Lakes "Turning Over" in the spring....

[Mr.Harry]

I've read about this as much as I can on-line, and still don't feel like I have an adequate understanding of how and when it occurs. The explanations I've read about it seem contrary, in my novice observation, than what I THINK I have experienced first-hand. Anyone properly schooled in this who can layout a definition - the how's, when's and whys to a simpleton? Thanks. I only know it's a time to be avoided as it shuts action DOWN; in my limited experience.

[zwiggles]

I agree it also makes my head spin, but are you referring to when the thermocline sets up, or the times when the lakes are mixing top to bottom?

[lowaccord66]

Hard to explain for sure.  One thing I read is not all lakes develop thermoclines and somtimes the ones that usually do have one setup, womt from one year to the next. I think there was a decent write up on Wikipedia.  Other thing is sometimes you can turn the gain up on the finder and "see" it.

[MikeF-NH]

I'm not a scientist (but I did sleep at a Holiday Inn last night) but here is my understanding of turn over.

The deep lakes stratify during the summer as warm water stays on the surface (warm air and water always rise) and cold water sinks to the bottom. There is a line that separates them called the thermocline (think of it as a border between two countries). For whatever reason bait fish (and thus predators) are attracted to this boarder which is why fishermen target it.

In the fall that warm water on the surface cools at a slower rate that the air but certainly it is a steady decline under eventually that warm water on top is colder than the water sitting on bottom all summer. At the magic point where the water on bottom is warmer than the water on time it all rises at once to the surface as the water previously above the thermocline sinks to the bottom...thus turn over. I've read that since the bottom has many nutrients due to decomposition etc that there is also "smell" that comes with turn over.

Given what I think I know above, we would not have a spring turn over because the water on top is constantly warming and is always warmer than the water on bottom until the following Fall. There is no sinking of surface water due to it being colder than bottom water in the Spring.

[Mr.Harry]

I agree it also makes my head spin, but are you referring to when the thermocline sets up, or the times when the lakes are mixing top to bottom?

it must be when they are  mixing top to bottom. All is good and right and tight once the thermocline has set up. But then, is the water body in a state of constant turn-over until that happens? As the surface water heats to temps above 37 degrees it becomes denser again than the cooler water beneath it, no? And then wants to flip over again, particularly if the winds are high, and if the cooler water beneath has warmed slowly too?

[esox_xtm]

Colder water is more dense, that's what keeps it on the bottom half of the thermocline. The greater the difference in temperature (between surface and below the TC) the harder it is to remix. Things that can impact that are extremely high winds, think tornado and the like. Additionally some bodies that have some current running through will not thermocline. Or, if they're large they may have some deep out of current areas that do while the rest does not.

As far as the "spring turnover", this does happen to some extent in places that get ice cover in the winter. Obviously, unless a lake freezes solid, the water at the top is colder than the water near(er) the bottom. As the ice melts that colder water either warms or, being more dense, drifts to lower levels. The impact on the system is different as the remixing takes place over time whereas a fall turnover can happen in a matter of minutes.

Here in WI late season algae blooms are often mistaken for turnover. If the surface temp is still above 55 its algae. Surface temps at 50 or colder generally indicate that turnover has taken place.

[dickbaker]

   Water is heaviest at 39 degrees.   As freezing ice out water warms to 39 degrees it will slowly sink to the bottom.   How long this process takes and when all the heavy water reaches the bottom ( and might create thermocline)  is beyond me?
Dick

[fishlessman]

as dick said, the water is heaviest at 39 degrees, at 39 degrees it starts to sink. what screws it up in some bigger deeper lakes is wind in the spring, the wind pushes the warm water to the windy side which draws up the cold water on the nonwindy side. if theres no wind at this stage the lake temps flip quickly, if its windy the dreaded 39 degree surface temp can take weeks to flip

[Jethro]

This is an interesting thread. I have nothing else to add.

[Fishermantim]

I think you have a very good understanding of the process (and a good night's sleep in a hotel as well).

The key factors that will affect the turnover would be the size of the body of water, whether or not there are springs and currents, weather conditions such as wind, rain and snow, and the ambient air temperature.

I've never seen the "actual" turnover, but I've come upon waters where it has already happened, and what was normally crystal clear water was cloudy. Not an algae bloom, not a churned up muddy bottom, just cloudy water.

Fortunately the process generally takes little time and the waters usually clear within a day or so.

I was intrigued to learn how the thermocline works, particularly in winter, where the warmest water in the pond/lake is at the bottom and not the top!

Gotta love nature!!!

[fishlessman]

I think you have a very good understanding of the process (and a good night's sleep in a hotel as well).

The key factors that will affect the turnover would be the size of the body of water, whether or not there are springs and currents, weather conditions such as wind, rain and snow, and the ambient air temperature.

I've never seen the "actual" turnover, but I've come upon waters where it has already happened, and what was normally crystal clear water was cloudy. Not an algae bloom, not a churned up muddy bottom, just cloudy water.

Fortunately the process generally takes little time and the waters usually clear within a day or so.

I was intrigued to learn how the thermocline works, particularly in winter, where the warmest water in the pond/lake is at the bottom and not the top!

Gotta love nature!!!

in winni in 100 foot water ive ice fished togue off the bottom full of small bass seeking that warmer water.  proves bass is a bait fish not a sport fish

[meatandmetal]

in winni in 100 foot water ive ice fished togue off the bottom full of small bass seeking that warmer water.  proves bass is a bait fish not a sport fish

I'm sure a few of these bass have had some small togue for an appetizer.  I mean the one in the front not the St Louis guy in the back. 

[Mr.Harry]

I'm sure a few of these bass have had some small togue for an appetizer.  I mean the one in the front not the St Louis guy in the back. 

NICE FREAKING TOAD!

[Mr.Harry]

And they sure as hell grow faster than lakers too...
my heart is owned by smallmouth, after June 1st.