Pond Boss Forums INTRO Questions & Observations Thermocline

At the lake where I fish most often the thermocline on average is about 30-40ft deep. I was wondering, why is it so deep compared to ponds? I know lakes are much more deeper, but I wouldnt think that would have much of a considerable effect. Also I was wondering if there were any type of pond design considerations to deepen the thermocline or prevent it in becoming shallow.

I know many have posted concerns and interests in stocking deep water fish which often times include Walleye, Perch, and Stripers. I just dont understand how a lake that is 50ft deep can be 80% liveable by fish when in a pond during summer it may only be 30%(a 15ft deep pond with a thermo at 4.5 ft.)

Also others have mentioned that a thermocline can be 'felt' when jumping into a pond or lake. Well from experience during summer I have felt this at around 5-6ft deep, however you will never find fish above the 5ft mark, only in deep waters around 20ft. From what I have 'heard' about the thermocline is that this region and up is the only area in which a fish can stay and live for an extended period of time. It just doesnt add up.

Maybe some of you can shed some light into this situation. I did a search but couldnt find anything as detailed as I'd liked.

Chris

We are taught that heat rises. For the most part, that's true, except for special cases with water.
As sun, wind and waves carry energy, in the form of heat, into water, that same heat tries to escape by rising.
Warm water expands, sucks in more heat, and more heat tries to rise.
Late spring, early summer, that heat can only go "down" so far, then it rises.
That's what creates the thermocline.
Look at water as a layer cake. Distinct layers seperate warm layers from the cooler waters below.
The consequences are...warmer water becomes most productive water. Deeper, larger lakes have more surface area, more volume, therefore the warm layer is deeper. The lower layer can't mix with surface air, and becomes stratified away from the rest of the lake. As a result, no contact with air means this water loses its oxygen content. Fish waste, organic matter, beer cans, normal bio byproducts make their way into the lower layer, with little outlet for escape.
So, fish can come into the cold layer, but they can't stay. Some fish head for cover, other species suspend. But, if they go down and stay down, they die.
Water is an amazing substance. It's most dense at 39 degrees, F. Warmer water is less dense, as is colder water. That's why ice floats and steam rises. So, in summer, the upper layer is warmer, but during cold months, the lower layer is warmer, somewhere near 39 degrees.
Great question.

One other thought....pond managers can change the thermocline in smaller ponds, using an aerator. A common reason to install an aerator is to create vertical currents, and mix lower layers of water, to expedite decomposition of pond byproducts and to cleanse water every day, as well as provide extra oxygen.