A river takes a long trip. Let us follow it from start to end.
Key idea
A river starts at its source, flows downhill, gets more water from smaller rivers called tributaries, and ends at its mouth, where it flows into a lake, a sea or the ocean.
Why it works
Water always runs downhill. A river begins up high, at a spring or melting snow, and follows the lowest path down. Mud and sand it carries can pile up at the mouth and build new flat land called a delta.
Worked example: Which way does it flow?
Does every river flow south, toward the bottom of the map?
- Rivers flow downhill, wherever downhill is.
- The Mississippi flows south. The Nile flows north.
Answer: No. Rivers can flow in any direction.
Common mistake
Many children think rivers flow "down" the map, toward the south. On a map, "down" just means south. Rivers flow downhill on the land, which can be any direction.
For the grown-up. After a rain, watch water run along the curb or down the driveway. Find where it "starts" and where it "ends": its source and its mouth.