Subject Area	Biology
Age/Grade Level	Freshmen or Sophomores
Estimated Length	1 50-minute class period
Prerequisite Knowledge/Skills	Students should know a little bit about watersheds and their functions as drainage basins.
Description of New Content	Introduces students to the concept of how pollution in one area of a drainage basin or watershed can spread to other areas due to normal weather patterns.
Goals	By the end of the lesson, students will have simulated the effects of the spread of pollution in a drainage basin due to natural weather patterns.  Students will then answer questions related to the activity.
Materials Needed	Plastic containers larger than a shoe box, newspaper, paper towels, blue cleansing solution in a spray bottle, colored dye
Procedure	Question to Start 1.  Why do you think scientists might be worried if someone polluted the environment in a mountain area or drainage basin out in the middle of nowhere?   Have the students take the newspaper pieces and crumple them into separate balls of paper.  Then have them put the paper into the plastic container, covering the bottom of the container completely.  Put the paper towels over the top of the newspaper and push down on them until they properly simulate hills or mountains.  This will serve as the watershed. Now give the students the spray bottle and tell them to squirt six times over the watershed, anywhere they want (as long as it is in the container). Tell the students that they are simulating rain. Ask the students what they notice about the water.   Questions 1.  Does the water stay on top of the "hills", or does it do something else? 2.  Where does most of the water end up? Now take the colored dye and put a drop onto an area of the watershed.  Tell the students that this represents an oil spill in the watershed environment.  Ask the students what they notice about where the dye is.  Is it all over the place, or just in one place? Now have the students simulate rain again with another six squirts from the bottle of cleansing solution.   Questions 1.  What happens to the "oil spill" when the rain comes?  Does it stay in one place or does it do something else? 2.  What do you think might happen if the rain started to evaporate over time? 3.  What would happen if there were a river flowing out of this drainage basin?
Evaluation	Questions to Answer 1.  What is a watershed? 2.  Why might scientists be very worried about pollution occurring in a watershed? 3.  What are some other places where pollution could be very bad for the environment in general? 4.  How might wildlife be affected by pollution in a watershed?
Extensions	This lesson could lead into a discussion of ecosystems and the effects of pollution on ecosystems.