4 ways we can avoid a catastrophic drought | David Sedlak

翻译人员: Hong Li 校对人员: Gu Yu

Our grandparents' generation created an amazing system

我们爷爷那一代人，

of canals and reservoirs that made it possible

修建了伟大的运河和水库系统，

for people to live in places where there wasn't a lot of water.

让人们可以在缺水的地方正常生活。

For example, during the Great Depression,

比如在大萧条时代，

they created the Hoover Dam,

他们修建了胡佛水坝，

which in turn, created Lake Mead

拦下的水形成了米德湖，

and made it possible for the cities of Las Vegas and Phoenix

为几个位于干旱地区的城市， 比如拉斯维加斯、凤凰城

and Los Angeles to provide water

和洛杉矶供水，

for people who lived in a really dry place.

让那里的市民有水可用。

In the 20th century, we literally spent trillions of dollars

在二十世纪，我们花费了数万亿美元，

building infrastructure to get water to our cities.

为我们的城市修建供水系统。

In terms of economic development, it was a great investment.

对经济发展而言，这是笔不错的投资。

But in the last decade, we've seen the combined effects

但在过去几十年间，我们看到

of climate change, population growth and competition for water resources

气候变化、人口增长 和水资源争夺带来的后果，

threaten these vital lifelines and water resources.

已经威胁到我们赖以生存的水资源。

This figure shows you the change in the lake level of Lake Mead

这张图表显示的是米德湖的水位

that happened in the last 15 years.

在过去15年的变化情况。

You can see starting around the year 2000,

差不多从2000年开始，

the lake level started to drop.

水位开始下降。

And it was dropping at such a rate

下降的速度如此之快，

that it would have left the drinking water intakes for Las Vegas high and dry.

很快，为拉斯维加斯 供水的管道将抽不到水。

The city became so concerned about this

拉斯维加斯很担心这一点

that they recently constructed a new drinking water intake structure

他们最近铺设了一条新的抽水管道，

that they referred to as the "Third Straw"

称之为“第三吸管”，

to pull water out of the greater depths of the lake.

从湖的更深处抽水。

The challenges associated with providing water to a modern city

向现代都市供水的难题

are not restricted to the American Southwest.

不仅仅发生在美国西南部。

In the year 2007, the third largest city in Australia, Brisbane,

2007年，澳大利亚第三大城市，布里斯班，

came within 6 months of running out of water.

整整6个月无水可用。

A similar drama is playing out today in São Paulo, Brazil,

同样的情况也在巴西圣保罗上演，

where the main reservoir for the city

圣市最主要的水库

has gone from being completely full in 2010,

在2010年还几乎全满，

to being nearly empty today

如今已几乎见底，

as the city approaches the 2016 Summer Olympics.

而他们还将举办2016夏季奥运会。

For those of us who are fortunate enough

我们足够幸运，

to live in one of the world's great cities,

能够生活在世界上最伟大的城市之一，

we've never truly experienced the effects of a catastrophic drought.

我们从未真正经历过大旱灾。

We like to complain about the navy showers we have to take.

我们会抱怨洗澡的水不够大。

We like our neighbors to see our dirty cars and our brown lawns.

我们也经常不洗车，不浇草坪。

But we've never really faced the prospect of turning on the tap

但我们从未经历过拧开水龙头，

and having nothing come out.

却无水可用的状况。

And that's because when things have gotten bad in the past,

因为在过去，如果发生这样的事情，

it's always been possible to expand a reservoir

我们总是能把水库修得更大些，

or dig a few more groundwater wells.

或者多挖几口水井。

Well, in a time when all of the water resources are spoken for,

但如果所有的水资源都枯竭了，

it's not going to be possible to rely on this tried and true way

那这种曾经屡试不爽的老办法

of providing ourselves with water.

可能就不适用了。

Some people think that we're going to solve the urban water problem

有些人觉得，要解决城市用水问题，

by taking water from our rural neighbors.

从临近的农村取水就好了。

But that's an approach that's fraught with political, legal and social dangers.

但这种方法充满了 政治、法律和社会风险。

And even if we succeed in grabbing the water from our rural neighbors,

即便我们能从农村取水，

we're just transferring the problem to someone else

那也不过是将问题转嫁到了别人头上，

and there's a good chance it will come back and bite us

而且很有可能，它会反噬到我们身上

in the form of higher food prices

要么会抬高食品价格，

and damage to the aquatic ecosystems that already rely upon that water.

要么会破坏水生生态系统。

I think that there's a better way to solve our urban water crisis

我认为可以用更好的办法 来解决我们的城市用水危机，

and I think that's to open up four new local sources of water

就是下面我将要说的4种新水源，

that I liken to faucets.

我把它们比作4个水龙头。

If we can make smart investments in these new sources of water

在未来数年里，如果我们 能对这4种新水源

in the coming years,

进行明智的投资，

we can solve our urban water problem

我们就能解决城市用水问题，

and decrease the likelihood that we'll ever run across

使我们遭遇大旱灾的可能性

the effects of a catastrophic drought.

大大降低。

Now, if you told me 20 years ago

如果在20年前，你告诉我，

that a modern city could exist without a supply of imported water,

现代城市可以在没有 外来水源的情况下得以发展，

I probably would have dismissed you as an unrealistic and uninformed dreamer.

我可能会觉得你是痴人说梦。

But my own experiences

但在过去的几十年里，

working with some of the world's most water-starved cities in the last decades

我一直在世界上最缺水的城市工作，

have shown me that we have the technologies and the management skills

这段经历告诉我，我们的技术和管理能力

to actually transition away from imported water,

已经可以不依赖于外来水源，

and that's what I want to tell you about tonight.

这就是今晚我想跟大家分享的。

The first source of local water supply that we need to develop

要解决城市用水问题，

to solve our urban water problem

我们需要发展的第一种本地新水源

will flow with the rainwater that falls in our cities.

就是从天而降的雨水。

One of the great tragedies of urban development

城市发展带来的最大灾难之一，

is that as our cities grew,

就是随着城市越变越大，

we started covering all the surfaces with concrete and asphalt.

我们将所有地面都用 水泥和沥青覆盖起来了。

And when we did that, we had to build storm sewers

这样一来，我们必须修建巨大的排水管道，

to get the water that fell on the cities out

将落在城市里的雨水排出去，

before it could cause flooding,

以免引发洪灾，

and that's a waste of a vital water resource.

这对水资源是极大的浪费。

Let me give you an example.

让我来举个例子。

This figure here shows you the volume of water

这张图表显示的是

that could be collected in the city of San Jose

圣何塞市能够收集到的雨水百分比，

if they could harvest the stormwater that fell within the city limits.

与收集到的雨水总量间的关系。

You can see from the intersection of the blue line and the black dotted line

注意看蓝线和黑虚线相交的地方，

that if San Jose could just capture half of the water that fell within the city,

如果圣何塞市能收集它降雨量的一半，

they'd have enough water to get them through an entire year.

就足够全市用上一年。

Now, I know what some of you are probably thinking.

我知道，有人可能会想，

"The answer to our problem is to start building great big tanks

“那要解决用水问题， 只要做一些巨大的储水罐

and attaching them to the downspouts of our roof gutters,

跟屋顶排水沟的落水管连在一起，

rainwater harvesting."

收集雨水就行了。”

Now, that's an idea that might work in some places.

这方法在某些地方可能有用。

But if you live in a place where it mainly rains in the winter time

但如果你居住的城市冬天经常下雨，

and most of the water demand is in the summertime,

而夏天用水量大，

it's not a very cost-effective way to solve a water problem.

这个方法就不是那么有效了。

And if you experience the effects of a multiyear drought,

而且，如果你所处的地方常年干旱，

like California's currently experiencing,

就像今天的加利福尼亚州一样，

you just can't build a rainwater tank that's big enough to solve your problem.

你做多大的储水罐也解决不了问题。

I think there's a lot more practical way

我认为有更加现实的方法

to harvest the stormwater and the rainwater that falls in our cities,

来收集城市里的雨水，

and that's to capture it and let it percolate into the ground.

那就是收集之后，让它渗入地下。

After all, many of our cities are sitting on top of a natural water storage system

这样一来，我们城市的地底下 就有了一个天然的储水系统，

that can accommodate huge volumes of water.

可以储存大量的水。

For example, historically, Los Angeles has obtained

比如说，在过去的洛杉矶，

about a third of its water supply from a massive aquifer

它的用水量的三分之一都来自

that underlies the San Fernando Valley.

圣费尔南多谷的地下蓄水层。

Now, when you look at the water that comes off of your roof

当你看到雨水从房顶滴落，

漫过草坪，流进沟渠，

and runs off of your lawn and flows down the gutter,

you might say to yourself, "Do I really want to drink that stuff?"

你可能会犹豫，“我真的要喝这样的水吗？”

Well, the answer is you don't want to drink it

毫无疑问，要想喝这水，

until it's been treated a little bit.

得先经过处理。

And so the challenge that we face in urban water harvesting

因此，在城市里收集（雨）水有三大挑战，

is to capture the water, clean the water

收集雨水，清洁雨水，

and get it underground.

灌入地下。

And that's exactly what the city of Los Angeles is doing

洛杉矶已经开始这么做了，

with a new project that they're building in Burbank, California.

他们在加利福尼亚州 伯班克市新建了一个项目。

This figure here shows the stormwater park that they're building

这是一个雨水收集园区

by hooking a series of stormwater collection systems, or storm sewers,

他们将众多雨水收集系统 或者排水沟连接起来，

and routing that water into an abandoned gravel quarry.

将雨水引入一个废弃的采石场。

The water that's captured in the quarry

采石场里的水

is slowly passed through a man-made wetland,

慢慢通过一个人造湿地

and then it goes into that ball field there

进入旁边的一个球型区域

and percolates into the ground,

然后渗入地下，

recharging the drinking water aquifer of the city.

补充洛杉矶的地下蓄水层。

And in the process of passing through the wetland

这些水在穿过湿地

and percolating through the ground,

渗入地下的过程中，

the water encounters microbes that live on the surfaces of the plants

会接触到生活在植物和土壤表面

and the surfaces of the soil,

的微生物，

and that purifies the water.

它们能净化水。

And if the water's still not clean enough to drink

如果水在经过自然净化处理后，

after it's been through this natural treatment process,

还是不能直接饮用，

the city can treat it again

管理人员会把

when they pump if back out of the groundwater aquifers

从地下蓄水层抽出来的水 进行二次处理

before they deliver it to people to drink.

然后再供市民饮用。

The second tap that we need to open up to solve our urban water problem

解决城市用水问题的第二个水龙头

will flow with the wastewater

是来自污水处理厂

that comes out of our sewage treatment plants.

处理过的废水。

Now, many of you are probably familiar with the concept of recycled water.

大家对于循环水应该已经不陌生了。

You've probably seen signs like this

你们也许都见过这样的牌子

that tell you that the shrubbery and the highway median

上面写着灌木丛、高速公路隔离绿化带

and the local golf course

本地高尔夫球场

is being watered with water

的灌溉用水

that used to be in a sewage treatment plant.

都来自污水处理系统。

We've been doing this for a couple of decades now.

几十年来我们都是这么做的。

But what we're learning from our experience

但几十年的经验告诉我们，

is that this approach is much more expensive that we expected it to be.

这样做的成本比我们预期的要高。

Because once we build the first few water recycling systems

因为一旦我们在污水处理厂附近

close to the sewage treatment plant,

建起水循环系统，

we have to build longer and longer pipe networks

我们就不得不建造越来越长的管网

to get that water to where it needs to go.

把水送到需要的地方去。

And that becomes prohibitive in terms of cost.

这笔开销真心不小。

What we're finding is

我们发现，

that a much more cost-effective and practical way of recycling wastewater

更加经济实惠和可行的办法

is to turn treated wastewater into drinking water

是将处理过的废水变成饮用水，

through a two-step process.

只需要两步。

In the first step in this process we pressurize the water

第一步是给水加压，

and pass it through a reverse osmosis membrane:

让它通过反向渗透膜

a thin, permeable plastic membrane

——一种很薄的、可渗透的塑料膜——

that allows water molecules to pass through

水分子可以通过，

but traps and retains the salts, the viruses and the organic chemicals

但废水中可能含有的盐、病毒和有机化学物

that might be present in the wastewater.

会被拦截下来。

In the second step in the process,

第二步，

we add a small amount of hydrogen peroxide

我们往水里加入少量的过氧化氢

and shine ultraviolet light on the water.

然后用紫外线进行照射。

The ultraviolet light cleaves the hydrogen peroxide

紫外线能将过氧化氢

into two parts that are called hydroxyl radicals,

分裂成两部分，称为氢氧基，

and these hydroxyl radicals are very potent forms of oxygen

氢氧基是一种非常强的氧气形式

that break down most organic chemicals.

能够消灭大部分有机化学物。

After the water's been through this two-stage process,

水经过这两步处理之后，

it's safe to drink.

就可以安全饮用了。

I know,

过去15年里，

I've been studying recycled water

我一直在运用

using every measurement technique known to modern science

现代科学的各种测量方法

for the past 15 years.

来研究循环水。

We've detected some chemicals

我们发现某些化学物质

that can make it through the first step in the process,

无法在步骤一被过滤掉，

but by the time we get to the second step,

但经过第二步：

the advanced oxidation process,

高级氧化过程之后，

we rarely see any chemicals present.

几乎没有化学物质能残留下来。

And that's in stark contrast to the taken-for-granted water supplies

这比我们一直喝的“毫无问题”的水

that we regularly drink all the time.

可安全多了。

There's another way we can recycle water.

还有另外一种方法来循环水。

This is an engineered treatment wetland that we recently built

这是我们最近修建的人工湿地

on the Santa Ana River in Southern California.

位于加利福尼亚州南部的圣安娜河上。

The treatment wetland receives water from a part of the Santa Ana River

圣安娜河的部分河水流入人工湿地，

that in the summertime consists almost entirely of wastewater effluent

每到夏天，圣安娜河里就全是污水，

from cities like Riverside and San Bernardino.

都来自里弗赛德市和圣贝纳迪诺市。

The water comes into our treatment wetland,

河水流入我们的人工湿地，

it's exposed to sunlight and algae

在阳光暴晒和水藻的作用下，

and those break down the organic chemicals,

有机化学物被分解，

remove the nutrients and inactivate the waterborne pathogens.

营养物被消耗，水生病原体被杀死。

The water gets put back in the Santa Ana River,

之后河水流回圣安娜河，

it flows down to Anaheim,

流向安纳海姆市，

gets taken out at Anaheim and percolated into the ground,

河水在那里被抽出， 渗入地下，

and becomes the drinking water of the city of Anaheim,

成为安纳海姆市的饮用水，

completing the trip from the sewers of Riverside County

通过这一过程，里弗赛德郡的废水

to the drinking water supply of Orange County.

就变成了橙郡的饮用水。

Now, you might think that this idea of drinking wastewater

也许你们会觉得，将废水变成饮用水，

is some sort of futuristic fantasy or not commonly done.

只是天方夜谭，或者还没有得到推广。

Well, in California, we already recycle about 40 billion gallons a year

实际上，运用我刚刚介绍的两步处理法，

of wastewater through the two-stage advanced treatment process

我们每年在加利福尼亚州循环利用的水

I was telling you about.

达到了1.5亿立方米。

That's enough water to be the supply of about a million people

这些水足够供应100万人，

if it were their sole water supply.

作为他们的主要水源。

The third tap that we need to open up will not be a tap at all,

我们的第三个水龙头并不是实体，

it will be a kind of virtual tap,

而是虚拟的，

it will be the water conservation that we manage to do.

指的是节约用水。

And the place where we need to think about water conservation is outdoors

而且主要指的是户外用水，

because in California and other modern American cities,

因为在加利福尼亚以及其他的美国都市，

about half of our water use happens outdoors.

差不多一半的用水发生在户外。

In the current drought,

即使在现在的干旱状态下，

we've seen that it's possible

我们的用水量下降了一半，

to have our lawns survive and our plants survive

但我们的草坪，我们的植物

with about half as much water.

还是活下来了。

So there's no need to start painting concrete green

因此我们还没到把水泥地喷成绿色，

and putting in Astroturf and buying cactuses.

或者改铺人工草皮，改种仙人掌的地步。

We can have California-friendly landscaping with soil moisture detectors

在土壤湿度探测器和智能浇灌系统的帮助下，

and smart irrigation controllers

加州式园林不是梦，

and have beautiful green landscapes in our cities.

我们的城市依旧可以绿意盎然。

The fourth and final water tap that we need to open up

我们需要打开的第四个， 也是最后一个水龙头，

to solve our urban water problem

来解决城市用水问题，

will flow with desalinated seawater.

是海水淡化。

Now, I know what you probably heard people say about seawater desalination.

也许你们听人们谈论过海水淡化，

"It's a great thing to do if you have lots of oil, not a lot of water

“海水淡化是很好， 前提是你石油多、淡水少，

and you don't care about climate change."

而且也不在乎气候变化。”

Seawater desalination is energy-intensive no matter how you slice it.

没错，海水淡化 是一项能源密集型产业。

But that characterization of seawater desalination

但如果仅仅因为这样，就将海水淡化

as being a nonstarter is hopelessly out of date.

视为没有前途，那就太落伍了。

We've made tremendous progress in seawater desalination

在过去20年间，我们在海水淡化上

in the past two decades.

已经取得了巨大进展。

This picture shows you

这张照片上

the largest seawater desalination plant in the Western hemisphere

是在建的西半球最大的海水淡化厂，

that's currently being built north of San Diego.

位于圣地亚哥市以北。

Compared to the seawater desalination plant

与25年前建在圣巴巴拉市

that was built in Santa Barbara 25 years ago,

的海水淡化厂相比，

this treatment plant will use about half the energy

这家海水淡化厂每生产一加仑淡水

to produce a gallon of water.

的能耗下降了一半。

But just because seawater desalination has become less energy-intensive,

当然，海水淡化的能耗降低了，

doesn't mean we should start building desalination plants everywhere.

并不意味着我们就该到处建海水淡化厂。

Among the different choices we have,

在我们的众多选择中，

it's probably the most energy-intensive

在4种新水源中，

and potentially environmentally damaging

海水淡化依然是能耗最大，

of the options to create a local water supply.

最有可能对环境造成危害的。

So there it is.

综上所述，

With these four sources of water,

有了这4种新水源，

we can move away from our reliance on imported water.

我们不用再依赖进口水。

Through reform in the way we landscape our surfaces and our properties,

通过改进我们绿化城市和居民区的方法，

we can reduce outdoor water use by about 50 percent,

我们可以将户外用水量下降50%，

thereby increasing the water supply by 25 percent.

因此提高25%的供水量。

We can recycle the water that makes it into the sewer,

我们可以循环利用废水，

thereby increasing our water supply by 40 percent.

以此提高40%供水量。

And we can make up the difference through a combination

我们可以综合利用

of stormwater harvesting and seawater desalination.

雨水收集和海水淡化。

So, let's create a water supply

让我们来创造稳定的水源供应，

that will be able to withstand any of the challenges

足以在未来几年承受气候变化

that climate change throws at us in the coming years.

给我们带来的挑战。

Let's create a water supply that uses local sources

让我们充分利用本地水源，

and leaves more water in the environment for fish and for food.

将更多的水留给环境， 留给动物，留给食物。

Let's create a water system that's consistent with out environmental values.

让我们创造环境友好型的供水系统。

And let's do it for our children and our grandchildren

让我们为子孙后代而努力，

and let's tell them this is the system

告诉他们，在未来的岁月里，

that they have to take care of in the future

他们也应该珍视这个系统

because it's our last chance to create a new kind of water system.

因为这是我们创建 新型供水系统最后的机会。

Thank you very much for your attention.

非常感谢大家。

(Applause)

（掌声）