Barrie Creeks, Lovers Creek, and Hewitt's Creek Subwatershed Plan

The Barrie Creeks, Lovers Creek and Hewitt’s Creek Subwatershed Plan
2.6.1.3.
Thermal Stability of Lake Simcoe
The thermal stability of the lake is important as it can have significant impacts on the biological
communities within the lake, which in turn can impact the lives of those who rely on the lake as
a resource. The thermal stability of the lake refers to the amount of energy needed for a water
column to mix completely, overcoming the vertical density differences of thermal stratification. In
a system where there is low stability, the lake completely mixes, whereas in a system where
there is high stability there is little to no mixing (remains stratified). In Lake Simcoe, which is a
dimictic lake, the water column is thermally stratified during the ice-free season, and mixes in
the spring and fall. Most winters, it completely freezes over.
To determine if the thermal stability of Lake Simcoe was changing in relation to mean air
temperatures (collected at Environment Canada’s weather station at Shanty Bay), Stainsby et
al. (2011) compared the water column stability of the lake at three locations (main basin,
Kempenfelt Bay, and Cook’s Bay), and the
timing of stratification in the spring and
turnover in the fall occurred over an
approximate 30 year time period (1980-
2008). For the purpose of this subwatershed
plan, the focus will be on Kempenfelt Bay
(and to some extent the main basin) as this
is the area most closely connected to the
subwatersheds within the study area.
Out of the three sampling areas, Kempenfelt
Bay generally has higher thermal stability
due to its deeper depths (max 42m; mean
26m), whereas Cook’s Bay tends to have
lower thermal stability because of its
shallower depths (max 21m; mean 8m) and
consequently smaller volume of water that
needs to mix or stratify (Stainsby et al.,
2011).
The first parameter studied was the
temperature of Kempenfelt Bay during the
ice-free period of the year. Figure 2-37
illustrates the temperature changes in
Kempenfelt Bay from 1980 (a) and 2002 (b)
as well as the stability of the lake. From it we
can see that in comparison to the 1980
graph, in 2002 there is a high degree of red
(warmer temperatures during the ice-free
season) and wider contours (the lake begins
to stratify earlier in the year and mixes later
in the fall, increasing the overall time the lake
remains stratified), all of which correspond
with the recorded higher lake stability (white
line) (Stainsby et al., 2011).
To further support these findings, Figure 2-38
illustrates the timing of the onset of
stratification in Kempenfelt Bay (Figure 2-38a)
Figure 2-37: Seasonal water column
temperature contour in degrees Celsius)
and stability (white line) in Kempenfelt Bay
in 1980 (a) and 2002 (b). Red triangles
show the sampling dates along the x-axis.
Source: Stainsby et al., 2011.
Chapter 2: Study Area: The Barrie Creeks, Lovers Creek and Hewitt’s Creek Subwatersheds 72