We've considered bentonite or maybe a 20mil plus liner under 4 to 6" of soil. Haven't looked much into clay but I'm sure it wouldn't be a huge issue. This isn't a huge priority where I'm at but would be nice to have it full most of the time.
Our area has been in a drought situation so I can't expect much. Once the runoff from our camp and front deck is routed to the pond, it should help with volume of water.
