GROUNDWATER
Chapter 6.3
What is Groundwater?
• It is hard to imagine groundwater because it is underneath
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our feet, but we can’t see it.
Believe it or not, there is more water underneath the
ground, then there is in lakes, rivers and streams.
In fact, if you drank some water today or took a shower, it
was most likely from groundwater.
The ocean has an abundance of water but it is mostly
unusable to us as humans because it is saltwater.
Groundwater moves underground through aquifers,
which are permeable rock layers or sediments that allow
water to flow through them freely.
Aquifers
Understanding Aquifers
• Underneath the ground there are two zones. The zone
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found under ground that does not contain groundwater is
called the zone of aeration.
The zone found under ground that does contain
groundwater is called the zone of saturation.
The line that separates these two zones is called the
water table.
The amount of water that can be stored in the zone of
saturation depends on how much empty pore spaces
there are, which is called its porosity.
The porosity of an aquifer can determine how fast water
can flow through it. The speed at which water can move
through an aquifer is called its permeability.
Understanding Aquifers
What are Springs
• When the water table intersects the ground surface, a
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spring forms.
When springs are close to magma underground, a hot
spring can be formed.
When a hot spring shoots up out of the ground at regular
intervals and then the water drains back into the aquifer
again, this can form a geyser.
A well is simply a man-made hole drilled into the ground
to reach the water table.
An artesian well is a natural well that forms when the
water table rises up against the force of gravity.
Springs and Wells
Geysers and Hot Springs
How does an artesian well form?
• In order to have an artesian well you have to have some
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unique conditions.
You must have an aquifer that is contained by aquicludes
(also sometimes called an aquitards).
An aquiclude or an aquitard is an impermeable layer of
rock or soil.
You must also have an aquifer that is on a slope so that
the recharge area (source of water) is higher than the
discharge area (the sight of the artesian well).
It is similar to using a siphon hose.
Artesian Wells
Caves and Karst Topography
• When rainwater that is acidic permeates into the ground
and reaches areas with limestone bedrock, the acid
dissolves the calcite (limestone) minerals.
• The empty spaces left behind when the limestone
dissolves forms caves (or caverns).
• The water that drips into the caves leaves behind small
amounts of calcite behind. This forms stalactites on the
ceiling and stalagmites on the cavern floor.
• The ground located above caverns can form uneven
ground with lots of depressions called sinkholes. This
type of terrain is called Karst Topography.
Caves and Karst Topography