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

旁白：听一段环境科学的讲座。

Professor: I'd like to continue with the topic of managing water resources, but I want to focus on a particular case.

教授：我会继续讲管理水资源的话题，但是我会着重在一个案例上。

Uh, um, an example of water management that's made us reconsider the methods we use when we make these decisions.

额，有一个关于水资源管理的案例让我们重新审视我们当初决定使用的方法是否正确。

So let's look at what's happening in the Colorado River basin.

好，我们来看一下在科罗拉多河流域发生了什么。

The Colorado River basin is a region in the Southwest United States.

科罗拉多河流域是西南部美国的一个地区。

Seven states rely on the Colorado's water.

有7个州依赖着科罗拉多河流。

And as you can imagine, as the populations of these states began to grow, it became clear that a system to distribute, uh, to make sure each state got its fair share of water…some kind of system had to be created.

就像你能想象的那样，随着这些州的人口的增长，建造一个系统去分配水流，去确保每一个州都得到公平的水的分配是必要的。

And in 1922, a water-sharing agreement was made.

并且在1922年，一个水共享协议建立了。

Elizabeth, you have a question?

Elizabeth，你有问题吗？

Student: Well, how exactly do you figure out how to share a river?

学生：那么，怎么去精确算出如何分享河流呢？

I mean, you can't…like cut it up into pieces.

我的意思是，你又不能……像是把它切成几片。

Professor: Well, let's start with the first step.

教授：好的，让我们先说第一步。

And that's trying to figure out how much water on average flows through the river each year.

那就是试图去算出每年从这条河流过的平均水量。

Now, researchers had started gathering data on water flow back in the late 1890s using instruments they placed in the river.

在1890年，通过放在河中的仪器，研究员们已经开始收集关于水流的数据。

When the 1922 water-sharing agreement was made, there were about twenty years of data on water flow available.

当1922年水资源共享协议建立的时候，已经有水流的20年的数据了。

The average annual flow was calculated.

年均流量被计算了出来。

And, well, the agreement was based on that calculation.

然后，这个协议就是根据这个计算来制定的。

The same basic agreement is in effect today.

至今这一个协定仍然有效。

Student: Wait! That was all the data they had?

学生：等等！这就是他们拥有的全部的数据了？

And they based their decision on that?

然后他们就根据那个做决定？

Professor: Yes. And we'll see why that was a bad decision in a moment.

教授：是的。我们会马上讨论为什么这不是一个正确的决策。

OK. As decades passed, it became clear that measuring river flow was much more complicated than we had thought.

好的，随着几十年过去了，很明确的是测量水流远比我们想象的要复杂的多。

See…a river has periods of low flow and periods of high flow.

一条河有枯水期也有高流量期。

And this wasn't taken into consideration when the 1922 agreement was made.

但是这个在1922年签订的协议中所没有纳入考量的。

In the 1970s, the population of the area was rising while the amount of water flowing through the river seemed to be falling.

在二十世纪七十年代，这块区域的人口在增长而水流量貌似在降低。

By this time, we had…what?

到那个时间为止，我们已经……怎么样了？

A hundred years of recorded data to look at?

有100年的数据去查看？

That's still a pretty short time for an ancient river.

对于一条古老的河流来说还是非常短的一段时间。

To get more data, we looked at a different sourc--a source that was able to tell us about hundreds of years of the river's histor--tree rings.

为了获得更多的数据，我们转向不同的来源，一个能告诉我们河流百年历史的来源。

OK. Let me explain.

好的，让我来解释一下。

You probably know that we can determine a tree's age by counting the rings on a cross section of its trunk.

你们可能知道我们能够通过树干横截面的年轮来决定一棵树的年龄。

Each ring represents one year of the tree's life.

每一个年轮都代表了一个树木一年的生命。

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.

因此如果你知道一棵树被砍的年份，你可以从外向内数年轮直到中心。

You can also tell how much moisture the tree got during each of those years by looking at the widths of the rings.

你也可以通过查看年轮的宽度说出在这些年中，树木获得了多少水分。

A wide ring means plenty of water while a narrow one indicates less.

一个宽的年轮意味着水分很多而窄的则代表水分少。

Fortunately for us, certain areas of the Colorado River basin are home to some very old trees, some 800 years old and older.

对我们来说幸运的是，科罗拉多河流域是许多古老树木的家，一些树木已经有800岁或者800岁以上了。

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.

研究员们可以钻洞获取树干中心的样品，主要是在不弄死树木的情况下获得树木的横截面，查看年轮，然后得出树木每一年的流域气候情况。

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.

结果告诉我们一些如果没有数据我们不会知道的东西，在过去约500年中，科罗拉多河流域经历了严重的干旱，有些比我们记录到的还要严重。

They also showed 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.

这些数据还显示了早在1900s中期，当大部分的数据被用到水共享协议中的时候，这正是在过去400年来最多雨的时期。

Well, obviously, had water management officials known then what we know now, the 1922 agreement would have been handled differently.

很明显，水资源管理的官员们如果知道我们现在所知道的的信息的话，1922年的这个协议可能就会不一样了。

But today we can use the past to help prepare us for the future.

但是，如今我们可以利用过去为我们的未来作准备。

With the demand for water in the basin stays 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.

随着科罗拉多河流域水资源需求的日益增高，也随着水流量可能会下降的可能性，如果历史是我们的老师，我们可以开发出水源保护的创新方法并且重新评估水资源改如何分配。