Thanks Theo, we are pretty confident that the rest of the pond is good. As you said we are concerned that there is some sand hiding under the trees sucking the water away. I guess I am hoping of a miracle and I wouldn't have to do anything, very unlikely.
Since I am not resident at the pond I am putting up a trail camera that takes time lapse photos of the water level measuring stick I put in a couple of weeks ago. I am doing this to monitor the levels of the pond and see if it stabilizes at some level, this may help identify roughly where the leak is (at least level).
