Kloot if you need to run a gravity siphon from the larger stream the most cost effective pipe would be 2" schedule 40 plastic pipe, it's less than 4 bucks for each 10ft length and they glue together great.
My 2" pipe runs 300ft from above a waterfall down to the pond with a vertical drop of about 12ft., the outflow is 60gpm.
The gravity siphon would probably work year round in your climate and even if it occasionally froze it wouldn't be for long.
