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olfishead

Thermocline?

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Does anyone know if the thermocline ever developed this summer?  Maybe the high water and subsequent high releases kept it from forming???

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I ran across this while addressing the thermocline discussion on Table Rock. I checked out the USACE- Kansas City website and found this page (link). This page contains Dissolved Oxygen and Temperature readings taken at the Dam, mid-lake (I'm guessing), and in the upper L Sac Arm near 245 Bridge. As for thermocline formation, they typically form every year in most lakes that aren't shallow.

It appears that the thermocline was starting to form in May. By June, there was definitely a thermocline in the Sac Arm around 26 to 30 ft. range. In the July readings the thermocline was around 20 ft (6m) at the dam and 16 ft (5m) and 13 ft (4m) in the sites up the lake.

I hope this helps.

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Thanks for the link Mojorig.

I use to monitor that information regularly and then in 2016 the website was shutdown. I am glad they have restarted it again.

I looked at those graphs and am afraid I saw no thermocline in any of those 9just my opinion). Usually with a thermocline there is a sudden drop in temperature at the depth of the thermocline. Those graphs generally looked like a slow steady decline in temperature as the depth increases.

 

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Again, Thanks for the link Mojorig.  Interesting that the July 10 readings indicate a thermocline on the upper little Sac at around 21 ft. Not so much from the temperature standpoint but from the D.O. reading. I have a feeling that the flow thru the system caused by the flooding is playing havoc with the thermocline. I image that there are areas of the lake that are more "protected" from the central or main lake flows that the thermocline does exist.  The sudden drop off of D. O. may be partially due to the accumulation of decomposing vegetation washed in by the floods.  All in All its been one crazy summer on the lake (s)!

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You all definitely know this lake better than I do. As for the Upper L Sac reading in July, I converted the depth from meters to feet and converted temperature from Celsius to Fahrenheit. 

I have always been taught that the thermocline is where the temperature changes sharply (I was told 3 to 5 degrees) over a short distance. 

Here is the convert Upper L Sac readings for July 10th. So Olfishhead, you are correct that the thermocline is around 21 ft.

Depth (ft) Temp (°F)
0.98 85.82
3.28 85.82
6.56 85.64
9.84 85.64
13.12 85.46
16.40 84.20
19.69 82.40
22.97 76.82
26.25 74.84
29.53 73.94
32.81 72.32
36.09 69.44
39.37 66.74
42.65 65.30
45.93 63.14
49.21 62.24
52.49 61.34
55.77 60.08
59.06 59.00
62.34 58.46
65.62 57.74
68.90 57.38
72.18 57.02
75.46 56.48
78.74 56.12
82.02 55.40

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you brought up a good point mojorig. I was taught in school at least a 10 degree drop. Around 3 degree drop centigrade. I will do some checking around and see if I can find a "standard" definition.

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I looked at dozens of definitions which all said a depth a which a sudden change in water temperature occurs. Well, that is no help. What is sudden to one person may not seem so for others  BUT I did find this definition in several research journals. It sounds as good as anything to go by. By this definition there would be no clear specific thermocline in many of the values on the MDC data. But that is not much of a change over 3 ft of water distance. I always measure my surface water temperature at the 5' depth mark because the probe is not exposed to too much direct heating and the top ft is often a few degrees warmer than at 5 ft. Does that mean the thermocline is in the top 5 ft. Not even.

The definition I saw the most often was "where the steepest change in water temperature on a temperature/depth graph. More of a common sense approach.

So in hind sight I would say I don't really see that sharp a change in the earlier graphs but I agree with you guys that the July 10th graph does reflect a thermocline round 21'.

https://www.canr.msu.edu/news/the_thermocline_a_summer_phenomenon_in_michigan_inland_lakes

The thermocline is defined as the “depth at which the temperature gradient is steepest during the summer; usually this gradient must be at least 1 degree Celsius per meter of depth” according to the University of Minnesota’s Water on the Web.

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Certainly the thermocline relates directly to temperature change over a short distance of depth.  But more importantly from a fishing standpoint, the oxygen content corresponds directly to how deep the fish can survive for any length of time. In other words, if oxygen is below 3 ppm below the thermocline the fish will not stay there for very long. I have often heard people talk about catching fish below the thermocline but I think that happens only when fish are pursuing prey species and for short periods of time. Keep in mind that larger fish tend to have higher oxygen demands than smaller fish (varies some by species). Also, most freshwater, warm water sportfish species become stressed at anything above 80-82 degrees F.  which usually results in less feeding activity. And, in turn causes them to seek thermal refuge in that thin transitional layer of mixed cool and warm water at the thermocline, only leaving that "comfort zone" for short feeding periods.  For the above reasons, I really don't buy the stories about giant catfish living at 100-200 ft. deep (reports by divers) in Missouri lakes, especially during the summer months. Anyone want to weigh in on that?

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