I really don't understand why such or similar system isn't often used by forum members. I watched numerous reports here but mostly I found simple spillway with pipe to avoid too much water. Nothing more.
I understand that it costs more but I'm sure it might be useful sometimes. Advantages: 1)drain the pond if you want to clean it; 2)drain the pond to get rid of unnecessary fish, animals and reptiles; 3)raise or lower water level to make better places for fish to spawn roe.
