LAKELSE LAKE CHARACTERISTICS
For most of the year, the water temperature in Lakelse Lake
varies relatively little from top to bottom (±3°C).
During summer, the lake stratifies vertically into three layers
known as the epilimnion (warm, well mixed surface layer), the
thermocline (transition zone), and the hypolimnion (deep,
cold layer). This summer stratification sets up in May but is
often weak, reduced by the effects of wind.
The stratification is strongest in September, with the thermocline located 20-22m below surface.
Wind Affects on Stratification
Generic lake characteristics are shown above and below. Note that for Lakelse Lake, water quality
data indicates that summer epilimnion temperatures are in the range of 17 to 18°C and hypolimnion
temperatures are approximately 10°C.
As the air temperature cools later in fall, the epilimnion cools until it is 4°C (where water is most
dense), and the upper layer sinks to the bottom causing the lake to “turn over”.
In the winter, the lake re-stratifies because the densest water (4°C) stays on the bottom. In the
spring, the temperature and density differences are reduced and wind pushes the lake to “turn over”
again.
Compared to many similar-sized lakes, the tributary inflow to Lakelse Lake is high. As a result, the
average water retention time in the lake is about 60-75 days. However, in some bays and shallow
zones the water is mixed much more slowly.
The characteristics of the Lakelse Lake will factor significantly in any lake discharge design. Although
most of the water in the lake is replenished approximately 5 – 6 times per year, under certain
conditions and in various locations, some water mixes only slowly with the main body of the lake.