This story is part of our series Water at Risk, which looks at Cape Town's drought and some potential risks to the water supply facing parts of Canada and the Middle East. Read more stories in the series.

Three years of drought mean Cape Town could become the first major city in the world to run out of water. As the countdown to "Day Zero" continues in South Africa, Canadian scientists are warning that some communities here could face their own water crisis in the not-so-distant future.

Cape Town's Day Zero, when the city says it will be forced to shut off the taps and ration water to its four million citizens, was initially expected to come in April. Water conservation efforts have now pushed the date to late August, but the day the taps run dry is still coming unless the region gets some serious precipitation.

The risk that changing weather patterns pose for water supplies is one reason Canadian researcher John Pomeroy is braving frigid winter temperatures to climb a metal observation tower in the shadow of Alberta's Fortress Mountain.

Snow melt from peaks like this one in the Rockies flow to three oceans, the Arctic, Pacific and Atlantic, providing water for tens of millions of people across North America. (Colin Hall/CBC )

Pomeroy and a team of researchers use equipment placed 2,000 metres above sea level in Alberta's Rockies to measure the snowfall and the weather here. Precipitation patterns have been changing along with the general climate in this mountain range, he says.

"We have been getting rain events even in the winter."

Pomeroy, the Canada Research Chair in Water Resources and Climate Change, has been studying the snowpack in this area for nearly 15 years in an attempt to predict both floods and droughts before they happen.

He points out that the snow in the Rockies provides everything from drinking water to irrigation for tens of millions of people across North America.

"The water from this mountain range flow into the Arctic Ocean and the Pacific and the Atlantic, so what happens here matters for the whole continent."

Pomeroy heads the Global Water Futures Program at the University of Saskatchewan that looks at how to mitigate the threats being placed on water resources by climate change. (Erin Collins/CBC)

It is a stark reality that in a country known for its abundance of fresh water, climate scientists are seeing changes in the ways our water flows. And it's a problem, in terms of providing people with water throughout the year.

Last year there was a record amount of snowfall in the Fortress Mountain region, but Pomeroy says he and his research team were surprised when all that snow wasn't enough to prevent a drought on the southern part of the prairies.

Pomeroy says a warming climate means the mountain snowpack is melting faster and earlier. As a result, the water is moving through river basins more quickly than in the past and leaving them parched by the end of summer.

It's a situation that, if prolonged, could lead to the kind of water shortages being seen in Cape Town and parts of California in recent years.

"That kind of extreme water shortage hasn't happened here, but it's not impossible that it can," he says, noting that the shortages facing Cape Town today were once unimaginable.

Shawn Marshall of the University of Calgary's geography department says glaciers will be 80 per cent gone by the end of the century. (Erin Collins/CBC)

Glaciers are also an important part of the equation, and receding ice sheets are affecting annual water cycles in the West.

In the past, melt from glaciers would have helped make up for shortages that arose during dry years on the prairies, getting the arid region through the dog days of summer.

But climate change means that this bank of extra water from glaciers has mostly been spent, and the balance is shrinking quickly.

Shawn Marshall, who studies glaciers at the University of Calgary's geography department, says the giant glaciers of the past are quickly disappearing. "The estimates right now are that about 80 per cent of the ice will be gone by 2100."

Marshall says that as the population grows and the climate continues to warm on Canada's prairies, trouble is brewing. Water shortages are likely the next time a multi-year drought hits Western Canada.

And that's something that may already be underway, according to Marshall.

"It might have started last year, actually. You know, we had the beginnings of a drought last year, and it's just a question of if we get a few more summers in a row like that."

It is a scenario that is far from hypothetical in the town of Milk River, Alta., which relies on the tributary of the same name for its irrigation and drinking water.

The headwaters of the Milk River, which provides water to about 1,600 people in the southern part of the province, are in Montana's Glacier National Park.

The Milk River went dry during the drought of 2000/2001, and some fear that it could happen again. (Terry Clayton)

But with the glaciers there mostly gone, the communities around the Milk River are particularly vulnerable to drought no matter how much snow and rain falls in the area.

In 2001, at the end of a particularly hot, dusty, summer, the Milk River actually ran dry. According to Tim Romanow, executive director of the Milk River Watershed Council Canada, it could happen again.

"Nobody is preparing for a three- to five-year drought," something Romanow says is likely to happen sooner rather than later.

Just last year, farmers in the area were told to stop irrigating their crops after Aug. 3, a move that cost producers as much as $1 million.

Romanow worries that despite heavy snow in the area this winter, another dry summer could be on the way. He says the rest of Canada should pay attention, because climate change means traditional weather models no longer apply.

"We are the canary in the coal mine, because we already had very precarious water security."

Researchers measure the snowpack in the Alberta Rocky Mountains. The snow in the Rockies provides everything from drinking water to irrigation for tens of millions of people across North America. (Erin Collins/CBC)

Back in the Rockies, Pomeroy brushes the snow off an instrument buried under half a metre of snow. Amidst all this snow, it's hard to believe that this part of the world actually gets less annual precipitation than Cape Town.

Pomeroy says that fact makes it all the more important to start preparing for future water shortages in Canada.

"I think Cape Town is a terrible event for that city and for Africa, but it can be a wake-up call for the rest of the developed world that we can have severe water shortages."

Pomeroy hopes Cape Town's experience will push Canadians to do more to prepare for extreme drought, including reducing water use and building up storage capacity to better carry communities through dry years.

"We need to manage our water much more carefully and be ready for these droughts when they hit."

Until then, Pomeroy and his team will keep watching and measuring the snow here, waiting for the inevitable — the day when no matter how much it snows, it won't be enough.

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