The concept of a how pesticides and other chemicals pass through a watershed can be difficult for younger learners to grasp without a concrete example. In the activity here, some blank paper, markers, and a spray bottle are all you need to have each of your eager ecologists create their own watershed. In just a few short minutes, the concept will become understandable and clear to learners of all ages. The follow-up questions may need to be adjusted, depending on the age of your kids, but the overall idea works very well.