H Ludi Tyler wrote:
I share Caleb's concerns. A pond in that kind of environment (low rainfall) will be evaporating vast amounts of water. 
I do have some concerns on the math of the amount of water.
However I do think it could be a really cool integration if done well!
My thought would be to do a really large pond with rain water harvesting features, fill it with the Ground source water and harvested water over time and then switch from ground water source to a closed loop with a pond heat exchanger, or pond sourced open loop.