happened. On this quiet, mid-week day, at an almost
vacant beach — a motor boat appeared and headed
straight for Elise. It pulled up alongside her and we
could see her being lifted to safety.
Moments later she was returned to
her mother’s arms and all was well.
Tragedy averted and a lesson
learned. For us city folk, it was
a lesson we’ve never forgotten:
Beware the offshore breeze!
The near-tragedy at Gull Lake
was the result of total ignorance.
None of us had ever heard of an
offshore breeze. We were lucky. Since
that time, I’ve learned some other things
about lakes; one was the odd phenomenon
of their ‘turning over.’ It turns out that, in normal
circumstances and in lakes of sufficient depth, the
water at the bottom of a lake trades places with the
water at the top. When? Why? You don’t even have to
grab a life preserver — just read on.
I reme
looking
toward t
and as I’d s
somethi
ami
Lakes Turning Over
Imagine your normal Alberta lake. It’s a hot (okay,
warm because this is Alberta), blue sky summer day.
The heat from the sun increases the temperature of
the surface water. The rays cannot permeate all the
way to the bottom so it’s cooler down there. During
the summer months, the three layers in a lake (my
friend Chad tells me they’re called the epilimnion
or top layer, the thermocline or middle layer, and
the hypolimnion or bottom layer) are kept separate
because of their density differences. (Warm water
is usually less dense than cooler water.) As summer
turns to fall, the surface temperature cools to the
critical temperature of 4 C — when water is at its
maximum density. Insulated from above, the middle
Epilimnio
Thermocl
Hypolimn