Transcript Water Resources - Alabama School of Fine Arts

WATER RESOURCES
SUPPLY, RENEWAL, AND USE
HOW MUCH IS AVAILABLE?
• 97.4% is salt water
• 2.6% is fresh water
• Locked in ice caps and
glaciers
• Polluted
• Salty or deep groundwater
• 0.014% available as soil
moisture, useable
groundwater, water
vapor, and surface
water
PLANET’S WATER BUDGET
HYDROLOGIC CYCLE FILTERS AND RECYCLES FRESHWATER
WATER RESOURCES ARE UNEVENLY DIVIDED IN THE WORLD
WATER SHORTAGES
• Water haves and have nots
• Average annual precipitation divide the world’s continents,
countries, and people
• Some places receive a lot of rain, others very little
• Example: Canada has only 0.5% of the world’s population
but 20% of the world’s freshwater. China has 20% of the
world’s population but only 7% of the water supply.
USABLE WATER
Surface Water
• Any precipitation that
does not infiltrate into
the ground
• 1/3 is reliable runoff
• 2/3 is lost by seasonal
floods
• Watershed or Drainage
Basin
• Region where water
drains into a stream, lake,
reservoir, wetland, etc.
Ground Water
• Water that infiltrates into
the ground, fills up pores
in rock and soil
• Area above
impermeable rock barrier
is the Zone of Saturation
• Water table—on top of
zone of saturation
• Zone of Aeration—above
the water table (air and
water)
Flowing
artesian well
Unconfined Aquifer Recharge Area
Precipitation
Well requiring a pump
Evaporation and transpiration
Evaporation
Confined
Recharge Area
Runoff
Aquifer
Infiltration
Stream
Water table
Lake
Infiltration
Unconfined aquifer
Confined aquifer
Less permeable material
such as clay
Confining permeable rock layer
HOW IS WATER USED WORLDWIDE?
• Mostly for irrigation (70%)
• Industry (20%)
• Cities and Residences (10%)
400,000 liters
(106,000 gallons)
1 automobile
1 kilogram
cotton
10,500 liters
(2,400 gallons)
1 kilogram
aluminum
9,000 liters
(2,800 gallons)
1 kilogram
grain-fed beef
7,000 liters
(1,900 gallons)
1 kilogram
rice
1 kilogram
corn
1 kilogram
paper
1 kilogram
steel
5,000 liters
(1,300 gallons)
1,500 liters
(400 gallons)
880 liters
(230 gallons)
220 liters
(60 gallons)
Amount of water needed
to produce some
common agricultural and
manufactured products.
WATER PROBLEMS IN THE U.S.
• Eastern states have ample precipitation
• Mainly used for energy production, cooling, and manufacturing
• Flooding, occasional urban shortages, pollution
• Western states have too little precipitation
• Mainly used for irrigation
• Shortage of runoff caused by low precipitation, high evaporation,
drought
PREVENTING WATER SHORTAGES
• Water shortages are caused by
• Drought—21 days or longer where precipitation is at least
70% below normal
• Desiccation of soil—deforestation and overgrazing
• Water stress—too many people and not enough water
• Increase water supply by
•
•
•
•
•
Build dams and reservoirs to store runoff
Bring surface water from other areas
Withdraw groundwater
Convert salt water to fresh water
Improve efficiency of water use
DAMS
USING DAMS
Benefits
Drawbacks
• Control floods
• Produce hydroelectric
power
• Supply water for
irrigation
• Recreation (swimming,
fishing, and boating)
• Reduces water flow
below the dam
• Silting at the dam
• Increase risk of flooding if
dam breaks
• Destroys natural
ecosystems
• Increases water pollution
• Promotes saltwater
intrusion
USING TRANSFER OF WATER
• Tunnels, aqueducts, and pipes
USING GROUNDWATER
• Pros—can be removed
year round, is not lost
by evaporation, less
expensive to develop
than surface water
systems
• Cons—lowers the water
table, land subsidence,
salt water intrusion,
moves contaminated
chemicals toward
wells, reduces stream
flow
Major irrigation
w ell
Well contam inated
w ith saltw ater
Water
table
Sea Level
Salt
w ater
Fresh
groundw ater
aquifer
Interface
Saltw ater
Intrusion
Interface
Norm al
Interface
Fig. 13.17, p. 308
Slide 19
USING DESALINIZATION
• Removing dissolved salts from ocean water or brackish groundwater
• Distillation
• Reverse osmosis
• Main plants are in the Middle East and North Africa
• Energy expensive
• Produces much waste water (brine)