Get the Groundwater Picture
Groundwater is one of Earth’s most valuable natural resources. The water stored in the pores, cracks, and
openings of subsurface rock material is groundwater. Wells dug by hand or machines have been used
throughout history to retrieve water from the ground. An aquifer is an underground formation that is capable
of storing and transmitting water. An aquifer may be confined, or bound above by impermeable layers, or
unconfined, in which the upper boundary is the water table.
The rate of movement of groundwater varies based on the rock material in the formation through which the
water is moving. After water percolates down to the water table, it becomes groundwater and starts to
move slowly down the gradient, or slope. The rate of movement also depends on the gravitational energy
generated by this difference in elevation of the recharge area and the discharge area. Pressure from the
overlying water and earth materials also influences the rate of movement. Groundwater moves toward areas
of least resistance.
Procedure
1. Obtain a well strip and locate the number of the strip on the “Well Log Data Chart”.
2. Complete the well log strip as follows:
a. Divide the strip into 12 inches (mark on the strip)
b. Mark the level of the water table by drawing a double line at the appropriate
point on the strip.
c. Starting at the top of the strip, illustrate the amount of fine sand by drawing
the designated symbols from the chart at the appropriate level.
d. Complete the strip for the other layers found in the well
3. After your strip is completed, answer analysis questions, part I.
4. Put your well log strip on the area designated by your teacher in the correct order.
5. Compare the class’s well logs with the “Ground Water Student Page”.
6. Answer analysis questions, part II.
Analysis Questions
Part I:
1. The horizontal scale of the cross section is 1 inch = 1 mile. The vertical scale is 1 inch = 50 feet.
How many miles are horizontally represented in the cross section (1 mile = 5280 feet)? How many
feet are vertically represented in the cross section?
2. How many feet below the surface is the water table?
3. Imagine a drop of water falling on the surface of your well. Describe the drop’s movement down
the column. Through which layers would it move the fastest? The slowest? At which layer might
the drop’s movement be restricted?
Part II:
4. Label the parts of a groundwater system on the “Well Log Groundwater Chart”: water table,
confined aquifer, unconfined aquifer, permeable layer, impermeable layer, zone of saturation, zone
of aeration
5. What direction would the groundwater move in the unconfined aquifer?
6. What are the water sources for the unconfined aquifer?
7. If the water moves at a constant rate and flows at 100 feet per day, how long would it take the
water in the sandstone formation to move from well #1 to well #5?
8. Look at the “Cone of Depression” diagram. The cone of depression results from water being drawn
up the well. Locate and label the cone of depression on the “Well Log Groundwater Chart”.
9. Look at the “Groundwater System” diagram. What are the possible sources of water in the
confined aquifer portion of the well.
10. Using the information you’ve learned in this activity, explain why it takes groundwater systems so
long to recover from a drought.