Chapter 17: Water Use and Management

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Chapter 17: Water Use
and Management
Surface Water, Bosnia
17.1 Water Resources
• The hydrologic cycle constantly redistributes
water
• Water supplies are unevenly distributed
The Hydrologic Cycle
17.2 Major Water Compartments
• Oceans hold 97 percent of all water on earth
• Glaciers, ice, and snow contain most surface
fresh water (69%)
• Groundwater Stores Large Resources (30%)
• Rivers, lakes, and wetlands cycle quickly (1%)
• The atmosphere is among the smallest of
compartments (1 ppm)
17.3 Water Availability And Use
• Many Countries Suffer Water Scarcity And
Water Stress
• Water Consumption Is Less Than Withdrawal
– Withdrawal: What’s Taken Out. Much May Return
Quickly To Source
– Some Returned Water May Be Degraded
– Consumed: Not Easily Returnable To Source
– Very Little Water Is Actually Destroyed
– What Is Destroyed Is Easily Reconstituted
17.3 Water Availability And Use
• Water Use Is Increasing
• Agriculture Is The Greatest Water Consumer
Worldwide
– Water Recycles Quickly But Not Necessarily Where
It Came From
• Domestic And Industrial Water Use Are
Greatest In Wealthy Countries
17.4 Freshwater Shortages
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Many people lack access to clean water
Groundwater is being depleted
Climate change threatens water supplies
Rivers are shrinking
Would you fight for water?
All-Time Life Savers
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Clean Water
Food Preservation
Antiseptics
Antibiotics
Vaccination
Surgery
Green revolution
Mosquito Control
Green Bay Case Study
Deep Aquifers of the Green Bay Area
Green Bay Piezometric Surface
1957
1960
Green Bay Piezometric Surface
1957
2003
The Russian Radioactive Waste
Injection Program
Center-Pivot Irrigation
Center-Pivot Irrigation
Some Places Have Too Much Water
Soluble Rocks
Karst in Wisconsin
Geothermal Systems: Mammoth Hot
Springs, Yellowstone
Yellowstone Canyon
Old Faithful Geyser, Yellowstone
17.5 Dams And Diversions
• Dam failure can be disastrous
• Dams often displace people and damage
ecosystems
• Dams kill fish
• Sedimentation limits reservoir life
• What Do You Think? Should We Remove
Dams?
– Near end of useful life
– Too small to contribute meaningfully
Banqiao Dam Failures, China, 1975
• Built 1950’s for power and flood control
• Hydrologist critical of design was sacked,
reinstated, and sacked again
• Designed to survive 1000 year flood (30 cm =
12 inches rain per day)
• In 1975, >2000 year flood occurred
– 19 cm (8 inches) in one hour
– 106 cm (40 inches) in one day
Banqiao Dam Failures, China, 1975
• August 1975: Cold Front collides with Super
Typhoon Nina
• Delay in opening gates because of
communications failures and concern about
downstream flooding
• Gates blocked by sediment
• August 8, 12:30 AM: Dam upstream fails
– Designed for 500 year flood but exceeded capacity
Banqiao Dam Failures, China, 1975
• August 8, 1 AM, Banqiao Dam overtopped and
failed
• Precipitated the failure of 62 dams
• Flood wave 10 km wide, 3-7 m high, moving
50 km/hour
• Numerous dams opened by air strikes to
control flow
Banqiao Dam Failures, China, 1975
• One commune of 9600 people was entirely
annihilated
• 26,000 people died from flooding
• 145,000 died from subsequent epidemics and
famine.
• 9 days after the flood a million people were
still stranded
• About 6,000,000 buildings collapsed
• Details declassified in 2005
Banqiao Dam After Failure
17.7 Increasing Water Supplies
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Desalination Provides Expensive Water
Domestic Conservation Can Save Water
Recycling Can Reduce Consumption
Prices And Policies Have Often Discouraged
Conservation (Encouraged Waste)
• What Can You Do? Saving Water And
Preventing Pollution
Desalination
• Passive Distillation
– Slow
• Active Distillation
– Energy Intensive
• Reverse Osmosis
– Energy Intensive
– Fragile Filters
Reverse Osmosis
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