TPO24阅读文本题目答案.doc

Contents
TPO 软件免费版下载 2
Lake Water 3
Questions for Passage 1 5
Passage 2: Breathing During Sleep 9
Questions for Passage 2 11
Passage 3. Moving into Pueblos 15
Questions for Passage 3 17
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Lake Water
<1>◆</1> Where does the water in a lake come from, and how does water leave it? Water enters a lake from inflowing rivers, from underwater seeps and springs, from overland flow off the surrounding land, and from rain falling directly on the lake surface. Water leaves a lake via outflowing rivers, by soaking into the bed of the lake, and by evaporation. [1]So much[/1] is obvious.
<2>◆</2><3>◆</3><4>◆</4> The questions become more complicated when actual volumes of water are considered: how much water enters and leaves by each route? Discovering the inputs and outputs of rivers is a matter of measuring the discharges of every inflowing and outflowing stream and river. Then exchanges with the atmosphere are calculated by finding the difference between the [2]gains[/2] from rain, as measured (rather roughly) by ram gauges, and the losses by evaporation measured with models that correct for the other sources of water loss. For the majority of lakes certainly those surrounded by forests, input from overland flow is too small to have a noticeable effect. Changes in lake level not explained by river flows plus exchanges with the atmosphere must be due to the net difference between what seeps into the lake from the groundwater and what leaks into the groundwater. [4]Note the word "net":[/4] measuring the actual amounts of groundwater seepage into the lake and out of the lake is a much more complicated matter than merely inferring their difference.
<5>◆</5><6>◆</6><13>◆</13> Once all this information has been gathered, it becomes possible to judge whether a lake's flow is mainly due to its surface inputs and outputs or to its underground inputs and output