Robinson, as your closest Pond Boss neighbor I can sympathize with you. Your problem sounds exactly like mine except on a much larger scale. My pond is full at present, but only because the flow in is so much greater than the flow out. I have springs feeding the pond on the upper end, a solid dam, but water showing up downstream of the pond. Just like you I expect that water is leaving in the old stream bed or going out one side of the pond.
I lost one inch a day all last summer and fall all the while with between 5 and 10 gallons a minute coming in. It got down to just under half full before filling back up. I wanted to drain it to see if we could locate the problem area, but mom-in-law(who funded the project) didn't want to lose any little fishes.
Keep us posted as what hopefully works for you I may end up having to de as well.
