Lesson 3: Water and Its Distribution


Activity 1: Understanding the Water Table

Materials: large clear cups (kit), masking tape*, pebbles (kit), permanent marker, sand (kit), scissors, sponge (kit)
In this activity, you will build a model to represent a geographical area that has the components necessary for the development of a water table. Before building the model, use the "Water Table Diagram" activity sheet to label a diagram of a water table that includes the following components: permeable layer, impermeable layer, aquifer, zone of saturation, zone of aeration, and the water table.

Once you have labeled the diagram, you will use a clear cup to build a model based on the diagram and develop labels to show each component in the model.
Complete the following steps:
  1. Gather your other materials — a clear cup, a sponge, sand, and pebbles. Optionally, you can gather some ground cover (layer of grass or moss) to add to the top of the model. Note that you will need to cut the sponge so it will fit in the cup.
  2. Consider what represents the impermeable layer. Label this layer (you can write on the cup using a permanent marker or write on a small piece of masking tape stuck to the cup).
  3. Consider which permeable layer would come first and what material you would use for it. Place it in the cup and label this layer.
  4. Place the layer and label each of them.
  5. If you are using ground cover, add it to the top of the model.
  6. Fill a cup with water and then pour the water into the container until the water begins to fill the top layer. The water does not have to go above all the layers, but you do want to look for the top of the water (water table) by looking at the side of the container.
After you add water to the container, consider the layers of your model and answer the following questions:
  • Is there a zone of aeration? If so, where is it?
  • Where is the zone of saturation?
  • What would happen to the water table if the impermeable layer were missing? The permeable layer?
  • How did adding water to the model you built change the model?
Student Activity Page
Water Table Diagram Key
In this activity, the goal is for your child to be thinking about what causes an aquifer or the absence of one in various geographical regions. The focus is not the geographical region but rather on how important the various components of the aquifer are.

There are several important points for your child to note.

First of all, it is important for your child to consider the presence of the water table. The water table is the top of the zone of saturation for groundwater. While labeling the diagram, ask or make sure that your child includes this specific component.
How the layers should work: The impermeable layer of the model is represented by the container within which the model is built. The next layer added to the model should be pebbles or small rocks (zone of saturation), followed by sand (also zone of saturation) and the sponge (zone of aeration). If your child can find a ground cover (layer of grass or layer of moss), that is fine, but it is not necessary. Once the layers have been placed, your child should pour water into the model. Ideally, have him stop prior to the water being visible while looking at the top of the model. (The water table should be visible by looking at the side of the container.)

NOTE: While the model activity has not called for it, adding sand or soil until all the water is beneath the material being added will help your child understand the idea of an aquifer even better. The sponge will effectively represent the zone of aeration, and the water visible through the sides of the model and looking at the bottom represents the zone of saturation.

After your child added the water, he should have answered the following questions:
  • Where is the zone of aeration? The zone of aeration will exist in the spaces of the model where there is both water and air. While not easily observable, if you are using a plastic container, your child may be able to see bubbles by looking through the side of the container. The zone of aeration is the upper part of the aquifer. The sponge can represent the zone of aeration.
  • Where is the zone of saturation? The zone of saturation will be anywhere that there is only water in the model. This zone will be closest to the impermeable layer of the aquifer.
  • What would happen to the water table if the impermeable layer were missing? With the absence of an impermeable layer, water will not collect. Rather, it will seep through the layers.
  • The permeable layer? Generally, the absence of a permeable layer means that the region has no topsoil and is made up of rock. Since rock is generally impermeable, there will be no water table.
  • How did adding water to the model you built change the model? Adding water may or may not have shifted the materials in the model. This is okay. Some of the lighter materials in the sand or pebbles (pieces of grass, pine straw or other organic matter) often start to float. They will float until they become saturated by the water. Also, the other materials may settle with the smaller particles lodging between the larger ones. Again, this is okay.