Let's think this out. Evaporation is liquid water turning into vapor and moving into the air. Evaporation is increased by 1) increasing water temperature at the air interface (your aeration would mix warm upper and cool lower water levels, lowering the temperature at the surface), 2) increasing the surface area of the interface (the hump of the boil does this so slightly as to be negligeable), 3) moving more air over the interface so that the relative humidity/partial pressure of water vapor in the air at the interface stays low (your aeration moves water to the interface, not air). Did I miss anything?

The biggest increase I can see is that the air going into the airstone/diffuser will come out of the pond pretty saturated with water vapor - but that volume of air is very small compared to all the air over the area of the pond. I think that aeration would increase your evaporation rate too little to notice.

This is the point where if I'me really, really wrong, a true expert will set you straight, make me look foolish (very politely) and we'll both learn how it actually works.


"Live like you'll die tomorrow, but manage your grass like you'll live forever."
-S. M. Stirling
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