Turning Over

[T-RockJaws]

I have heard a few comments on the lake starting to turn over. I have not seen this in the areas I have been fishing. Can anyone give a status on the Big M to Shell Knob area?

[LouDog]

Not in that area but I can confirm it in some areas around point 12......

[LouDog]

Wow, what a difference a few days makes. I went out of Buttermilk last night and the brown leaf littered water has been replaced by clear green water. Looks like the turnover is over in my area of the lake....

[Phil Lilley]

How can the water be turning? When it turns in the winter, the temperatures are falling on the surface and warm down deep. The colder, heavier water "flips" with the warmer water on the bottom... hot is lighter than cold. Right now, it doesn't make any sense.

But I have a question in to Shane Bush, fisheries for MDC, I am curious to see what he says.

[T-RockJaws]

I would be interested to find out as well. I have always heard that the lake turns over twice per year, once in the winter and once in the spring. In the spring, when it turns over you start to see a lot of debri and stuff coming up from the bottom. I also always thought the term refered to the time when the water temp became warmer on top than on the bottom in the spring and vice versa for in the winter.

Thanks for checking in on this, it is greatly appreciated!

[dtrs5kprs]

How can the water be turning? When it turns in the winter, the temperatures are falling on the surface and warm down deep. The colder, heavier water "flips" with the warmer water on the bottom... hot is lighter than cold. Right now, it doesn't make any sense.

But I have a question in to Shane Bush, fisheries for MDC, I am curious to see what he says.

This has never made sense to me either and I have a B.S. and am just short of a chem minor. But...there used to be an article in the Table Rock visitor's guide that tried to explain the spring flip. Seems like the deeper water would somehow have to warm faster than the surface layer(s) for it to happen in the spring. Not quite sure how that could happen. I'm just not convinced it isn't a run-off issue, wind issue, etc.

Would be great to hear from MDC on it. I did win a bass club bet one time with the visitor's guide story after seeing similar water at Pomme though.

[Phil Lilley]

Shane sent me this. I think it's very helpful for what you're seeing-

I was reading some of the posts on your forum and you may want to include some information about phytoplankton. That's often what gives the water the green or brown appearance and it responds to nutrients just like the algae. Spring is the time for both to grow at their best, so I imagine different parts of the lake have different nutrient loads, which would cause the differences in water clarity (amounts of phytoplankton) and the differing levels of algae (clearer water = more algae, dirtier water = less algae); due to photosynthesis and the depths at which it can occur based on the clarity of the water.

Just some thoughts. Reservoirs are complex systems. The fish are going to move up and spawn regardless of the algae, phytoplankton levels, etc. It may just affect how deep they spawn. It seems like it warms early every year, then cools down, then warms back up. I'm a believer that photoperiodism (daylight length) has just as much of an effect on fish spawning as water temperature, and in some cases like Taneycomo, probably more. It's still early, I bet fishing picks up and stays steady in the next couple weeks. Hopefully we can take advantage of it when it does!

[dtrs5kprs]

An answer that makes sense on "spring turn over" and spawn triggers. Explains why we used to catch nest fish in Iowa about the last 2 weeks of April in mid 50 deg water and also in the tri-lakes in mid 60 deg temps. Put daylight together with the full moon that usually occurs in those same last 2 weeks and off they go regardless.

Maybe water temps are more of a spawn trigger farther south (TX, FL) where warmer temps occur earlier. Might also explain why the fish down there have reputations for being more put off by cooling temps, if they lack what appears to be the stabilizing effect of daylight length by moving up in Feb vs Apr.

Thanks for looking into it Phil. Now does anyone have an answer for why the temp readings are so scattered right now? Just variance due to color?

[OzarkFishman]

Lake Turnover

In simpler terms from Minnesota's DNR website:

The key to this question is how water density varies with water temperature. Water is most dense (heaviest) at 39º F (4º C) and as temperature increases or decreases from 39º F, it becomes increasingly less dense (lighter). In summer and winter, lakes are maintained by climate in what is called a stratified condition. Less dense water is at the surface and more dense water is near the bottom.

During late summer and autumn, air temperatures cool the surface water causing its density to increase. The heavier water sinks, forcing the lighter, less dense water to the surface. This continues until the water temperature at all depths reaches approximately 39º F. Because there is very little difference in density at this stage, the waters are easily mixed by the wind. The sinking action and mixing of the water by the wind results in the exchange of surface and bottom waters which is called "turnover."

During spring, the process reverses itself. This time ice melts, and surface waters warm and sink until the water temperature at all depths reaches approximately 39º F. The sinking combined with wind mixing causes spring "turnover."

This describes the general principle; however, other factors (including climate and lake depth variations) can cause certain lakes to act differently. A more detailed description of the physical characteristics of lakes, including temporal and density interactions, can be found at the Water on the Web site, sponsored by the University of Minnesota - Duluth and funded by the National Science Foundation.

[techo]

Babler told me the same thing about two years ago. Surface water temp is not the temp of the entire water column (of course) and the water temp does not have as much affect on the fish as the amount of daylight.

So spawn is more related to amount of daylight versus water temp. I think that is what he said.