托福TPO閱讀真題及譯文：Lake Water

第一段：

托福TPO閱讀原文：
　　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. So much is obvious.

托福TPO閱讀翻譯：
　　湖里的水從哪里來,又流向哪里去呢?湖中的水來自于河流的水,地下水的滲透以及溫泉,還有從四周地面流進來的水,另外還有直接降到湖面的雨水.湖中的水通過向外流的河流,滲透進河床以及蒸發(fā)離開湖泊.這些都是顯而易見的.

第二段：

托福TPO閱讀原文：
　　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 gains from rain, as measured (rather roughly) by rain 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. Note the word "net": 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.

托福TPO閱讀翻譯：
　　當考慮到水的含量的時候問題就會變得更加復雜:水通過上述方式流進和流出的具體含量是多少?發(fā)現(xiàn)河流水量的流進和流出量是測量河水進出容量的一種方法.和大氣水分的交流是通過發(fā)現(xiàn)雨水中得到的水(按雨量的測量規(guī)格計算)和那些通過其他方式測得水損失量的蒸發(fā)的水的差別來計算的.對于大多數(shù)的湖來說,特別是那些被森林環(huán)繞的湖,從四周流進湖中的水的含量很少以至于可以忽略不計.湖中水平面的變化不能被河水和大氣水量變化的凈差量所解釋是因為地下水的滲入和滲出.注意一下”凈”這個詞:測量真正的地下水滲入和滲出量比僅僅推斷它們的差量要復雜的多。

第三段：

托福TPO閱讀原文：
　　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 outputs. If the former are greater, the lake is a surface-water-dominated lake; if the latter, it is a seepage-dominated lake. Occasionally, common sense tells you which of these two possibilities applies. For example, a pond in hilly country that maintains a steady water level all through a dry summer in spite of having no streams flowing into it must obviously be seepage dominated. Conversely, a pond with a stream flowing in one end and out the other, which dries up when the stream dries up, is clearly surface water dominated.

托福TPO閱讀翻譯：
　　一旦所有的這些信息都收集到了,那么判斷一個湖的水流量是由表面蒸發(fā)決定的還是由地下水進出量決定的就變得可能了.如果前者大,那么湖泊就是一個表面水決定的湖,如果是后者,那么它就是一個滲透水決定的湖.有時候常識會告訴你這兩種可能性哪一種是對的.比如說一個多山地區(qū)的池塘在整個干燥的夏天都保持著穩(wěn)固的水含量,而并沒有河流流進這個湖泊,那么顯然它是一個滲透水決定的池塘.相反,一個池塘有河流流進和流出,河水干枯的時候池塘就干枯,那么這就是一個表面水決定的池塘.

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第四段：

托福TPO閱讀原文：
　　By whatever means, a lake is constantly gaining water and losing water: its water does not just sit there, or, anyway, not for long. This raises the matter of a lake’s residence time. The residence time is the average length of time that any particular molecule of water remains in the lake, and it is calculated by dividing the volume of water in the lake by the rate at which water leaves the lake. The residence time is an average; the time spent in the lake by a given molecule (if we could follow its fate) would depend on the route it took: it might flow through as part of the fastest, most direct current, or it might circle in a backwater for an indefinitely long time.

托福TPO閱讀翻譯：
　　不管怎么說，湖泊是在不停地流進和流出水，它的水不會停留在湖里，或者說不會長久的停留。這個會提升湖泊的停留時間。停留時間指的是特定水分子在湖中停留的平均時間長度，通過計算湖水流量流出湖泊的速度來計算。停留時間是一個平均數(shù)，這個時間是特定分子沿著特定路線走過所花的時間，它可能是最快最直接的那一部分，或者在某個回流中花上很長時間。

第五段：

托福TPO閱讀原文：
　　Residence times vary enormously. They range from a few days for small lakes up to several hundred years for large ones; Lake Tahoe, in California, has a residence time of 700 years. The residence times for the Great Lakes of North America, namely, Lakes Superior, Michigan, Huron, Erie, and Ontario, are, respectively, 190,100,22,2.5, and 6 years. Lake Erie’s is the lowest: although its area is larger than Lake Ontario’ s, its volume is less than one-third as great because it is so shallow-less than 20 meters on average.

托福TPO閱讀翻譯：
　　停留時間變化非常的大，從小湖的幾天到大型湖泊的幾百年。加利福利亞州的Tahoe湖的停留時間就長達700年，北美大型湖泊的停留時間如Superior, Michigan, Huron, Erie, 和 Ontario湖分別是190,100,22,2.5和6年。Erie湖是最低的，盡管它的湖面比Ontario湖要大，它的容量少于后者的三分之一因為它的平均深度還不到20米。

第六段：

托福TPO閱讀原文：
　　A given lake’s residence time is by no means a fixed quantity. It depends on the rate at which water enters the lake, and that depends on the rainfall and the evaporation rate. Climatic change (the result of global warming?) is dramatically affecting the residence times of some lakes in northwestern Ontario, Canada. In the period 1970 to 1986, rainfall in the area decreased from 1,000 millimeters to 650 millimeters per annum, while above-average temperatures speeded up the evapotranspiration rate (the rate at which water is lost to the atmosphere through evaporation and the processes of plant life).The result has been that the residence time of one of the lakes increased from 5 to 18 years during the study period. The slowing down of water renewal leads to a chain of further consequences; it causes dissolved chemicals to become increasingly concentrated, and this, in turn, has a marked effect on all living things in the lake.

托福TPO閱讀翻譯：
　　一個給定的湖泊的停留時間是一個確定的值。它取決于水流進湖的速率，而水流進湖的速率取決于降雨量和蒸發(fā)速率。氣候變化(全球變暖的結(jié)果？)戲劇性的影響著加拿大西北部的Ontario湖群中的一些湖泊的停留時間。在1970到1986這段時間里，這個地區(qū)的降雨量由1000毫升降到了650毫升，而同時平均溫度的上升提升了蒸發(fā)的速率（這個速率指的是水蒸發(fā)到大氣的速率以及植物的這一過程的速率）。在這段研究時間內(nèi)停留時間的研究結(jié)果已經(jīng)從5年提升到了18年。湖水的緩慢更新導致了一系列后果，它導致了溶解的化學物質(zhì)更加集中，反過來會對湖中的生物造成顯著的影響。