New Pond - Outlet question....

[pilot-werx]

As part of the construction of my new dairy barn, I have constructed a pond that will eventually stocked with rainbow trout. The question I have is in regards to the outlet. Currently, I had the excavazion company use a slab of granite as the overflow control point and then used rip-rap on the outfall. Although it is not apparent, the banks are sloped so no run-off from the surrounding ground can enter. Although it does not show in the pictures, the pond is hydraulically connected to a smaller pool via a 4" pipe. The water that feeds the smaller pools is 100% spring fed and flows at a rate of 7,000 GPD.
My question is, is the outlet sufficient? The pond is 100% clay lined (20' deep) with the top 6' being coated in fabric and rip-rap.

 

[jinman]

I'm not sure I understand your question. Are you saying that no water will enter the overflow besides what comes from the spring-fed pond at a rate of 7,000 GPD? Does neither pond catch overflow from the surrounding ground? If so, your flow equates to a garden hose running at 4-5 gpm for 24 hours a day [7,000 gal / (60 minutes x 24 hours) = 4.86 gpm]. Of course, if you get a 3" rain, you have to figure that amount for the surface of both ponds and add it to the total. A heavy rain might cause a bit of a surge.

 

[Fossil Farm]

The only outlet from the pond is a slab of granite and some riprap?
You have 7,000 gallons of water coming in per day, and in the winter, 7.000 gallons will be going out. probably not much evaporation during the summer either in Maine. Your outlet as it has been constructed will be wet all the time and be a maintenance problem once the pond fills. Since you will have no surface water coming into the pond, I would suggest a 6 inch outlet pipe and use the granite area as the emergency spillway. We never recommend anything less than a 6 inch because a smaller pipe can easily become plugged and is harder to clean out if you are talking much length. You can direct the 6 inch pipe to a suitable outlet site much easier than a grass or riprap spillway that will be always wet. I hope I am reading your post properly. Good luck.