Transcript 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
Flow Rates
Washing hands/face
2-5 gal /min
Showering
5 gal/min/ lo flow 12 gal/five min
Bath
30 gal / tub
Brush teeth
5 gal/min
Wash food
5 gal/min
Flush toilet
Low flow 2-4 gal/flush
Wash clothes
Top load 20 -40 gal/load
HE- 18-25 gal/load
Front load 20-25 gal/load
Wash dishes by hand
Run water 30 gal/ sponge wash rinse
5 gal
Dishwasher (read your manual)
Full cycle 15 gallons/ short cycle 7 gal
Clean house
8 gallons
Water Uses
Use of Fresh Water
United States
China
• 41% agriculture
• 38% power plant cooling
• 11% industry
• 10% public
• 87% agriculture
• 7% industry
• 6% public
Water Use Globally
People and Planet
• 70% of water withdrawn
for human use is soaked
up by agriculture (mostly
in the form of irrigation)
• Industry accounts for 23%
• Domestic use (household,
drinking water, sanitation)
accounts for about 7 %
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50
40
30
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10
0
Irrigation
Industry
Dome stic
Agriculture-70%
• In LDC, 60-70% never reaches crop. Much is
lost to evaporation b/c they use flood or furrow
irrigation.
• Sprinklers are more efficient & can be used on
uneven land. Cost $ and still have problem with
evaporation
• Best method- Drip irrigation- system of tubes
deliver water directly to roots. Most efficient but
used only 1% of time- expensive
• AGRICULTURE IS BY FAR THE BIGGEST
USERS AND POLLUTERS OF WATER
Agriculture & Aquifers
• Largest aquifer:
Ogallala Aquifer
• 95% of water taken
from Ogallala is used
for irrigating crops
Industry- 23%
• Cooling power plants
• Many industries
locate on rivers b/c
– Used in manufacturing
process
– Used for transportation
of goods
Domestic Use- 7%
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Cooking
Cleaning
Drinking
Bathing
Clothes washing
Flushing toilet
Washing Car
Etc.
Water Use Per Person
People and Planet
• The average person needs a minimum of
5 L (1.3 gallons) of water per day to
survive in a moderate climate at an
average activity level, according to UN
figures.
• The minimum amount of water needed for
drinking and cooking, bathing and
sanitation is 50 L (13 gallons).
Water Use - (minimum 13 gallons) People and Planet
• The average person in the
United States uses between
250 to 300 L of water (65-78
gallons) per day for drinking,
cooking bathing, and
watering their yard.
• The average person in the
Netherlands uses 104 L per
day (27 gallons).
• The average person in the
African nation of Gambia
uses 4.5 L per day (1.2
gallons of water).
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15 0
Uni t e d
St at es
Ne t he r l a nd
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10 0
50
0
Ga m b i a
Water
Availability
Water Availability
• Varies across world
• Rainfall interannual variabilityabundant rainfall one year, not
others (drought cycles)
– Has led to many past cultures
developing ways to divert
water, or store water in
reservoirs
– U.S. has a drought cycle
about every 30 years (1870’s,
1900’s, 1930’s, 1970’s)
– 1930’s- Dust Bowl- poor
farming techniques & drought
led to major erosion & dust
storms
Freshwater Shortages
• In 1977, UN Water Conference declared every person
has right to clean drinking water & sanitation no matter
socioeconomic status
• Still, 1.5 billion have no access to water & 3 billion no
access to good sanitation
• Water is abundant but unevenly distributed or too
polluted for use.
• 45 countries in serious water stress- most in Africa and
Middle East
• Water cleaner in cities than in rural areas
• Many women must travel 2 hrs/day to collect & carry
water. If clean water available, could cut to 25 minutes.
More time gardening, tending livestock, trade in market,
etc.
http://www.peopleandpla
net.net/graphs/Freshwate
ravailability.jpg
Freshwater Shortages
• Natural
– Rains fail
– Hot winds dry up reservoir
– Rivers change course
• Human caused
– Increased population =
increased competition
– Urbanization- no recharge
zone
– Overgrazing- dries out soilmore runoff- less recharge
– Poor farming technique
– Lack of adequate sewage
removal causes
contamination
Depleting Groundwater
• Supplies 40% of drinking & irrigating water in US
• Sometimes called “fossil water” because it takes so long
to recharge- 100’s to 1,000’s of years
• When this happens called “water mining” because it
becomes non-renewable- can’t recharge fast enough
• Withdrawn faster than recharge process can occur
– Via wells
– Diverting runoff with dams & channels
– Covering with urban development- building roads & homes
decreases the recharge area
• Massive pumping creates a cone of depression (see
next slide) which makes shallower wells run dry
Depleting Groundwater
Withdrawal of large amts of
water (overdrafts) causes
• Subsidence- settling of
ground or sinkholes
– Mexico city has dropped
7.5 meters (bottom pic)
• Saltwater intrusions
– Decrease in pressure in
aquifer allows saltwater
from ocean to infiltrate &
contaminate
SALTWATER
INTRUSION
As cone of
depression
increases &
water table
decreases, the
zone of diffusion
increases or is
drawn up
allowing pump to
draw water from
saltwater source
Increasing
Freshwater
Supply
Seeding Clouds & Towing Icebergs
• Seeding clouds
– Use dry ice or potassium
iodide particles
– Disrupts weather patterns
& may cause
contamination
• Towing icebergs
– Made of freshwater
– No method of containing as
it melts
– May be too expensive
Desalination
(removing salt
from ocean water)
• Distillation- evaporation &
recondensation
• Reverse Osmosis- forcing
salt water thru semipermeable membranes
which capture salt &
purify water
• Used mostly in Saudi
Arabia, Kuwait, & United
Arab Emirates
• Very expensive process
Dams, Reservoirs, Canals, &
Aqueducts
• Water diversion has been used
for 1000’s of years (Romans
built Aqueducts, Egyptians built
canals for irrigation)
• Reservoirs- water contained by
dam
• Canals- divert water from
original source to be used for
irrigation or transportation
• Aqueducts- divert water from
original source to be used as
water supply for city
Large Dams - Pros
• Collect and store water from rain and
snow
• Produce electricity
• Irrigate land below the dam
• Control flooding
• Provide water to cities, towns and rural
areas
• Provide recreational activities such as
swimming, boating, fishing
Large Dams - Cons
• Enormous loss of water due to evaporation
• Flooded land destroys forests or cropland and
displaces people
• Danger of Dam collapse
• Downstream areas deprived of nutrient-rich
soil, which will eventually clog the reservoir
• Migration and spawning of fish disrupted
• Causes water wars between states &
countries
• Expensive to build
Fish Bypass System
Hoover Dam
Notable Water
Diversion Projects
Mono Lake, CA
• In 1941, L.A. started
diverting Mono Basin
streams to add to L.A.
Aqueduct.
• Mono Lake’s volume halved
while salinity doubled. The
simple ecosystem began to
fail and threatened migrating
birds and nesting gulls.
• The state and courts now
mandate raising the level of
the lake 17 feet. It will take
about 20 years.
• Should make more habitable
for birds & fish
Hetch Hetchy:
San Francisco Water
• Hetch Hetchy Valley, in
Yosemite National Parkbeautiful valley with
waterfalls & green meadows.
• Dammed in 1931
• 175 mile aqueduct and
O’Shawnasy Dam
powerhouse- provide cheap
power to the city of San
Francisco.
• John Muir (founder of Sierra
Club) was greatly opposed to
this water diversion project.
Before
After
Three Gorges Dam
• World's largest hydroelectric dam, Three
Gorges, Yangtze River.
• 1.2 - 1.9 million people will be displaced.
• The entire project is to be completed in 2009.
The Geography of Large Dams
• Over 39,000 large dams by 1986
What happens when you
have too much water?
Too Much Water: Floods
• Natural flooding from
• heavy rain
• rapid melting snow.
• This causes water in a stream to overflow it normal
channel & flood the adjacent area, called a floodplain.
• Floodplains, which include highly productive wetlands,
help to:
—Provide natural flood & erosion control
—Maintain high water quality
—Recharge groundwater
• When the floodwater recede, deposits of silt are left
behind, creating a nutrient-rich soil.
Too Much Water: Floods
People have been settling in floodplains for several
reasons:
1. Fertile soil
2. Sufficient water for irrigation
3. Flat land suitable for agriculture
4. Use of nearby rivers for transportations
However, each year floods (“natural disasters”) kill
thousands of people & cause tens of billons of dollar in
property damage. Human activities have contributed to
the sharp rise in flood frequencies which dramatically
increased flood deaths & damages.
Flooding
Human activities
that increase
flooding:
• removing vegetation
• logging
• overgrazing
• forest fires
• mining
• destruction of
wetlands
• building on
floodplains
• urbanization
© Brooks/Cole Publishing Company / ITP
Too Much Water: Floods
Natural phenomena
Aggravated by
human activities
Renew and replenish
Reservoir
Dam
Levee
Floodplain
Flood
wall