BL-12: WETLAND IN A PAN
MATERIALS LIST
(Each set is for two students in a team)
1 one liter container – to hold water/rain
Relief map showing S. F. Bay
5 paint trays
1 roll aluminum foil – to use as student created watersheds
Red food coloring – pollution
5 eye droppers – to apply pollution
27 chamois strips – wetland
6 clear plastic measuring cups use milliliters to encourage good science
6 plastic cups with holes in the base – rain cloud
1 dish pan – to hold discarded water between rotations
11 pencils
5 gloves
2 measuring cups
3 liter bottles
Environmental Volunteers
Wetland In A Pan
BL – 12
WETLAND IN A PAN
February, 1998
BL – 12
SOURCE: Modified for EV use from, WOW!: The Wonders of Wetlands,
Environmental Concern, Inc., 1991
OBJECTIVE: Demonstrates, through a simple model, the role of watersheds, and wetlands as a filter of
sediments and pollutants. As well as, how a watershed and wetland act as a retainer for
water and a refuge for many different organisms.
GRADE LEVELS: 5 – 8
FOCUS WORDS:
Wetland, marsh, pollutant, filter, absorption, watershed
BACKGROUND INFORMATION:
The productivity of wetlands is enormous. Salt marshes can produce ten times as much organic matter per
acre as our most productive hayfields. Marshes can yield 3400 pounds of shellfish per acre, far more than
most pastures yield in beef.
Today, when we think of salt marshes, we think of foul odors. The complaint is ill-founded. A healthy
tidal flat, one with sufficient oxygen, smells of salt and wind and sugar. The odor produced from the
anaerobic bacteria living deep in the mud is not a bad smell. It can be an indication of health, the result of a
balanced ratio of decaying organic matter to living organisms.
Water resources everywhere have been severely impacted by growing human populations. By 1977
America had drained forty percent of its original wetlands. The remainder declines by 500,000 acres a year.
Only four percent of the wetlands of California's Central Valley remain. Tidal flats in Louisiana are
disappearing as flood-control works dump precious marsh water into the Mississippi. Freshwater marshes
in Minnesota are being drained rapidly. Of the acres of wetlands that we are losing each year, ninety-seven
percent are inland freshwater marshes.
The greater Bay Area is currently inhabited by nearly 6 million people, making it the fourth largest
metropolitan area in the United States. Scientists consider the San Francisco Bay one of the most modified
estuaries in the United States. Over eighty-five percent of the San Francisco Bay’s original wetlands have
been destroyed. Natural waterways have been diverted, filled, cemented, and buried. There are not any creeks
or marshes in the Bay Area that are untouched by human development.
The San Francisco Bay watershed is a large area that reaches all the way to the Sierra Nevada and the coastal
hills. Watersheds affect the water quality that flows in to wetlands. If there are any surface toxins or erosion,
the water quality that reaches the wetland and bay will also be impacted. The wetlands around the bay are at
the bottom of this great watershed. Water that flows in to San Francisco Bay may pass through wetlands
before reaching the bay and, ultimately, the ocean. A healthy wetland acts as a sponge to slow the flow of
water and filter out pollutants and sediments. If there is enough time, some pollutants can break down in to
less harmful components.
The combination of mud, plants and animals are the actual filters. Whenever we lose some wetland area there
is a greater influx of sediment and pollutants in to the Bay. These affect the complex bay food web, which
includes humans.
ACTIVITY:
1. Have one wetland in a pan model to show the students. Foil (represents the watershed) is spread over the
upper third (approx.) of the tray. Mold some hills, valleys and push in a stream bed or two into the foil.
Make sure the foil is well sealed along its edges. Add a chamois strip at the bottom of the foil. See the
diagram on page 3.
2. There is enough material to accommodate up to 5 teams at a time, with two students per team, for a total
of 4 rotations. (You will need to give each team, in a new rotating group, fresh dry chamois strips).
Environmental Volunteers
Wetland In A Pan
BL – 12
3. Take time to ask and inform about watersheds and wetlands. Use the map of S.F. Bay to point out the
surrounding watershed. What can the students tell you, then fill in as needed. Be sure they understand the
role a wetland plays in holding water and filtering pollutants and sediments. You can use your model tray
to show the foil watershed and the chamois strip at the bottom of the paint tray which represents the
wetland.
4 Each team sets-up their trays. The foil will stay in the trays(reduces the amount of foil used) for the other
teams. To save time, bring the trays with the foil already set in, then give the groups time to shape the
contours of their watershed.
5. Once the teams have their trays ready to go, ask each team to make a prediction. Will there be more runoff or less when the chamois (wetland) is added to the bottom of the watershed? They must write their
predictions on their worksheets.
6. Each team must then carefully measure 75 ml water into the cup. This represents the rainfall.
7. For this first part rain falls on a watershed that does not have a wetland. One student can pour this water
into the plastic rain cloud, the other will collect the run-off and measure it. Have the students make up a
reason for the lack of a wetland. The foil watershed can be lifted carefully from the tray without spilling
so none of this water gets mixed with the runoff. Dump the water left on the watershed into the dishpan.
The runoff water is poured back in to the measuring cup, the amount should be recorded on their work
sheets.
8. Teams will now add the chamois strip at the bottom of their watershed. Again, 75 ml of gentle rain will
fall. (Students can switch roles here; the rain-maker becomes the water runoff measurer, etc.) Teams
record their quantities on their work sheet.
9. Ask the group, was there more or less water collected when the chamois (wetland) was present? What
does this confirm about wetlands? Students can squeeze out the chamois and measure the amount of
water it retained.
IF THERE IS TIME DO THE POLLUTION PORTION OF THIS ACTIVITY
10. You will place small drops of red food dye (pollutant) in random spots on each team’s watershed, ask the
students where they want the pollution placed. What will happen to the pollutant with the wetland
(chamois strip) present and when it is gone? Each team will write their prediction on their worksheet.
11. Begin with the damp chamois still in the pan. Seventy-five ml of rain falls from the rain cloud.
12. Ask them to record the amount of run-off water collected as well as how it looks.
13. The final step is having a gentle rain with the wetland removed. You will again place small drops of red
food dye on each team's watershed. The polluted water will be collected, measured and described. How
does the color compare to the polluted water collected with the wetland in place?
Conclusion:
The group can compare their results. Ask how many predicted what would happen? How many had
results different from their prediction? What can they now say about the role a wetland plays? Did they
find out that a wetland acts as sponge? What is the advantage in having the flow of water to the bay
slowed? Can they think of places where they have seen erosion, what does that look like?
If you did the pollutant part, ask them what role a wetland plays when water contains pollutants? Ask
how filtering out pollutants would be helpful to animals or plants that live in the bay? What about
animals and plants that live in the ocean? Up river? Do wetlands help people? Is it O.K. to have polluted
run-off if there are wetlands present? If too much polluted water gets into the wetland, what might
happen?
Environmental Volunteers
Wetland In A Pan
BL – 12
WETLAND IN A PAN DIAGRAM
Environmental Volunteers
Wetland In A Pan
BL – 12
WORK SHEET
ENVIRONMENTAL VOLUNTEERS
YOUR NAME:
PARTNER’S NAME:
PART ONE
WHAT YOU BOTH PREDICT:
WILL THERE BE MORE RUN-OFF OR LESS WHEN THE CHAMOIS STRIP (WETLAND) IS ADDED TO
THE BOTTOM OF THE WATERSHED?
AMOUNT OF WATER YOU PUT IN YOUR RAIN CLOUD
AMOUNT OF RUN-OFF WATER COLLECTED WITHOUT A WETLAND
AMOUNT OF RUN-OFF WATER COLLECTED WITH A WETLAND
AMOUNT OF WATER SQUEEZED FROM THE WETLAND
DETERMINE HOW MUCH WATER STAYED IN THE WATERSHED
WAS YOUR PREDICTION THE SAME AS YOUR RESULTS?
YES
OR
NO
PART TWO
WHAT YOU BOTH PREDICT:
WHAT WILL HAPPEN TO THE POLLUTANT WITH THE WETLAND (CHAMOIS STRIP) PRESENT AND
WHEN IT IS GONE?
AMOUNT OF POLLUTED WATER COLLECTED WITH A WETLAND (CHAMOIS STRIP)
DESCRIBE THE COLOR OF YOUR RUNOFF WATER WITH A WETLAND (CHAMOIS STRIP)
AMOUNT OF POLLUTED WATER COLLECTED WITHOUT A WETLAND (CHAMOIS STRIP)
DESCRIBE THE COLOR OF THE RUNOFF WATER WITHOUT A WETLAND (CHAMOIS STRIP)
WAS THE RUNOFF POLLUTED WATER LIGHTER OR DARKER WHEN IT WENT THROUGH THE
WETLAND (CHAMOIS STRIP)?
LIGHTER
Environmental Volunteers
DARKER
Wetland In A Pan
BL – 12
WAS YOUR PREDICTION THE SAME AS YOUR RESULTS?
YES
OR
NO
RUNOFF POLLUTED WATER
THROUGH CHAMOIS
RUNOFF POLLUTED WATER
WITHOUT CHAMOIS
CHAMOIS
FOIL
PAINT TRAY
RUNOFF WATER
Environmental Volunteers
Wetland In A Pan
BL – 12