I just had a pond built on my farm. The gentlemen who did the excavation discussed surface vs bottom withdrawal spillway concepts with me when I asked about pond turnover avoidance. He had never installed one but said he didn't mind trying a bottom draw system if I wanted to. He finished levee construction just prior to all of the rains this late fall/winter 2015. I have gone out daily to observe the water level anticipating the flow of water through the 6" spillway pipe for the past two days. It began overnight last night apparently. When I observed the pond late yesterday afternoon, it was nearly to my estimated apex point on the levee (water level about 15 feet). We received a couple more inches of rain overnight. This afternoon when I arrived, the water level had dropped approximately 6 feet. Immediately, I thought the levee had failed in some place. Finding no evidence of this I next thought seepage was occurring in some other way (new pond, still unknowns). Then it occurred to me that perhaps a siphon had occurred when the spilling began through the pipe. The pipe is not vented. This appears to be what occurred. I hate to oversimplify the fix but does tapping into the pond side of the pipe before the apex with a two inch pipe saddled around the six inch pipe sound reasonable?
