12
________.
A) trucked to special biohazard landfills for disposal
B) used as part of the “fill” to develop wetlands into agriculture or housing areas
C) loaded onto barges and sent to underdeveloped countries to use as fertilizer
D) used as crop fertilizer in Canada
E) placed in deep injection wells to keep it out of the water table
26) As of 2007, the saga of the Colorado River’s water resource allocation is being complicated
by ________.
A) several years of drought coupled with the rapid growth of Las Vegas
B) large numbers of people moving out of Nevada
C) sinkhole collapses in Arizona and southern California
D) the rapid growth of vegetable farms in southern Arizona
E) saltwater intrusion into the Colorado estuary near San Diego
27) Global climate change is causing many glaciers to melt rapidly. Should they disappear
entirely, this will adversely affect the water supply in areas ________.
A) such as the Mississippi watershed, which is supplied by melt water
B) such as the Everglades and Okeefenokee wetlands in the southeast United States
C) along watersheds in the Urals, Himalayas, and Alps fed by seasonal glacial melts
D) such as the Great Lakes
E) on large islands adjacent to continents, such as Madagascar and Taiwan
28) Freshwater resources in Canada are ________.
A) mostly used for drinking
B) mostly used for industrial needs
C) inexhaustible because they are renewed by the hydrological cycle
D) used primarily for crop irrigation
E) concentrated in western Canada
29) India uses 87% of its water for agriculture, while Lithuania uses 78% for domestic use. The
reason for this difference is that ________.
A) Lithuania has very little agriculture
B) Lithuania is a poor country that cannot afford irrigation
C) India has a much higher population
D) India has an arid climate
E) India is rapidly industrializing
30) The overuse of groundwater does NOT contribute to the fact that ________.
A) many cities, such as Mexico and Bangkok, are sinking
B) drinking water in Venice may be getting more salty
C) sinkholes are created
D) zone of saturation replaces zone of aeration
E) soil is compacted
12.5 True/False Questions
1) Only 5% of Earth’s human population relies directly on groundwater for its needs.
2) Automatic dishwashers use more water than washing dishes by hand.
3) The World Commission on Water concluded that over half of the world’s major rivers are
depleted and polluted.
4) The Great Lakes hold close to 20% of the world’s surface freshwater.
5) Artificial wetlands can help cleanse water while providing recreational opportunities.
6) The second largest dam in the world is in Alberta (around tar sand tailings).
12.6 Essay Questions
1) What is meant by the statement, “We are truly ‘replumbing the planet'”? Provide an example.
2) Using the Three Gorges Dam on China’s Yangtze River as an example, what are the benefits
and costs associated with building dams?
3) How can agricultural irrigation practices be altered to decrease a loss of freshwater?
4) Define water pollution, point source, and nonpoint source pollution. Is point source or
nonpoint source pollution easier to identify? Which is easier to legislate? Which currently poses
the greatest threat to freshwater in Canada?
5) Describe the benefits obtained by the creation of artificial wetlands.
6) What are the arguments for and against export of water from Canada to the United States?
7) What were the environmental and economic consequences of the large-scale irrigation in the
former Soviet Union in which waters from two rivers flowing into a big inland sea in Central
Asia were used?
8) How do mountain glaciers and snow affect water levels in rivers flowing down from the
mountains? What other component of the freshwater system can have similar impact on river
levels?
12.7 Scenario-Based Questions
Read the following scenario and answer the questions below.
On a September day in 1999, folks began to notice that Lake Jackson in the panhandle region of
northern Florida was shrinking. Within a few days, it was almost gone. A sinkhole had opened
beneath the lake and drained it, along with all of the fish and alligators.
As aquifers lose water, their substrates can become weaker and less capable of supporting
overlying strata and any human structures built on them. In such cases, the land surface above
may subside. Sometimes subsidence can occur locally and suddenly, in the form of sinkholes,
areas where the ground gives way with little warning. Once the ground subsides, soil becomes
compacted, losing the porosity that enabled it to hold water. Recharging a depleted aquifer may
therefore become more difficult.
Although Canada has several aquifers, it has not yet experienced sinkholes from water being
depleted from any of them. However, there is a natural sinkhole in the Sahtu, Northwest
Territories, southeast of Normal Wells. As well, there have been sinkholes as a result of broken
water mains.
1) Sinkholes can occur when ________.
A) too much weight above an aquifer causes it to cave in
B) the water level in an aquifer rises, pushing through to the surface
C) the water in an artesian aquifer is under sufficient pressure that it breaks through to the
surface
D) excessive water use lowers a water table and weakens the substrate
E) nonconsumptive use lowers an aquifer
2) Sinkholes are an extreme form of ________.
A) aquifer
B) water table
C) subsidence
D) artesian aquifer
E) consumptive use
3) A serious problem that results from excessive water withdrawn from aquifers is that
________.
A) the water tends to overflow and flood the entire area
B) the surrounding soils are compacted and the size of the aquifer is reduced
C) the soils contaminate the aquifer, making it unfit for human use
D) the aquifer increases in size, draining a larger surface area and leaving less water in rivers,
streams, and lakes
E) the aquifer decreases in size and new aquifers form
4) One reasonable way to prevent sinkholes might be to ________.
A) install supports to maintain the shape of the underground aquifer
B) increase groundwater recharge by constructing artificial wetlands that use treated municipal
wastewater
C) pump wastewater and sewage directly into the aquifer to maintain the water table
D) have the local water company regularly transfer water from one local aquifer to the next,
maintaining the average water level
E) pump sand and gravel into the aquifer to fill in the bottom levels, thus raising the water table
5) The number of human-induced sinkholes in North America has doubled since 1930. Insurance
claims increased 1200% from 1987 to 1991, costing nearly $100 million. Several areas in
Canada are at risk for sinkhole development . A major reason for this is ________.
A) global warming
B) increased rainfall, eroding underground sediments
C) roadway construction, leading to increased runoff
D) increased water consumption
E) decreases in agriculture
6) In July 2001, the town of Spring Hill, Florida, about 70 km north of Tampa, had 18 sinkholes
appear in a single day. The largest holes were nearly 30 m deep. This is an indication that
________.
A) earthquakes had recently occurred, and the water table sank
B) hurricanes had recently occurred, and the water table rose
C) prolonged rainstorms had recently occurred, and the water table rose
D) agriculture had increased, and the water table rose with irrigation recharge
E) a drought had recently occurred, along with increased development
7) You have been hired by a small town on the Florida coast to give its residents advice about
avoiding further sinkholes. You tell them that ________.
A) if they stay here, sinkholes will occur; they should move
B) they should limit development and recycle water
C) because sinkholes are a natural occurrence, nothing they do will help
D) they should increase groundwater pumping
E) pumping in ocean water will recharge the aquifer