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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 negligiblenatural 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 currentwithdrawal 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.
TPO3托福阅读Passage2题目
Question 1 of 14
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..
Question 2 of 14
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..
Question 3 of 14
Which of the sentences below best expresses the essential information in the highlighted sentence 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..
Question 4 of 14
The word “ensuing ” in the passage is closest in meaning to
A. continuing.
B. surprising.
C. initial.
D. subsequent.
Question 5 of 14
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.
Question 6 of 14
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.
Question 7 of 14
The word “virtually ” in the passage is closest in meaning to
A. clearly.
B. perhaps.
C. frequently.
D. almost.
Question 8 of 14
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..
Question 9 of 14
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.
Question 10 of 14
The word “inevitable ” in the passage is closest in meaning to
A. unfortunate.
B. predictable.
C. unavoidable.
D. final.
Question 11 of 14
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..
Question 12 of 14
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..
Question 13 of 14
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..
Question 14 of 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..
TPO3托福阅读Passage2解析
Question 1 of 14
正确答案：D
题目解析：
排除法，以1880s做关键词定位至第一句，说1880s农牧民定居在High Plains，没说1880前没有人，A错：The vast grasslands of the High Plains in the central United States were settled by farmers and ranchers in the 1880s.以climate做关键词定位至第二句，原文说semiarid，没说温度，B错;D中small amount of farming and ranching和原文第二句中的low-intensity是同义替换，选。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.以人名做关键词定位至最后一句，说这个人是inhibit在这儿的，没说是他发现的，C错：This aquifer was named the Ogallala aquifer after the Ogallala Sioux Indians, who once inhabited the region.
Question 2 of 14
正确答案：B
题目解析：
A以两个地名，D以sandstone做关键词定位至第一句，A和D都对，不选：The Ogallala aquifer is a sandstone formation that underlies some 583,000 square kilometers of land extending from northwestern Texas to southern South Dakota.C以30000 years做关键词定位至第二句，C对，不选：Water from rains and melting snows has been accumulating in the Ogallala for the past 30,000 years.从这句话同时可以看到地下水是来自rain and melting snow，不是泉水，所以B错，选。
Question 3 of 14
正确答案：A
题目解析：
A, 文的结构是估计水很多，足以填满休伦湖，但在半干旱天气下，补充的少。主要逻辑是转折，转折之后是重点强调内容。A答案完整地反映了这两个方面，正确;B强调的点搞反，原句强调的是补充的少，B强调的是现在的量大;C的added和原句不符，而且遗漏了主要的内容;D说补充的持续增长，原文没说。
Question 4 of 14
正确答案：D
题目解析：
ensue跟随，接下来，所以subsequent是答案。原文说第一批水井是1930s挖掘的，ensuing所在的那句话又说1950s什么样的农业的快速扩张，这两个时间说明动作是有先后的，而且first一般必然有下文的，所以应该是接着的。注意continuing是个很大的迷惑项，继续是指一个动作的延续，而接下来是两件事情接着发生，B令人吃惊和C最初的，起始的都不对。
Question 5 of 14
正确答案：C
题目解析：
功能目的题，40%明显是一个例子，往前看，说这个地方的水养活了high plains地区的很多农作物，in addition说明进一步，也就是除了农业还有牧业，所以是C，provide another example，没有说农业和牧业谁重要，A错;牧业确实不依赖灌溉，但也依赖这个地方的水，所以B无关;没有对比，D错。
Question 6 of 14
正确答案：C
题目解析：
unprecedented: 史无前例的，un表示没有，pre前，想到precede，在……之前。A是很难控制;B是没有限制;C是和过去的任何东西都不同;D是快速扩张。根据词意，C正确。对应原文：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.A难以控制和B毫无限制都有轻微贬义，而原词只是在叙述一个事实，属中性。D快速扩张也不沾边，而且A/B/D三个选项在意思上有共同点，唯独C不同，只要知道pre是前就一定能选出答案。
Question 7 of 14
正确答案：D
题目解析：
virtually几乎。注意virtual有虚拟和真实两个截然相反的意思，破折号之前说negligible recharge rate，补给可以忽略，就是很少，但还是有的，后面解释说什么没有水补充，如果选除了almost之外的三项，都说明可能没水，与原文意思不符。
Question 8 of 14
正确答案：A
题目解析：
排除法，分别以recharge rate，water tables，wells，powerful pumps做关键词定位至本段前三句：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.B/C/D三项在原文中都有说，而A的recharge rate在第一句中提到，但不是heavy use的结果，所以A错，选。而且跳出这道题看，随着地下水位的下降，井必须打得更深，水泵必须功率更大，这是一系列的因果关系，只有A不是这个因果序列中的。
Question 9 of 14
正确答案：C
题目解析：
以Texas为关键词定位至倒数第二句，说德州气候最干燥，地下水最少，面临的问题最严峻，C是原文的同义改写。
Question 10 of 14
正确答案：C
题目解析：
inevitable: 不可避免的，必然的。A是不幸的;B是不可预测的;C是不可避免的;D是最终的。根据词意，C正确。对应原文：The reaction of farmers to the inevitable depletion of the Ogallala varies.上段整个都在说地下水位在剧烈下降，depletion指的是水用光，承上启下应该是地下水一定会用光，作者只是在陈述事实，没有好坏之说，所以unfortunate不对，不要主观猜想水没了对当地人一定不好;predictable可预见的也不对，因为原文没给出任何预见性的信息;就单词本身看，in前缀表示否定，所以必须答案也有类似的部分，unavoidable无疑是最好的选项。
Question 11 of 14
正确答案：B
题目解析：
以some farmers who try to conserve water为关键词定位至最后一句，说那些不省水的农民因为没有节约水获得利润，众多选项中只有B提到了利润问题，是正确答案。
Question 12 of 14
正确答案：B
题目解析：
以transport water做关键词定位至本段第一句，第二句开始的unfortunately清楚的表明了这句话会说一个运水产生的问题，就是成本太贵，使产品价格失去竞争力，B和C提到成本，而只有B提到了产品价格升高，正确。
Question 13 of 14
正确答案：C
题目解析：
C 两个决定点，第一个是uncooperative farmers，那些不合作的农民，根据这个点，A和C是可能的答案，第二个点就是even if的让步，既然待插入句说即使那些人愿意合作，正确插入点之前就必须的说那些人不合作，所以C是正确答案，而且A前后的many一句和other一句衔接很紧密，不插入句子。
Question 14 of 14
正确答案：ABF
题目解析：
文章题目暗示文章有几种可能展开方向：现象解释、历史过程，问题解决。 文站首段、二段解释的是Ogallala Aquifer, 属于背景介绍。 三段叙述OA水资源开采的过程，经济贡献，暗示depletion的原因。 四段首句概括depletion问题，描述问题的严重性。 五段介绍居民的反应，暗示问题得不到解决，会更加严重。 末段介绍几种可能的解决方案，末句评论说问题得不到彻底解决，便宜水资源不再可能。 提示句是对于首段、二段内容概括，正确选项应该概括以下各段大意。 A选项对应原文第三段，水资源利用改变了当地经济，正确。 B选项对应原文第四五段，正确。 C选项原文未说，末段没有说哪个方案比哪个方案好。 D选项原文也没说，不选。 E选项原文也没说，不选。 F选项概括原文第六段，正确。
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