How many GPM is your ground source heat pump going to use? Most of the systems I have seen use very high volume.
I assume that since you are talking about a dump you are using a pump and dump system not a closed loop. Is this system already installed?
I work a lot with condensing boilers
solar thermal systems, and bio mass boilers. I do not install Geo Thermal, but I do get the opportunity to see many systems, so I do have some knowledge about them. However most of my knowledge is based on systems that are not working properly, and pump and dumps that do not have an adaquete recieving well are very common in our area.
My main concern is pulling a high volume of water out of the ground and not replacing in the earth. Are you pulling from an aquifer?
I do think that a keeping a pond as a useful production is a cool way of maximizing the
energy used in pumping the water though.