Practice these TOEFL iBT listening tests to help you score high in the TOEFL Listening Section. Check the correct answers and audio transcripts below. This video is in the series of NEW TOEFL iBT Tests 2015.
Listen to part of a talk in an Environmental Science class.
Professor
So, I wanted to discuss a few other terms here . . . actually, some, uh some ideas
about how we manage our resources.
Let’s talk about what that . . . what that means. If we take a resource like water . . .
well, maybe we should get a little bit more specific here—back up from the more general
case—and talk about underground water in particular.
So, hydrogeologists have tried to figure out . . . how much water can you take out
from underground sources? This has been an important question. Let me ask you
guys: how much water, based on what you know so far, could you take out of, say, an
aquifer . . . under the city?
Male Student
As . . . as much as would get recharged?
Professor
OK. So, we wouldn’t want to take out any more than naturally comes into it. The implication
is that, uh, well, if you only take as much out as comes in, you’re not gonna
deplete the amount of water that’s stored in there, right?
Wrong, but that’s the principle. That’s the idea behind how we manage our water
supplies. It’s called “safe yield.” Basically what this method says is that you can pump
as much water out of a system as naturally recharges . . . as naturally flows back in.
So, this principle of safe yield—it’s based on balancing what we take out with what
gets recharged. But what it does is, it ignores how much water naturally comes out of
the system.
In a natural system, a certain amount of recharge comes in and a certain amount
of water naturally flows out through springs, streams, and lakes. And over the long
term the amount that’s stored in the aquifer doesn’t really change much. It’s balanced.
Now humans come in . . . and start taking water out of the system. How have we
changed the equation?
Female Student
It’s not balanced anymore?
Professor
Right. We take water out, but water also naturally flows out. And the recharge rate
doesn’t change, so the result is we’ve reduced the amount of water that’s stored in the
underground system.
If you keep doing that long enough—if you pump as much water out as naturally
comes in—gradually the underground water levels drop. And when that happens, that
can affect surface water. How? Well, in underground systems there are natural discharge
points—places where the water flows out of the underground systems, out to
lakes and streams. Well, a drop in the water level can mean those discharge points
will eventually dry up. That means water’s not getting to lakes and streams that
depend on it. So we’ve ended up reducing the surface water supply, too.
You know, in the state of Arizona we’re managing some major water supplies with
this principle of safe yield, under a method that will eventually dry up the natural
discharge points of those aquifer systems.
Now, why is this an issue? Well, aren’t some of you going to want to live in this
state for a while? Want your kids to grow up here, and your kids’ kids? You might be
concerned with . . . does Arizona have a water supply which is sustainable—key word
here? What that means . . . the general definition of sustainable is will there be enough
to meet the needs of the present without compromising the ability of the future to
have the availability . . . to have the same resources?
Now, I hope you see that these two ideas are incompatible: sustainability and safe
yield. Because what sustainability means is that it’s sustainable for all systems dependent
on the water—for the people that use it and for . . . uh, for supplying water to
the dependent lakes and streams.
So, I’m gonna repeat this: so, if we’re using a safe-yield method, if we’re only balancing
what we take out with what gets recharged, but—don’t forget, water’s also
flowing out naturally—then the amount stored underground is gonna gradually get
reduced and that’s gonna lead to another problem. These discharge points—where
the water flows out to the lakes and streams—they’re gonna dry up. OK.
Correct Answers:
1. A
2. C
3. C,D
4. D
5. A
6. B