The Missouri River Floodplain:
Additional Science Experiment for Lesson II, Grades 9-12
Try the following experiment, or some other you have devised, to illustrate to students the value of
wetlands or a floodplain in filtering out pollutants.
Time: 1 class period plus preparation
Materials: 1/2 gallon samples of different soil types: sand, clay, gravel & humus, collected in
one-gallon plastic bottles; scissors; a nail; a large funnel; several aluminum pans; 2 glass
containers for each soil type; water
Procedure: Cut off the top of each plastic bottle and punch numerous small holes in the bottom
of each. Have students collect soil samples, either as a class or in advance as a homework
assignment, filling each plastic bottle halfway.
Ask students to predict what will happen when they pour water over the soil. What will the
quality of the soil be that filters through the holes? Then, dividing the students in pairs,
have them hold one bottle over an aluminum tray and pour a glass container of water on the soil.
Collect the drainage in an aluminum tray, and using the funnel, transfer the drainage to another
glass container. What do we call this process? When in nature does this occur? Where does this
"eroded" soil go when it washes away?
Next, have students predict what will happen when you pour the dirty water over the soil a second
time? What about a third and fourth time? Have students repeat the experiment several times,
recording on each occasion what the water looks like. Is the water becoming clearer?
Try this experiment with each of the types of soil collected. Which soil filtered the water best?
Why? If there is still muddy water left from one or more of the experiments, try pouring it
through the best filter and observing the results.
As a wrap up, ask students to think of places in nature where this kind of filtering would take
place. What would the effect of roots and/or small plants be on this filtering process? Which
would act as a better filter, a cleared field or a wooded forest? Why? (You might wish to
demonstrate this principle to students by having students quickly pour a glass of water on a
rock and then a sponge to see the difference in run off.)
