I have a bunch of data on my pond, but it was not collected with just Temp, DO, and air time as the focus. So, it does not really lend itself to good test results (too many changing variables - nature and personally induced) I have monitored water temps and found that running the air during the hot summer days seems to increase the temps while reducing the DO levels. I can't say for sure which is better...high temps/higher DO vs lower temps/lower DO. Decreasing air time certainly decreases DO levels. A very simple test would have to be done with two BOW's side by side, one with circulation and the other stagnant. I wish I had twin ponds, but even neighboring ponds can be different.

I think this type of data collection would be difficult to evaluate given such an ever changing environment (what wbuffetjr was saying).

My theory is that, given the volume of water in a BOW and constantly and thoroughly exposing it to warmer ambient air (as with an aerator)...it will heat up. Smaller BOW's are much more susceptible to a faster temp change.

When no aeration (water turning over actually) is applied, the deeper water stays deep and cools or stays cool being stagnant against the underlying cooler soils. The surface water heats up quite a bit during the day, but remains there on top and cools back off quickly at night time with the cooler temps because it is close to the surface.

The real defining point whether a pond heats up (or cools of in the winter) with aeration lies in the Delta T's (the differnces between the water temps and the surrounding air or soils that can affect the water). Most of our sub-soils are about the same temp regardless of the region (within reason)...most of our ponds (small BOW's) will have similar deep water temps without aeration. This yields a small detla T in general (pomd water temp versus surrounding soil temp). But, depending on climate...the delta T between water temps and ambient air can vary greatly. simply put, common knowledge that warmer areas have more trouble with hot water. Shaded versus non-shaded waters will make a big difference to. Air to water temperature exchanges are known as convection heat transfer while the effects from the sun are radiant in nature. I would think the soil to water transfer would be conduction.

I believe that the delta T between the ambient air during the hot summer months has more of an affect on changing the water's temperature than does the conduction transfer from the surrounding soils. Partly because the air to water interface is immediate (no insulation) whereas the conduction between the soils and water is spread out over several inches of soil that has to all change in temp together to make a noticeable change (the temp gradient is gradual through those inches of soil - it acts like insulation). The Delta T between water temp and soil temp is likely to be higher than that of the ambient air and water surfce, but the heat transfer through the layers of soil could be lower. Throw in the radiant power of the sun along with the convection transfer and the water will heat up...given the proper detla T.

Other contributing factors would be wind action and humidity (I think you mentioned the effects of evaporative cooling in a different thread -somebody did anyhow). The lower the humidity and the more wind action...the more cooling from evaporation. I really can't say how much this effects the pond temps, but it's still a factor.

Just my theory, I'm not trying to convince anyone, but it seems to back up my loose pond readings. Any heat transfer wizards among us that could put some calcs on paper?

Fish on!,
Noel