It all seem sort of strang to me as well. I talked with the NRCS guy and he thinks its just springs near and around the back of the dam. I am not sure I just think it should be filling up more than it is. Of course we have had a drought this summer as well. He said let this new 2 acre pond with the over flow going in this big lake take effect first and see if it make a difference.
The flow into the big lake is around 20 gallons per minute.

Where it seem it's leaking is near the back of the dam in and around the the creek channel. I can go dwon streem about 20 feet from the bottom of the dam and see water flowing. This what leads me to believe there is a leak. I was told by hime that I could try to RE core the whole back area of the dam. Have any of you herd of this?