We used to live on a creek that had a family of beavers. The creek fed a lake that was dam controlled. In the spring, the water agency would raise the water level in the lake and the creek would back up until it was an extension of the lake. In the fall, they would drop the dam, the lake would drain and the creek would start running again

Every fall the beavers would make a half-hearted attempt at building a dam on the creek, which at best would make a large puddle, and the rest of the year, they just relied on the human-made dam on the lake