Cecil,

My guess is that you are seeing seepage. I don't think you need to be overly concerned about it. I have it also on a 50 plus year old pond. It isn't enough water loss to hurt anything and doesn't seem to get worse. I also experienced it on a new pond and after two years it went away almost completely on its own.

My earlier post, however was talking about more than seepage. I could actually see water trickle from a spot in the corner of my newly built dam. That is a problem which if left untreated can lead to a wash-out.