4/15/2013
The Hydrosphere
Groundwater and Precipitation
Hydrosphere – the water on and in
Earth’s crust
 97% of water is contained in oceans
 3% is freshwater found on land

 2% is held in polar ice caps and glaciers
 That leaves 1% for use by living things
Precipitation brings atmospheric
moisture back to Earth’s surface.
 Infiltration – process by which
precipitation that has fallen on land
trickles into the ground and becomes
groundwater.

Groundwater Storage

The Earth’s crust is composed of soil,
sediment, and rock that contain
countless small openings, called pore
spaces.
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4/15/2013
Porosity
Zone of Saturation

The amount of pore space in a material
defines its porosity.
 The greater the porosity, the easier
water can flow through the material.



This is a region below
Earth’s surface in which
groundwater
completely fills all the
pores of a material.
The water table is the
upper boundary of the
saturated region.
The zone of aeration
sits above the water
table with air occupying
most of the pores.
The Water Table
Groundwater Movement
The depth of the water table often varies
depending on local conditions.
 The topography (relief or elevation) of
the water table generally follows the
topography of the land above it.
 Because of its dependence on
precipitation, the water table fluctuates
with seasonal and weather conditions.


Usually flows downhill in the direction of
the slope of the water table.
 Permeability – the tendency of a
material to let water pass through it
 Aquifers – permeable sediment and rock
layers that collect groundwater flow
Springs

Natural discharges of groundwater
where the water table intersects with
Earth’s surface.
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Hot Springs
Springs have a temperature higher than
the human body.
 Most of the springs in the US are found
on the west coast in areas that are
warmed by igneous activity.

Geysers
Explosive hot springs produced by
Earth’s underground thermal energy.
 Water is heated past its boiling point,
causing it to vaporize.
 The water vapor builds up tremendous
pressure fueling the eruption.

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YouTube - Old Faithful Up Close!
Old Faithful Geyser, Yellowstone National Park
Carbonic Acid
Most groundwater is slightly acidic due
to carbonic acid.
 It forms when carbon dioxide gas is
dissolved in water.
 Limestone rock is especially affected by
carbonic acid, which creates interesting
rock formations across the globe.

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Groundwater Deposits
Stalactites – drip formations that hang
from a cave’s ceiling like icicles
 Stalagmites – water drips to the floor of
the cave creating mound formations

Karst Topography
When limestone dissolves, sometimes a
depression is left behind called a sinkhole.
 Sinkhole – depression in the ground
caused by the collapse of an underground
cave or cavern.
 Multiple sinkholes found in a given region
is called Karst topography.
 The name Karst comes from the region in
Croatia where these landforms were first
discovered.

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
Water is not always available in the
quantities and in the locations where it is
needed and might be compromised by
pollution.
Wells
Wells are holes dug or drilled into the
ground to reach an aquifer.
 Overpumping occurs when the water is
drawn out of the well faster than it can
be replaced.

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Threats to our Water Supply
Pollution in Groundwater
Human demands for freshwater are
enormous because it’s essential to life.
 Water is also used in agriculture and
industry.
 The United States uses:


 48% of available water for power generation
 35% for agriculture/irrigation
Sources of groundwater pollution
include sewage from faulty septic tanks
and farms, landfills, and other waste
disposal sites.
 Pollutants usually enter the ground
above the water table and eventually
infiltrate to the water table.
 11% for residential
 5% for industrial
Pollution Sources
Infiltration from fertilizers and pesticides
 Leaks from chemical storage tanks
 Drainage of acid from mines
 Seepage from faulty septic tanks
 Leaks from waste disposal sites
 Radon – comes from uranium in rocks;
could be one of the leading causes of
cancer in the US; test your home
regularly

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