Recommended Grades: K-12
You will need:
A watershed is a geographic area in which water, sediments, and dissolved minerals all drain into a common body of water like a stream, creek, reservoir, or bay. A watershed includes all the plants, animals, and people who live in it, as well as the non-living components like rocks and soil. We are all part of watershed, and everything we do can affect the surface and ground water that runs through this system. When you create your miniature watersheds, be sure to use water soluble makers -- as the markers “bleed,” they demonstrate how rain moving through the watershed affects soil erosion and urban runoff.
To create the watershed, crumple a piece of paper into a tight ball. 
Gently open up the paper, but don’t flatten it out completely. The highest points on the paper will be mountain tops, and the lowest wrinkles will be valleys.
Choose one color of marker and use it to mark the highest points on the map. These points are the mountain ridge lines.
Choose a second color and mark the places where different bodies of water might be. Are there creeks? Lakes? Rivers?
With a third color, mark four to five places to represent human settlements. For example, houses, factories, shopping centers, office buildings, schools, etc.
Make rain fall into your watershed by spraying it with the spray bottles. Watch how the water travels through the system.