Most of the heat energy of sunlight is absorbed in the first
few feet on Lake Ouachita's' surface, which heats up during the day, and
cools at night (as heat energy is lost to space by radiation). Waves mix the
water near the surface layer and distribute heat to deeper water, such that
the temperature may be relatively uniform for up to 15 feet or so, depending
on wave strength and the existence of surface turbulence caused by currents.
Below this mixed layer, however, the temperature remains relatively stable
over day/night cycles.
The temperature of Lake Ouachita drops gradually with depth. On Lake Ouachita, water temperatures
tend to settle into horizontal layers of warm water and cold
water that are separated by a moderating layer known as the "thermocline".
The thermocline will
be the most active "feeding zone".
The thermocline varies in depth. often deepest during the summer, and
shallow to nonexistent in the winter.
One result of this stability is that as the summer wears on, there is less
and less oxygen below the thermocline, as the water below the thermocline
never circulates to the surface, and organisms in the water deplete the
available oxygen.
As winter approaches, the temperature of the surface water will drop as nighttime cooling dominates heat transfer.
A point is reached where the density of the cooling surface water becomes greater than the density of the deep water, and overturning begins as the dense surface water moves down under the influence of gravity.
This process is aided by wind or any other process (currents
for example) that agitates the water. This effect brings water to the surface which, although low in oxygen, is higher in nutrients than the
original surface water. This enriching of surface nutrients may produce blooms of phytoplankton, making these areas productive.
As the temperature continues to drop, a new thermocline develops where the densest water sinks to the bottom, and the less dense water rises to the
top. Once this new stratification establishes itself, it lasts until the water warms enough for the 'spring turnover,' which occurs when the surface
water temperature rises. During this transition, a thermal bar may develop.
Waves can occur in the thermocline, causing the depth of the thermocline as
measured at a single location to oscillate. Alternately the waves may be
induced by flow over a raised bottom, producing a thermocline wave which
does not change with time, but varies in depth as one moves into or against
the flow.
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Current lake level
Fish Spawning Temperatures Lake Ouachita.
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