TOEFL reading test 7 with answers
Depletion of the Ogallala Aquifer
The vast grasslands of
the High Plains in the central United States were settled by farmers and
ranchers in the 1880s. This region has a semiarid climate, and for 50 years
after its settlement, it supported a low-intensity agricultural economy of
cattle ranching and wheat farming. In the early twentieth century, however, it
was discovered that much of the High Plains was underlain by a huge aquifer (a
rock layer containing large quantities of groundwater). This aquifer was named
the Ogallala aquifer after the Ogallala Sioux Indians, who once inhabited the
region.
The Ogallala aquifer is a
sandstone formation that underlies some 583,000 square kilometers of land
extending from northwestern Texas to southern South Dakota. Water from rains
and melting snows has been accumulating in the Ogallala for the past 30,000
years. Estimates indicate that the aquifer contains enough water to fill
Lake Huron, but unfortunately, under the semiarid climatic conditions that presently
exist in the region, rates of addition to the aquifer are minimal, amounting to
about half a centimeter a year.
The first wells were
drilled into the Ogallala during the drought years of the early 1930s. The ensuing
rapid expansion of irrigation agriculture, especially from the 1950s onward,
transformed the economy of the region. More than 100,000 wells now tap the
Ogallala. Modern irrigation devices, each capable of spraying 4.5 million
liters of water a day, have produced a landscape dominated by geometric
patterns of circular green islands of crops. Ogallala water has enabled the
High Plains region to supply significant amounts of the cotton, sorghum, wheat,
and corn grown in the United States. In addition, 40 percent of American
grain-fed beef cattle are fattened here.
This unprecedented development of a
finite groundwater resource with an almost negligible natural recharge
rate—that is, virtually
no natural water source to replenish the water supply—has caused water tables
in the region to fall drastically. In the 1930s, wells encountered plentiful
water at a depth of about 15 meters; currently, they must be dug to depths of
45 to 60 meters or more. In places, the water table is declining at a rate of a
meter a year, necessitating the periodic deepening of wells and the use of
ever-more-powerful pumps. It is estimated that at current withdrawal rates,
much of the aquifer will run dry within 40 years. The situation is most
critical in Texas, where the climate is driest, the greatest amount of water is
being pumped, and the aquifer contains the least water. It is projected that
the remaining Ogallala water will, by the year 2030, support only 35 to 40
percent of the irrigated acreage in Texas that is supported in 1980.
The reaction of farmers
to the inevitable
depletion of the Ogallala varies. Many have been attempting to conserve water
by irrigating less frequently or by switching to crops that require less water.
[■] Others, however, have adopted the philosophy that it is best to use the
water while it is still economically profitable to do so and to concentrate on
high-value crops such as cotton. [■] The incentive of the farmers who wish to
conserve water is reduced by their knowledge that many of their neighbors are
profiting by using great amounts of water, and in the process are drawing down
the entire region’s water supplies. [■]
In the face of the
upcoming water supply crisis, a number of grandiose schemes have been developed
to transport vast quantities of water by canal or pipeline from the
Mississippi, the Missouri, or the Arkansas rivers. [■] Unfortunately, the cost
of water obtained through any of these schemes would increase pumping costs at
least tenfold, making the cost of irrigated agricultural products from the
region uncompetitive on the national and international markets.Somewhat more
promising have been recent experiments for releasing capillary water (water in
the soil) above the water table by injecting compressed air into the
ground.Even if this process proves successful, however, it would almost triple
water costs. Genetic engineering also may provide a partial solution, as new
strains of drought-resistant crops continue to be developed. Whatever the final
answer to the water crisis may be, it is evident that within the High Plains,
irrigation water will never again be the abundant, inexpensive resource it was
during the agricultural boom years of the mid-twentieth century.
Questions:
1. According to paragraph
1, which of the following statements about the High Plains is true?
A.
Until farmers and ranchers settled there in the 1880s, the High Plains had
never been inhabited.
B.
The climate of the High Plains is characterized by higher-than-average
temperatures.
C.
The large aquifer that lies underneath the High Plains was discovered by the
Ogallala Sioux Indians.
D.
Before the early 1900s there was only a small amount of farming and ranching in
the High Plains.
2. According to paragraph
2, all of the following statements about the Ogallala aquifer are true EXCEPT:
A.
The aquifer stretches from South Dakota to Texas.
B.
The aquifer’s water comes from underground springs.
C.
Water has been gathering in the aquifer for 30,000 years.
D.
The aquifer’s water is stored in a layer of sandstone.
3. Which of the sentences
below best expresses the essential information in the highlighted sentence (underscored)
in the passage? Incorrect choices change the meaning in important ways or leave
out essential information.
A.
Despite the current impressive size of the Ogallala aquifer, the region’s
climate keeps the rates of water addition very small.
B.
Although the aquifer has been adding water at the rate of only half a
centimeter a year, it will eventually accumulate enough water of fill Lake
Huron.
C.
Because of the region’s present climatic conditions, water is being added each
year to the aquifer.
D.
Even when the region experiences unfortunate climatic conditions, the rates of
addition of water continue to increase.
4. The word “ensuing”
in the passage is closest in meaning to
A.
continuing
B.
surprising
C.
initial
D.
subsequent
5. In paragraph 3, why
does the author provide the information that 40 percent of American cattle are
fattened in the High Plains?
A.
To suggest that crop cultivation is not the most important part of the economy
of the High Plains
B.
To indicate that not all economic activity in the High Plains is dependent on
irrigation
C.
To provide another example of how water from the Ogallala has transformed the
economy of the High Plains
D.
To contrast cattle-fattening practices in the High Plains with those used in
other region of the United States
6. The word “unprecedented”
in the passage is closest in meaning to
A.
difficult to control
B.
without any restriction
C.
unlike anything in the past
D.
rapidly expanding
7. The word “virtually”
in the passage is closest in meaning to
A.
clearly
B.
perhaps
C.
frequently
D.
almost
8. According to paragraph
4, all of following are consequences of the heavy use of the Ogallala aquifer
for irrigation EXCEPT:
A.
The recharge rate of the aquifer is decreasing.
B.
Water tables in the region are becoming increasingly lower.
C.
Wells now have to be dug to much greater depths than before.
D.
Increasingly powerful pumps are needed to draw water from the aquifer.
9. According to paragraph
4, compared with all other states that use Ogallala water for irrigation, Texas
A.
has the greatest amount of farmland being irrigated with Ogallala water
B.
contains the largest amount of Ogallala water underneath the soil
C.
is expected to face the worst water supply crisis as the Ogallala runs dry
D.
uses the least amount of Ogallala water for its irrigation needs
10. The word “inevitable”
in the passage is closest in meaning to
A.
unfortunate
B.
predictable
C.
unavoidable
D.
final
11. Paragraph 5 mentions
which of the following as a source of difficulty for some farmers who try to
conserve water?
A.
Crops that do not need much water are difficult to grow in the High Plains.
B.
Farmers who grow crops that need a lot of water make higher profits.
C.
Irrigating less frequently often leads to crop failure.
D.
Few farmers are convinced that the aquifer will eventually run dry.
12. According to
paragraph 6, what is the main disadvantage of the proposed plans to transport
river water to the High Plains?
A.
The rivers cannot supply sufficient water for the farmer’s needs.
B.
Increased irrigation costs would make the products too expensive.
C.
The costs of using capillary water for irrigation will increase.
D.
Farmers will be forced to switch to genetically engineered crops.
13.Look at the four
squares [■] that indicate where the following sentence could be added to the
passage. Where would the sentence best fit?
But
even if uncooperative farmers were to join in the conservation efforts, this
would only delay the depletion of the aquifer.
14. Directions: An
introductory sentence for a brief summary of the passage is provided below.
Complete the summary by selecting the THREE answer choices that express the
most important ideas in the passage. Some sentences do not belong in the
summary because they express ideas that are not presented in the passage or are
minor ideas in the passage. This question is worth 2 points. The Ogallala
aquifer is a large underground source of water in the High Plains region of the
United States.
A.
The use of the Ogallala for irrigation has allowed the High Plains to become
one of the most productive agricultural regions in the United States.
B.
Given the aquifer’s low recharge rate, its use for irrigation is causing water
tables to drop and will eventually lead to its depletion.
C.
Releasing capillary water and introducing drought-resistant crops are
less-promising solutions to the water supply crisis than bringing in river
water
D.
The periodic deepening of wells and the use of more-powerful pumps would help
increase the natural recharge rate of the Ogallala.
E.
In Texas, a great deal of attention is being paid to genetic engineering
because it is there that the most critical situation exists.
F.
Several solutions to the upcoming water supply crisis have been proposed, but
none of them promises to keep the costs of irrigation low.
======================================================================
Answers:
1.D, 2.B, 3.A, 4.D, 5.C,
6.C, 7.D, 8.A, 9.C, 10.C, 11.B, 12.B, 13.C, 14.ABF
hope it could have more explanation about the answers.
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