They are the highest points surrounding a stream or river. If a drop of water falls on one side of a divide, it eventually drains into that watershed s stream or river. If the drop lands on the other side of the divide, it drains into the stream or river of a neighboring watershed. Two factors responsible for the varying natural characteristics of watersheds are geology and climate . Geologic processes, including glaciers, volcanoes and plate tectonics, determine the rock formations and how they change over time.
Climatic processes erode and shape the rock formations.
Through the process of carving valleys, streams break large rock material down into smaller pieces. They transport fine materials, or sediment throughout their watersheds. In fast flowing streams, sediment adds erosional force to the water, cutting through valleys and scouring stream bottoms. In slow flowing streams, sediment is deposited, settling out to form sandbars, levees, and fertile flood plains. Like water, sediment is crucial to life.