tablecloth or shower curtain also works) laid over balled newspapers (one can also use a ready-made EnviroScape® watershed model). I invite the class to gather around as I make it “rain” onto the model using water from spray bottles or cups, illustrating how runoff moves downhill into rivers and lakes. Next, I use a “stormwater metaphor” game to get
students thinking about the potential contaminants in storm- water. Each group of three to four students receives one of the following items and must tell the class how the item is related to stormwater:
• toy car (motor oil, gasoline, antifreeze) • pet leash (pet wastes) • snow shovel (road salt) • toy house (fertilizers and pesticides on lawns) • fast food bag (litter/garbage)
• plastic turf or golf ball (fertilizers and pesticides from lawns, gardens, farms)
• paintbrush (paints and paint thinner poured down the storm drain)
• packet of seeds (exposed soil contributes sediments such as sand and silt)
• toy bulldozer (sediment from new construction)
Simple watershed demonstration model using a plastic tarp laid over crumpled newspapers
I begin the unit by asking students these questions: • How does community growth change the land cover?
• How do these changes in land cover affect the quantity, quality and timing of stormwater runoff?
• How will creating more pavement affect the groundwater table and drinking water wells?
• How does the loss of natural vegetation along riverbanks and shorelines change the water quality of streams and lakes and alter the aquatic ecosystem?
• How do all of these changes affect a community’s appear- ance and natural character?
Investigating runoff
Stormwater runoff occurs when water from rainfall or snow- melt flows over the surface of the ground instead of percolat- ing down into soil. As water flows over roads, lawns, parking lots and construction sites, it picks up fertilizers, pesticides, dirt, road salt, motor oil and animal wastes. Often these contaminants are then carried into nearby lakes, streams, rivers, wetlands or coastal waters. In some cities, any rain- water that enters a storm drain is discharged untreated into local water bodies — the same ones that people use for swimming, fishing and possibly even drinking water. In cities that have a combined sewer and storm drain system, millions of gallons of untreated or partially treated sewage can be released into lakes and rivers during large rainstorms when wastewater treatment plants become overloaded. I demonstrate the movement of runoff with a simple watershed model that I create using a plastic sheet (a picnic
Page 10
• toilet paper (human wastes from wastewater treatment plant overflow) After discussing stormwater — where it comes from
and where it goes — I take my class on a short walk out- side to identify areas that might contribute to runoff and to discuss the types of contaminants that could be carried from those areas to the nearest body of water. When possible, we take this walk during or right after a rainfall. I liken it to being environmental detectives and looking for clues or evi- dence. One day, as we walked to the river near our school, the maintenance department was painting the soccer field and a worker rinsed the paint sprayer in the parking lot. As they watched a plume of white paint come down the river, the kids quickly recognized the source of the pollution. It was a non-toxic, water-based paint, but we stenciled the storm drain and alerted the maintenance supervisor to the potential problem. If you can locate the pipes in your com- munity that discharge storm water, you may have similar opportunities to see a plume of contaminated water outflow into the river or lake.
Using best management practices
Students investigate the potential impact of land use changes on the quality and quantity of surface water. As a class, we brainstorm different land uses and list potential contaminants associated with each. I remind students that land use changes aren’t inherently bad, that it depends on how they are imple- mented. Best management practices (BMPs) are structural or nonstructural methods of preventing or reducing the movement of runoff carrying sediment, nutrients, pesticides and other pollutants from land to surface water. We identify several BMPs for each land use (see table “Runoff Control: Best Management Practices”).
GREEN TEACHER 83
Joan Chadde
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56
