Waders and dams

I was bought some waders for my birthday. They are wellington boots that are attached to a rubber pair of trousers that reach my chest. So I tried them out the other day, and waded down the river looking for any obstructions to clear. I found a small dam that had been built by someone which was trapping a lot of vegetation. I cleared it, and dismantled some of the stones that were holding back the water partially. The trouble is, the water level has gone down by about 8 inches! I'll have to rebuild the dam. Damn!