Transcript Chapter 1 Notes

Chapter 1: The Flow of
Fresh Water
Over 70% of the Earth’s surface is
covered with water. However, over 97%
of this water is salt water and cannot
be used by living things.
3% of the Earth’s water is freshwater,
but only about .5% is usable by living
things. The other 2.5% is frozen as
glaciers and ice caps.
If this supply of usable freshwater is so
low, why don’t we run out?
The water cycle (aka hydrologic cycle) is
the continuous movement of water that
renews our freshwater supply.
3 steps of the water cycle:
1. Evaporation: energy from the
sun causes liquid water to change
to a gas. Plants also remove water
from the ground and change it to
a gas (transpiration)
2. Condensation:
water vapor changes
back into a liquid as air
is cooled.
3. Precipitation: water
returns to the Earth in
the form of rain, snow,
sleet, or hail.
A reservoir is a man-made lake built by
damming a stream or river so that water
accumulates. Reservoirs are often used as
a supply for drinking water, irrigation, or to
make hydroelectric power.
Erosion is the process by
which weathered rock
and soil particles are
moved from one place to
another.
Erosion carries away the
products of weathering!
Deposition is the
process by which
sediments are laid down
in new locations.
Not all of the water that
reaches the Earth’s surface
becomes runoff. Some water
sinks into the ground
(infiltration).
Groundwater exists because
precipitation moves slowly
into the soil through pore
spaces between the rocks
and soil.
Material through which water can easily
move is said to be permeable. This
material generally has a lot of pore
space.
Example: sandstone
Material through which water cannot pass is
said to be impermeable. This material
generally has very small pore spaces, which
prevents the water from sinking.
Example: clay
Once groundwater reaches an impermeable
layer, it gets trapped and begins to fill in the
layers above it. The soil layer that holds all of
the water that it possibly can is called the
zone of saturation.
Above the zone of saturation is the zone of
aeration. This area has mostly air between
its pore spaces.
The boundary between the zone of
saturation and the zone of aeration is called
the water table.
When water collects above an impermeable
layer, it starts to move sideways along that
layer. This forms an aquifer, which is an
underground pool where water collects. Wells
are often dug or drilled into an aquifer.
The taste, odor, and appearance of ground
water varies from area to area. Often, these
differences are caused by the types of
materials dissolved in the water.
The hardness of water depends on the
source of the water and the types of rocks
and soil the water comes from.
Hard water: contains large amounts of
dissolved minerals, usually calcium and
magnesium.
Soft water: does not have dissolved minerals
Because water is such a strong solvent,
it can dissolve layers of rock
underground. This can form a
sinkhole.
Water is a necessity for all living things.
Your body is almost 65% water!
Therefore it is important that we
protect this natural resource.
Water Pollution
1. Point-source pollution: pollution that
comes from a single source
2. Nonpoint-source pollution: pollution
that comes from many sources. This is the
hardest to control!
Water Usage at Home