Open the dam and wait out of sight and downwind within good shooting distance. They will come to fix it as the sun starts to go down. If you can position yourself to the east, you can use the reflected light off the water to locate and aim. Be careful of shooting any rifle at a beaver in the water, especially a .22 LR when you have neighbours across the lake. Those .22 bullets are very likely to skip like rocks, and they won't stop for a looong ways. A 12 ga. shotgun with full choke and goose loads would be my choice in that situation. A .22 hornet rifle or bigger works real well on beaver in unpopulated areas. I use my hornet to shoot several beaver every year.