Lake turnover

[kybass8]

How does the turn over of a lake affect the fishing . just woudering how fish react if the go shallow or deep or stay with the thermocline. thanks

[condusivecranker]

Turnover causes the oxygen and temperature levels throughout the water colum to be equal throughout. After turnover, themoclines are non-existant, they are a summer phenomenoa. For example, during the summer, from 0-15 feet, the tempuratures and oxygen levels are pretty constant, and from 15 feet deeper, the temperature and oxygen levels are much much lower. After turnover, all levels in the water colum have virtually the same temperature and oxygen levels. Therefore, fish can survive at any depth in the lake during this time and are, thus, very scattered. Turnover is generally a stressful time for fish and their metabolisms generally shut down during turnover, and coupled with the scattering, makes fish very hard to catch. About 1-2 weeks after the turnover and after the lake settles, the fish will generally move into a fall feeding frenzy chasing shad.
So therefore, forgettabout fishing during turnover. If you have to do, fish slowly and fish a lot of water. Just wait for a week after and watch for groups of shad....

[Todd2]

So what temp range does this turnover usually occur. Has it already happened around here? Thanks

[condusivecranker]

From what I understand, turnover has already occured in lakes around the region. It is very easy to see when the turnover has occured, since lakes will turn color from the usual clear blue to a murky, almost coffee state since the mixing of the water generally also stirrs up the sediment on the bottom. The lake will also take on a stagnant, almost sulfur-like smell for a few days. Turnover can occur at any water temperature, it simply depends on how cool the bottom of the water colum is. Generally, the bottom of a average KY corps lake is about 30 ft. deep and is about 58 degrees in summer. Therefore, when the water surface temp is 57.9, turnover will occur.

[stockcars6]

can a lake turn over twice in one fall? i been fishing in lake breshear (760 acre lake in western ky) i fished there about 3 weeks ago after the cold snap, water was brown and had all kinds of particulate suspended at all depths (caught lots of nice fish that day)... went back 2 weeks ago and the water had returned to its deep green color, similar to barkley, and the fishing returned to normal (caught 3 keepers in 6 hrs).... went back last weekend and the lake was brown again (like 3 weeks ago) and the fishing was horrible, no fish in the boat (only 2 decent bites).

so can it happen twice?

was this some kind a phenominon?

water temp has been been dropping like a brick, any relevance?

[Moose1am]

It does get confusing at times. It all depends on the water temperature though out the water column in a lake. Water temperature effects the density or you could say the buoyancy of the water. Yes water is buoyant to some degree. Hot water is more buoyant that cold water. And yes hot water is less dense than cold water. Just like oil and water. Oil being lighter and will float on top of the hot water because it less dense.

Does that make sense?

Now a lake that has a lot of different bays and depths can have turn over in different areas over a period of time.

Also this time of the year the lake water is cooling off or going into a cooling trend. But the lake surface waters can warm back up if it gets warm again. We have had a lot of days where it got cold for a week and then the air temperatures jumped back into the 70's.

Now water has a high specific heat which really just means that it takes longer to cool down and to heat back up that AIR. You could also say that water retains it's heat energy better.

And finally seeing a dirty lake is may not always signal the lake has turned over. Sometimes a rain can dirty or muddy up a lake. Without a long lined temperature probe that you can lower down though the water column to take temperature readings with it's hard to tell what the bottom waters are really doing.

High winds can also help break up a thermocline when the surface water temps drops to near equal the bottom lake temperatures. High winds or River currents can help break up a thermocline on a big reservoir. High winds create waves which in turn can create currents in the lake.

Think of a thermocline in terms of stability. A lake is very stable when it's got hot water on top and colder water on the bottom. Just like a pyramid it's got a heavy base and a lighter top. So to speak.

If you are seeing lots of stuff floating in the water and it's coming from the lake bottom you may have turnover.

I have a YSI Dissolved Oxygen/Temperature Monitor that I use to measure the lakes temperatures from the top to the bottom. Well the probe wire is only 25 ft long so I can't take readings below 25 ft. In some lakes the thermocline I have found to be at 27 ft and I never could find it. I use the data from the Corp of Engineers who used the same type of meter but with a 50 ft long cord on their probe. I need to buy one of them 50 ft probes someday.

Did you observe the turnover occurring in the same area of the lake both times?

Also some deeper lakes may stay colder than a shallower lake. The deep waters may have a lower temperature and the surface waters will have to cool down to that lower temperature before the lake becomes unstable and mixes ... turnover...

Some shallow lakes don't have a thermocline at all and these lakes are always able to mix from top to the bottom.

Water will warm from the top down. It takes a lot of sun energy and time to warm a large body of water. And large bodies of water have to take a long time to cool down.

Small lakes will gain heat and lose heat much faster than larger lakes.

If you smell rotten eggs that can also be a good sign that the lake is turning over right then. Lake that stratify and that are productive (eutrophic type lakes) can have lots of organic matter falling down to the bottom of the lake. When this type of lake stratified and a thermocline develops and there is no mixing of the surface water with the bottom waters the lake's bottom will become depleted of oxygen. Bacteria that live in the lake bottom muck and eat the organic matter and use up oxygen in the process. Since the surface waters have plenty of oxygen above the thermocline the fish will stay up in the surface waters. As the bacteria eat more and more organic matter over the summer they use up all the oxygen in the bottom layers. Sometime other bacteria that don't need oxygen will take over. These anaerobic type bacteria are the ones that produce the H2S gas in the bottom waters. H2S gas is easily detected by the human nose. We can smell it in very small concentrations. And it smells just like rotten eggs. H2S is soluble in water ie it will dissolve in water. But it's trapped in the lake bottom waters due to the stratification of the lake into layers.

Once turn over happens the H2S is free to mix to the surface where it will enter into the air where we fisherman can smell it.

I have drive by some deep strip pits in Oct and Nov and actually smell the H2S while driving near the lake. One road goes though an low lying area that has a deep strip pit on each side of the road. The low laying ground helped to trap and concentrate the H2S gas if there is calm winds. Normally if it's really windy you can't smell the H2S. Hydrogen Sulfide is the name of this H2S gas.

Hope this helps to explain a little bit more about how the lakes turn over.

BTW: A thermocline is where the density and temperature of the water changes quickly. If you detect a rapid decrease in water temperature in a few feet of depth change then you have found the thermocline. I think the temp has to change by so many deg in so many feet vertical distance.

can a lake turn over twice in one fall? i been fishing in lake breshear (760 acre lake in western ky) i fished there about 3 weeks ago after the cold snap, water was brown and had all kinds of particulate suspended at all depths (caught lots of nice fish that day)... went back 2 weeks ago and the water had returned to its deep green color, similar to barkley, and the fishing returned to normal (caught 3 keepers in 6 hrs).... went back last weekend and the lake was brown again (like 3 weeks ago) and the fishing was horrible, no fish in the boat (only 2 decent bites).

so can it happen twice?

was this some kind a phenominon?

water temp has been been dropping like a brick, any relevance?

[stockcars6]

makes sense

there was no smell on the lake(either time it was brown) and it wasn't just parts of the lake, it was the whole thing(granted it is only 760 acres)... i would say there is enough water to produce a thermocline, it maintians 25-35' over most of the lake.

thanks for the input

do you think it actually turned over twice?

[small boat basser]

makes sense

there was no smell on the lake(either time it was brown) and it wasn't just parts of the lake, it was the whole thing(granted it is only 760 acres)... i would say there is enough water to produce a thermocline, it maintians 25-35' over most of the lake.

thanks for the input

do you think it actually turned over twice?

Nope, not likely at all because to turn over twice it would have to restratify. Not going to happen. Two things to keep in mind though. One is that the whole process usually takes weeks to complete. It's not a show up to the lake one day it it turned over overnight. That said, once a section has completed turnover it is very susceptable to full mixing with heavy winds.

The other thought that hasn't been mentioned is related to algae/plankton, or related blooms. As water temps change, certain planktons and algaes die off (clearing water) but others get fired up (stained water). This is referred to as algal succession. That brown particulate colored water you're seeing is very common around here (Indiana) this time of year and is usually attributable to a diatom bloom. These blooms can come and go as water temps cycle through rising and falling temps due to local weather patterns. My guess is that that is what is occuring on your lake.