Get Outdoors!: What’s going on under the ice in the Okanagan?

Water’s chemistry creates interesting changes in low or freezing temperatures

Ice covering Swan Lake in winter in the North Okanagan. (Roseanne Van Ee)

As valley dwellers, we are aware of our lakes and how they dramatically change from summer’s warm recreational reservoirs to cold, and sometimes frozen, winter expanses.

But how often do we stop to ponder the lakes’ seasons?

I can remember a winter where the temperature dropped so low in November and stayed cold long enough for bays in the south end of Kalamalka Lake to freeze. Bitter winds swept off the snow leaving it as clear as glass. Skating on the ice was eerie; weeds, bubbles and even some fish were suspended in the glassy lake surface. It was fascinating! I wondered what was happening below that winter?

Water temperatures don’t fluctuate as rapidly as air temperatures. It’s the water’s chemistry that’s interesting and creates change. Water molecules contract and become denser (tightly packed) as temperatures lower. But at 4 C something unusual happens; water molecules start binding together, expand and become lighter, solid ice by 0 C. They can expand up to nine per cent. That’s why ice floats on the denser liquid water molecules.

Our smaller to mid-size valley and mountain lakes, such as Swan Lake, Otter Lake, Wood Lake and Duck Lake have interesting seasonal water cycles causing temperature layering and “turn overs” of oxygen and nutrients. Once the ice thaws from these lakes, the water temperature is an even 4 C. Winds push the surface water, pushing and stirring oxygen rich surface water to the lake’s bottom. This circulating current then rises plankton and other nutrients up to the top.

In summer, the upper water layer is warmed by the sun. It becomes less dense, floats and doesn’t mix with the lower, colder water. The temperature differences increase causing less mixing of the water. The warm, well-oxygenated surface is a paradise rich in life. This is where the summer action is—the algae blooms, the zooplankton (microscopic animals that feed on phytoplankton) graze and the insects and fish feed.

The lakes colder bottom gets depleted of oxygen from decomposition of lake life waste and by oxygen consumption from its deep water organisms—mostly bottom feeding scavengers. Autumn’s colder nights cool the surface again bringing the water to a uniform 4 C and the breezes result in re-circulation or turn-over, redistributing oxygen throughout.

This is critical as winter’s ice surface cuts off the air-oxygen exchange and reduces oxygen-producing photosynthesis by aquatic plants. Animals such as fish and hibernating frogs, toads and turtles wintering beneath the ice have to survive on the depleted oxygen.

Our larger valley lakes, however, such as Okanagan and Kalamalka Lakes, have massive, well-oxygenated deep water zones and enough water mass to maintain warm rising water through our moderate winters to prevent total freeze over. In past years, though, during long cold spells, certain shallow bays froze up. Stories are recounted of Kelowna and Vernon bays freezing paddlewheelers in solid.

It takes many years for our large lakes to turn over its nutrients.

Loons and grebes leave their smaller lake summer homes to winter on our larger lakes as they need open water to feed and take flight. Watch for them this month as they start to pair up.

Roseanne Van Ee enthusiastically shares her knowledge of the outdoors to help readers experience and enjoy nature. Discover exciting and adventurous natural events, best trails, and wild places. Follow her on Facebook for more.

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Okanagan rinks have mixed results as BC Seniors Curling finals begin

A total of 15 rinks are competing in Vernon for right to go to nationals in Manitoba

Vernon Chamber says 2020 budget lacklustre for small buisnesses

‘There was absolutely nothing meaningful in the budget for entrepreneurs,’ Chamber GM

Vernon paying more at pumps than Central Okanagan

Central Okanagan pump prices fall, North Okanagan lags behind

Dust advisory in effect for Vernon

Keep strenuous exercise away from busy streets, intersections

Vernon reporter’s roots linked to Montreal school fire that killed 17

Vernon and District Family History Society runs open house during Heritage Week

VIDEO: 7 things you need to know about the 2020 B.C. budget

Surplus of $227 million with big spending on infrastructure and capital projects

Trees Cannabis director fined $1.5M for selling marijuana

Fine follows provincial crackdown on popular dispensary

World Cup skier from Okanagan dies suddenly at 19

Kuroda, who made his World Cup debut earlier this year, passed away suddenly Monday night.

Coastal GasLink pipeline investor committed to closing deal despite protests

Developer TC Energy Corp. — formerly TransCanada Corp. — is to remain the operator of the $6.6-billion pipeline

New highway proposed between Alberta and B.C.

The route would connect Red Deer to Kamloops

What’s in a name? The story of Revelstoke’s Mt. Begbie

It’s likely the iconic peak had several Indigenous peoples’ names before settlers arrived

Budget 2020: B.C. Liberals blast ‘Netflix tax,’ lack of economic plan

ICBC rates still go up, except in election year, Shirley Bond says

Teen snowmobiler from Kelowna found after air force’s overnight search

The teen had been missing since just after 6 p.m. on Monday

Town of Osoyoos voices support for proposed casino

Osoyoos council voted to submit a letter of support for a proposed casino on OIB land

Most Read