water resources - henry county school...
TRANSCRIPT
GEORGIA WATER ISSUES/ TAPPED???
http://www.atlantaregional.com/environment/tri-state-water-wars
http://www.huffingtonpost.com/2013/12/04/water-shortage_n_4378418.html
Will We Have Enough Usable Water?
How much of the Earth’s surface is covered with
water?
• About 70%
How much of that water is freshwater?
• About 2.5% (97.5% is saltwater)
Of the freshwater, how much is ice & glaciers?
• 77.28% (= 1.9% of the earth’s water)
Out of Earth’s Water, less than 1% is accessible
for human use.
Less than 1% is Accessible Fresh Water
0.55% is groundwater
0.01% is in surface water
0.001% is water vapor in the atmosphere
We Manage Water Poorly
Hydrologic cycle: would naturally purify, if we
didn’t overload it and destroy wetlands/forests
•Major forces of purification
•Evaporation
•Infiltration – water
enters soil through
gravity and capillary
action
Problems with water
Water is not distributed evenly
• Haves
• Canada (0.5% world pop. & 20% world supply)
• Have Not's
• China (20% world pop & 7% world supply)
We are managing our water poorly
• We take too much, too fast
• We pollute the water we do have
Global Water Issues
Access to water is
• A global health issue
• An economic issue
• A women’s and children’s issue
• A national and global security issue
We Get Freshwater from Groundwater
Ground water: water that sinks into the soil and
is stored in slowly flowing and slowly renewed
underground reservoirs
Zone of saturation: zone where all available
pores in soil and rock in the earth’s crust are
filled by water
Water table: upper surface of the zone of
saturation
Aquifers: porous, water-saturated layers of
sand, gravel, or bedrock that can yield an
economically significant amount of water
More about Aquifers
Aquifers
• Confined: held by impermeable rock layers
• Can create an artesian well & springs
• Unconfined: held by less permeable layers (like clay)
Recharge types – Animation/ Youtube
• Natural recharge (top)
• Lateral recharge (side)
-process by which rainwater
seeps down through the soil into
an underlying aquifer.
Groundwater Overpumping Has Other
Harmful Effects
Limits future food production
Land subsidence
Sinkholes
• sediments that cover buried cavities in the aquifer
systems are delicately balanced by ground-water
fluid pressure
Groundwater overdrafts near coastal regions
• Contamination of the groundwater with saltwater
• Undrinkable and unusable for irrigation
Cone of Depression
Pumping water creates a
“cone of depression” since
water in an aquifer takes so
much time to flow
• Picture yourself drinking a
McDonald’s milkshake… the
shake goes down near the
straw first.
The cone of depression
lowers the water table, which
dries up streams and wells.
Land Subsidence & Sinkholes
Land subsidence
is a gradual
settling or sudden
sinking of the
Earth's surface
• Major Causes:
• Groundwater
depletion
• Mining
Basic (gradual) Subsidence
Rapid Subsidence = Sinkhole
Guatemala 2010 – 30 stories deep
Saltwater Intrusion
When groundwater
is removed from the
water table near the
ocean, pressure
forces the salty
water inland, where
it may eventually
infiltrate the well.
Case Study: Aquifer Depletion in the
United States
Ogallala aquifer: largest known aquifer
• Irrigates the Great Plains
• Water table lowered more than 30m
• Cost of high pumping has eliminated some of the
farmers
• Government subsidies to continue farming
deplete the aquifer further
• Biodiversity threatened in some areas
• https://www.youtube.com/watch?v=XXFsS94HF0
8
Active Figure: Threats to aquifers
US Water Use
Half of our water is from groundwater
Half of our water is from surface water
• Rivers, lakes & reservoirs
When you remove groundwater, you deplete
surface water as well…why??
We Get Freshwater from Surface Water
Surface Water: precipitation that does not infiltrate the ground or return to the atmosphere by evaporation or transpiration
• Surface runoff: water flowing off the land into bodies of surface water
• Watershed (drainage) basin: land area that delivers water, sediment, and dissolved substances via small streams to a major stream (river)
• Reliable runoff: surface runoff of water that generally can be counted on as a stable source of water from year to year
• 1/3 of total
We Use a Large and Growing Portion of
the World’s Reliable Runoff
In the last century, human population tripled and
water withdrawal increased sevenfold
More water used by the rich
• It takes 2,400 bathtubs to make a small car (120,000 gal)
• 37 gallons to produce 1 cup of coffee
• 25 bathtubs to make 1 T-shirt
Case Study: Freshwater Resources in the
United States
We have more than enough renewable
freshwater, but it is unevenly distributed
TRIVIA
What's the rainiest city in the US?
• For the last 30 years, the rainiest 3 in order are:
• Mobile, AL
• Pensacola, FL
• New Orleans, LA
Case Study: Freshwater Resources in the
United States
In the east
• Water is used for:
• Energy production, manufacturing
• Water problems are:
• Flooding
• Urban shortages due to pollution
• Occasional Drought
• A prolonged period in which precipitation is at
least 70% lower and evaporation is higher than
normal
Case Study: Freshwater Resources in the
United States
In the west
• Water is used for:
• Irrigation (85%)
• Water problems are:
• Shortage due to low precipitation, evaporation and
recurring drought
2007: U.S. Geological Survey projection
• Water hotspots: places where competition for
scarce water could trigger political and legal
conflicts in the next 20 years (36 states)
Long-Term Severe Drought Is Increasing
Causes
• Extended period of below-normal rainfall
• Diminished groundwater
Harmful environmental effects
• Dries out soils
• Reduces stream flows
• Decreases tree growth & biomass
• Lowers NPP & crop yields
• Shifts biomes (desertification)
Building More Dams
Main goals of a dam and reservoir system
• Capture and store runoff
• Runoff is released to control floods
• Dams are also used for/to
• Generate electricity
• Supply irrigation water
• Recreation (reservoirs)
Some Rivers Are Running Dry and Some
Lakes Are Shrinking
Dams disrupt the hydrologic cycle
Major rivers running dry part of the year
• Colorado and Rio Grande, U.S.
• Yangtze and Yellow, China
• Indus, India
• Danube, Europe
• Nile River-Lake Victoria, Egypt
Lake Chad Africa: disappearing
Water Transfers
CA, U.S., Transfers Water from Water-Rich
Areas to Water-Poor Areas
• Water transferred by
• Tunnels
• Aqueducts/Canals
• Underground pipes
• May cause environmental problems
Removing Salt from Seawater Seems
Promising but Is Costly (1)
Desalination
• Distillation (boiling, condensing)
• Reverse osmosis (sending water through a
filtration system using pressure to go against
typical osmosis force)
15,000 plants in 125 countries
• Saudi Arabia: highest number
Removing Salt from Seawater Seems
Promising but Is Costly
Problems
• High cost and energy footprint
• Kills many marine organisms and algae
• Large quantity of brine wastes
• super concentrated by-product that results from
treating brackish water or seawater
In Water-Short Areas Farmers and Cities
Compete for Water Resources
Some countries import grain to free up water
2007: National Academy of Science study
• Increased corn production in the U.S. to make
ethanol as an alternative fuel
• Decreasing water supplies
• Aquifer depletion
• Increase in pollution of streams and aquifers
Using Water More Sustainably
Water Waste:
• Worldwide 65 – 70% of water used is wasted
• Evaporation, Leaks, misuse
We Can Cut Water Waste in Irrigation
Flood irrigation
• Wasteful
Center-pivot, low pressure sprinkler
Drip or trickle irrigation, microirrigation
• Costly; less water waste
Hydroponic Agriculture
The cultivation of crops in
greenhouse conditions with
roots fed a nutrient rich
solution, but no soil.
• Water not taken up is
reused
• Takes 95% less water
• Higher yields per hectare
• Vertical growing capacity
• Year round conditions
We Can Cut Water Waste in Industry
and Homes
Recycle water in industry
• Especially in energy generation (steam)
Fix leaks in the plumbing systems
Use water-thrifty landscaping: xeriscaping
Use gray water: waste water from baths,
showers, bathroom sinks, & washing machines
Water saving fixtures
Outside the Home
Xeriscaping – low water landscaping
Use native vegetation that can survive local
climate without additional water
New Mexico Georgia
How do you use your water?
For the average American:
• 41% Toilet Flushing
• 32% Bathing
• 21% Laundry
• 5% Cooking and Drinking
Case Study: The Colorado River Basin—
An Overtapped Resource
Supplies water and electricity for more than 25
million people
• Irrigation of crops
• Recreation
Four Major problems
• Colorado River basin has very dry lands
• Modest flow of water for its size
• Legal pacts allocated more water for human use
than it can supply
• Amount of water flowing to the mouth of the river
has dropped
Case Study: China’s Three
Gorges Dam
World’s largest hydroelectric dam and reservoir
• 2 km long across the Yangtze River
Benefits
• Electricity-producing potential is huge
• Holds back the Yangtze River floodwaters
• Allows cargo-carrying ships
Case Study: China’s Three
Gorges Dam - Problems
Harmful effects
• Displaces about 5.4 million people
• Built over a seismic fault
• Significance?
• Rotting plant and animal matter producing CH4
• Worse than CO2 emissions
• Will the Yangtze River become a sewer?
Case Study: The Aral Sea Disaster
Large-scale water transfers in dry central Asia
Salinity
Wetland destruction and wildlife
Fish extinctions and fishing
Wind-blown salt
Water pollution
Climatic changes
Restoration efforts