turn over

[x2c]

I have heard statments about the fishing is bad because the lake has turned over, how do you tell if that has happened?

[MOfishmgr]

It really takes an oxygen meter to determine if a lake has turned over. We were doing some water quality work at Blue Springs Lake a couple weeks ago and it had turned over. I imagine most lakes have. Often times you will see a change in the water color, it'll get a little darker, or have an earthy smell. Sometimes you can see rotten leaf debris on the surface of the lake. The affect on fish feeding behavior is short lived. Remember though that once the lake turns over fish can occupy the entire lake. They will get scattered and harder to find. Fall is a great time to crappie fish, the fish will move shallower and really feed heavy to put on weight before winter. I usually take the depth I've been catching them during the summer and cut that in half to find them. I'm hearing reports of fish being caught in 10 - 12 feet of water at Smithville right now. They may only be 4 - 5 feet down in those depths. Good luck.

[vic n]

Great question and great answer! I thought the turnover happened when the temp at the surface was less than the temps at depth....is that a wrong assumption? I guess it obviously is......duh. But isn't there some relationship of upper water to lower water that has to be met? Something like the heavier water at the surface sinking below the lower water (hence the term "turnover"), but what is the exact cause?

[skeeterxs170]

Gee & I received a couple crappy messages saying I didn't know what I was talking about when I said Smithville is showing signs. From now on mums the word on all I know, which isn't much!!!
Tight lines & Good Luck!!!

[ibfestus]

It really takes an oxygen meter to determine if a lake has turned over. We were doing some water quality work at Blue Springs Lake a couple weeks ago and it had turned over.

Rich Zalesty (sp?) had a great article on fall turnover years ago in In Fisherman magazine. I am neither a scientist nor a biologist but you do not need an O2 meter to determine 'turn over." Essentially it is a function of temperature and the O2 levels change when the temperature changes.

Consider this: The ambient temperature at the bottom of a deep lake is somewhere around 54F in the summertime. If, for example, the surface temp is 85F, the temp will slowly drop down to 15-18' and then suddenly drop 10 degrees or more in 2 - 3' feet. This layer of water, (the metalimnion) is where the thermocline is located. The colder and more dense water below this level will loose it's O2 concentrations and the fish will stay above this layer until it breaks up.

In the fall, when the surface water becomes cooler than the water at the metalimnion, it will begin to break up. However the event we call the "turnover" cannot occur until the water near the surface (epilimnion) is more dense (cooler) than the water below it (hypolimnion). and will not be complete until the temperature in the lake gets to 39F. 39.4F is the temperature at which water is at it's most dense state. Below that the water begins to "expand" down to the point where it freezes and floats.

Yes, the "turnover" is in progress but is far from done. just my $.03

Here is a better explanation:

http://www.epa.state.il.us/water/con...tification.pdf

[MOfishmgr]

Complete turnover can occur in just a few hours, especially in the fall. In the spring it may take longer for the mixing to occur. This is evident when oxygen levels in deep water approach those of the upper layer. Turnover has to do with the breakdown of the thermal barrier that separates the two layers. This can occur in the middle of the summer in high wind. We were curious as to whether wind would be enough to accomplish this and braved a very windy summer day on Pony Express Lake and found the lake had mixed in 3 hours of high wind (40+ mph). Oxygen levels were constant from the surface to the bottom in the deepest part of the lake which indicated the upper and lower layers had mixed. Turnover is a short term event, but stratification can last months in the winter and summer. The EPA article is a good reference.

[MOfishmgr]

Oxygen levels at the deepest parts of the lake are the key factor in determining whether a lake is stratified or not. If the lake isn't stratified then oxygen-rich water can mix down to the bottom. What keeps oxygen from reaching the bottom is the temperature barrier. Temperature is the cause of stratification and when the temperatures difference is small, then mixing can take place. The lower layer of the water column doesn't produce oxygen because light isn't penetrating to the depths and allowing microscopic algae to produce oxygen. Oxygen in deeper parts of the lake comes from the surface layer. Stratification is dependent on temperature. The depth a lake stratifies is determined by the clarity of the lake. The deeper light can penetrate, the deeper the stratification. Table Rock may stratify at 40 feet while Smithville will stratify at 14 - 17 most years. A really muddy lake may stratify just a couple feet down. Hope this clears things up a bit.

[crappiedave55]

Thanks for the input,I thought that it turns over only at the 39 degree change.Now I understand how it can change sooner.

[MOfishmgr]

It can be confusing. Took me a while to understand it once I moved to Missouri. Where I grew up in Florida the lakes don't stratify much if at all because they are clear and shallower. It takes a pretty good temperature difference before it stratifies. Wind energy is amazingly powerful on water and the longer the open stretch of water the more effect it has. A 10 mph wind a half mile from the shoreline creates small waves. That same 10 mph wind blowing over 5 miles of open water can create much larger waves. Wave action is much more than surface disturbance. It can create significant currents below the surface as well and that keeps the lake mixed except when great temperature differences occur. Namely middle of summer and deep winter. With last year's mild winter we may not have stratified at all.

[ibfestus]

There are huge differences in the type lake you are dealing with. For example, a man made reservoir like table Rock is a "highland" lake, Smithville is a "lowland" lake, Wappapello is a "flatland," and Lake Mead is a "canyon" lake.

They all stratify differently and the effect of winds are vastly different in different types and then there is what I call the "X" factor, and that would be the presence of current. Some lakes have a current all the time, others have one only when used for flood control.

Some may say this is merely speculation and doesn't translate into results on the water. Here is a tip... try it and you may be surprised. After the water temp gets below 40F, you can catch bass on lowland lakes using crappie jigs where the deep water comes closest to the shallow water (a bluff).

Understanding lake types is very important for anybody that fishes a lot of different lakes.

Again just my $.03