Water Underground: *Where we get
most of our freshwater!!!*
How Water Moves Underground
 Water underground trickles down between
spaces in soil and through cracks and spaces
in layers of rock.
Effects of Different Materials
 Different types of rock and soil have
different-sized spaces between their particles.
 The size of the spaces determines how easily
water moves through rock and soil.
 If the spaces are connected, this too affects
water movement.
 Because they have large and connected
spaces, materials such as sand and gravel
allow water to pass through, or permeate.
They are thus known as permeable
materials.
 As water soaks down through permeable rock
and soil, it eventually reaches layers of
material that it cannot pass through.
 These materials have few or no spaces or
cracks.
 Clay and granite are impermeable, meaning
that water cannot pass through.
 When water reaches the impermeable
materials it is trapped and forms the water
table – where we get our water.
Water Zones
 Once water reaches an impermeable layer, it
is trapped. It can’t soak any deeper.
 Instead, the water begins to fill up the spaces
above the impermeable material.
 The area of permeable rock or soil that is
totally filled, or saturated, with water is
called the saturated zone.
 The top of the saturated zone is the water
table.
 Soil and rock layers above the water table
contain some moisture, too. Here the pores
contain air as well as water and are not
saturated.
 Therefore, the layer of rocks and soil above
the water table is called the unsaturated
zone.
Bringing up Groundwater
 Any underground layer of rock or sediment
that holds water is called an aquifer.
 Aquifers can range in size from a small
underground patch of permeable material to
an area the size of several states
 The water is moving, seeping through layers
of rock.
 The depth of a water table can vary greatly
over a small area.
 People can obtain water from an aquifer by
drilling a well below the water table.
 In an artesian well, water rises because of
pressure within an aquifer (natural well).
Uses of Water
(1) How many categories of water use are shown
on the graph?
4
(2) What are the two largest categories of water
use combine to make up about what percentage
of the total water used in the United States?
Agriculture and Power Plants combined make
up 80.5% of total water used in the U.S.
(3) Which of the categories of water use shown in
the graph represents the largest use of water in
the United States? Which represents the
smallest?
Agriculture = largest, industries and mining =
smallest
(4) How would an increase in the number of farms
affect this graph?
The percentage for agriculture would increase,
and the percentage available for all of the other
uses would have to decrease.
Water Underground Questions:
1. What happens to water in the ground when
it reaches the impermeable materials?
- It is trapped and forms the water table.
2. What two factors determine how easily
water can move through underground
materials?
- The size of the spaces of the
underground materials and whether the
spaces are connected.
3. Would an impermeable material have large
or small spaces? Would the spaces be
connected or unconnected?
- Impermeable material would have small
spaces or none and they would be
unconnected.
4. How could people obtain water from an
aquifer?
- They could drill a well down below the
water table.