i like putting the valve on the dry side of the dam and have the pipe stubbed out to the deepest part with a stainless inlet screen. usually make the screen out of 1/2" stainless expanded metal. i have done that on both ponds (i don't have a forage pond) and run it in the same trench as the main stand pipe.
Sure makes it easy to drop the pond a foot or 2 for maintenance/weed control.
