1. Water Use and Management
Chapter 11 Section 2

2. Global Water Use
The three major uses of water are residential, agricultural, and industrial
Most fresh water worldwide is used to irrigate crops
Availability of fresh water, population size, and economic conditions affect how people use water

3. Residential Water Use
The average person in the U.S. uses about 300 gallons of water every day--only half is used inside, the rest is used outside for watering, washing cars, etc.
In India, the average person uses 41 gallons of water every day

4. Water Treatment
Most water must be treated to make it potable (safe to drink)
Water treatment removes mercury, arsenic, and lead as well as pathogens (organisms that cause illness or disease)

5. Steps of Water Treatment
First filtration--the source of water supply is filtered to remove large organisms and trash
Coagulation--alum is mixed in to form sticky globs (flocs). Bacteria clings to the flocs which settle to the bottom
Second filtration--layers of sand, gravel, and coal filter remaining impurities
Chlorination--added to prevent bacteria from growing
Aeration--air is forced through to release unwanted gases reducing odor and improving taste
Additional treatment--some communities add fluoride for teeth, sodium or lime to soften water. Treated water is then pumped from storage tanks to homes and industry

6. Industrial Water Use Industry accounts for 19% of water use worldwide
It is used to manufacture goods, dispose of waste, and generate power
1,000 L of water is used to produce 1 kg of aluminum and 500,000 L of water is used to manufacture 1 automobile
Most is used to cool power plants

7. Agricultural Use of Water
It can take as much as 300 L of water or produce one ear of corn!
Agriculture accounts for 67% of water used worldwide
80% of water used in agriculture evaporates and never reaches the plants roots

8. Irrigation
Fertile soil is sometimes found where there isn't much rainfall
Irrigation is a method of providing plants with water sources other than precipitation
Some crops are watered by shallow, water filled ditches. The U.S. uses high-pressure overhead sprinklers (this is very inefficient)

9. Water Management Projects
2,000 years ago, Romans built aqueducts that brought water from the mountains to dry areas of France and Spain
People live in areas where the natural distribution of water is inadequate
Water management projects such as dams and water diversion canals are designed to meet people's needs
Goals of such projects can range from making a dry area habitable to creating a reservoir for recreation

10. Water Diversion Projects
To supply dry regions with water, all or part of a river can be diverted into canals that carry water great distances
The Colorado River is diverted to meet the needs of 7 states
It is used for irrigation and drinking water in Arizona, Utah, and California
Many times the river is dry before reaching the Gulf of California

11. Dams and Reservoirs
When a river is dammed, an artificial lake (reservoir) is formed behind
Water from the reservoir can be used for flood control, drinking water, irrigation, recreation, and industry
Dam are also built to generate electrical power--20% of the world's power is produced by hydroelectric dams
When a dam is built, entire ecosystems can be destroyed

12. 50 million people worldwide have been displaced from dams being built
As the river enters the reservoir, it slows down and deposits sediment that it carries. This fertile sediment builds up behind the dam instead of enriching land farther down the river
Farmland below the dam becomes less productive
If the dam bursts, people living below the dam can be killed

13. Water Conservation
As water becomes depleted, water becomes more expensive because wells must be drilled deeper, polluted water must be cleaned before it can be used, etc.
Water conservation is one way to ensure everyone will have enough water at reasonable prices

14. Water Conservation in Agriculture
Most water loss in agriculture comes from evaporation, seepage, and runoff
Drip irrigation systems offer a promising step toward conservation
Drip irrigation systems deliver small amounts of water directly to plant roots using perforated tubing

15. Water Conservation in Industry
Many industries have developed water conservation plans
Most involve the recycling of cooling water and waste water
Some cities, like Denver, CO, pay small businesses to conserve water

16. Water Conservation at Home
A few changes in residential water use will make a significant contribution to conservation
Low-flow toilets and showers
Water lawns at night to prevent as much evaporation
Xeriscaping involves designing landscaping that requires minimal watering

17. Solutions for the Future: Desalination
Some coastal communities rely on the ocean to provide fresh water
Desalination is the process of removing salt from salt water
Most desalination plants heat salt water and collect the fresh water that evaporates

18. Transporting Water
Where fresh water resources are not adequate, water can be transported from other regions
This is being done in the Greek Isles because tourism is taxing the fresh water supply
It is being considered in the U.S. where almost half the fresh water is in Alaska
77% of Earth's fresh water is in ice caps and icebergs

19. Copy now, answer later
Write a description of the evaporative method of desalination using terms from the water cycle.
Describe the drinking water treatment process in your own words.
Describe the benefits and costs of dams and water diversion projects.
List at least three things you can do to help conserve the world's water supply.
Describe three ways that communities can increase their freshwater resources.