TPO是托福备考生的备考首选资料，单就托福阅读来说，有的考生围绕着TPO反复做、反复练，才能获得“备考安全感”。但是往往资料解析不够详细，没有穿插做题思路，参考性不强。所以小编要给大家分享这份最全解析，本文带来的是托福阅读TPO1，希望对大家的备考有所帮助。
GROUNDWATER
Groundwater is the word used to describe water that saturates the ground, filling all the available spaces. By far the most abundant type of groundwater is meteoric water；this is the groundwater that circulates as part of the water cycle. Ordinary meteoric water is water that has soaked into the ground from the surface, from precipitation (rain and snow) and from lakes and streams. There it remains, sometimes for long periods, before emerging at the surface again. At first thought it seems incredible that there can be enough space in the “solid” ground underfoot to hold all this water.
The necessary space is there, however, in many forms. The commonest spaces are those among the particles—sand grains and tiny pebbles—of loose, unconsolidated sand and gravel. Beds of this material, out of sight beneath the soil, are common. They are found wherever fast rivers carrying loads of coarse sediment once flowed. For example, as the great ice sheets that covered North America during the last ice age steadily melted away, huge volumes of water flowed from them. The water was always laden with pebbles, gravel, and sand, known as glacial outwash, that was deposited as the flow slowed down.
The same thing happens to this day, though on a smaller scale, wherever a sediment-laden river or stream emerges from a mountain valley onto relatively flat land, dropping its load as the current slows: the water usually spreads out fanwise, depositing the sediment in the form of a smooth, fan-shaped slope. Sediments are also dropped where a river slows on entering a lake or the sea, the deposited sediments are on a lake floor or the seafloor at first, but will be located inland at some future date, when the sea level falls or the land rises；such beds are sometimes thousands of meters thick.
In lowland country almost any spot on the ground may overlie what was once the bed of a river that has since become buried by soil；if they are now below the water’s upper surface (the water table), the gravels and sands of the former riverbed, and its sandbars, will be saturated with groundwater.
So much for unconsolidated sediments. Consolidated (or cemented) sediments, too, contain millions of minute water-holding pores. This is because the gaps among the original grains are often not totally plugged with cementing chemicals；also, parts of the original grains may become dissolved by percolating groundwater, either while consolidation is taking place or at any time afterwards. The result is that sandstone, for example, can be as porous as the loose sand from which it was formed.
Thus a proportion of the total volume of any sediment, loose or cemented, consists of empty space. Most crystalline rocks are much more solid；a common exception is basalt, a form of solidified volcanic lava, which is sometimes full of tiny bubbles that make it very porous.
The proportion of empty space in a rock is known as its porosity. But note that porosity is not the same as permeability, which measures the ease with which water can flow through a material；this depends on the sizes of the individual cavities and the crevices linking them.
Much of the water in a sample of water-saturated sediment or rock will drain from it if the sample is put in a suitable dry place.█ But some will remain, clinging to all solid surfaces.█ It is held there by the force of surface tension without which water would drain instantly from any wet surface, leaving it totally dry.█ The total volume of water in the saturated sample must therefore be thought of as consisting of water that can, and water that cannot, drain away.█
The relative amount of these two kinds of water varies greatly from one kind of rock or sediment to another, even though their porosities may be the same. What happens depends on pore size. If the pores are large, the water in them will exist as drops too heavy for surface tension to hold, and it will drain away; but if the pores are small enough, the water in them will exist as thin films, too light to overcome the force of surface tension holding them in place；then the water will be firmly held.
疑难词：
Saturate v. 使饱和；使充满；浸透
Meteoric adj. 大气的；流星的；疾速的
Soak vt. 吸收，吸入
Precipitation n. [化学] 沉淀；降水
Sediment n. 沉积；沉淀物
Overlie vt. 在…上面
Cement n. 水泥；接合剂vt. 巩固
crevices n. 裂缝
长难句解析：
1.Most crystalline rocks are much more solid；a common exception is basalt,( a form of solidified volcanic lava), which is sometimes full of tiny bubbles that make it very porous.
句子类型：同位语+定语从句+that引导的主语从句
难词解析：
Crystalline结晶的
Basalt 玄武岩
Solidified 使凝固；固化的
Porous多孔的
句子拆分：
主干：rocks are…；a common exception is…
同位语：a form of solidified volcanic lava== basalt
定语从句： is sometimes full of tiny bubbles，which引导的非限制性定语从句，先行词是basalt
主语从句：that make it very porous，that引导，先行句which is sometimes full of tiny bubbles
翻译：绝大多数结晶厌食都更加坚固，但玄武岩是个例外，它是一种固化的火山熔浆，有时会遍布小气泡，使其结构呈现多孔状。
2.Wherever a sediment-laden river or stream emerges from a mountain valley onto relatively flat land,( dropping its load as the current slows): the water usually spreads out fanwise, (depositing the sediment in the form of a smooth, fan-shaped slope).
句子类型：结果状语
难词解析：
Fanwise adj. 呈扇形展开的
句子拆分：
主干：a sediment-laden river or stream emerges …
结果状语：
dropping its load as the current slows
depositing the sediment in the form of a smooth, fan-shaped slope
翻译：当携带沉积物的河流或溪水从山谷而下，流至相对平坦的地面时，砂石便随着流速减慢而逐渐沉淀：水流通常呈扇形蔓延，进而使所承载的砂石以光滑扇形的斜面形式沉积下来。
3.It is held there by the force of surface tension( without which water would drain instantly from any wet surface), leaving it totally dry.
句子类型：定语从句+结果状语
句子拆分：
主干：It is held there by the force of surface tension
定语从句：surface tension( without which water would drain instantly from any wet surface)，先行词surface tension
结果状语：leaving it totally dry
翻译：这是由于水的表面张力使水分得以存留，否则样本将迅速完全干燥。
文章结构分析：
段落大意：
第一段：地下水的定义及来源，论证对象的介绍
第二段：地下水储存方式多种多样，以及方式介绍
第三段：在第二段引出的冰水沉积概念上继续延伸，讲现代的冰水沉积。
第四段：在第三段基础上，曾经是河床的低地区域下可能会有地下水
第五段：引入除了松散沉积物，另一种地下水存在：地下水存在于坚固沉淀物的孔隙中
第六段：总结以上存水方式，沉积物利用其中的孔隙储存地下水。
第七段：存水原因下概念分析，孔隙度和渗透率的区别
第八段：地下水试验样本中包含的两种水分
第九段：两种水的相对含量因岩石与沉积物种类不同而改变
所以，文章可以分为三大部分：
第一部分：第一段，地下水定义及来源
第二部分：第二、三、四、五、六段，存水方式，松散及坚硬沉积物存水。
第三部分：关于为什么存水以及相关的概念
之后就是所有题目及完整解析了，请点击TPO1阅读题目史上最全解析，看过来!继续查看关于本篇阅读题目的解析!
还要分享给大家的做题注意点有：比如关于定位，需要常练习以快速找到相关句，不浪费时间；关于代词还原，题目中会常常涉及，要有相关练习；长难句的分析在做题时一定用的到；如果在做题时没有文章整体的概念，常常会有这样的感觉，单独做前面的题还可以，做到最后一题忽然不知道从何下手，只得再返回文章，这样容易耗时太多，所以在做题目前先用3~4min了解一下文章很有必要。
这些就是要分享给大家的关于TPO1-1 GROUNDWATER的解析及做题需要注意的问题，希望本文的内容能够帮助大家备考，前程百利祝大家都能取得理想的考试成绩。
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