turnover

[gr8buzz]

 Hey!,can anyone tell me what takes place to cause a lake to turn over?Im curious to know how to tell for spring and fall.How long does it last?
Thanks

[rgfixit]

Turnover can sometimes be attributed to sustained winds from a particular direction. On a large body of water like Lake Ontario, the warm surface water is blown off shore and the cold (48 deg) water replaces it in shore. I have seen the inshore water temperature drop from 75 deg to 52 deg in less than 48 hours.

On smaller waters turnover can be dramatic in spring  when the lake is flushed out by thawing snow and rains. It generally renders a  lake unfishable. When the water warms a few degrees and starts to clear,  the fish become very active.  Oxygen levels are high and there's abundant emerging weed growth..

Fall turnover is a slower process. Weeds die as the water temperature drops and sunlight is diminished. Oxygen levels drop and fish become less active until they acclimate to the changes.

There's a couple of Marine Biology students out there...I hope they respond....I could be all wet!

RG

[bubby]

It depends on what region you live in. Most northern temperate lakes are dimictic, meaning they have two mixing stages anually (spring and fall). In the summer, most lakes are stratified. They have different layers of temperatures and oxygen levels from surface to bottom (Epilimnion, medalimnion=thermocline, and hypolinmion).

Once fall comes along the wind and surface temps degrade these layers and eventually mix completely together (fall turnover). Then you you have consistant temps from top to bottom. Once you have ice over, the densest water (4 degrees celsius) will sink to the bottom which is a few above freezing and the warmest water temps during the winter.

When spring comes, warm surface temps and wind melt the ice and begin to circulate the water once again until stratification happens.

Where I live in Maine, fall turnover occured on November 18 this year.

[asphalt_kid]

Well Jack hit the nail on the head on that one.


Big words. Confusing words. But all true.

[bubby]

I guess that class in Limnology finally became resourseful.

[asphalt_kid]

Yes I would say it has.

[rgfixit]

WOW!
40 years of fishing...1 flush....gurgle...gurg le....gurgle

Thanks for the clarification Jack.

RG

[gr8buzz]

Well, thatks for that info.I understand what laketurnover is. Now more-so than ever,however I was wondering for more specifics.Is there a certain temperature  of the water at a certain depth that has to take place?How do I find out more exact when my lake and pond will turnover besides in the spring and in the fall? temp,barometer, any readings i can take to determine this, or am I sposed to just assume when the fish arn't bitin' its cause the waters turning? Or does anyone know a site I can find info like this from?! thnx-

[AJPeacock]

Turnover in the fall as follows:

As water cools in the fall, a natural circulation occurs.  Surface water cools  and sinks, as it is denser than the warmer water below.  This continues until the water is 39degrees.  Water is at its most dense at 39 degrees, at that point, the surface water gets colder than 39 degrees and stays on the surface.  As the water towards the surface gets colder, the layer of 39degree water  sinks to the bottom.  I believe that this point (actually it will occur over a span of time, depending on the wind,  temperature and current) is when the Fall turnover is complete.

Once the Turnover occurs, the entire water column has a near consistent temperature (39 degrees) and the oxygen content is consistent as well.

I always found it interesting that water that is cooler AND
warmer than 39 degrees is lighter than 39 degree water.

Hope this helps.

Don "AJ" Peacock

[Bussman]

AJ said it so well I hate to post this now but it goes into more detail and is in english. Check it out.

http://www.conservation.state.mo.us/fish/ponds/laketurn/

Good luck

George

[gr8buzz]

Thanks everyone very helpfull