William R Bennett Bridge is still floating.

Image Credit: Submitted/Kevin Hamakawa

This is shaping up to be the driest year on record in terms and if this continues, by the end of winter, could set a modern-day low water level record for Okanagan Lake.

That very unlikely event would force a lot of considerations, not least of which is to the only floating bridge in Canada.

In a very worst case scenario, the floating bridge across Okanagan Lake could be stretched to its limit in an effort to stay floating in the water.

“I always do that joke, when I make a public presentation, about how it’s designed to be a floating bridge, not a suspension bridge,” Anna Warwick Sears, executive director of the Okanagan Basin Water Board told iNFOnews.ca.

READ MORE: All drought records for Kelowna, Kamloops set to be broken this year

But the Ministry of Transportation and Infrastructure assured iNFOnews.ca that there really is no cause for alarm.

“Because a portion of the bridge floats, there is a transition from the fixed portion to the floating portion with specialized joints that accommodate the lake fluctuations,” the Ministry said in an email to iNFOnews.ca. “The bridge joints, bearings and shorelines are continuously monitored and adjusted for tension through lake fluctuating periods.”

The difference between maximum and minimum recorded lake levels can be more than 2.5 metres.

There are 24 anchors on the floating section that are tightened as the lake drops.

“The Ministry of Transportation and Infrastructure can’t estimate an exact level, but we do take steps to enhance monitoring of structural components during periods of significantly low and high lake levels,” the email says. “The bridge components have tolerances in place for at least a metre below current levels.”

The current lake level, according to Shoreline Pile Driving, which has been monitoring it daily for more than 40 years, was 341.601 metres above sea level on Dec. 15 (rising 1.5 cm by Dec. 19 with the wetter weather this week.)

So, can the lake drop another metre over the winter where inflows are traditionally quite low?

An undated Government of BC report that looked at lake level data back to at least 1904, puts the all-time low at 341.21 metres above sea level.

READ MORE: Okanagan Lake starting to recover from unusually low water level

That means the lake still has to drop about 40 cm to reach that level and another 60 cm to reach the level where the bridge’s anchor cables may be really stressed.

Which begs the question: with all the talk about ongoing droughts in the Okanagan (interspersed with flood years), is there really anything for the average Okanagan resident to be worried about?

“There are different ways of talking about drought,” Warwick Sears said. “If you have a lack of rainfall but nobody is using it, then is it really a drought?”

The shortage of precipitation is offset to a great degree both by the ability of Okanagan Lake to hold a huge amount of water and by upland reservoirs that ensure the spring runoff is held back so it can be gradually released over the summer.

Those inflows weren’t always as well managed as they are today and, despite some pretty dry years of late, the amount of water running into Okanagan Lake has not come near historic lows.

The lowest inflows were during the three years leading into the Great Depression of the 1930s.

In 1929 only 79.1 cubic megametres of water flowed into Okanagan Lake, followed by 106.7 the next year and 86.7 in 1931.

One cubic megametre equals one quintillion cubic metres (that is, one cubic metre followed by 18 zeros).

Few years on record had less than 200 cubic megametres, including 2003 with 124, 2009 with 141 and 1970 with 131. In contrast, one of the highest inflows was in 1997 with 1,330 cubic megametres.

A lot has changed since the 1930s.

For one thing, the dam to control outflows from Okanagan Lake was built in Penticton in 1953 following the 1948 floods.

Irrigation techniques have also changed from open flumes to pipes, leaving more water to flow in the creeks.

On the other hand, the population of the Valley has climbed to more than 600,000 from about 25,000 back in the 1930s.

That dramatic growth in both population and agriculture in the Okanagan Valley also brought better management of the water system with it.

A perfect example is the Black Mountain Irrigation District, the largest non-municipal water supplier in BC.

It has its roots in the early 1900s. It initially pulled water from creeks but has since built and maintained extensive upper elevation reservoirs, like Belgo, James, Graystoke and Fishhawk lakes.

It channels that water into Mission Creek, which is not only its prime source of water for its 10,000 customers in the Black Mountain and upper Rutland areas of the city, but is also the largest single inflow into Okanagan Lake.

Black Mountain can’t simply suck the creek dry since it provides vital spawning habitat for the landlocked Kokanee salmon along with trout and an increasing number of Sockeye salmon that the Okanagan Nation Alliance is bringing back into the system.

Black Mountain Irrigation District is just one example. There’s lots of upland storage for other communities, like Vernon and Summerland.

The system operates on the expectation that those reservoirs will fill each year. But there are no guarantees.

After all, Warwick Sears pointed out, those dramatically low inflow years from 1929 through 1931 happened before the world was hit by the dramatic climate change happening today.

“There’s definitely conversations about how we may be needing more water if the weather is hotter and drier in the summer,” Warwick Sears said. “Then the farmers need more water for irrigation because the crops need more water under those conditions and you’re not helped out by rain and we are having larger salmon come into the system now with the chinook and the sockeye that are being restored.

“People who are concerned about fish are already taking it seriously because, in streams that are not supported by storage, the flows have been very, very low.”

Some, like Vaseux Creek, dried up totally this past summer.

Still, while the people who manage the water and fish in the Okanagan Lake system are concerned about long-term water supplies in the face of climate change, the reality is that, with a properly managed water supply system, most residents have little to actually be worried about.

“The ironic thing is, how do we get people to care about water supply when we don’t actually want them to have to worry about it?” Warwick Sears said. “We want them to know about it. We want them to care. We want them to understand but we don’t want them to worry. Those two things are kind of at odds with each other.”

In fact, if all those who manage the Okanagan water system are doing their jobs properly, people are left to wonder why so much time, effort and money are being spent on things like the basin-wide water board.

“Somebody once said – this was a newspaper editor in the North Okanagan about 15 years ago – ‘Why are we spending so much money on Eurasian water milfoil control? I've never even seen it in the lake,’ Warwick Sears said. “I called him up and said: ‘Hello. The reason you don’t see it is because we control it.’ He had to write a whole editorial retracting his mean comments.”

If all goes according to plan, she may have to make a call like that again to some future skeptic.

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