Busy beavers have constructed an impressive dam at the outlet of Round Lake.  Unfortunately it is right on top of the trail which goes around the lake, requiring a detour downstream.  I assume this is the location of the bridge mentioned in the trail description as there is no other bridge on that trail.  Maybe the beavers used it as a foundation for their dam.

Very cool!  How much deeper do you think the water level is due to the beaver's hydrologic engineering skills?

Between two and three feet.  Here's a close-up of the outlet creek (including the remains of the trail boardwalk) to give a better idea of the height of the dam.