Activity 1: A Model Aquifer

Materials
Each group of students will need:

• a clear rectangular 3-gallon-sized, plastic box or tub. Use the longest box you can find,
• potter's clay or natural clay soil,
• sand,
• gravel,
• measuring scoop made of a plastic gallon milk jug with the top cut off,
• graduated cylinder,
• two pie plates or petri dishes for catching water that flows out of the aquifer,
• a ten-penny nail for making holes in boxes,
• water, and
• a copy of the illustration of the model aquifer.

Model Aquifer (Activity 1)

Procedure

1. Introduce students to the diagram of the aquifer. Tell students that they will be working in groups to build model aquifers. Explain that different groups will be using different mixes of materials in their aquifers. Some will be using all sand; some will be using all gravel; some will be using a mix of sand and gravel.

2. Instruct students to punch holes in the plastic tub. Holes should be no smaller than 1 mm and no larger than 2 mm.

3. Have students measure out the different aquifer materials using the measuring scoop. Make sure each group uses the same volume of material - sand, gravel, or half and half - for the aquifer. Have the students who are using the half-sand half-gravel mixture prepare the mixture before measuring it or packing the mixture into the aquifer.

4. Students should then pack the tubs with the "aquifer" materials. The bottom layer of clay should be very thin - 2 mm - and well packed. Students should then add the aquifer material - 2-3 scoops, depending on the size of the tub. The upper layer of clay - 1-2 cm thick - should also be well packed.

5. The next step is to elevate the tub or place it on the corner of a table so the holes where water will emerge are accessible. The tub could be elevated with coffee cans or blocks, or placed diagonally on a table corner. Students should position the two pie plates or petri dishes to catch the water that comes out of each hole.

6. To observe how the aquifer model works, students should pour water in the hole in the clay at the top, 10 mL at a time, until drops appear at the holes. After drops appear, students should pour in one final graduated cylinder full of water. Students should record the amount of water that is poured into the model. In the pie plates or petri dishes, they will collect the water that comes out of each hole, then measure the amount of water in an empty graduated cylinder.

7. When students have finished pouring water into their aquifer models, gather the class together. Have the students in different groups compare the water-holding capabilities of different materials.

8. Refer students to the section of the Student Packet that explains porosity and permeability. Review these concepts. Then hold a general discussion of what students expected to discover and what actually happened. Students are likely to be surprised to find that even a thin layer of impermeable material will not allow water through.

Extension

1. Describe how a town built on top of this model could access and use the water in the aquifer for its water supply.
2. Invite a local well driller to class to discuss information related to local aquifers, drilling depth, and costs.