I have a pond with a concrete spillway - 3' across that we use for irrigating the garden. I use 2x4 and 2x6 to dam up the water. Here's the problem: there is a small pocket of concrete that has eroded, right where the spillway meets the bottom board. It's small, just a small scoop but water runs under the board. Also, I am getting some seepage under other sections of the bottom board. Not a lot but the stream dries up in the summer and I can't afford to lose any water. Nothing I've tried so far seals the bottom. Any ideas? I saw some spools of stove gasket and wondered about stuffing it along the bottom board but I'm sure it would allow water thru sooner or later...probably sooner. I'd like a quick fix for now. Later I might try a small pond liner to extend a ways in front of the spillway and that would go up the boards - usually 3 or 4 2x6 high.