Water Underground
Underground water comes from precipitation that soaks into the ground. The force of
gravity causes the water to be pulled down in a process called percolation. The water
underground trickles down between particles of soil and through cracks and spaces in
layers of rock. Different types of rock and soil have different-sized spaces, or pores,
between their particles. The size of the pores and if they are connected will determine
how easily water will move through a material. Materials that allow water to pass
through easily are called permeable. Materials that do not allow water to pass through
easily are called impermeable.
When water soaks down into
the ground, it passes through
permeable materials. Eventually it
reaches an impermeable layer,
usually solid rock. There, it stops
trickling down and begins to fill the
spaces in the permeable layer
above it. The permeable layer that
becomes filled with water is called
the saturated zone. The level of
the top of the water in the
saturated zone is called the
water table. The layer of rocks and soil above the water table is called the unsaturated zone.
An aquifer is an underground layer of rock or sediment where water has collected.
The water in an aquifer seeps through the permeable rock layers where it is stored. With
mechanical equipment people can obtain groundwater from an aquifer by drilling a well
below the water table.
Pumping water out of an
aquifer lowers the water level
near the well. The aquifer
refills when new water from
the surface, called recharge,
enters the aquifer. If the
water is used up faster than it
can be replaced, the water
table may drop and the well
may become dry.
In some aquifers, the water
that has collected between
impermeable layers is under great pressure. If a hole is drilled in the impermeable layer
above it, the water flows out of the aquifer without being pumped. A well in which water
rises because of pressure within the aquifer is called an artesian well.
A spring is a place where groundwater bubbles or flows out of cracks in the
rock. It is a flow of water from the ground at a place where the surface of the land dips
below the water table. Spring water has a clean taste and
many water companies bottle this water to sell.
The water in some springs is warm or even hot. The
water is heated by hot rocks deep underground. A geyser
is a hot spring in which the water is under pressure. From
time to time, the pressure causes the hot water and steam
to erupt into the air. One famous geyser is Old Faithful in
Yellowstone National Park.
Name_________________________
Water Underground
1. Precipitation that soaks into the ground trickles downward due to _____________________
Match the term with its definition
_____ 2. pore
a. allows water to pass through
_____ 3. permeable
b. area that is totally filled with water
_____4. impermeable
c. space between rock and soil particles
_____5. saturated zone
d. does not let water pass through
_____6. water table
e. layer above the water table
_____7. unsaturated zone
f. top of the saturated zone
8. In the drawing, label the water table, the saturated AND unsaturated zones, permeable and
impermeable layers .
9. In the picture above what is the underground layer of rock or sediment that holds water called?
__________________________________________
10. The aquifer refills when new water from the surface, called a __________________, enters the aquifer.
11. Explain how sand and stones in the ground are beneficial for those who rely on aquifers for their fresh
water. _____________________________________________________________________________
__________________________________________________________________________________
12. Circle the letter of the choice that best explains how to get water form an aquifer with a well.
a. By drilling below the water table.
c. By drilling through impermeable rock
b. By drilling below the aquifer
d. By drilling near a dry well
13. A well in which water rises because of pressure within an aquifer is called
a(n) ___________________ __________.
14. Places where groundwater bubbles or flows out of cracks in the rock are called ___________________
15. A type of hot spring from which the water bursts periodically into air is called a(n) ________________