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托福阅读TPO12(试题+答案+译文)第3篇:Water in the Dert
托福阅读原文
Rainfall is not completely abnt in dert areas, but it is highly variable. An annual rainfall of four inches is often ud to define the limits of a dert. The impact of rainfall upon the surface water and groundwater resources of the dert is greatly influenced by landforms. Flats and depressions where water can collect are common features, but they make up only a small part of the landscape.
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Arid lands, surprisingly, contain some of the world’s largest river systems, such as the Murray-Darling in Australia, the Rio Grande in North America, the Indus in Asia, and the Nile in Africa. The rivers and river systems are known as "exogenous" becau their sources lie outside the arid zone. They are vital for sustaining life in some of the driest parts of the world. For centuries, the annual floods of the Nile, Tigris, and Euphrates, for example, have brought fertile silts and water to the inhabitants of their lower valleys. Today, river discharges are increasingly controlled by human intervention, creating a need for international river-basin agreements. The filling of the Ataturk and other dams in Turkey has drastically reduced flows in the Euphrates, with potentially rious conquences for Syria and Iraq.
写给四年后的自己The flow of exogenous rivers varies with the ason. The dert ctions
of long rivers respond veral months after rain has fallen outside the dert, so that peak flows may be in the dry ason. This is uful for irrigation, but the high temperatures, low humidities, and different day lengths of the dry ason, compared to the normal growing ason, can prent difficulties with some crops.
Regularly flowing rivers and streams that originate within arid lands are known as "endogenous." Th
e are generally fed by groundwater springs, and many issue from limestone massifs, such as the Atlas Mountains in Morocco. Basaltic rocks also support springs, notably at the Jabal Al-Arab on the Jordan-Syria border. Endogenous rivers often do not reach the a but drain into inland basins, where the water evaporates or is lost in the ground. Most dert streambeds are normally dry, but they occasionally receive large flows of water and diment.
Derts contain large amounts of groundwater when compared to the amounts they hold in surface stores such as lakes and rivers. But only a small fraction of groundwater enters the hydrological cycle—feeding the flows of streams, maintaining lake levels, and being recharged (or refilled) through surface flows and rainwater. In recent years, groundwater has become an increasingly important source of freshwater for dert dwellers. The United Nations Environment Programme and the World Bank have funded attempts to survey the groundwater resources of arid lands and to develop appropriate extraction techniques. Such programs
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are much needed becau in many arid lands there is only a vague idea of the extent of groundwater resources. It is known, however, that the distribution of groundwater is uneven, and that much of it lies at great depths.
Groundwater is stored in the pore spaces and joints of rocks and unconsolidated (unsolidified) diments or in the openings widened through fractures and weathering. The water-saturated rock or diment is known as an "aquifer". Becau they are porous, dimentary rocks, such as sandstones and conglomerates, are important potential sources of groundwater. Large quantities of water may also be stored in limestones when joints and cracks have been enlarged to form cavities. Most limestone and sandstone aquifers are deep and extensive but may contain groundwaters that are not being recharged. Most shallow aquifers in sand and gravel deposits produce lower yields, but they can be rapidly recharged. Some deep aquifers are known as "fossil waters. The term "fossil" describes water that has been prent for veral thousand years. The aquifers became saturated more than 10,000 years ago and are no longer being recharged.
Water does not remain immobile in an aquifer but can ep out at springs or leak into other aquifers. The rate of movement may be very slow: in the Indus plain, the movement of saline (salty) groundwaters has still not reached equilibrium after 70 years of being tapped. The mineral content
of groundwater normally increas with the depth, but even quite shallow aquifers can be highly saline.
托福阅读试题
1.Which of the following statements about annual rainfall can be inferred from paragraph 1?
A.Flat dert areas receive more annual rainfall than dert areas with mountains.
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B.Areas that receive more than four inches of rain per year are not considered derts.
C.Many areas receive less than four inches of annual rainfall, but only a few are derts.
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D.Annual rainfall has no impact on the groundwater resources of dert areas.
2.The word “drastically” in the passage(Paragraph 2)is clost in meaning to
A.obviously
B.unfortunately
C.rapidly
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立冬吃饺子的由来D.verely
3.In paragraph 2, why does the author mention the Ataturk and other2年级作文
