Download WATER USE & DISTRIBUTION

WATER USE &
DISTRIBUTION
APES
CH. 21
Key H20 Characteristics
• Water is the prime constituent
of all living organisms.
• Water moves easily-from one
physical state to another, and
from one place to another.
• Water slowly absorbs and
releases large quantities of
energy.
– Creates habitable climate &
moderates world temp.
• Water is a superior solvent.
•
Michael D. Lee Ph.D. Geography and Environmental
(Source: Wright & Nebel 2002)
The Hydrologic cycle
• Driven by sun
Gets into the air by…
• Evaporation of surface water or sublimation of snow & ice
• Transpiration from plants & animals
• Evaporation + transpiration = evapotranspiration
• Water enters atmosphere leaving behind salts & other contaminants
• Amount of water in atmosphere is humidity
– Warm air holds more water than cold
• When air has all the water it can hold it has reached its saturation point.
(Relative humidity is the amount of water vapor in the air expressed as a %
of max amount (saturation point) that could be held at that particular
temperature.)
• When saturation point is exceeded the water molecules aggregate in
process called condensation.
• Condensation nuclei (particles that water adhere to) initiate the cloud
forming process
• When water droplets are too big for air currents to suspend, they fall to the
ground as precipitation.
Hydrologic Cycle
When water reaches land…
– Runoff- into lakes, rivers, streams
– Infiltration- percolates thru soil
– Temporary storage as snow and ice
– Temporary storage in lakes
– Temporary storage in plants (transpiration)
and animals
– Chemical reactions with rocks and minerals
– Source of additional water? volcanism
(steam)
Hydrologic Cycle
Rainfall & Topography
• Rainfall uneven over planet
• Rainshadow Effect
– Air sweeps up winward side of
mtn, air cools, condenses, and
rains.
– As air falls down leeward side
of mtn, air warms & rainfall
decreases
– EX: Mt. Waialeale in Hawaii,
Himalayas in south Asia,
Sierra Nevada of CA, Oregon
& Washington State
• Desert Belts
– Located at Tropics of Cancer
& Capricorn (around 20-40
latitude)
– Evaporation & precipitation
happen at equator and as air
circulates toward poles it has
less water and falls as hot dry
air, creating deserts.
Global Precipitation Patterns
Available Water
• Total = 326 million cubic
miles
• 97% of Earth’s water is in
oceans
• 2.997% is locked up in ice
caps and glaciers
• 0.003% is easily accessible
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Soil moisture
Groundwater
Water vapor
Lakes
Streams
Water Supply & Use
http://ga.water.usgs.gov/edu/waterdistribution.html
Amount of water
on planet
From Water Exhibit @ Natural
History Museum in New York
Amount of
USABLE water on
planet
Major Water
Reservoirs
Oceans
• Regulates earth’s temp by absorbing and
releasing heat
• Too salty for human use- without expensive
distillation process
• 90% of earth’s living biomass is in the ocean
• Warm & cold water occurs in layers
– Sun warms surface, colder water is denser so
sinks. Warm water sits on cold water
• Average life of a water molecule in the ocean
is 3000 years
Glaciers, Ice & Snow
• Glaciers- rivers of ice
flowing downhill very
slowly
• Make up 2.4% of
freshwater on earth
• Made of freshwatersalt is excluded
during freezing
Groundwater
• Water infiltrates thru soil and is stored
underground
• Zone of aeration
– Upper soil layer where air & water mix
– Contaminants may be removed here- but not all
• Zone of saturation
– Lower soil layer where all spaces are occupied by water
– Top of this zone is the water table
• Water table changes due to amnt of precip & infiltration rates
• Aquifers- layers of porous sand, gravel or rock with underlying layer
of solid bedrock that stores water
• Confined Aquifer- if crust changes due to geologic processes,
aquifer can be trapped btwn two layers of bedrock. Under pressure.
Can gush out of ground as spring or artesian well.
– Powder Springs use to be called Seven Springs because of the 7
mineral springs that bubbled up from ground.
• Recharge zones- areas of land that allow seepage of water back
into aquifer
HOW RIVERS
WORK: the role of
groundwater
www.elmhurst.edu/.../chm110/ outlines/groundwater.html
Surface Water
Surface runoff flows into rivers, streams,
lakes, ponds, and wetlands
Watershed- area of land that drains into a
body of water
• Moving water- rivers & streams
• Standing water- lakes, ponds, wetlands
Moving Waters
(streams & rivers)
• Originate as
– Meltwater from snow or ice
– Seepage from groundwater (spring)
– Precipitation
• Usually headwaters of stream are in mountainous areas
– Cold (elevation), highly oxygenated (gravity pulls down over rocks),
often small
• As stream reaches level ground, deepens and slows & becomes a
river
• Small streams that empty into river are known as tributaries
– EX: Sweetwater creek is a tributary to Chattahoochee River
– EX: McEachern creek is a tributary to Noses Creek
• Not all rivers carry same amount of water
• This measured as discharge- amount of water that passes a fixed
point in a given amount of time (cubic meters/second)
Standing Water
(lakes, ponds, and wetlands)
• Ponds
– Shallow enough to allow
plants to root across bottom
• Lakes
– Inland depressions that hold
standing freshwater all year
• Both are relatively temporaryeventually fill in with sediment
from rivers or are emptied by
water diversion projects
• More accessible than
groundwater or glaciers
• More plentiful than rivers &
streams
Lake Lanier
Chattahoochee
River
West Point
Lake
Flint River
Walter F.
George
Lake
Lake
Seminole
Apalachicola
River
Standing Waters
(lakes, ponds, and wetlands)
• Wetlands
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Bogs, swamps, marshes
Plant roots stabilize soil
Slow water for infiltration
Filter pollutants
• In the US, 20% of the 1 billion hectares of land
were wetlands. About ½ of this has been
drained (for agriculture), filled or degraded
• Results in
– Reduced water holding capacity→ more flooding
– Dry stream beds on other side of wetland
– Reduction in biological diversity
Atmosphere
• Smallest major water
reservoir
• Water molecule lasts
10 days in
atmosphere on
average
• Important in
redistribution of water
across planet