Age: grades 3-8
Subject: Water action and processes
Skills: observation, measuring, hypothesizing
Duration: 60 minutes
Group size: any
Setting: indoors
Key vocabulary: water table, porous, saturated, ground water
Materials:
balance
sandstone samples
water
jar
cardboard tube (from a paper towel roll)
coarse sand
aquarium
Objectives:
The student will be able to:
1. Predict from a rock sample whether a water well could be drilled in that type of rock.
2. Predict what conditions would be necessary for the well to produce water.
Method:
The students will measure the amount of water a porous rock will soak up and then observe a model of a water table and a well.
Overview
Rain, falling an the earth, runs off as streams, evaporates, is held by soils, and soaks into the earth. Water that soaks into porous rocks is called underground water, or ground water. Water will flow into porous rocks until the rocks become saturated. The level of saturation depends upon weather conditions and is higher during rainy seasons and lower during dry seasons. The surface between the level of saturation and nonsaturation is called the water table. Underground water does not flow in streams, nor does it occur in lake-like pools, but is very similar to the model in this activity. A water well is a hole drilled in the earth to a point below the water table. Dry spells may cause the water table to lower, thus causing a well to go dry.
Procedure
1. Obtain a sandstone sample. Weigh the sandstone rock and record its weight.
2. Place the sandstone rock in a jar of water and let it soak overnight.
3. After the rock has soaked overnight, shake the excess water from the rock and weigh it again. Record the weight.
How can you account for any change in the weight of the rock? Will rocks hold water?
4. Obtain a cardboard tube and an empty aquarium. Hold the tube in the center of the aquarium and fill the area around the tube with sand. pack the sand firmly to help support the tube.
5. Slowly pour water all over the surface of the sand until the sand is wet.
Where does the water go?
6.. Carefully add more water. Observe the bottom of the aquarium through the tube for several minutes. Record your observations.
Is this like a well?
7. Look through the glass of the aquarium side. Record your observations.
Would you call this a water table? What is a water table?
Extension
What is the depth of the water table in your area at different locations and different times of the year? This information can be obtained from local land or geologic agencies.
Evaluation
Give the student a rack sample and have her/him determine whether a water well drilled in this type of rock might produce water.
Source
Sund, R., Tillery, B.,& Trowbridge, L. (1973) Elementary Science Discovery Lessons: The Earth Sciences. Boston, MA: Allyn and Bacon, Inc.