Soak It Up: Test The Permeability Of Soils

You've just been hired as an engineer to work for SciScape city. Heavy rains are forecasted for the winter, so the SciScape city planners want to determine if the city could flood. They know that certain types of soil may be better at absorbing water than others.

As an engineer, you will help test different types of soil and determine which types may help prevent flooding. Your project results will go to the SciScape city planners. With your results, the planners can decide if the city is vulernable to flooding. Let's get started.

Setting: First, talk to your "Project Manager" (a parent). Tell them about your project and find a suitable "office" for this muddy project, either in the garage or outside.

Print out this web page, then print out this Data Table for the SciScape Engineer.

Materials: Ask your "Project Manager" to help you find your project materials in your yard or at a gardening store.

3 types of soil (substitutions okay)

--Dry sand, 1 cup

--Potting soil, 1 cup (or dry peat moss)

--Clay soil, 1 cup (or dry soil from your yard)

tap water

1 glass measuring cup

1 extra measuring cup

1 small bowl

Funnel

3 Coffee filters

paper and pencil

1. Set the funnel up in the glass measuring cup. Line the funnel with one coffee filter.

2. With your other measuring cup, scoop out 1/2 cup of your first soil type into the filter.

3. Measure 1/2 cup of water and slowly pour it on the soil in the funnel. Be sure that all the water goes into the funnel and soaks every dry part of the soil.

4. Wait 1 minute for the water to soak through. Do not squeeze or press the soil.

5. Carefully remove the filter and soil and place it into the bowl. Don't throw it away. You will use this again.

6. Measure the amount of water that drained into the glass measuring cup. Write this measurement down and label it as soil type number 1 in your data table.

7. Repeat steps 1-6 for your other types of dry soil, labeling the soil types 2 and 3. If you make a mistake, start over with your extra soil.

Now you'll do the same process again for the wet soil types. Here you may definitely notice a difference!

1. Carefully replace wet soil type 1 and its filter back into the funnel.

2. Measure 1/2 cup of water and slowly pour it on the wet soil.

3. Wait one minute without squeezing or pressing the soil.

4. Remove the funnel and place the filter and soil into the bowl.

5. Measure the amount of water that drained into the glass measuring cup. Record your data.

6. Repeat steps 1-5 for the other wet soil types 2 and 3.

7. Clean up and prepare your report for SciScape City.

Once you've finished your experiment, use your data table to present your findings to your Project Manager. Be sure to address the following questions:

1. Which soil type held the most water when it was dry? Why do you think that happened?

2. Was there a difference in drainage when the soil was already wet? If so, why? How much was this difference?

3. Did you notice if the water went through slowly or quickly in certain types of soils? How does that relate to flooding?

4. Which type of soil will likely cause flooding problems? Which type of soil will help reduce flooding?

Extra credit:

Repeat the experiment using different types of soil, a mixture of soils, or soil with rocks. Set a timer and see how long it takes for the soil to drain. Be sure to write down all the data so you can understand the differences. Graph your results to compare soil drainage times for the soil types. Or you can graph the amount of water that drained for each soil type.

Images:

Top: A scientist in a soil lab. Photo courtesy of USDA NRCS.

Bottom: Scientists evaluating the composition of soil. Photo courtesy of USDA NRCS.