What is a Watershed?

During a rainstorm, the water that flows over the land as runoff collects in channels such as streams, canals, rivers, etc. The land area that drains water is called a watershed.

Areas of higher elevation called divides separate watersheds from each other. Water flows through a series of channels and eventually it collects in a wide river that empties into a body of water such as an ocean or lake.
From an aerial view, drainage patterns in a watershed resemble a network similar to the branching pattern of a tree. Tributaries, similar to twigs and small branches, flow into streams, the main branches of the tree. Streams eventually empty into a large river, comparable to the trunk. Like other branching patterns (e.g. road maps, veins in a leaf, the human nervous system), the drainage pattern consists of smaller channels merging into larger ones.


  • Understanding influences on the watershed.
  • Predict where water flows within a watershed.
  • Observe drainage patterns in a watershed

Materials Needed

  • Sheet of white paper
  • Shallow pan
  • Water-based color markers
  • Spray bottle of water


  1. Crumple sheet of paper and then partially smooth it out being careful to leave some ridges.
  2. Using markers, color along the crease using different colors. The colors will represent pollutants such as fertilizers, pesticides, litter, pet waste, etc.
  3. Lay sheet of paper in pan and shape it so it looks like a watershed.
  4. Spray paper with water and watch colors begin to flow.

Topics for Discussion

  • Describe what happened at the highest and lowest point in the watershed.
  • Did the different pollutants mix together?