Originally Posted by iolo

There is a tiny stream running through my lawn and the previous owner of my house decided to turn it into a succession of six waterfalls and six ponds. When I moved in water was gurgling over each fall, from pool to pool, down the slope of the lawn. Two years later, however, only ONE waterfall is working. All of the other five walls (mini-dams) which he built out of small rocks and cement have developed leaks. Only one of the ponds is currently full - and that's the one that is sending excess water over the lip to fall into the next pond. But the rest of the ponds are only almost full - their water is moving from pond to pond through small holes in the walls. Each wall only has one or two holes.

To dry up the stream in preparation for concreting repairs, by emptying all the ponds, would be a back-breaking task, and anyway, diverting new incoming water would be difficult.

So, is there some thick substance which I can ram into each hole and which will then set solid, despite the pool of water on one side of hole and the wet conditions on the other?

I have concrete, of course. And I believe one can get hold of "plasticiser" to mix with it. But I am not sure if that's the solution and if it is I'm not sure what proportions to mix it in.

Any ideas most gratefully received!