Miller Text Summary on Water Resources:
Water Resources
Summary
1.
Approximately 0.024% of the earth’s water supply is available as liquid freshwater. Management of the
world’s water supply is a huge 21st century challenge.
2.
Freshwater shortages are caused by dry climate, droughts, desiccation, and water stress. Solutions for this
problem include building dams and reservoirs, transporting freshwater between locations, withdrawing
groundwater, and desalination.
3.
Advantages of dams and reservoirs include cheap electricity, reduction of downstream flooding, and yearround water for irrigation. Disadvantages include displacement of people and disruption of aquatic systems,
and the hydrological cycle.
4.
Transferring large amounts of water from one area to another can give stream runoff from water-rich areas to
water-poor areas and aid in irrigation of farmland. It can also cause ecological, economical, and health
disasters.
5.
The advantages of withdrawing groundwater include water for drinking and irrigation; availability and locality;
low cost, no evaporation losses; and it is renewable. Disadvantages include aquifer depletion from over
pumping, subsidence, pollution, saltwater intrusion, and reduced water flow. Desalination increases the supply
of fresh water but is expensive and produces large quantities of wastewater.
6.
We can waste less water by lining canals, leveling fields, irrigating at night or using new irrigation techniques,
polyculture or organic farming, seasonal farming, irrigating with treated waste water, and importing waterintensive crops and meat.
7.
Flooding is caused by heavy rain or melting of snow within a short time. To reduce flood damage or the risk of
flooding we can avoid building on floodplains, removing water-absorbing vegetation, or draining wetlands.
8.
Methods for achieving more sustainable use of the earth’s water include not depleting aquifers, preserving
aquatic systems and water quality, integrated watershed management, agreements among regions and countries
sharing surface water resources, outside party mediation of water dispute nations, marketing of water rights,
raising water prices, wasting less water, decreasing government subsidies for reducing water waste, and
slowing population growth.
Key Questions and Concepts
13-1 Will we have enough usable water?
CORE CASE STUDY: The Colorado River is 1,400 miles long and has been altered by 14 major dams and
reservoirs. This river provides water and electricity for 30 million people and irrigation to grow 15% of the
nation’s crops and livestock.
A. Water keeps us alive, moderates climate, sculpts the land, removes and dilutes wastes and pollutants, and
moves continually through the hydrologic cycle.
B. Only about 0.024% of the earth’s water supply is available to us as liquid freshwater in accessible
groundwater deposits and in lakes, rivers, and streams. The hydrologic cycle collects, purifies, recycles,
and distributes the world’s freshwater supply. Some countries have more water than they need; some
countries have far less.
C. Some precipitation infiltrates the ground and percolates downward through spaces in the soil, gravel, and
rock. This water is known as groundwater, an important fresh water source.
D. Water that does not sink into the ground or evaporate into the air runs off into bodies of water. This is
known as surface water.
E. We currently withdraw 34% of the world’s reliable runoff of surface water and could be using 90% by
2025.
F. Irrigation is the biggest user of water (70%), followed by industries (20%) and cities and residences (10%).
CASE STUDY: The United States has plenty of freshwater, but supplies vary in different areas depending on
climate. This unequal distribution of water can be seen in Figure 14-4. There are water hot spots in 17 western
states (Figure 14-5), that could trigger intense conflict in the next 20 years.
SCIENCE FOCUS: Water footprint refers to the rough measure of volume of water used by each of us
directly and indirectly. Direct use in the United States amounts to about 69 gallons per person. In addition,
virtual water accounts for water that is not directly consumed, but is used to produce food and other products.
G. More than 30 countries now face water scarcity. By 2050, 60 countries, mostly in Asia, with ¾ of the
world population will suffer from water stress.
H. Conflicts between nations over water resources are likely to grow, as many nations that share water
supplies to not have water sharing agreements.
13-2 Is extracting groundwater the answer?
A. Most aquifers are renewable resources unless water is removed faster than it is replenished or the aquifers
are contaminated. Aquifers provide almost one-fourth of the world’s water.
B. In many parts of the world, aquifers are being depleted faster than they are renewed.
1. Water tables are falling in many areas of the world because the rate of pumping out water (mostly to
irrigate crops) exceeds the rate of natural recharge from precipitation.
2. The widespread drilling of inexpensive tube wells by small farmers, especially in Asia, has accelerated
aquifer overpumping.
3. Saudi Arabia gets 70% of its water from the world’s largest desalination complex.
CASE STUDY: In the United States, groundwater is being withdrawn four times faster than it is being
replenished. In the Central U.S., government subsidies to farmers have increased depletion of the Ogallala
aquifer.
C. Groundwater overpumping can increase the gap between the rich and the poor, cause land to sink, and
contaminate freshwater aquifers near coastal areas with saltwater.
D. Deep aquifers may be a future water source. There are major concerns with their use.
1. They are nonrenewable.
2. Little is known of the geological or ecological impacts of their use.
3. Some flow under more than one nation.
4. The costs are unknown and could be high.
13-3 Is building more dams the answer?
A. Large dams and reservoirs can produce cheap electricity, reduce downstream flooding, and provide yearround water for irrigating cropland, but they also displace people and disrupt aquatic systems.
1. There are more than 45,000 large dams in the world.
B. The Colorado River is an example of unsustainable water use.
1. 80% of this water is used for agriculture, and much is lost to seepage and evaporation.
13-4 Is transferring water from one place to another the Answer?
A. Transferring water can make unproductive areas more productive but can cause environmental harm.
CASE STUDY: The California Water Project provides for a massive transfer of water from water-rich
northern California to water-poor southern California. This has allowed for the development of agriculture and
urban areas in desert-like conditions. However, this has degraded river ecosystems and fisheries.
CASE STUDY: Diverting water from the Aral Sea and its two feeder rivers mostly for irrigation has created a
major ecological, economic, and health disaster. This activity has increased the salinity of the sea sevenfold
since 1961, the surface area has decreased, and 90% of its water volume has been lost. About 85% of the
area’s wetlands have been eliminated; roughly half the birds and mammal species have disappeared. The
fishing industry has disappeared, and salt and contaminant-rich dust from exposed lake sediments are creating
a major dust pollution source for the region. Some artificial wetlands and lakes have been constructed to help
restore aquatic vegetation, wildlife, and fisheries. With the various improvements, the water volume in the
Aral Sea has stabilized though at a much lower level than prior to water diversions.
13-5 Is converting salty seawater to freshwater the answer?
A.
Removing salt from seawater by current methods is expensive, produces large amounts of salty
wastewater that must be disposed of properly, and can be detrimental to many marine organisms. The
process is known as desalination. Methods include distillation and reverse osmosis.
SCIENCE FOCUS: The search for improved desalination technology has led to dramatic reductions in cost,
and many ideas and methods that would reduce the environmental impact.
13-6 How can we use water more sustainably?
A. We waste about two-thirds of the water we use, but this waste could be cut to 15% through reduced
evaporation and leakage and improved efficiency of use.
B. Higher water costs would reduce waste.
C. Sixty percent of the world’s irrigation water is currently wasted, but with improved irrigation techniques
such as center-pivot, low-pressure sprinkler irrigation, Low-Energy Precision Application (LEPA), and
drip irrigation systems could cut this waste to 5–20%.
D. Many poor farmers in developing countries use low-tech methods to pump groundwater and make more
efficient use of rainfall.
E. Industries can recycle much of the water they use; and homeowners can use water-saving toilets,
appliances, and showerheads, fix leaks, use drip irrigation and yard plants that need little water
(xeriscaping), save and reuse rainwater, and reuse wastewater for some purposes.
13-7 How can we reduce the threat of flooding?
A. Heavy rainfall, rapid snowmelt, removal of vegetation, and destruction of wetlands cause flooding. Floods
occur when a stream overflows its normal channel and spills into a floodplain.
1. Flood can be beneficial in recharging groundwater and depositing nutrients.
2. Floods can also be detrimental to communities and property.
3. Several factors increase flooding
a. The removal of water absorbing vegetation
b. Draining and building on wetlands
c. Climate change
CASE STUDY: Bangladesh has experienced increased flooding because of upstream deforestation of
Himalayan mountain slopes and the clearing of mangrove forests on its coastal floodplains. Bangladesh is one
of the world’s most densely populated countries, and is very flat. The people of Bangladesh depend on the
moderate annual flooding to maintain soil fertility. Great floods used to occur about every 50 years or so, but
since the 1970s they now occur about every 4 years.
B. We can reduce flooding risks by controlling river water flows, protecting mountainside forests, preserving
and restoring wetlands, identifying and managing flood-prone areas, and, if possible, choosing not to live
in such areas.
Miller Resources on Water Pollution, relates to chapter 14 F and R
Water Pollution
Summary
1.
Water pollutants include infectious agents from human or animal wastes; oxygen-demanding wastes from
sewage, paper mills, and food processing; inorganic chemicals from surface runoff, industrial effluents, and
household cleaners; organic chemicals from oil, plastics, pesticides, and detergents; sediment from erosion;
and thermal pollution from power plant cooling.
2.
Water pollution problems in streams and lakes relate to chemical and biological pollutants, with the greater
problems being cultural eutrophication.
3.
Groundwater pollution is caused by leaks from waste ponds and underground storage tanks, chemical dumping
or spilling, surface runoff, and fertilizers. It can be prevented by finding substitutes for toxic chemicals,
installing monitoring wells near landfills and underground tanks, requiring leak detectors on underground
tanks, banning hazardous waste disposal in landfills and injection wells, and storing harmful liquids in
aboveground tanks.
4.
Water pollution of oceans relates to nitrogen oxide from industry and cars, heavy metals from effluents, toxic
sediment, sewage, runoff of pesticides, manure, fertilizers, and red tides from excess nitrogen.
5.
Reduction or prevention of water pollution can be achieved through reduction of use of toxic pollutants,
banning of ocean dumping of sludge, protection of sensitive areas from oil drilling and oil transport, regulation
of coastal development, and regulation of sewage treatment.
6.
The U.S. Safe Drinking Water Act of 1974 requires that drinking water contain less than the maximum
contaminant levels for any pollutants that may have adverse effects on human health. Restructuring of water
treatment systems, enforcing current regulations, banning the use of lead in new structures, and chemical tests
and biological indicators can be used to make drinking water safer.
Key Questions and Concepts
20-1 What are the causes and effects of water pollution?
A. Water is polluted by infectious bacteria, inorganic and organic chemicals, and excess heat. Water pollution
is any chemical, biological, or physical change in water quality that has a harmful effect on living
organisms.
SCIENCE FOCUS: Scientists monitor water quality by using bacterial counts, chemical analysis, and
indicator organisms.
B. Water pollution can come from a single source or from a variety of dispersed sources. Point sources
discharge pollutants at specific locations through drain pipes, ditches, or sewer lines into bodies of surface
water. Non-point sources are scattered and diffuse and can’t be traced to any single site of discharge.
C. The leading sources of water pollution are agriculture, industries, and mining.
D. Common diseases are transmitted to humans through contaminated drinking water (Table 212). The World Health Organization (WHO) estimates that 3.2 million people, most of whom are
children, die prematurely every year from infectious diseases spread by contaminated water or
lack of water for adequate hygiene.
20-2 What are the major water pollution problems in streams and lakes?
A. Streams can recover from moderate levels of degradable water pollutants if the flows are not reduced.
A combination of dilution and biodegradation can allow recovery of stream pollution if they are not
overloaded, or have reduced flow due to damming, agricultural diversion, or drought.
B. Most developed countries have reduced point source pollution, but toxic chemicals and pollution from nonpoint sources are still problems. CASE STUDY: The U.S. Experience with reducing point source
pollution.
CASE STUDY: Ganges River. Stream pollution in most developing countries is a serious and growing
problem. Half of the world’s 500 major rivers are heavily polluted and most of them run through
developing countries where waste treatment is minimal or nonexistent.
C. Religious beliefs, cultural traditions, poverty, little economic development, and a large population interact
to cause severe pollution of the Ganges River in India.
D. Lakes have little flow and so are less effective at diluting pollutants that enter them.
E. Human activities can overload lakes with plant nutrients that reduce dissolved oxygen and kill some aquatic
species. Nutrient enrichment of lakes from runoff is called eutrophication.
CORE CASE STUDY: An example of lake recovery is Lake Washington in Seattle, Washington.
20-3 What are the major pollution problems affecting groundwater and other drinking water sources?
A. Groundwater is vulnerable to contamination because it can’t effectively cleanse itself and dilute or disperse
pollutants. Contaminated water in the aquifer will slowly flow along and create a plume of contaminated
water. It can take hundreds of years to cleanse degradable wastes; non-degradable wastes are there
permanently.
B. The extent of groundwater contamination is generally unknown since there has been little tracking and
testing done on aquifers.
C. Prevention is the most effective and affordable way to protect groundwater from pollutants.
D. Groundwater pollution can include human pollutants and natural pollutants such as Arsenic.
CASE STUDY: Arsenic in Groundwater.
20-4 What are the major water pollution problems affecting oceans?
A. Oceans can disperse and break down large quantities of degradable pollutants if they are not overloaded.
B. Pollution of coastal water near heavily populated areas is a serious problem. About 40% of the world’s
population lives on or within 62 miles of the coast, and this puts a tremendous burden on the wetlands,
estuaries, coral reefs and mangrove swamps found along the coast.
C. Pollutants from six states contaminate the shallow Chesapeake Bay estuary, but cooperative efforts have
reduced some of the pollution inputs. Introduction of disease-resistant oysters into the Chesapeake Bay
could greatly reduce water pollution because oysters filter algae and silt from water.
D. Parts of the world’s oceans are dump sites for a variety of toxic materials, sewage, and garbage from ships.
Dumping industrial wastes off U.S. coasts has stopped, but large quantities of dredge spoils are still legally
dumped at 110 sites in the Atlantic, Pacific, and Gulf Coasts of the U.S.
E. Most ocean pollution comes from human activities on land such as changing and dumping motor oil.
F. Oil pollution can have a number of harmful ecological and economic effects, but most disappear within 3
to15 years. Only about 15% of the oil spilled can be recovered with current techniques, so prevention is the
best strategy.
G. Preventing or reducing pollution from the land and from streams is the key to protecting the oceans.
30-5 How can we best deal with water pollution?
A.
B.
C.
D.
E.
F.
G.
H.
Reduce non-point pollution by preventing it from reaching bodies of surface water.
Most developing countries do not have laws to set water pollution standards.
Septic tanks and various levels of sewage treatment can reduce point-source water pollution.
Sewage sludge can be used as a soil conditioner, but may cause health problems if it contains infectious
bacteria or toxic chemicals.
Preventing toxic chemicals from reaching sewage treatment plants would eliminate these from sludge and
water that is discharged.
Natural and artificial wetlands and other ecological systems can be used to treat sewage.
Water pollution laws have significantly improved water quality in many U.S. streams and lakes, but more
needs to be done particularly for non-point source pollution sources.
Drinking water quality.
1. Centralized water treatment plants can provide safe drinking water for city dwellers. Water is settled,
filtered, and chlorinated to meet government drinking standards.
2. The U.S. is upgrading water purification and delivery systems. This is such a vast system that it is hard
to secure, but also difficult to adequately poison. Both chemical and biological indicators are being
developed to indicate a contamination problem.
3. Several simple, inexpensive ways for individuals and villages to purify drinking water have been
developed. Exposure of contaminated water to intense sunlight in a clear plastic bottle is one method.
It takes as little as three hours to kill bacteria in the sun and heat.
4.
5.
About 54 countries have standards for safe drinking water.
Some bottled water is not as pure as tap water and costs much more.