Download 14.1 Water in the Ground

14.1 Water in the
Ground
Key Idea:
Factors such as the porosity and
permeability of soil and rock materials
affect the storage and movement of
water in the ground.
Groundwater

The natural conditions of a region
determine the direction where the water
from precipitations goes. For example:
-in the mountains, much of the water will
flow on the slopes as run-off, and will be
collected by streams and rivers.
- in the desert the water will evaporate
quickly.
-in areas with loose soil and rocks that are
permeable, much of the water will seep
into the ground, and stored as
groundwater.
Groundwater
Properties of Rocks that Allow
Groundwater to Accumulate.
1. Porosity
Ground water accumulates in rocks that
allow the water to seep through. The rocks
must have cracks, or spaces in between
particles; these spaces are commonly
called pores. The property of having
pores is called porosity.
2. Permeability
The pores must be connected together in
order to let the water seep through. The
rate at which water passes through the
pores of rocks is called permeability.
Porosity
 Porosity
depends upon a number of
factors, such as:
- particles’ shape: materials
consisting of rounded particles have
more porosity than the materials
having angular particles.
- sorting: the amount of pore space
is is greater in materials that have
particles of the same size.
Example of Porosity
Various Types of Porosity
2. Permeability
Permeability differs greatly among rocks:
 Loose rocks such as gravel and sand have food
permeability.
 Larger grains will have larger pore spaces.
 The finer the grains of the rock, the less porosity
and permeability the rock has.
 Some rocks have pores but the pores are not
connected at all. Pumice is an example of such a
rock.
 Limestone is not a porous rock, but it is has
many cracks that make this rock permeable.
Aquifers
The water that seeps into the ground will
be collected in porous rocks, such as sand
and gravel; this water will form an aquifer.
 At the base of all aquifers there is a layer
of impermeable rocks.
 Sometimes there are alternating layers of
permeable and impermeable rocks, that
might favor the formation of more than
one aquifer (like in the above picture).

Aquifers
The Water Table
 An
aquifer is an accumulation of
underground water.
 The area where water fills the aquifer
is called the saturated zone (or
saturation zone). The top of this
zone is called the water table. The
water table may be located only a
foot below the ground’s surface or it
can sit hundreds of feet down.
The Water Table
Factors Affecting The Water Table
The water table can be at the surface of the
ground, such as in swamps and some
lakes; its depth depends on many factors:
 Amount of rainfall
 Amount of time that passes between rains
 Season
 The slope of the ground
 Thickness of the soil
 Climate type.
Factors Affecting The Water Table
In humid climates the water table is close
to the surface.
 In desert regions the water table may be
hundreds of yards below the surface.
 In the woods it is likely to be closer to the
surface, where the tree roots can reach it.
 In hilly country it is closer to the surface
in the valleys.

Wells
Wells provide drinkable water to many
people that have no access to other
sources of water.
 People who live in the desert have to
dig very deep wells to get the water
table.
 Many rural communities all over the
world rely mainly on ground water.
A Well Diagram
Contamination of Groundwater
Springs
 On
a hillside where the groundwater
meets the surface, groundwater may
flow out as a spring.
Afka
Spring
in
Lebanon
Artesian Springs
Sometimes the aquifers form in hilly
areas. If the aquifer is trapped in between
two impermeable layers of rocks and it is
charged at the top by precipitations, then
the water table might be way above the
ground level at the base of the hill.
 If a well is dug at the base of the hill, then
the water might spout upward with
pressure, rising several feet, or yards
above the ground level. This is an artesian
well.

Artesian Well
Artesian Well
Hot Springs, Geysers, and
Fumaroles
 Hot
springs, geysers and fumaroles
are manifestations that are related to
magma- tic activity.
Hot springs
If the ground water travels nearby a
mass of hot magma, the water can
easily reach boiling point, and its
pressure increases. The water comes
out the ground as a hot spring.
Geysers
A
geyser is an intermittent hot
spring. It shoots hot water and
steam into the air at certain intervals
of time: weeks, days, or hours.
 In Yellowstone Park there is one
geyser named Old Faithful which
erupts every 89 minutes.
Old Faithful
Fumaroles
 In
areas with recent volcanic activity,
where magma is still very hot, the
groundwater is heated to the boiling
point, and reaches the surface at hot
steam.
 These columns of hot steam are
called fumaroles. (The Latin work
“fumus” means steam)
Fumaroles at Yellowstone National
Park