turnover

[ff oldtimer]

Is it turned over yet? It should have with the cold nights this weekend. Anybody know what water temps are?

[Zeke]

I had 62.5 mid week.

[mikesgotone]

What does turnover mean? I'm coming up this weekend, hows the fishing? We usually come up in the spring, which we did this year. had a great trip fishing. its been since I was a kid, that I made it up in the fall. Any tips would be great. We go for whatever action we can find. Oh yeah, and how bout them Bears?

[dmh]

Here is a good explanation of turnover in lakes. It happens twice a year and it is the reason that lakes remain healthy. The bottom water comes to the top and is reoxygenated twice a year. The explanation comes straight off a site on the internet: Answers.com.

"There actually exists a process known as Lake Turnover.
The first, known as lake turnover occurs on many large and/or deep bodies of water. As air temperatures drop so does the water temperature of the upper layers of a body of water. As these upper layers cool they become denser and heavier. Eventually they become cold enough and heavy enough to the point they begin to sink. As this heavy dense layer sinks it displaces the water at the lake bottom forcing the lower layers to the surface. It is the unique properties of the water molecule which causes water to contract down to 40 degrees F and then to begin expanding at 39 degrees F to 32 degrees F that makes this process possible without freezing the lake through."

[DonH]

Does anyone know it there is a definite surface temperature that will indicate when a lake turns over in the fall. I've heard when the surface temp hits 50 degrees, but I wonder if there is anything definite considering how every lake has such different characteristics.

[Randy]

At around 50 degrees the surface water will start to sink down and through the thermocline turning over a lake. I don't think the molecilar structure of water changes from lake to lake (sarcasm) but surface temperature variation will occur from lake to lake based on depth, water clarity and the amount of 98.6 degree fluid put back into the system from fishermen. Since the only thing in our control is the 98.6 degree fluid, please do your best to keep the water temps up so we don't hit turnover on our yearly trip this weekend.

On a more serious note, does anyone have any information on the current water temps? Also, has anyone been up there when the flowage turns over? If so, does it all turn at roughly the same time and do areas like the Beaver Flats (8' deep) turnover at all?

Thanks!

[Hot Runr Guy]

we saw about a 1.5 degree drop from 9/11 until we left on 9/16, it was in the mid-58's last Thursday morning, around the dam/Sportmans Landing area. Even with the addition of some 98.6 degree fluids.
HRG

[ff oldtimer]

Lakes turn over from 52 to 57 degrees from what i've read .Fishing will be poor for a couple 3 days or so after turnover.Only the deeper lake areas with themocline will turn over,but fishing will be tough all around the flowage.

[the other andy]

Not much of the Flowage actually turns over. Usually happens in the upper 50's, which is where we were at as of Sunday.
Beaver flats or 95% of the horseshoe won't turn.

[BlueRanger]

This page has been around for years, and is one of the most thorough explanations of turnover online:

http://www.islandnet.com/~see/weather/elements/turnlakes.htm

This is another good link:

http://dnr.wi.gov/lakes/CLMN/reportsanddata/station.asp?folder=CLMN&stationid=263059

This contains the TFF reports from the Wisconsin Citizen Lake Monitoring Program (you can also look up other lakes around the state here: http://dnr.wi.gov/lakes/CLMN/reportsanddata/index.asp?project=clmn&folder=CLMN). The reports from 2000-2006 include readings from later in the season so you can compare how the temperature and dissolved oxygen profiles change from the summer stratification period to the fall turnover period. Note that the event most people refer to as turnover is really only the beginning of a turnover period when the lake is not thermally stratified and water can mix from the surface to the bottom. It may start in an abrupt and visible way, but it continues until the lake freezes over.

The shallow areas never fully stratify, so if you wanted to think of them as separate bodies of water, it would be just as correct to say that they are in a constant state of turnover throughout the open water season. But they're not disconnected, and as a practical matter, the gases and debris that are brought up from the bottom of the basins are circulated throughout all but the most protected areas by wind and currents. So as oldtimer said, it affects the fishing everywhere.

If you look at the late summer readings from all years, you'll see that temperatures in the bottom layer below the thermocline ranged from about 45-52 degrees, but are typically in the upper end of that range. The amount of wind and current influences how close the upper layer has to get to that before it's able to completely break through the thermocline. That usually translates to surface temperatures in the lower 50s.

As to whether the whole TFF begins turning over at the same time, it depends on how abruptly it cools and how much wind and current are present to mix the water. Some years you'll head out one morning after a particularly cold and/or windy night and find that all of the basins have started turning over violently and the whole lake has turned to pea soup, while other years when the surface water cools in a less extreme manner and there isn't as much wind, you see a more gradual onset. If you look at the 2002 data in the lake monitoring link, you can see a great example of this in the early October readings. Surface temps were at 56 degrees, and it's clear from the dissolved oxygen measurements that the surface layer wasn't circulating all the way to the bottom yet. But the circulation had pushed below the level of the summer thermocline, which suggests that some of the trapped gases and bottom debris may have been reaching the surface. And the shallower basins already may have been fully destratified. Depending on what happened with the weather over the following days, it may have been in full turnover a day or two later, or it could have stayed in this condition for another week or two.

[mikesgotone]

Now I know. just left the tff. Tough weekend fishing. We braved the weather on friday, although travels were limited. We did ok. 2 boats, 3 walleye,5 bass and 8-10 northern. Sat and sun, a little different. We got nearly skunked, but then before dark we got a few bass, one was 19" 4 lbs. also one muskee 30 in. All in all it was fun. It always is.