1. How We Use Water
Discuss how we use and later freshwater systems

2. Climate change may bring shortages
Climate change will cause
Altered precipitation patterns
Melting glaciers
Early season runoff
Intensified droughts
Flooding
Lake Mead is already hurting from drought

3. How we use water
We have achieved impressive engineering accomplishments to harness fresh water
60% of the world’s largest 227 rivers have been strongly or moderately affected
Dams, dikes, and diversions
Consumption of water in most of the world is unsustainable
We are depleting many sources of surface water and groundwater

4. There are more than 1,000 dams in the Connecticut River watershed
There are more than 1,000 dams in the Connecticut River watershed. The States of Vermont, New Hampshire, Massachusetts and Connecticut are included in the watershed.

5. Water supplies houses, agriculture, and industry
Proportions of these three types of use vary dramatically among nations
Arid countries use water for agriculture
Developed countries use water for industry
Consumptive use = water is removed from an aquifer or surface water body and is not returned
Irrigation = the provision of water to crops
Nonconsumptive use = does not remove, or only temporarily removes, water
Electricity generation at hydroelectric dams

6. Why does agriculture use so much water?
Rapid population growth requires more food and clothes
The Green Revolution uses irrigation
We use 70% more irrigation water than 50 years ago
Irrigation can double crop yields
18% of land is irrigated but produces 40% of our crops
Irrigation is highly inefficient
Water evaporates in “flood and furrow” irrigation
Overirrigation leads to waterlogging and salinization
Reducing world farm income by $11 billion

7. Governments subsidize irrigation
Irrigation subsidies promote food self-sufficiency
But irrigation uses up huge amounts of groundwater for little gain
Water in the Colorado River Valley is diverted for cotton and other crops grown in the desert
Farmers in California’s Imperial Valley pay only 1 penny for 220 gallons of water

8. We divert surface water for our needs
People divert water to farm fields, homes, and cities
The once mighty Colorado River has been extensively diverted and used

9. Water-poor regions take water from others
Politically strong, water-poor areas forcibly take water from weaker communities
Los Angeles commandeered water from rural areas
Turning the environment into desert, creating dustbowls, and destroying the economy
In 1941, L.A. diverted streams that fed Lake Mono
Lake levels fell, salt concentrations doubled
Las Vegas wants to import water from sparsely populated eastern Nevada
An ecologically sensitive area

10. We build dikes and levees to control floods
Flooding = a normal, natural process where water spills over a river’s banks
Spreading nutrient-rich sediments over large areas
In the short term, floods damage property
Dikes and levees (long, raised mounds of earth) along the banks of rivers hold water in channels
Levees make floods worse by forcing water to stay in channels and then overflow
Dams prevent flooding and change a river’s nature
Releasing water periodically simulates flooding

11. Levees increase flooding
A major levee along the Mississippi River failed after Hurricane Katrina, allowing parts of New Orleans to be flooded

12. We have erected thousands of dams
Dam = any obstruction placed in a river or stream to block the flow of water to prevent floods, provide drinking water, allow irrigation, and generate electricity
45,000 large dams have been erected in more than 140 nations
Only a few major rivers remain undammed
In remote regions of Canada, Alaska, and Russia
Dams are great engineering feats
Many stand hundreds of feet tall

13. A typical dam

14. China’s Three Gorges Dam
The dam, on the Yangtze River, is the largest in the world
186 m (610 feet) high, 2.3 km (1.4 mi) wide
Its reservoir stretches for 616 km (385 mi)
Provides flood control, passage for boats, and electricity

15. Drawbacks of the Three Gorges Dam
Cost $39 billion to build
Flooded 22 cities and the homes of 1.24 million people
Submerged 10,000-year-old archaeological sites
Drowned farmland and wildlife habitat
Tidal marshes at the Yangtze’s mouth are eroding
Pollutants will be trapped
It will cost $5 billion to build sewage treatment plants to treat water

16. Some dams are being removed
Some people feel that the costs of dams outweigh their benefits
They are pushing to dismantle dams
The Federal Energy Regulatory Commission (FERC) renews licenses for dams
If dam costs exceed benefits, the license may not be renewed
400 dams have been removed in the U.S.
Property owners who opposed the removal change their minds once they see the healthy river

17. We are depleting surface water
In many places, we are withdrawing water at unsustainable rates
Reduced flow drastically changes the river’s ecology, plant community, and destroys fish and invertebrates
The Colorado River often does not reach the Gulf of California

18. The Aral Sea Once the fourth-largest lake on Earth
It lost 80% of its volume in 45 years
The two rivers leading into the Aral Sea were diverted to irrigate cotton fields
60,000 fishing jobs are gone
Pesticide-laden dust from the lake bed is blown into the air
Cotton cannot save the region’s economy

19. Can the Aral Sea be saved?
People have begun saving the northern part of the Aral Sea

20. Irrigation wastes water
15–35% of water withdrawals for irrigation are unsustainable
Water mining = withdraws water faster than it can be replenished

21. The world is losing wetlands
Wetlands are being lost as we divert and withdraw water
Channelize rivers, build dams, etc.
As wetlands disappear, we lose ecosystem services
Filtering pollutants, wildlife habitat, flood control, etc.
Many are trying to protect and restore them
The Ramsar Convention on Wetlands of International Importance (1971)
Seeks the conservation and wise use of wetlands in the context of sustainable development
1,900 sites covering 185 million ha are protected

22. We are depleting groundwater
Groundwater is easily depleted
Aquifers recharge slowly
Used by one-third of all people
As aquifers are mined, water tables drop
Salt water intrudes in coastal areas
Sinkholes = areas where ground gives way unexpectedly
Aquifers can’t recharge
Wetlands dry up

23. Salt water intrustion
Saline water flows upward through the nearly vertical structural features in response to ground-water pumping from the uppermost aquifer.

24. Can we quench our thirst for bottled water?
Groundwater is being withdrawn for bottled water
An average American drinks 29 gallons/year
People drink bottled water for portability, convenience
They think it tastes better or is healthier
Bottled water is no better than tap water
It is heavily packaged and travels long distances using fossil fuels
Bottles are not recycled
Corporations move in, deplete water, and move away

25. Bottled water is popular but problematic
Bottled water is popular but it has several problems
Energy costs of bottled water are 1,000–2,000 times greater than those of tap water

26. Will we see a future of water wars?
Freshwater depletion leads to shortages, which can lead to conflict
261 major rivers cross national borders
Water is a key element in hostilities among Israel, Palestinians, and neighboring countries
Many nations have cooperated with neighbors to resolve disputes
They sign water-sharing treaties

27. QUESTION: Review Why do governments subsidize irrigation?
It promotes food self-sufficiency.
Governments have to or food could not be grown.
Governments want to lower water tables.
Governments do not subsidize irrigation.
Answer: a

28. QUESTION: Review
Which of the following statements is NOT true about dams?
They change habitat.
They generate electrical power.
They have created more farmland upstream.
Pollutants are trapped in reservoirs.
Answer: c