If you're pond will be fed by a year round spring or a well you could probably build another small pond above the main one you don't need much water if you have lots of shade and relatively cool weather. The water coming into my pond is curently runing at 1 gpm and the temperature is 63 degerees but My pond doesn't hold very many fish.
Good point Lee. The overflow from the smaller trout pond can keep the larger pond topped off and may even keep the temps down during heat waves. If it's not terribly hot my big pond stays about 10 degrees below what it normally would without the trout pond overflow. The effect is especially pronounced once the sun goes down.
