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When rain falls, it ends up in many places. Some rainwater is taken in by plants. Some seeps into the ground, where it replenishes groundwater supplies. Some rainwater gathers in puddles or closed ponds, where it may provide water for wildlife. The rest flows across the ground, pulled by gravity. This water follows many paths, depending on local topography and development. Rainwater may flow into a stream, then into a larger stream or river. The water may flow through a wetland such as a bog, a marsh, a wet meadow, a shrub wetland, a tree swamp, or a stormwater management pond. A stream or river may flow through an open pond or lake that was formed by a beaver dam or a human-constructed dam. A natural stream’s permeable surface, winding course, and vegetation help to slow the flow of water and filter out pollutants. People affect the flow of water through their communities. Rainwater flows across pavement, where it picks up oil leaked from cars as well as litter and other pollution. In concrete gutters, channels, and storm sewers, water flows quickly and picks up pollutants. These manmade channels are often hot and dry between rains, and, as a replacement for natural streams, the channels provide an inhospitable habitat for wildlife. Gravity pulls rainwater to lower and lower altitudes until it reaches sea level. Most of Virginia is in the Chesapeake Bay watershed, which means the water in its streams, rivers, open ponds and lakes, and even storm drains will enter the Chesapeake Bay. There are four major rivers that flow into the Chesapeake: the Potomac, the Rappahannock, the York, and the James. Each river is surrounded by land that drains into the river; this area is considered the river’s watershed. These watersheds combine with the others that drain into the Bay to make the larger Chesapeake Bay watershed. Even if your school is outside the Chesapeake Bay watershed, your students will benefit from this lesson. Whatever your watershed, the concepts in the lesson are the same. In this lesson, students will use maps to determine the path a raindrop follows from the schoolyard to the Chesapeake Bay. (See Using Maps in the Project Action Guide.) They will record their findings in the form of a “watershed address.” A mailing address lists a house number, street, town, and state and conveys a location based upon manmade boundaries. A watershed address lists the streams, rivers, and Bay to identify a location based upon the flow of water. Both list information in order from smallest to largest. A watershed address may be long or short, depending on the path water takes to reach the Bay. Here are examples of both:
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