Bureau of Economic Geology

Lab 1: Aquifer Model in a Tank

Contents

Purpose

This simple model is intended for student inquiry into ground-water systems. Have your students try things (within the context of the model), observe what happens, and record and interpret their observations. After this inquiry they will better understand aquifers and the issues of climate, spring flow, environmental protection, and water use that are so hotly debated in Austin and elsewhere in Texas.

   

The model can be productively used in the context of process TEKS (4.3) and (5.3) to "represent the natural world using models and identify their limitations" and concept TEKS (5.5) describing groundwater as part of the water cycle; (5.11) renewable resources, (6.14) groundwater and surface water relationships.

 

Vocabulary

  1. Recharge
  2. Discharge (spring, well)
  3. Aquifer
  4. Vadose zone
  5. Water table
Materials
  1. 10-gallon tank
  2. PVC pipe with holes drilled to serve as screen interval. Screen interval can be at the bottom or about 10 cm from the bottom end of the pipe. Pipe 2.5 cm in diameter and 38 cm long
  3. Plug to fit the bottom of the PVC pipe
  4. Several liquid-soap pumps
  5. Plastic tubing to extend the tubing on the soap pump (the end of the plastic pipe should reach the screen interval in the PVC pipe.)
  6. Scoops to handle gravel and sand
  7. 80 lbs gravel
  8. 20 lbs sand
  9. Labels
  10. Binder clips to hold hoses to tank and buckets
  11. Squirt bottle or rain maker (container with holes punched in bottom)
  12. Several graduated (1- or 2-liter) pitchers to measure water
  13. Dishpan or 1- to 2-gallon tub for ocean
  14. Plastic tubing for siphon (river)
  15. Flashlight to look down well
  16. 1 small plastic container (yogurt or butter tub) with holes punched in the bottom for spring swimming pool

Procedure for Lab 1: Aquifer Model in a Tank

  1. Make the well casing out of the PVC pipe:
  • Using a nail or drill, make numerous holes in the pipe. Make one well casing with holes in the bottom 2 cm of the pipe and another with holes about 8 to 10 cm from the bottom of the pipe. These are the screen intervals, the parts of the well that the water from the aquifer goes through. In the real world, we normally drill a well until we hit the water table and then set the screen interval at the top of the aquifer. In our model, we push the well casing to the bottom of the aquifer to keep it from wobbling during our experiment, and the 10-cm screen interval will be near the top of the aquifer.
  • Cap the bottom of the PVC pipe well casing.
  • Making the pump: Extend the tube on the soap pump by attaching plastic tubing to the bottom of it, such that it reaches from the top of the PVC pipe to the screen interval (holes made in the pipe).

 

  1. Make the aquifer:
  • Put gravel in the tank. It will serve as the first laid-down layer of the aquifer. Make the layer approximately 6 cm thick.
  • Put a 1-cm sand layer on top of the gravel layer. It will serve as another layer of the aquifer. You can experiment with various sand thicknesses.
  • Lay another layer, 5 to 12 cm thick, of gravel on top of the sand. Make it hilly. Total thickness of the fill in the tank should be 12 to 17 cm.
  • Make a spring by digging into the fill and placing there a plastic container with holes in the bottom.
  • If you like, decorate the land with vehicles or a house.
  1. Recharge the aquifer. Slowly pour/squirt a measured volume of water onto the land. Start with 3 L of water. Observe what happens and record this event on the data sheet.
  2. Label aquifer, vadose zone, water table, spring, and well.
  3. Measure the water level with respect to a datum (the bottom of the tank); record on data sheet.
  4. Start spring discharge.
  5. Make a siphon. This is going to be the "river" to transfer the water from the spring to the "ocean."
  • Cut 3 ft of plastic tubing.
  • Fill the tubing with water; make sure there are no bubbles. You can do this in a tub full of water or at tap.
  • Use your thumbs to seal both ends of the pipe so that there are no air bubbles in it.
  • Put one end of the pipe into the spring and the other into the ocean tub, which must be at a lower level than the spring. Release both thumbs from the ends of the pipe. You will see the water coming into the tub from the spring. Use the squirt bulb to restart flow if it stops.
  1. Drill the well (push PVC pipe down into the aquifer). Start with the well screened at 10 cm.
  2. Pump the well and collect and measurethe water in a cup. See what happens.
  3. Record what happens on your data sheet. Be sure to fill in all the columns each time an event occurs.
  4. Recharge the aquifer by slowly raining on the surface. Be sure to measure the volume of water that you add.
  5. Experiment with the variables. Stop the rain and have a drought. Try recharge events of different magnitudes (a sprinkle and a flood). Install the deeper well and pump the wells hard. Be sure to measure and record volume of water added and removed and the effect of each experiment.
  6. Analyze the data qualitatively.
  7. Analyze the data quantitatively.

Data Sheet for Lab 1: Aquifer Model in a Tank

   

Time
Event
Observation
     
     
     
     
     
     
     
     
     
     
 

 

Aquifer Model in a Tank: Analyze the Data Qualitatively

Sketch and label the parts of the aquifer using the vocabulary.

 

For discussion:

Show with arrows how the water moves in the system.  

What happens to the system when it rains?

What happens to the system when it stops raining (during a drought)?

How does what we see in the model matter in the real world?

Lab 1: Aquifer Model in a Tank: Analyze the Data Quantitatively  

On your data sheet, circle all the volumes of water that you added as rain (recharge), and then add them together. Total recharge = ____ L

On your data sheet, box all the volumes of water that you pumped out (well discharge), and then add them together. Well discharge = _____L

Measure the volume of water that flowed out of the spring, down the river and to the ocean. Spring discharge = _______L

Make a histogram of the water budget of your aquifer:  

 

Lab 2: Contaminants in a Tank, Cleaning up Spills  

This lab is a continuation of lab 1. In that lab we focused on water resources, that is the quantity of water in the system and how it works as a cycle. In this activity we look at water quality and how human activities can make an impact on surface and ground water.

Vocabulary

Contaminants

Analog

Materials

In addition to the set-up from lab 1, make the following analogs for contaminants:

 

Contaminant
Analog
Properties
Industrial contaminants 2 to 5 mL yellow food coloring in 100 mL water Liquid spill, water soluble
Fertilizer, pesticides, and herbicides 2 to 5 mL green food coloring in 100 mL sugar Dissolved into solution by rain
Oil and gasoline Cooking oil Nonsoluble in water, less dense than water
Runoff from landfill and disposal sites, sewage 5 mL red food coloring, 100 mL cornstarch, 100 mL elbow macaroni. Add cooking flavor of your choice to add garbage "aroma." Water soluble, leached from disposal sites by rain
 

Experiment

Consider how each contaminant enters the environment.

Set your ground-water system to running, with spring flow, pumpage, and recharge. Experiment with contaminating the environment to simulate various contamination events that have happened or might happen and observe what does happen.

Clean up the model, recycling the materials.

Lab 2: Contaminants in a Tank: Observations and Conclusions

  1. How does the contaminant get into the groundwater?

  1. How does it come to the surface to affect people and animals?

  1. What could the people who live in the model do to clean up their contaminated water?

  1. Try your clean-up plan.

  1. Did it work?

  1. What conclusions did you come to from observing the model that you can tell people?

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