and have adapted for instance, building farms father apart but prolonged and more severe dry spells would place an even greater strain on water supplies.

South-central British Columbia

British Columbia's Okanagan Valley is one of the driest places in Canada, and agriculture puts pressure on water supplies.

Climate change could mean even hotter summers in the region, making it more vulnerable to drought.

"Most models show it getting drier toward the end of the century," said Bonsal.

British Columbia has been dependent on snowpack to provide moisture through the spring and summer, but it may getmore rain in winter, which would run off the land rather than melting slowly as snow does, Bonsal said.

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Then early springs andhotter summers could mean the moisture dries up more quickly.

The Lower Mainland of B.C. isaccustomed to seeing lots of rain, but with places like the lower Fraser region and Vancouver Island seeing less of it, they'll have to rely more and more on water reservoirs, according to Pomeroy.

However, since those regions don't usually have to rely on reservoirs, he says, the ones they havearen't adequateto offset the lack of rain. In fact, the shortage has prompted water restrictions in the province and instances of hydrological drought, which is when lakes, rivers and ground water supplies are depleted.

Yukon and Northwest Territories

In Yukon and Northwest Territories, there is not a large population to draw on water supplies, nor are summers hot enough to evaporate moisture from the ground, says Price.

That could change with global warming. "The impact of climate change is being felt rapidly in the far North," Price said. "We could see a dry winter followed by a hot summer that would make drought quite possible."

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Bonsalpoints to the earlier springs and longer periods of warmth the North is already experiencing. He predicts not much change in Yukon and N.W.T. to about 2065, but says whether the area is vulnerable will depend on weather in individual seasons.

Ontario and Quebec

Southern parts of Canada's two most populous provincesare mainly protected from drought because of the Great Lakes, which create their own wet weather systems. Climate change models vary in their predictions ofwhether water levels in the Great Lakes will rise or fall as weather patterns change.

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But there still could be a need for water restrictions if demand exceeds supply, Bonsal said.

Northern parts of Ontario and Quebec are less influenced by the Great Lakes, and their forests could be threatened.

"You only need a couple of years of very dry conditions to make those forests tinder-dry," Price said. That means elevated risk of forest fire.

Be ready for dry periods

By contrast, Atlantic Canada and eastern Quebec are predicted to become wetter as the century progresses, under most climate change models.

Pomeroy says Canadian municipalities should be looking at ways to store water and encouraging reduced consumption.

"Every community and province needs a drought plan how they will deal with water shortages to maintain supplies to priority users and how they will apportion water when it runs short," he said.

"We like to think of ourselves as a water-rich nation. That's not quite the case anymore."

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