托福 新托福 03 - Depletion of the Ogallala Aquifer
题目
1 2 3 4 5 6 7 8 9 10
5.The word “virtually” in the passage is closest in meaning to
  • A.clearly
  • B.perhaps
  • C.frequently
  • D.almost
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    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.

    19世纪80年代,在美国中部北美大平原的广阔草原上定居着农场主们和牧场主们。这里有着半干旱的气候,在人们定居50年后,它支撑了一个以畜牧业和小麦种植为主的低密度农业经济。然而,在20世纪初,人们发现北美大平原的大部地下是巨大的蓄水层(含有大量地下水的岩层)。这个蓄水层因曾经在这里定居过的奥加拉拉苏族印第安人而得名,被称作奥加拉拉蓄水层。 奥加拉拉蓄水层属于砂岩结构,在从德克萨斯州西北到南达科塔州南部的地下绵延了58.3万平方公里。雨水和融雪自3万年前便开始在奥加拉拉蓄积。据估计,奥加拉拉蓄水层的含水量足以填满休伦湖,但不幸的是,在目前该地区半干旱的气候条件下,奥加拉拉蓄水层的蓄水能力极低,每年仅半厘米左右。 20世纪30年代初,奥加拉拉正处于干旱时期,人们打出了第一口井。灌溉农业的迅速扩张,特别是20世纪50年代之后,改变了这一地区的经济。目前人们已经在奥加拉拉地区共开凿了10万多口井。日喷水量达到450万升的现代灌溉设备,形成了一个圆形绿岛作物为主的景观。奥加拉拉蓄水层支撑了北美大平原地区棉花、高粱、小麦、玉米的灌溉需求。此外,美国40%谷饲养的肉牛在这里被育肥。 考虑到几乎没有补充率(实质上没有自然水资源进行补充),这种有限地下水资源前所未有的发展已经引起了该地区地下水位的急剧下降。在20世纪30年代,井下15米就有丰富的水资源,而现在,必须挖掘到45米到60米甚至更深的地方才行。有的地方地下水位的下降速度甚至达到了每年1米,迫使人们周期性的加深水井并使用更有力的水泵。按现今的下降速度来估计,大部分地下蓄水将在40年内耗尽。这种现象在气候最干旱的德克萨斯州尤为严重。大量的水被从地下抽起,蓄水层含水量最少。据估计,到2030年,德克萨斯州余下的奥加拉拉含水只能支持1980年灌溉面积的35%到40%。 农场主们对无法避免的奥加拉拉蓄水层枯竭的反应各不相同。很多人已经开始尝试通过降低灌溉频率或者改种需水较少的庄稼来节约水资源。而另外一些人却抱着趁水资源还能产生经济效益就应抓紧利用的想法,继续种植高价值的棉花等农作物。当那些想节水的农场主得知邻居们通过大量耗水的种植而盈利的时候,他们的热情降低了,从而导致了整个区域的供水量的减少。 在即将到来的水资源供应危机面前,人们提出了一些宏伟的供水计划,比如将密西西比河、密苏里河或者阿肯色河的水通过运河或管道运到需要用水的地方。不幸的是,通过以上任何一种方式获得水资源都会将抽水的成本提高10倍以上,进而导致这一地区的灌溉农产品成本在国内和国际市场上失去竞争力。最近一些有希望获得成功的试验试图通过向土壤中注入压力,释放水层上方土壤中的毛细管水。即使这样行之有效,抽水成本会变到原来的3倍。基因工程也会通过继续研发抗旱作物新品种,帮助解决部分难题。无论这次水资源危机的最终结果如何,显然,北美大平原地区灌溉水资源再也不会像20世纪中期农业繁荣时期的那样充足并且廉价了。  

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    最新提问
    • wx_6697
      觉得B C 意思一样,不知道选哪个
    • wx_5576
      这道题C为什么对,E为什么不对?
    • wx_5576
      B为什么不能选啊?
    • wx_6697
      TPO30 passage 2 Q5我选的 D,不明白为啥不对?
    • wx_6697
      鑫哥,TPO6passage3Q5 答案是给错了吗?好多人都选A
    • wx_6697
      这题也很容易选错选成了D
    • wx_6697
      这道题A为什么错了
    • 芊儿
      为什么这道题不选c??a中的variety不是应该对应文中的differentiating 吗??求解!
    • wx_1000
      这道题不选E是因为太细节了吗
    • 王金阁
      这个题为什么不选C啊。。。
    • 芊儿
      这道题的D选项不是和文中的better able to reproduce in open settings相对应么??
    • 风荨火
      有大佬解释一下这个为啥选D嘛?
    • 以沫
      请问这个D 在哪里提现?为什么D错?
    • 芊儿
      第六题 的C选择为什么不对,感觉A是明显驳斥啊...
    • wx_6697
      鑫哥,这道题D是从哪里看出来的
    • wx_6697
      这题选的A,根据是Joly’s calculations clearly supported those geologists who insisted on an age for Earth far in excess of a few million years.想问鑫哥为啥不选A
    • wx_6697
      这题我选的是C依据是into a new habitat outside of its natural range, it may adapt to the new environment and leave its enemies behind.C为啥错了呢?鑫哥
    • wx_8861
      F选项的weather-related destruction在哪里体现了呢?原文最后一段的开头Among the costs里的costs是不是打错了?应该是coast?
    • wx_6697
      求问这道题B为啥不选,原文依据:viable seeds of pioneer species can be found in large numbers on some forest floors.
    • 与托福的斗争史
      与托福的斗争史 去解答 去解答
      这题为什么选C?
    • 小雨淅沥哗啦的下
      小雨淅沥哗啦的下 去解答 去解答
      B哪里错了
    • 小雨淅沥哗啦的下
      小雨淅沥哗啦的下 去解答 去解答
      B为啥不对
    • 李浩然
      B选项错误,是因为残缺么?
    • wx_100
      请问在做题的时候如何排除c呢。看了答案,感觉是该选a的,但是当时做题脑子一热,就特别钟爱c,也没看其他选项。。求敲醒。。
    • wx xxxxx
      请问鑫哥,这段开头有写As one pesticide replaces another为什么不是对应a new pesticide is developed?
    • wx_7695
      鑫哥,从哪里看出来这个masks 不是use呀,原文说了wear呀
    • haiyuqiao
      @鑫哥,这题the damage will continue 不应该对应前面的 the target species evolves resistance to it,然后As one pesticide replaces another,不应该是结束了time cycle 吗
    • wx_2065
      鑫哥,想知道E错在哪里?
    • wx_7695
      鑫哥,B选项 cannot extended to earlier geological periods. 原文说的意思是后来的进化无法估计吧
    • wx_2163
      B为什么不选
    • wx_7780
      鑫哥,这个哪里看不use了。BD是修饰错,C是无中生有,怎么能直接选出A?
    • 100
      看到第一句话,以为是中心句就选了A... 为什么不能选A呢
    • 100
      为什么选b?
    • gu33
      请问下 这里选D的原因是 因为 evolutionary approach 对应着 原文的 Rates of evolution 嘛? 这里我选了C。。不是很懂 插入句和 D的关系 求解答
    • 我是啦啦啦
      我是啦啦啦 去解答 去解答
      这个题A哪里错了?是因为主语不对吗?这个C比A多一步推理啊
    • haiyuqiao
      鑫哥,D选项里的19世纪出现了很多假设,原文中并没有提到啊
    • wx_7060
      为什么选a 呢。我觉得a是细节。F哪错了?
    • wx_1105
      我想问一下,这道题为什么不能选A呢?
    • wx_8122
      D为什么不选
    • wx_1655
      f选项哪里说了
    • chaulaw
      鑫哥,原文是below经济损害水平,D是一触发经济损害就用,这也对吗?
    • chaulaw
      interclan婚姻是对的吗?不是只在自己的family结婚扩大家族吗?
    • wx_6697
      鑫哥,这道题答案是不是错了,好多人选D 我也选的D求解答
    • wx_6697
      这道题应该是一道易错题,每个选项的都有,然而我选的A错了,求解
    • wx_6697
      鑫哥,这题的C是怎么得到的?B也没有找到啊?难道不是应该选B
    • wx_6697
      鑫哥,还有这个,好多人选A答案是不是错了
    • wx_6697
      求问D是从哪里得出来的,我选的B呀哎呀
    • wx_4185
      it is difficult to say how far they were intended to be portraits rather than generalized images 这句话怎么理解呢
    • 此楠楠
      请问下这个插入题怎么选的呢?
    • 此楠楠
      求鑫哥讲解下A选项。。。 Even though in error, Joly’s calculations clearly supported those geologists who insisted on an age for Earth far in excess of a few million years.