Pond Contraptions: What are they, and do they really serve a useful purpose?

[MitchM]

...

As for Mitch's question about my pond, normally with my pumps running I won't see any difference between the top and bottom, and in the winter when the pond is frozen over and no pumps or aerators were going, I have read a difference similar to what you have experienced, little more then a couple deg Celsius, but that was a flipped temperature with about 4 C at the very bottom and around 2 C just under the ice layer. I always run a pump in the winter now so the temps are more consistent now.
However on one occasion in the summer my GFI circuit blew on my pumps and I didn't notice for I'm not sure how long. And I did have a top and bottom thermometer in my pond at the time and saw that 5 deg difference, which was probably a lot less than the temperature difference I experienced in the swimming pool.. And no I didn't measure the layers or get in and swim to see if if felt exactly like the swimming pool, but it was obvious there was some stratification going on.

I wondered if it was during the summer that you registered that temperature difference.
Your pond is surrounded by those high stucco walls, and I'm thinking that the sun's energy was concentrated in your pond area and magnified the effect on your pond's temperature more than usual.

My temperature sensors are accurate to +/- 0.5 celcius, so the temperature difference could have only been 1 degree. One sensor is on the north wall of the pond, so it receives the south sun.
Doesn't really matter, I guess. It's nice to have the sensors to verify, anyways.

.

 

[Mucky_Waters]

Well I'm just reading the definitions you sent, and looking and the graph you posted and comparing it to what I actually experienced. Definition eg: a "temperature gradient in a thermally stratified body of water", That's exactly what I experienced in our swimming pool. Top 1 ft about 80 C <> 2 ft level sharp change in temp <> 3-5 ft much colder water. How does that not match the definition of a thermocline? Please somebody besides Meyers answer this.

 

[Mucky_Waters]

I wondered if it was during the summer that you registered that temperature difference.
Your pond is surrounded by those high stucco walls, and I'm thinking that the sun's energy was concentrated in your pond area and magnified the effect on your pond's temperature more than usual.

My temperature sensors are accurate to +/- 0.5 celcius, so the temperature difference could have only been 1 degree. One sensor is on the north wall of the pond, so it receives the south sun.
Doesn't really matter, I guess. It's nice to have the sensors to verify, anyways.

.

Mitch are you taking those readings with your pump running? The one time I saw that difference was when the pond had been sitting with no pumps running at least for a full day, as I said when the pumps are running the water turns over way too fast for any stratification to occur.

 

[Mike in Vermont]

I think for a true thermocline, the water below should be warmer than the center, colder water.

 

[Meyer Jordan]

Let me add just one more point concerning thermocline formation and depth. The clarity of the water greatly influences the depth of the thermocline. In turbid waters the thermocline depth will be fairly shallow (4 - 6 feet). In clear water the depth of the thermocline will often be 30 feet or more. This is due to radiational heating produced by sunlight.
A Garden pond would need to be have extremely poor water clarity for a thermocline to develop and then the pond would need a depth greater than 4 - 6 feet.
This ends my participation in the discussion of thermoclines. Repeating the same scientific facts repeatedly accomplishes nothing.

Next 'contraption'?

 

[Mucky_Waters]

I think this definition says it best "a layer of water where the temperature gradient is greater than that of the warmer layer above and the colder layer below."
Certainly this is most often applied scientifically to ocean waters and lakes that scientist study all the times for environmental and biological reasons. Probably pretty hard for scientist to get funding to do much in depth studies into thermocline formation in backyard above ground swimming pools that don't have their pumps running, which might have something to do with the lack of scientific papers that can be found on the subject.

 

[MitchM]

Mitch are you taking those readings with your pump running? The one time I saw that difference was when the pond had been sitting with no pumps running at least for a full day, as I said when the pumps are running the water turns over way too fast for any stratification to occur.

No, this is with no pumps running.
With any pumps running, big or small, there has been no temperture difference between the levels.

 

[Mucky_Waters]

A Garden pond would need to be have extremely poor water clarity for a thermocline to develop

Next 'contraption'?

Now you are hitting below the belt. That is obviously a subliminal dig at the cleanliness of my pond?

OK how about Skimmers.
Not really a very "Natural" contraption, and you don't necessarily need them, but they can certainly keep your pond a lot cleaner, especially the surface of the water.


Oh and I'm still open to debate or listening to someone explain to me why the description of water temperature gradients in my swimming pool don't fit with the temperature gradients described in the thermocline definitions link Meyers posted. Anyone??? Meyers keeps accusing me of not listening to scientific fact, I'm reading the exact same info he has and yet the descriptions of the temperature gradients seem the same to me.
Warm top layer, a layer with an abrupt change in temperature, then cold water below with much slower gradient temperature. Is that a description of my swimming pool or what happens in a temperature stratified lake?

 

[Meyer Jordan]

OK how about Skimmers.
Not really a very "Natural" contraption, and you don't necessarily need them, but they can certainly keep your pond a lot cleaner, especially the surface of the water.

Agreed, but even the best skimmer is not 100% efficient. Really, I think that this falls under that 'it depends' category. If your pond is far enough from trees to eliminate leaf litter issues, then a skimmer probably isn't necessary. On the other hand, if your pond is under Oak trees like mine, two (2) skimmers,which is what I have, is not enough. Also if a skimmer is considered to be a pre-filter for the pump then it is certainly justified, for it serves that purpose very well.

 

[MitchM]

...
Oh and I'm still open to debate or listening to someone explain to me why the description of water temperature gradients in my swimming pool don't fit with the temperature gradients described in the thermocline definitions link Meyers posted. Anyone??? Meyers keeps accusing me of not listening to scientific fact, I'm reading the exact same info he has and yet the descriptions of the temperature gradients seem the same to me.
Warm top layer, a layer with an abrupt change in temperature, then cold water below with much slower gradient temperature. Is that a description of my swimming pool or what happens in a temperature stratified lake?

Here's the thing with the thermocline stuff -

Thermocline, epilimnion, metalimnion, hypolimnion, stratification are all terms that deal with how water at different temperatures behaves.
Add in geographical differences, weather differences and throw in some man made aeration with some fish kills for drama and for me it's a lot of work to pinpoint how and why something changed.
I'm not comfortable trying to identify the correct terminology for what is happening in my pond regarding water density and temperature. I'm happy just observing for now.
I'm more interested in somehow monitoring the oxygen level, because that's what is more important, imo.
I'm just now comfortable with the math around pond heat loss.

Stir up some bottom layer detritus, mix it with some cold low oxygen water, have some fish that will be sluggish because of the cold water and you have the conditions for a fish kill.

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[Mucky_Waters]

Agreed, but even the best skimmer is not 100% efficient. Really, I think that this falls under that 'it depends' category. If your pond is far enough from trees to eliminate leaf litter issues, then a skimmer probably isn't necessary. On the other hand, if your pond is under Oak trees like mine, two (2) skimmers,which is what I have, is not enough. Also if a skimmer is considered to be a pre-filter for the pump then it is certainly justified, for it serves that purpose very well.

Agreed. My pond skimmer also serves as a mechanical pre-filter for one of my pump. Without it that pump would likely be getting plugged up fairly often.
Of course there are also skimmers that have their whole pond filtrations and pumps built right into them and they rely on nothing else.
But I must add that any pond I've ever seen in person without a skimmer, where there wasn't someone manually scooping up stuff off the surface of the pond all the time, always had a lot of stuff floating around on the surface or against the shoreline somewhere, be it bubbles, foam scum or leaves. And in the case of the stuff against the shoreline this often leads to extra algae growth in those areas. So I believe their greatest value is one of cosmetics.
Of course I'm looking at it from the point of view of having another pond contraption (a bottom drain) that would eventually catch leaves and stuff after they sink. without a bottom drain or skimmer you stand to get a lot more accumulated debris in your pond that could eventually greatly increase your DOC levels.

 

[Mucky_Waters]

Here's the thing with the thermocline stuff -

Thermocline, epilimnion, metalimnion, hypolimnion, stratification are all terms that deal with how water at different temperatures behaves.
Add in geographical differences, weather differences and throw in some man made aeration with some fish kills for drama and for me it's a lot of work to pinpoint how and why something changed.
I'm not comfortable trying to identify the correct terminology for what is happening in my pond regarding water density and temperature. I'm happy just observing for now.
I'm more interested in somehow monitoring the oxygen level, because that's what is more important, imo.
I'm just now comfortable with the math around pond heat loss.

Stir up some bottom layer detritus, mix it with some cold low oxygen water, have some fish that will be sluggish because of the cold water and you have the conditions for a fish kill.

.

Like you said in another thread Mitch, it would be nice to have an dissolved oxygen sensor you could drop in to your pond and take readings at different times and different levels. That would be interesting contraption to have.

 

[MitchM]

...Oh and I'm still open to debate or listening to someone explain to me why the description of water temperature gradients in my swimming pool don't fit with the temperature gradients described in the thermocline definitions link Meyers posted. Anyone??? ...

A bit more on this -
My understanding of the causes of thermoclines is heating from an external source. The top layer of water is heated and mixes with lower layers.
It sounds like it shouldn't matter whether the cause of the heating is from the sun's radiation or an external radiant heat source.

 

[MitchM]

Like you said in another thread Mitch, it would be nice to have an dissolved oxygen sensor you could drop in to your pond and take readings at different times and different levels. That would be interesting contraption to have.

They are available, but they are about $300 and pretty difficult to use in freezing temperatures.

 

[Mike in Vermont]

I don't see scuba gear, life rafts and beer coolers either.

Next May, I am going to buy fish for my lower pond. (Rainbow Trout) I am also going to go diving with them regularly. My goal will be to get them used to me, so I can sit on the bottom and watch them swim around me.