Russ,
The problem with springs and such is that they can go both ways, i.e. what looks like a source of water or inflow can become an outflow when the pond is full and water pressure causes the spring to reverse directions. Combined with dropping water tables and its a recipie for major leaks. I learned this in building my firat pond in East Texas from a veteran pond builder...my excitement at hitting at spring and eternal water supply was entirely deflated by his explaination as to why we had to pack it in two feet of clay.
