Keywords: watershed, groundwater, runoff, water erosion; Grade Level: 3; Total Time Required: 45 minutes; Setting: classroom
Subject Covered: science (environment), math
Topic Covered: How forests maintain water absorption and how people have altered the forests' ability to replenish groundwater
Goals for the Lesson
* Students will describe the steps of the water cycle
* Students will name three examples of soil/ground composition
* Students will measure the water than runs off in three soil scenarios
* Students will explain how people can improve a watershed's ability to absorb water
Materials Needed:
* Booklet "Watersheds" From the Woods series, Penn State College of Agricultural Sciences/Cooperative Extension
* Three same size plastic flower pots that hold at least two quarts of soil, with drainage holes
* Well established plant growing in one of the flower pots
* Two quarts of dry dirt (not potting soil)
* Two quarts of large pebbles or gravel
* Three large containers that will hold at least a quart of water.
* Quart measuring cup
* Plain paper, pencils, and crayons
State Standards Addressed:
4.1.4E Recognize the impact of watersheds and wetlands on animals and plants
Methods
1. Ask students where the water comes from when we turn on a faucet. Accept answers, always asking where it came from before that until students mention precipitation. Explain that every drop of water on earth was at one time rain or snow.
2. Pass out the "Watersheds" booklet and look at the diagram of the water cycle and read about it, or if not available for all students, draw a sketch of the water cycle on the board. Point out the "circular" nature of the water cycle.
3. Explain that groundwater is deep under the earth's surface, but will eventually erupt from the surface as a spring or be held within fractures in the rocks deep below the surface until a well is drilled to tap into it. Point out that if there's less ground water, our wells can dry up. Ask students what would cause less rainwater to reach the ground water level.
4. Demonstrate three soil conditions by using three plastic pots: one with a well-established plant in good quality soil with lots of humus (the more root bound, the better), one with dry, packed dirt, and one with pebbles or large gravel. These represent the forest, land where forests have been cut down, and pavement with little soil content. Make sure the pots are the same size and that they are filled to the same level.
5. Set each pot in a large container that will catch water that runs through the drainage hole. One at a time, slowly pour a quart of water into each pot, allowing the water to perk down through the pot, not flow out over the pot.
6. One at a time, after each pot has no more standing water, carefully pour the water that has dripped into the holding container into the quart container. Measure the quantity, record the amount, and list descriptions of the way the water looks. Explain that the amount retained in the pot represents water that eventually becomes groundwater while the amount that ran out of the drainage hole represents run off water that doesn't become usable drinking water.
7. Compare the results, and discuss why there were differences. Ask which soil type would be best if we were trying to increase the amount of groundwater. Which has the "dirtiest" look, representing erosion of the soil? Which had the highest quantity of "unusable" water?
8. Ask students how we could improve the ability of the soil and gravel pots to retain water? Guide them to see that planting plants in them would do this. Extend the discussion to what we can do in real life with forests, grasslands, and paved areas to increase water that goes into the groundwater and decrease erosion and runoff.
Evaluation
Give each student a piece of paper. Have them fold it into four sections. Label the four sections: Water Sheds (the title), Forest, Field, and Pavement. In Forest, Field, and Pavement, students will draw a picture depicting the scene with rain coming down and water running off. Each picture should represent the following:
Forest--trees with little run off; any run off should be clean looking
Field--grass or cropland; moderate run off should be muddy looking, perhaps showing erosion
Pavement--little vegetation, lots of run off, mostly clean.
Literature/Sources Cited
Swistock, Brian and Sanford S. Smith. From the Woods, Watersheds.
College of Agricultural Science/Cooperative Extension. University Park, Pa.: Pennsylvania State University
Author
Barb Neuhard, State College Area School District (Park Forest Elementary School)
