Water watch: what B.C.'s facing after a warm, wet winter

Crocuses bloom in downtown Vancouver on february 14, 2015
Valentine's Day is greeted with blooming crocuses in downtown Vancouver. Meanwhile, the snow has already vanished from the North Shore mountains. (Photo by Eric Thorkelsson)

Lower-level snowpack is way below normal in many areas across province

Note: This story was updated on May 20, 2015.

No snow on the North Shore mountains. Mount Washington closed to skiing for the season. A record high temperature of 14°C at Vancouver airport a month after Christmas.

What's going on here? And what does it mean to 2015 water levels in B.C., including BC Hydro's reservoirs?

To answer those questions, and to take a deeper dive into the effects of climate change, we sat down in February with BC Hydro meteorologist Tim Ashman, author of a popular in-house weather blog that goes out to more than 1,000 BC Hydro employees.

A member of BC Hydro's hydrology and technical services team, Ashman agreed that it was a weird winter in B.C.  

"It's been unusual in B.C. and in much of Western North America," he said. "It's been warm quite consistently, pretty much all winter, with only a couple exceptions."

What made the winter of 2014-2015 so unusual is just how warm and wet it was compared to other so-called El Nino years. We had one in 2009-2010 during the 2010 Winter Olympics in Vancouver, but that winter was largely dry. Not this time around, because this El Nino year is different.

"All of our storm cycles have been warm," he said. "And that's had a significant effect on our snowpacks. We've had to deal with water runoff instead of storage into the snowpack. At elevations where we're generally storing snow at this time of year, we've seen runoff."

That runoff was significant enough that BC Hydro was forced to spill water at several dams, notably in the Campbell River system. Meanwhile, a rainy October in the north recharged ground water and increased streamflows into BC Hydro's largest reservoir, Williston, in what amounted to an unusual, but welcome, pre-winter influx of water heading into the peak season for electricity demand.

BC Hydro map of snowpack levels in B.C. as of Feb. 1, 2015.
BC Hydro snowpack update for February 1, 2015, shows most snowpacks on Vancouver Island and southwest B.C. well below normal. But BC Hydro's ability to generate hydroelectric power won't likely be much affected in 2015, as snowpack in the interior and the north, in basins that feed reservoirs supplying our largest dams, are in good shape, especially at higher elevations.

Reservoirs and snowpack both 'store' electricity

With more than 95 per cent of BC Hydro's electricity coming from hydroelectric generation, B.C. has a natural advantage in power generation over many other areas of North America. Our reservoirs essentially store power, in the form of water, for use when we need it.

And not all that stored power is in our reservoirs. BC Hydro relies on the snowpack to store water until it melts — often in a process that can take months, depending on the snowpack's elevation as well as spring and summer temperature patterns — to replenish those reservoirs.

It was a good news, bad news scenario for snowpack in 2015. Much of the snowpack in our river basins, especially those in southwestern B.C. and on Vancouver Island, was well below normal. But at higher elevations, especially in the north and in the Interior, we saw snowpacks that were normal or even deeper than normal.

"It's very beneficial that our generation system is so diverse," said Ashman. "We have huge storage with reservoirs in the Interior, and even when we're not getting snow in the lower elevations, we're still storing snow higher up. That will be melting off in the summer.

"With the upper elevation, alpine snowpack, we're expecting streamflows possibly late into the summer."

That adds up to what should be a closer to normal year for streamflows into the basins that feed W.A.C. Bennett, Mica and Revelstoke dams, which supply the vast majority of B.C.'s power.

So what will likely be the greatest impacts from our warm, wet winter?

Water restrictions for those who live in B.C.'s southwest.

"There's a lot of snowpack that would have to be made up to give us a normal water supply year for southwest B.C.." he says. "That could affect municipal water supply, but also BC Hydro reservoir operation, including things like recreation at our reservoirs and flows for fish. Just trying to maintain reservoir levels with less runoff than usual can be a challenge."

Get the latest on water restrictions in Metro Vancouver, Campbell River and the Capital Regional District (Victoria). 

Map showing temperature anomolies in North America from October 2014 to February 2015
Overlay of North America shows temperature anomalies through the first part of BC Hydro's "water year", starting October 2014 through January 2015. Red, followed by orange, then yellow, indicate more extreme anomalies in terms of seasonal temperatures above normal. White reflects seasonal norms, while blues indicate below-average seasonal temperatures.

Big news on climate change is about shorter-term extremes

Ashman says a lot of the dialogue about climate change had been about what the world might be like decades from today. But that dialogue is changing as dramatic anomalies in short-term weather hit hard across the world.

"The focus used to be on one number, the global rate of warming — such as a 1.8-degree temperature increase over so many decades," he says. "That doesn't sound like much, but really it's the extremes on the relative shorter term — weeks to a month, as opposed to years — in one region and not another that are really driving the impacts of climate change."

Ashman gets particularly passionate in explaining a trend climatologists have tracked in recent years, the difference in the pace of "warming" between the northern and southern latitudes. Because northern latitudes are warming faster than southern latitudes, there's less of a difference in temperatures between the two regions. And that appears to be messing with jet streams, and the weather they produce. "Where there's a sharp contrast in temperatures, you end up with a very strong jet stream and storm track, which tends to be zonal — west to east — and that tends to result in storms that move through progressively with fairly normal temperatures," he says. "But when you have less contrast in temperatures between north and south, the jet stream is weaker and meanders more."

As Ashman explains this, he uses his arm to carve in the air a horizontal path with deep undulations: high ridges and low troughs that can produce dramatic, "locked-in", weather anomalies.

"As the jet stream meanders, we get locked into weather for longer periods, whether that's hot and dry — in California, for example — or extremely wet," he says. "Some areas of the globe have seen almost Biblical rains because they've been locked into a storm pattern for a week or two, where seasonally they wouldn't see storms like that."

What will climate change bring to B.C?

So far, B.C. has been immune from the extremes of climate change that are contributing to an ongoing historical drought in California, which suffered through their hottest year and one of the driest on record in 2014 and could face something similar this year.

Ashman sees subtler changes, including the possibility that higher summer temperatures could eventually produce cooling challenges at homes and businesses, in B.C.

"Changes in the amount and timing of seasonal water supply are likely one of the more perceptible ways we will see the effects of climate change in B.C.," says Ashman.

Still wondering what happened to that snow this winter? Take a look at how a man in Summerside, P.E.I. dug a 25-foot tunnel to get to his car.

See what BC Hydro has learned about climate change and B.C. in our Climate change: How BC Hydro is adapting [PDF, 2.83 MB].