Transcript The Water Cycle

The Water
Cycle
Or
The Hydrologic Cycle
Arguably the most important natural
phenomenon on Earth, the water cycle, also
known as the hydrologic cycle, describes the
constant movement and endless recycling of
water between the atmosphere, land surface,
and under the ground. The hydrologic cycle
supplies the force needed for most natural
processes, thus supporting life itself.
The Water Molecule

H20 consists of one
atom of oxygen bound
to two atoms of
hydrogen. The water
molecule has a positive
charge on the side of
hydrogen atoms and a
negative charge on the
other side. Water
molecules tend to attract
each other because the
positive ends attract to
the negative ends.
 Water
is a
“universal
solvent: and
wherever it
goes
throughout the
water cycle, it
takes up
valuable
chemicals,
minerals and
nutrients.
Condensation
The change from water
vapor (gas) to liquid. In the
water cycle, the change is
from water vapor to a form
of precipitation.
Condensation
& Convection
 Warm
air rises
 Air cools and
can no longer
hold vapor
 Process known
as
CONVECTION
Condensation & Cloud
Formation
 Cooling
of
water vapor
forms CLOUDS
 Other ways
clouds are
formed
 Convergence
 Lifting of air
by fronts
Precipitation
Snow
 Snow
is a type
of precipitation
like rain but at
cooler
temperatures
 Usually reaches
the ground and
stays
 Eventually melts
and becomes
runoff in streams
Rain
 Type
of
precipitation
during warmer
weather
 Occurs when
clouds become
too full
 Falls to earth in
the form of
water and runs
off to streams &
rivers
Freshwater Storage
 Water
may be
stored
temporarily in
the ground,
oceans, lakes,
rivers, and in
ice caps and
glaciers.
 The
world’s two
main reservoirs
of fresh water
are the great
polar ice caps,
and the ground.
 If all of the ice
in the ice caps
and other
glaciers melted,
it would raise
the sea level by
about 260 ft.
 In
temperate
climates, water
is found in
depression
storage or
surface water
puddles,
ditches, and
anywhere else
that runoff
water can
gather. This is a
temporary form
of storage
Freshwater Flow
A
hydrologist is
particularly
interested in
stream flow -the 31% of
precipitation
which runs off
into rivers,
streams and
lakes.
 About
3% of this
water will seep
underground
 About 31% will
run off into
rivers, streams
and lakes
 About 66% of the
water returns to
the atmosphere
through
evaporation and
transpiration
Surface Runoff
 When
precipitation
rate exceeds
infiltration rate,
or when soil is
saturated,
water begins to
move down
slope on ground
surface.
Surface Runoff

surface runoff
gradually flows
into gullies,
streams, lakes, or
rivers. Water in
streams and
rivers flows to the
ocean, seeps into
the ground, or
evaporates back
into the
atmosphere.
Water Storage in Oceans
 The
largest
reservoir is the
oceans. There
is about 50
times as much
water in the
oceans than in
the next largest
reservoir, polar
ice and glaciers.
Water Storage in Ice
and Snow
Water
precipitates
into cooler
areas of
land and
freeze into
ice and
snow.
Snowmelt Runoff to Streams
 Precipitation
falls in the form
of rain and snow
 When the snow
melts it runs
into streams
which eventually
dump into the
ocean
Infiltration
-Rain water soaks
into ground through
soil and underlying
rock layer.
-Water cleaned
as impurities
filtered

-Some water
remains
underground as
groundwater.
-Some water returns
to surface at springs
or low spots
downhill.
Groundwater
Storage
- water seeps downward
underground into soil and rock
crevices
-then stored
underground in rock
crevices and in the
pores of geologic
materials that make
up the Earth's crust
-Water storage under the ground largely
depends on the geologic features related
to the types of soil and the types of rocks
present at the storage locations.
-underground
storage occurs in
the soil, in aquifers,
and in the crevices
of rock formations
Evaporation
 Conversion
of
water from a
liquid into a gas
 Water
transferred
from surface to
atmosphere
through
evaporation
Evaporation & the Sun
The sun heats
up water in the
ocean, rivers, or
lakes, turning it
into vapor,
which then
goes into the
air
Evaporation
Cont.
80% of

evaporation from
ocean
 20% of
evaporation from
inland water and
vegetation
 Winds transport
evaporated water,
influencing
humidity around
the world
Transpiration
The process of
evaporation
from plants.
Basically,
plants
sweating.
Transpiration Cont.
Environmental
factors that
affect
transpiration:
 Light
 Temperature
 Humidity
 Wind
 Soil water
Good For Plants!!

Transpiration is
the “engine” of
plant life, pulling
water up from the
roots. This allows
for
photosynthesis,
brings minerals
from the roots to
the rest of the
plant, and cools
the leaves.
Water Storage in
Atmosphere
-atmosphere holds only very small
percentage of Earth’s water supply at
any given time
-rapid
Source
% of Supply recycling of
Oceans
97.08
water must
Ice Sheets and Glaciers
1.99
occur
Ground Water
0.62
between
Atmosphere
0.29
earth's
Lakes (Fresh)
0.01
Inland Seas / Salt Water Lakes 0.005
surface and
Soil Moisture
0.004
atmosphere
World Water Supply
Rivers
0.001
- Water stored in the atmosphere
can be moved relatively quickly
from one part of the planet to
another part of the planet