ACTIVITY 4

If You Build It, It Will Flow

Activity Overview

In this activity student groups will either observe groundwater flow in a commercial model or build a physical model of a groundwater system. They will observe the rate of saltwater intrusion as a result of different forces of nature and human activities. Groups will then construct a flow diagram to show how multiple variables interact to determine the recharge and discharge of water in the groundwater system. They will then construct a simple STELLA model of the groundwater system to simulate these relationships. They will then predict how changes in variables affect the amount of water in the aquifer.

Objectives

Students will:

  • Build and observe a physical model of a groundwater system.
  • Discover the relationships between the forces of nature and human activities that impact the amount of groundwater.
  • Construct a flow diagram of the groundwater system to visualize the effects of multiple variables on the system.
  • Construct a simple STELLA model of the groundwater system and make predictions about how changes in the variables affect the amount of groundwater.

Cross Curricular

Mathematics

Students will measure the soil layers when constructing their physical groundwater models.

Process Skills

observingmodelingsynthesizing inferring

collaboratingcommunicatingvisualizingdiagramming

Materials

  • STELLA modeling software or concept mapping software

(

*NOTE: A groundwater flow and contaminationmodel may be used instead of the students building their own. Fisher Scientific is one source for this

model. ()

  • 3L plastic soda bottle or other suitable plastic container
  • hot glue gun
  • plastic sealant
  • 20 mL disposable syringe with tip
  • small diameter tygon tubing or aquarium tubing
  • transparent plastic straws
  • pump sprayer from a bottle
  • small rocks
  • sand
  • topsoil
  • food coloring
  • spray bottle
  • 10% saline solution
  • 100-watt lamp with metal reflector
  • activity sheet

Suggested Time Frame

Approximately four 50-minute periods

Procedure

Day 1 – Model Construction

  1. Assign the roles of timer, recorder/precipitation monitor, saltwater monitor, and use/drought monitor to the members of the group.
  2. Ask each group to clean and remove the labels from a 3L plastic soda bottle. Cut the top of the bottle off at the shoulders and follow the directions below.
  3. Layer rocks up to approximately 1/3 height of bottle.
  4. Insert the pump sprayer down into the rocks, 1 cm from one of the sides of the bottle. This will simulate a well and pump.
  5. Holding the pump sprayer in place, put 1 cm of lime (simulates clay soil), 3 cm layer of sand on top of the lime (clay), 1 cm of lime (clay), followed by a 2 cm layer of topsoil as shown in the diagram. This is to simulate geologic composition of the aquifer.
  6. Next, use the hot glue gun to melt a hole in the side of the bottle opposite the pump and midway into the sand layer. Insert a piece of tubing, approximately 3 cm long into the hole. Fit the exterior end of the tube flush with the opening in the bottle. Seal around the edges of the opening and tape over the opening with waterproof tape to prevent leakage. Saline water will be injected into the aquifer at this opening.

Day 2 – Modeling Groundwater

  1. Give each student activity sheet for activity 4 to record their responses.
  2. Before beginning the activity, the heat lamp should be turned on to allow time for adequate warming.
  3. Slowly fill the model with water to the interface of top layer of lime and topsoil. This water level represents the water table.
  4. Add food coloring to the 10% saline water and fill the syringe with it. The saline water monitor should slowly and steadily inject the saline water into the aquifer through the tubing at a rate of 2 mL per 15-second intervals. The timer should time the saline injection. The groups should observe and describe the flow of the saline water through the aquifer.
  5. The use/drought monitor should gently press down on the pump sprayer adding pressure to force water out of the aquifer. This simulates water use. The groups should observe and describe the effects of water use on the aquifer.
  6. The recorder/precipitation monitor will simulate rain by spraying water from the spray bottle onto the surface of the land at the topsoil interface. Groups will observe and describe how precipitation affects the level of the water table.
  7. Drought will be simulated when the use/drought monitor places the lamp approximately 5 cm from the topsoil surface for a minimum of 20 minutes. The groups should observe and record any changes in the water table level and/or the saline intrusion flow.
Days 3 and 4
  1. Instruct the student groups to use their understanding of the variables in their groundwater flow model to construct a 2-D flow diagram showing how these variables affect the amount of freshwater in an aquifer. Next, have them to extend their model and add the effects of porosity.
  2. Have each group present its model to the class for class discussion.
  3. Have each group develop a realistic mathematical model of the groundwater system being sure to define all terms used. They will use the following data which is also shown on the activity sheet.

The city aquifer lies 500 ft. beneath ground level in a sand formation. It is recharged by rainfall that percolates through a layer of clay with a permeability factor of 0.5 and a layer of silt with a permeability factor of 0.9. (real flow= permeability factor*flow) Last year, rainfall totaled 8.23 x 1011 gal, but the average city rainfall is 1.54 x 1012 gal. When the freshwater level in the aquifer is low, saltwater flows into the aquifer from the Gulf of Mexico. The city population is 500,000 and per capita water use is 40,000 gal/year.

  1. Finally, each group will construct a simple STELLA model or other computer model ( based on their mathematical model using the recharge and drawdown data given.
  2. Directions for constructing the STELLA model can be found at Each group should turn in a printed copy of the STELLA model.

Thought Provoking Questions

  • What variables recharge the amount of water in an aquifer?
  • What variables drawdown water from an aquifer?
  • Explain how varying the amounts of rock, sand, clay and topsoil would affect the flow of groundwater through the aquifer.
  • Describe how an aquifer might become depleted of its groundwater.
  • Propose solutions to the problem of an imbalance between groundwater drawdown and recharge.

Assessment

  • Physical groundwater model
  • Activity sheet with:
  • 2-D flow diagram of groundwater model
  • mathematical model
  • participation in class discussion

Resources

  • Fischer Scientific groundwater flow model and contamination model (
  • Physical groundwater flow model was adapted from Oklahoma Aqua Times Teacher’s Guide developed by the Oklahoma State Cooperative Extension Service
  • Stella Twin Cities Groundwater Flow Model –

Louisiana Team 11 National Computational Science Leadership Program

Activity 4Page 1 of 4