Chapter 13 Water Resources
description
Transcript of Chapter 13 Water Resources
LIVING IN THE ENVIRONMENT 17THMILLER/SPOOLMAN
Chapter 13Water Resources
Case Study: The Colorado River Basin— An Overtapped Resource
• Colorado River flows 1,400 miles (2,300 km) through 7 U.S. states to the Gulf of California.
• 14 dams and reservoirs to supply water to farmers, ranchers, industries and cities.
• Supplies water and electricity for about 30 million people• Las Vegas, Los Angeles, San Diego
• Located in a desert area, water supplied mostly from snowmelt of the Rocky Mountains.
• So much water is withdrawn that very little water reaches the Gulf of California
The Colorado River Basin
Fig. 13-1, p. 317
Aerial View of Glen Canyon Dam Across the Colorado River and Lake Powell
Fig. 13-2, p. 317
Freshwater Is an Irreplaceable Resource That We Are Managing Poorly
• Why is water so important?• Needed for survival• Takes huge amounts to produce food and energy• Sculpts the earth’s surface• Controls earth’s climate• Removes or dilutes pollutants and wastes that we produce
Freshwater Is an Irreplaceable Resource That We Are Managing Poorly
• Access to water is • A global health issue – about 3900 children under 5 die
from waterborne disease each day• An economic issue - vital to reduce poverty and produce
food and energy• A women’s and children’s issue - about 50% of people do
not have easy access to water• A national and global security issue - increase tension
between countries• An environmental issue – declining water quality problems
and overuse reduces aquifers and water tables
Girl Carrying Well Water over Dried Out Earth during a Severe Drought in India
Fig. 13-3, p. 319
Most of the Earth’s Freshwater Is Not Available to Us
• About 70% of Earth is covered by water…97% of it is salt water
• Freshwater availability: 0.024%• Groundwater, lakes, rivers, streams
• Hydrologic cycle • Movement of water in the seas, land, and air• Driven by solar energy and gravity
• Not evenly distributed• Canada has .5% of world population but 20% of the liquid
freshwater; China has 19% of the population and 7% of the supply; Asia has 60% of the population and 30% supply.
Fig. 3-16, p. 67
Condensation Condensation
Ice and snow
Transpiration from plants
Precipitation to land Evaporation of
surface water Evaporation from ocean
Runoff
Lakes and reservoirs Precipitation
to oceanRunoff
Increased runoff on land covered with crops, buildings and pavementInfiltration and
percolation into aquifer
Increased runoff from cutting forests and filling wetlands
Runoff
Groundwater in aquifers
Overpumping of aquifers
RunoffWater pollution
Ocean
Natural process
Natural reservoir
Human impacts
Natural pathwayPathway affected by human activities
Groundwater and Surface Water Are Critical Resources
Case Study: Freshwater Resources in the United States
• More than enough renewable freshwater, unevenly distributed and polluted by agricultural and industrial wastes.
• In 2005 groundwater and surface water in the US was used for:• 41% cooling power plants, 37% crop irrigation (85% in
western US), 13% public water use, 9% industry and livestock.
• Problems include:• Flooding, clean water shortages, drought
Fig. 13-4, p. 322
Average annual precipitation (centimeters)Less than 41 81–122
More than 122
Acute shortageShortageAdequate supplyMetropolitan regions with population greater than 1 million
41–81
Natural Capital Degradation: Stress on the World’s Major River Basins
Fig. 13-6, p. 323
Groundwater is Being Withdrawn Faster Than It Is Replenished (1)
• Most aquifers are renewable
• Aquifers provide drinking water for half the world
• Water tables are falling in many parts of the world, primarily from crop irrigation (can cause subsidence)
• India, China, and the United States• Three largest grain producers• Overpumping aquifers for irrigation of crops
Fig. 13-7, p. 325
Trade-Offs
Withdrawing Groundwater
Advantages Disadvantages
Useful for drinking and irrigation
Aquifer depletion from overpumping
Exists almost everywhere
Sinking of land (subsidence) from overpumping
Renewable if not overpumped or contaminated
Pollution of aquifers lasts decades or centuries
Deeper wells are nonrenewable
Cheaper to extract than most surface waters
Case Study: Aquifer Depletion in the United States
• Ogallala aquifer: largest known aquifer• Irrigates the Great Plains• Very slow recharge• Water table dropping• Government subsidies to continue farming deplete
the aquifer further• Biodiversity threatened in some areas
• California Central Valley: serious water depletion
Subsidence in the San Joaquin Valley
Fig. 13-11, p. 327
Fig. 13-12, p. 327
Solutions
Groundwater Depletion
Prevention Control
Waste less water Raise price of water to discourage waste
Tax water pumped from wells near surface waters
Subsidize water conservation
Set and enforce minimum stream flow levels
Limit number of wells
Do not grow water-intensive crops in dry areas
Divert surface water in wet years to recharge aquifers
Deep Aquifers Might Be Tapped
• Deep aquifers may contain enough water to provide for billions of people for centuries.
• Major concerns1. Nonrenewable2. Little is known about the geological and ecological
impacts of pumping deep aquifers3. Some flow beneath more than one country4. Costs of tapping are unknown and could be high
California Transfers Water from Water-Rich Areas to Water-Poor Areas
• Water transferred from north to south by• Tunnels• Aqueducts• Underground pipes
• California Water Project • Inefficient water use• Environmental damage to Sacramento River and San
Francisco Bay
The California Water Project and the Central Arizona Project
Fig. 13-16, p. 331
Fig. 13-13a, p. 328
Provides irrigation water above and below dam
Flooded land destroys forests or cropland and displaces people
Large losses of water through evaporation
Provides water for drinking
Deprives downstream cropland and estuaries of nutrient-rich silt
Reservoir useful for recreation and fishing
Risk of failure and devastating downstream flooding
Can produce cheap electricity (hydropower)
Reduces down-stream flooding of cities and farms Disrupts
migration and spawning of some fish
Natural Capital Degradation: The Aral Sea, Shrinking Freshwater Lake
Fig. 13-17, p. 332
Removing Salt from Seawater Is Costly, Kills Organisms, Creates Briny Wastewater (1)
• Desalination• Distillation: evaporate water, leaving salts behind• Reverse osmosis, microfiltration: use high pressure to
remove salts
• 14,450 plants in 125 countries• Saudi Arabia has the highest number
Removing Salt from Seawater Is Costly, Kills Organisms, Creates Briny Wastewater (2)
• Problems1. High cost and energy footprint2. Keeps down algal growth and kills many marine
organisms3. Large quantity of brine wastes
Reducing Water Waste Has Many Benefits
• One-half to two-thirds of water is wasted - subsidies mask the true cost of water by lower cost
• Water conservation• Improves irrigation efficiency to lower wasted water• Improves collection efficiency• Uses less in homes and businesses
Major Irrigation Systems
Fig. 13-18, p. 335
Less-Developed Countries Use Low-Tech Methods for Irrigation
• Human-powered treadle pumps• Harvest and store rainwater
17THMILLER/SPOOLMAN
LIVING IN THE ENVIRONMENT
Chapter 20Water Pollution
Water Pollution Comes from Point and Nonpoint Sources
• Water pollution • Change in water quality that can harm organisms or
make water unfit for human uses• Contamination with chemicals or heat
• Point sources• Located at specific places; Easy to identify, monitor,
and regulate• Nonpoint sources• Broad, diffuse areas; Difficult to identify and control;
Expensive to clean up
Water Pollution Comes from Point and Nonpoint Sources
• Leading causes of water pollution1. Agriculture activities• Sediment eroded from the lands• Fertilizers and pesticides• Bacteria from livestock and food processing wastes
2. Industrial facilities3. Mining• Runoff from waste rock
Nonpoint Sediment from Unprotected Farmland Flows into Streams
Fig. 20-4, p. 530
Lake Polluted with Mining Wastes
Fig. 20-5, p. 531
Plastic Wastes in Mountain Lake
Fig. 20-6, p. 531
Major Water Pollutants Have Harmful Effects
• Infectious disease organisms: contaminated drinking water
• The World Health Organization (WHO) • 1.6 million people die every year, mostly under the
age of 5
Common Diseases Transmitted to Humans through Contaminated Drinking Water
Table 20-2, p. 532
Science Focus: Testing Water for Pollutants • Variety of tests to determine water quality and
chemical analysis – check for Coliform bacteria: Escherichia coli
• Level of dissolved oxygen (DO) • Indicator species • Mayfly vs. leeches
• Bacteria and yeast glow in the presence of a particular toxic chemical
• Color and turbidity of the water
Water Quality as Measured by Dissolved Oxygen Content in Parts per Million
Fig. 20-A, p. 533
Streams Can Cleanse Themselves If We Do Not Overload Them
• Dilution• Biodegradation of wastes by bacteria takes time
Global Outlook: Stream Pollution in Developing Countries
• Half of the world’s 500 major rivers are polluted
• Untreated sewage, Industrial waste
• India’s and China’s rivers worst in the world
Natural Capital Degradation: Highly Polluted River in China
Fig. 20-8, p. 535
Trash Truck Disposing of Garbage into a River in Peru
Fig. 20-9, p. 536
Too Little Mixing and Low Water Flow Makes Lakes Vulnerable to Water Pollution
• Less effective at diluting pollutants than streams• Little of no water flow• Can take up to 100 years to change the water in a
lake• Biological magnification of pollutants
Cultural Eutrophication Is Too Much of a Good Thing (1)
• Eutrophication• Natural enrichment of a shallow lake, estuary, or slow-
moving stream• Caused by runoff into lake that contains nitrates and
phosphates
• Oligotrophic lake• Low nutrients, clear water
Case Study: Pollution in the Great Lakes
• 1972: Canada and the United States: Great Lakes pollution control program• Decreased algal blooms• Increased dissolved oxygen• Increased fishing, swimming beaches reopened• Better sewage treatment plants• Fewer industrial wastes• Bans on phosphate-containing household products
• Problems still exist• Raw sewage• Nonpoint runoff of pesticides and fertilizers• Biological pollution• Atmospheric deposition of pesticides and Hg
Case Study: Pollution in the Great Lakes
• 2007 State of the Great Lakes report• New pollutants found• Wetland loss and degradation• Declining of some native species• Native carnivorous fish species declining • What should be done?
The Great Lakes of North America
Fig. 20-12, p. 538
Ground Water Cannot Cleanse Itself Very Well
• Source of drinking water• Common pollutants• Fertilizers and pesticides, Gasoline, Organic solvents
• Pollutants dispersed in a widening plume• Slower chemical reactions in groundwater due to• Slow flow: contaminants not diluted • Less dissolved oxygen• Fewer decomposing bacteria• Low temperatures
Principal Sources of Groundwater Contamination in the U.S.
Fig. 20-13, p. 540
Solutions: Groundwater Pollution, Prevention and Cleanup
Fig. 20-14, p. 541
Case Study: Is Bottled Water the Answer?
• U.S.: some of the cleanest drinking water
• Bottled water• Some from tap water• 40% bacterial contamination• Fuel cost to manufacture the plastic bottles• Recycling of the plastic• 240-10,000x the cost of tap water
• Growing back-to-the-tap movement
Reducing Surface Water Pollution from Nonpoint Sources
• Agriculture• Reduce erosion• Reduce the amount of fertilizers• Plant buffer zones of vegetation• Use organic farming techniques• Use pesticides prudently • Control runoff• Tougher pollution regulations for livestock operations• Deal better with animal waste
Laws Can Help Reduce Water Pollution from Point Sources
• 1972: Clean Water Act 1987: Water Quality Act
• EPA: experimenting with a discharge trading policy that uses market forces• Cap and trade system• Could this allow pollutants to build up?
Sewage Treatment Reduces Water Pollution
• Septic tank system – household waste
• Wastewater or sewage treatment plants• Primary sewage treatment• Physical process
• Secondary sewage treatment• Biological process with bacteria
• Tertiary or advance sewage treatment • Special filtering processes• Bleaching, chlorination
Sewage Treatment Reduces Water Pollution
• Many cities violate federal standards for sewage treatment plants
• Should there be separate pipes for sewage and storm runoff?
• Health risks of swimming in water with blended sewage wastes
What Can You Do? Reducing Water Pollution
Fig. 20-22, p. 554
Unit 4 test review
• Benefits provided by coral reefs.• How are coral reefs being damaged/destroyed?• The percentage of earth’s surface covered by water?• % of liquid freshwater available on Earth?• The 4 major problems associated with the use of the Colorado
River.• By 2025, how many of the world’s people will lack access to
clean water?• The US withdraws water from underground how much faster
than the recharge rate?• The 7 states using the Colorado River are supposed to do
what to help with the problems?
Unit 4 test review
• The Aral Sea case study- question and essay• Problems with desalination?• How can desalinization be improved?• Efficient means to delivery water to crops.• Leading cause of water pollution.• The WHO says how many people do not have access
to clean water?• Safe drinking water can contain ___ colonies of
coliform per 100 ml sample? How m uch for swimming water?
• Examples of point source and nonpoint source
Unit 4 test review
• Global Water Policy Project says ___% of untreated sewage is dumped by most cities in developing countries.
• Great Lakes hold ___% of surface water in the US?• Less than __% of water from Great Lakes leaves the St. Lawrence
River?• How long does it take for Great lakes to flush pollutants?• Effective ways to prevent groundwater?• % of bottled water from tap.• 3rd largest dead zone is found in Gulf of Mexico…what’s it caused by
and which river?• Essay: Could water shortages lead to wars? Should there be more
controls on water usage to help protect freshwater availability? Global warming can cause a lessening of freshwater…how will that change the downhill flow of freshwater?