Official 33 Set 3

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Colorado's Water

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What is the lecture mainly about?
  • A. The use of tree rings to measure water usage rates

  • B. Collecting data that are useful for planning water distribution

  • C. Investigating the history of water use in the Colorado River basin

  • D. The need for more government involvement in water distribution

显示答案 正确答案: B

我的笔记 编辑笔记

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    NARRATOR: Listen to part of a lecture in an environmental science class.

    MALE PROFESSOR: I'd like to continue with the topic of managing water resources, but I want to focus on a particular case, a—uh, an example of water management that's made us reconsider the methods we use when we make these decisions.So let's look at what's happening in the Colorado River basin.

    The Colorado River basin is a region in the southwest United States.Seven states rely on the Colorado's water, and as you can imagine,as the populations of these states began to grow, it became clear that a system to distribute, ah, to make sure each state got its fair share of water, some kind of system had to be created.And in 1922, a water-sharing agreement was made.Elizabeth, you have a question?

    FEMALE STUDENT: Well, how exactly do you figure out how to share a river? I mean, you can't, like, cut it up into pieces.

    MALE PROFESSOR: Well, let's start with the first step. And that's trying to figure out how much water, on average, flows through the river each year.Now, researchers had started gathering data on water flow back in the late 1890s, using instruments they placed in the river.When the 1922 water-sharing agreement was made, there were about twenty years of data on water flow available.The average annual flow was calculated, and, well, the agreement was based on that calculation.The same basic agreement is in effect today.

    FEMALE STUDENT: Wait. That was all the data they had? And they based their decision on that?MALE PROFESSOR: Yes, and we'll see why that was a bad decision in a moment.OK. As decades passed, it became clear that measuring river flow was much more complicated than we had thought.See, a river has periods of low flow and periods of high flow,and this wasn't taken into consideration when the 1922 agreement was made.

    In the 1970s, the population of the area was rising,while the amount of water flowing through the river seemed to be falling.By this time we had-what-a hundred years of recorded data to look at?That's still a pretty short time for an ancient river.To get more data, we looked at a different source... a source that was able to tell us about hundreds of years of the river's history. Tree rings.OK, let me explain.You probably know that we can determine a tree's age by counting the rings on a cross section of its trunk.Each ring represents one year of the tree's life.So if you know the year the tree was cut, you can count inwards and date each ring all the way back to the center.

    You can also tell how much moisture the tree got during each of those years by looking at the width of the rings.A wide ring means plenty of water, while a narrow one indicates less.

    Fortunately for us,certain areas of the Colorado River basin are home to some very old trees, some 800 years old and older.Researchers can drill core samples, uh, basically get a cross section of a tree without having to kill it, look at the rings, and get a picture of what the climate was like in the basin for each of the tree's years.

    Well, the results tell us something we wouldn't have known without this data-that over the past 500 years or so, the Colorado River basin has experienced severe droughts, some worse than any we've ever recorded.They also show that the early to mid-1900s- when most of the data that led to the water-sharing agreement was collected- well, this was the wettest period in the past 400 years.

    Well, obviously, had water management officials known then what we know now, the 1922 agreement would have been handled differently.But today, we can use the past to help prepare us for the future.With the demand for water in the basin states increasing and with the real likelihood of lower flows in the river- if history is our teacher-we can develop innovative methods of water conservation and reevaluate how water is distributed.

  • 旁白:听一段环境科学课程。

    教授:我想继续水资源管理的话题,但我想重点讲一个具体的例子,一个水资源管理的例子,让我们重新思考我们在做决策时采取的方式。所以让我们看看在科罗拉多河流域发生的事。

    科罗拉多河流域是美国西南部的一个地方。有七个州依赖着科罗拉多的水资源。正如你所想,随着这些州的人口开始增长,很明显为了确保每个州的水资源得到公平分配,就需要建造某种分配系统。在1922年达成了一项水资源分享协议。伊丽莎白,你有问题吗?

    学生:你认为该如何确切地计算出怎样分享一条河流呢?我的意思是你不能把它切分成一片一片的。

    教授:让我们从第一步开始。那就是试图计算出每年该河流的平均流量是多少。研究者们开始从19世纪90年代末用他们施放在水中的工具收集水流量数据。当1922年水资源分享协议达成时,那里已经有约20年的关于水流的可用数据。年平均流量已经算出,而且这项协议是以这个计算为基础的。同样的基本协议在今天一样有效。

    学生:等等!这就是他们所有的数据吗?而且他们的决定就基于这个?教授:是的。我们马上就能看到为什么这是一个错误的决定。好的。当数十年过去后,很明显测量河水流量要比我们想象的复杂得多。你看,一条河有低流量期和高流量期。在1922年协议达成时并没有把它考虑在内。

    在20世纪70年代,该地区的人口上涨了,而该河流的水流量似乎下降了。到这时我们已经有了什么?100年的记录数据可以查看?这对于一条古老的河流来说,时间还是太短了。为了获取更多的数据,我们查看了不同的来源,有一个来源可以帮助我们了解河流数百年的历史--树的年轮。好的,让我来解释。你可能知道我们可以根据计数树干横截面圈数来确定一棵树的年纪。每一个圈代表树木生长的一年。所以如果你知道树木被砍伐的年代,你就能从外向里计算并确定每个圈的年代直到树木的中心。

    你还可以通过年轮的宽度分辨出在每一年里,这棵树受到了多少水分。一条宽的圆圈(年轮)意味着水分充足,而窄的则表示水分不足。

    对我们来说幸运的是科罗拉多河流域的某些地方,有一些约800年之久甚至更老的古树。研究人员们可以钻出核心样本,在不杀死树的情况下,基本上得到树的横截面,观察年轮并根据树的每一年了解到流域的气候状况。

    结果告诉我们一些在没有这些数据的情况下我们无从了解的情况--在过去的500年左右,科罗拉多河流域曾经历了很多极度的干旱,有一些比我们记录下的严重得多。它们还说明在20世纪早到中期,为了水资源分享协议而收集的大多数数据时是过去400年最多雨的时期。

    显然,水资源管理官员若是在那时像我们这样了解的话,1922年的协议就会处理得有所不同。但是今天我们可以用过去帮助我们为未来做准备。随着该流域对水资源需求的增长和该河流存在低流量的可能性,如果历史给我们经验,我们就能建立水源保护的革新性方法并重新评估水资源该如何分配的。

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  • 本题对应音频:
    3 感谢 不懂
    音频1
    解析

    题型分类:主旨题

    原文定位:

    I’d like to continue with the topic of managing water resources, but I want to focus on a particular case, a—uh, an example of water management that’s made us reconsider the methods we use when we make these decisions.

    选项分析:

    文章开始就说要聚焦在一个例子上面,这个例子会让我们重新考虑分配水资源时候的方法。后面全部都在说收集数据的事

    B项 收集对分配水资源有用的数据

    其他项不是主要论述对象

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