Couppedeville, my lake, 13 acres when full, has an inverted V drain pipe. The lake side draws from the bottom, and the outlet hits a small dry creek bed behind the dam. It is a 14" pipe.
This has worked well for several reasons. One, if repairs have to be made, which they haven't in 10 years, there's little damage to the dam. Any work needed would be 4-5' above the water line. Two, as fresh water comes in, the vacuum pulls the old deep water out. I too have a tremendous water shed, and only once in the lakes history has it not been able to handle the water volume. And 3rd, I have a riser (4' pipe), that acts as the vacuum break, and I can adjust the water level if need.
All very cheap, and has worked perfectly for me.
