Has Big D turned over? I'd guess not, but it must be close...

Don't think so, Friday it was 61.5 degrees. I think it will come soon especially after all this cold rain.

I was at Waptus lake over the weekend, and it was reading 55 everywhere I went out there.

Would someone explain to me what happens when the lake rolls over and the direct result to fishing. Ive heard mixed opinions, but I would like to hear from my fishing MN peers. I understand it has something to do with the thermocline? Hot water goes under it and the cool water comes up bringing baitfish and thus fish? Please Help

heres some good info. on it.
http://www.islandnet.com/~see/weather/elements/turnlakes.htm

Hiya -

Scoot, it might have turned over the weekend. It was awfully murky on Saturday, and it was about at the temp where it generally does turn. Think the wind might have pushed it over the edge. Not always easy to tell though.

SJ - turnover is really an unpredictable deal, with tons of variables - how 'hard' or pronounced the thermocline is, how rapidly water temperatures fall, how high water temps got over the summer...wind and rain, etc.

Basically though, as you probably know, most deeper lakes stratify during the summer. A thermocline - a band of rapidly decreasing water temps - forms, with water above it that gradually increases in temerature as you get closer to the surface. Below the thermocline, the water is relatively uniform in temperature. The thermocline acts almost like a lid on the lake basin. On most lakes, there's little to no oxygen below the thermocline. Since there's no photosynthesis beyond the level of sunlight penetration, there's no oxygen being created, and what is there is used up by the process of decay going on with any organic matter that falls through the thermocline. So below that layer, it's a no oxygen environment, except on lakes that are spring fed.

When the water cools in fall, the surface water cools to a temperature below that of the water underneath it, and sinks, displacing the water below it. When this displacement is fast enough and with enough volume, it breaks up the thermocline and the mixing process can bring up stagnant water from below the thermocline that gets re-oxygenated.

The effects and severity of turnover can really vary. Sometimes, when the process is very gradual, or when there was a weak thermocline to begin with, it's barely noticeable. Other times, often when the process is accelerated by high winds and/or a rapid drop in surface temps, it can pretty profound. The water gets very murky with lots of gunk floating everywhere, and the whole lake can smell bad. I can remember one fall a few years back when I pulled into the public access, opened the door, took one whiff, shut the door and drove off - the turnover smell was overpowering. When there's a rapid turnover, it really seems to put most species of fish off for a few days. But it's pretty temporary.

A long winded explanation that's still probably only part of the story, but that's turnover in a nutshell... Hope that helps.

Cheers,
Rob Kimm