The ups and downs of river levels

🕔Apr 07, 2010

When it comes to spectator sports, river-watching in the North has an audience that just might exceed the capacity at BC Place.

Each spring, residents keep a close eye on the banks of rivers like the Bulkley. In recent years, this river has seen dramatic flooding followed by record-low flows. Residents watched the waters recede, then braced themselves for the worst as they rose to record highs, then scratched their heads as the waters again diminished.

Is hydrological drama simply part of the climatic game, or is the region in for more spectacular highs and lows?

“In the last four years the Bulkley River has experienced three significant hydrologic events,” says Bruce McGonigal, formerly the water stewardship officer for Ministry of Environment in Smithers. “Climate change implies erratic weather over the next many generations. This implies not only lower low flows, but also means higher high flows.”

Few will forget the epic three-foot snowfall that occurred in late October, 2006. What many didn’t realize was that, at the same time, the Bulkley River was flowing near an all-time low. The following spring, as the mountains released their unusually deep snowpack, the Bulkley Valley logged the highest recorded freshet in more than 80 years of record-keeping, overflowing its banks as residents scrambled to fill sandbags.

Then, in October 2009, an even lower water discharge than fall 2006 was recorded on the Bulkley and many other rivers in northwest BC. Last fall, the Bulkley was discharging at approximately 30 cubic metres per second, McGonigal says, compared with 37 cubic metres per second in 2006. Normal flow for that time of year is approximately 115 cubic metres per second, he adds.

“Most people really fail to comprehend the consequence of what our society is doing not only to our regional environment, but our global environment. Our societal values really are about the economy, jobs and what is best for the individual,” says McGonigal, pinning the blame directly on human-caused climate change. “A ton of gold has no value if you cannot grow a potato.”

Ocean currents
Jeffrey Anderson is a geoscientist who recently completed his master’s thesis relating climate change events, such as El Nino and La Nina, to landscape responses. He says that while the 2006 epic snowfall—and subsequent stellar ski season—were the result of an El Nino cycle, cooler-than-normal temperatures originating in the Pacific Ocean in 2008 were responsible for creating a La Nina cycle that resulted in higher air pressure and clearer skies last summer.

“In July 2009, the National Ocean Atmosphere Administration released an El Nino advisory. During an El Nino event, warmer-than-normal sea-surface temperatures originate at the equator and migrate up the west coast of North America, eventually residing in the northeast Pacific,” Anderson says. This leads to warm, low-pressure weather systems.

“Such warm weather during late fall 2009 and early winter 2010 was the result of the current El Nino conditions. Warmer-than-usual air temperatures—coupled with inversions producing temperatures above 0ºC in the alpine—have led to melting of snow and reductions in the snowpack. These conditions have contributed to above-average stream flow in January and February this year.”

This all means that, although the region has seen El Nino’s traditionally warmer temps and higher river levels, 2010 isn’t experiencing—so far—El Nino’s usual promise of a big powder season. Unlike 2002 and 2007, the current snowpack in most of BC is below average, and in some places even at an all-time low.

In late February, after two months of mild temperatures and little precipitation, the snowpack was average or slightly below average in the Tsai Creek and Lu Lake areas. Located in the Skeena watershed’s southern region, they are most likely to affect runoff in the Bulkley. Meanwhile, the Shedin Creek and Cedar-Kiteen areas, located north of the Skeena River, had dramatically low snowpacks, both dipping below the lowest ever recorded.

Across the North, the Skeena, Nass and Peace river basins were all below normal. “River stream flow is a very good indicator of all the conditions that go into a climate for an area, so you can gain a lot by analysing stream flow from an area,” says Ministry of Environment forecasting and information manager Bill Kuhnke. He cautions, however, against reaching any hasty conclusions about long-term effects on the landscape from weather cycles. “You can understand what’s been happening to the climate in a lot of different ways, but it’s still something you have to take with a grain of salt. It’s not the only thing that’s going on.”

Kuhnke adds that scientific records on climate and water levels have only been kept for about the last hundred years, making it difficult to draw long-term conclusions about changes in weather patterns.

“Besides the climate change that everybody talks about these days, global warming and such, climate over the last hundred years has fluctuated quite a bit. Back in the 1940s, ’50s and ’60s, particularly, that’s known as a relatively wet period for northwest North America, whereas the period following that—starting in the late ’70s and into the ’80s and early ’90s—was a relatively dry period. We’ve had these several-decade oscillations that you have to keep in mind when it comes to an analysis of climate and stream flow,” he says.

“I don’t think there is good evidence that we are seeing more extreme conditions. Certainly, when people talk about climate change, the scientists are warning us that it looks likely that the climate will be more extreme or have wider fluctuations between dry and wet periods in the future. But, strictly speaking within the last few decades, it’s still pretty hard to make that case definitely.”

Sign of things to come?
Whether current river highs and lows are an anomaly or a sign of things to come is apparently up for debate. For the upcoming season, it still remains to be seen how the rivers’ currently high levels coupled with the snowpack’s significantly low levels will play out during spring runoff. McGonigal cautions not to put away your sandbags just yet. Shallower water can raise the potential for ice jams, increasing chances of early-spring flooding in low-flow years.

“Flood? Don’t know what to say,” adds Anderson. “It would be unusual to have an El Nino and not have, at the very least, really high water. The lack of snowfall is looking unlikely for flooding, but anything can happen.”

Describing El Nino as “the principal component of global weather,” Anderson notes connections between climate, stream flow, forest health, snow responses, and animal migration and mating (such as the moose rut). The potential for greater hydrological highs and lows can mean increased flooding and impacts to developments on floodplains. It can also affect fisheries, with impacts to spawning and rearing grounds. Climate change could affect river water temperatures, stressing both resident and migrating fish and wildlife, McGonigal adds.

Interested river-watchers can keep an eye on the local snowpack here: Also, Environment Canada’s real-time hydrometric data provides current and historic flow levels for rivers across northern BC: