Trout are one of the cheapest fish to buy which is why most just restock trout when needed. Why go to all the work and maybe frustration trying to reproduce trout in your pond? Unless you want the challenge and it will be a challenge. Are you familiar with redds and their structure and function; the natural way most trout spawn? It may be difficult to duplicate redds in your stream. You could easily buy fingerlings pretty low cost and supplimentally stock them into your pond as a put and take fishery.
Your idea of a 1/2 acre pond may be too big to maintain an adequate low temperature from the stream flow. Have you done a flow calculation and thermal study for the stream during low flow when adequate cool water will be needed. Too deep of a pond may be more of a problem than a benefit depending on specific conditions. Annual Leaf inputs may be a problem for the DO budget of the pond.

One easy option would be to buy small lost cost fingerling trout raise them in cages until they are big enough to escape predation of large remaining trout.


aka Pond Doctor & Dr. Perca Read Pond Boss Magazine -
America's Journal of Pond Management