Hi Lance this is a tough question. First do you notice any seepage at you dam on the outside? Second in my 1/3 of an acre pond until I started using my well to keep it topped off I was losing about 1 to 1 1/2 inches per day earlier this year when there was no rain for an extended period of time and this is a totally excavated pond with no dam and a very good clay content on the bottom. Hope that gives you a little idea of what to expect. Pond is full now and had to drain about 3 inches out over the weekend to get my spillway poured now have to build up the south side 5 inches with left over dirt. Never seem to finish which is good! Bob