Would there be any downside to pumping the well water directly into a 3/4 or 1 inch pipe to say maybe 1-2 ' off the bottom and then using a venturi type aeration directly into the pipe at the surface ?
This would carry super oxygenated water to the bottom along with the fresh cold water. As stated above it would only work when the fresh water is flowing so maybe pumping sessions of 8-10 hours in the evening.
I could set this up relatively easy by adding about 12' of pipe to my current system but I have nothing in the way of thermo's or tests to document the results.
My main concern would be whether the water output is sufficiently oxygenated. Maybe you could run the output from this pipe into a large bucket, then see if a small trout can survive in the bucket up to 65F? This is probably the best way to test how well it will work in the pond.
These guys seem to have done a lot of work on the subject:
http://leisure.prior-it.co.uk/diy-build-pond-venturi.shtmlWhat temperature does water come out of the faucet at?
Your venturi idea is really interesting, I look forward to reports on how well it works. Even if it requires more electricity than a recirculating hypolimnetic aerator, the reliability and and fixed-cost savings could be well worth it. The equipment for your system could also all be contained in a small shed onshore, with the outflow pipe to the pond buried underground.
Maybe you could rig up some kind of system using the 2HP pump you mentioned, so that you pump water from the pond bottom back through the venturi if the pond bottom is below maybe 65F, and cuts off the pump and turns on the well water hose only when the pond bottom is above 65F? This would prevent you from constantly pumping well water, and might control overflow and introduction of minerals to the pond.
One of the more interesting aspects of a system that pumps water out of, then back into a pond is that it could be used to not only keep the pond cool in summer, but also to aerate and warm the water in winter. It would be neat to do some research into solar water heating systems. With a small enough pond, a solar heating system might be able to make enough of a difference in temperature to impact growth rates.
