0:00:00.880,0:00:04.576
Our grandparents' generation[br]created an amazing system

0:00:04.600,0:00:07.176
of canals and reservoirs[br]that made it possible

0:00:07.200,0:00:10.616
for people to live in places[br]where there wasn't a lot of water.

0:00:10.640,0:00:13.176
For example, during the Great Depression,

0:00:13.200,0:00:14.816
they created the Hoover Dam,

0:00:14.840,0:00:17.256
which in turn, created Lake Mead

0:00:17.280,0:00:20.896
and made it possible for the cities[br]of Las Vegas and Phoenix

0:00:20.920,0:00:22.656
and Los Angeles to provide water

0:00:22.680,0:00:24.880
for people who lived[br]in a really dry place.

0:00:25.760,0:00:29.656
In the 20th century,[br]we literally spent trillions of dollars

0:00:29.680,0:00:33.096
building infrastructure[br]to get water to our cities.

0:00:33.120,0:00:37.056
In terms of economic development,[br]it was a great investment.

0:00:37.080,0:00:40.056
But in the last decade,[br]we've seen the combined effects

0:00:40.080,0:00:45.856
of climate change, population growth[br]and competition for water resources

0:00:45.880,0:00:49.536
threaten these vital lifelines[br]and water resources.

0:00:49.560,0:00:53.696
This figure shows you the change[br]in the lake level of Lake Mead

0:00:53.720,0:00:55.976
that happened in the last 15 years.

0:00:56.000,0:00:58.336
You can see starting around the year 2000,

0:00:58.360,0:01:00.256
the lake level started to drop.

0:01:00.280,0:01:02.096
And it was dropping at such a rate

0:01:02.120,0:01:06.000
that it would have left the drinking water[br]intakes for Las Vegas high and dry.

0:01:06.720,0:01:09.456
The city became so concerned about this

0:01:09.480,0:01:13.416
that they recently constructed[br]a new drinking water intake structure

0:01:13.440,0:01:15.496
that they referred to as the "Third Straw"

0:01:15.520,0:01:18.240
to pull water out[br]of the greater depths of the lake.

0:01:19.080,0:01:22.736
The challenges associated[br]with providing water to a modern city

0:01:22.760,0:01:25.816
are not restricted[br]to the American Southwest.

0:01:25.840,0:01:31.176
In the year 2007, the third largest[br]city in Australia, Brisbane,

0:01:31.200,0:01:34.136
came within 6 months[br]of running out of water.

0:01:34.160,0:01:38.416
A similar drama is playing out today[br]in São Paulo, Brazil,

0:01:38.440,0:01:40.256
where the main reservoir for the city

0:01:40.280,0:01:43.176
has gone from being[br]completely full in 2010,

0:01:43.200,0:01:45.376
to being nearly empty today

0:01:45.400,0:01:48.880
as the city approaches[br]the 2016 Summer Olympics.

0:01:50.000,0:01:52.536
For those of us who are fortunate enough

0:01:52.560,0:01:54.616
to live in one[br]of the world's great cities,

0:01:54.640,0:01:58.776
we've never truly experienced[br]the effects of a catastrophic drought.

0:01:58.800,0:02:02.536
We like to complain[br]about the navy showers we have to take.

0:02:02.560,0:02:06.936
We like our neighbors to see[br]our dirty cars and our brown lawns.

0:02:06.960,0:02:10.496
But we've never really faced[br]the prospect of turning on the tap

0:02:10.520,0:02:12.040
and having nothing come out.

0:02:12.920,0:02:15.736
And that's because when things[br]have gotten bad in the past,

0:02:15.760,0:02:18.816
it's always been possible[br]to expand a reservoir

0:02:18.840,0:02:21.040
or dig a few more groundwater wells.

0:02:22.080,0:02:25.936
Well, in a time when all[br]of the water resources are spoken for,

0:02:25.960,0:02:29.336
it's not going to be possible[br]to rely on this tried and true way

0:02:29.360,0:02:31.696
of providing ourselves with water.

0:02:31.720,0:02:35.496
Some people think that we're going[br]to solve the urban water problem

0:02:35.520,0:02:37.520
by taking water from our rural neighbors.

0:02:38.400,0:02:44.656
But that's an approach that's fraught[br]with political, legal and social dangers.

0:02:44.680,0:02:48.216
And even if we succeed in grabbing[br]the water from our rural neighbors,

0:02:48.240,0:02:50.736
we're just transferring[br]the problem to someone else

0:02:50.760,0:02:53.376
and there's a good chance[br]it will come back and bite us

0:02:53.400,0:02:55.296
in the form of higher food prices

0:02:55.320,0:02:59.280
and damage to the aquatic ecosystems[br]that already rely upon that water.

0:03:00.200,0:03:03.576
I think that there's a better way[br]to solve our urban water crisis

0:03:03.600,0:03:08.016
and I think that's to open up[br]four new local sources of water

0:03:08.040,0:03:09.776
that I liken to faucets.

0:03:09.800,0:03:13.896
If we can make smart investments[br]in these new sources of water

0:03:13.920,0:03:15.216
in the coming years,

0:03:15.240,0:03:17.576
we can solve our urban water problem

0:03:17.600,0:03:20.936
and decrease the likelihood[br]that we'll ever run across

0:03:20.960,0:03:23.200
the effects of a catastrophic drought.

0:03:24.280,0:03:26.336
Now, if you told me 20 years ago

0:03:26.360,0:03:30.976
that a modern city could exist[br]without a supply of imported water,

0:03:31.000,0:03:34.640
I probably would have dismissed you[br]as an unrealistic and uninformed dreamer.

0:03:35.480,0:03:37.016
But my own experiences

0:03:37.040,0:03:41.416
working with some of the world's most[br]water-starved cities in the last decades

0:03:41.440,0:03:45.376
have shown me that we have[br]the technologies and the management skills

0:03:45.400,0:03:48.296
to actually transition away[br]from imported water,

0:03:48.320,0:03:50.640
and that's what I want[br]to tell you about tonight.

0:03:51.240,0:03:55.616
The first source of local water[br]supply that we need to develop

0:03:55.640,0:03:57.776
to solve our urban water problem

0:03:57.800,0:04:01.056
will flow with the rainwater[br]that falls in our cities.

0:04:01.080,0:04:04.496
One of the great tragedies[br]of urban development

0:04:04.520,0:04:06.496
is that as our cities grew,

0:04:06.520,0:04:10.176
we started covering all the surfaces[br]with concrete and asphalt.

0:04:10.200,0:04:12.616
And when we did that,[br]we had to build storm sewers

0:04:12.640,0:04:14.736
to get the water[br]that fell on the cities out

0:04:14.760,0:04:16.696
before it could cause flooding,

0:04:16.720,0:04:19.560
and that's a waste[br]of a vital water resource.

0:04:20.200,0:04:21.976
Let me give you an example.

0:04:22.000,0:04:25.216
This figure here shows you[br]the volume of water

0:04:25.240,0:04:27.856
that could be collected[br]in the city of San Jose

0:04:27.880,0:04:31.656
if they could harvest the stormwater[br]that fell within the city limits.

0:04:31.680,0:04:36.456
You can see from the intersection[br]of the blue line and the black dotted line

0:04:36.480,0:04:40.776
that if San Jose could just capture half[br]of the water that fell within the city,

0:04:40.800,0:04:44.136
they'd have enough water[br]to get them through an entire year.

0:04:44.160,0:04:46.776
Now, I know what some of you[br]are probably thinking.

0:04:46.800,0:04:50.376
"The answer to our problem[br]is to start building great big tanks

0:04:50.400,0:04:53.256
and attaching them[br]to the downspouts of our roof gutters,

0:04:53.280,0:04:54.520
rainwater harvesting."

0:04:55.160,0:04:57.576
Now, that's an idea[br]that might work in some places.

0:04:57.600,0:05:00.856
But if you live in a place[br]where it mainly rains in the winter time

0:05:00.880,0:05:03.296
and most of the water demand[br]is in the summertime,

0:05:03.320,0:05:07.056
it's not a very cost-effective way[br]to solve a water problem.

0:05:07.080,0:05:10.096
And if you experience the effects[br]of a multiyear drought,

0:05:10.120,0:05:12.296
like California's currently experiencing,

0:05:12.320,0:05:16.536
you just can't build a rainwater tank[br]that's big enough to solve your problem.

0:05:16.560,0:05:18.576
I think there's a lot more practical way

0:05:18.600,0:05:22.096
to harvest the stormwater and[br]the rainwater that falls in our cities,

0:05:22.120,0:05:25.896
and that's to capture it[br]and let it percolate into the ground.

0:05:25.920,0:05:31.096
After all, many of our cities are sitting[br]on top of a natural water storage system

0:05:31.120,0:05:33.520
that can accommodate[br]huge volumes of water.

0:05:34.240,0:05:37.896
For example, historically,[br]Los Angeles has obtained

0:05:37.920,0:05:40.936
about a third of its water supply[br]from a massive aquifer

0:05:40.960,0:05:43.000
that underlies the San Fernando Valley.

0:05:44.400,0:05:47.176
Now, when you look at the water[br]that comes off of your roof

0:05:47.200,0:05:49.656
and runs off of your lawn[br]and flows down the gutter,

0:05:49.680,0:05:52.800
you might say to yourself,[br]"Do I really want to drink that stuff?"

0:05:53.520,0:05:55.696
Well, the answer is[br]you don't want to drink it

0:05:55.720,0:05:57.536
until it's been treated a little bit.

0:05:57.560,0:06:00.656
And so the challenge that we face[br]in urban water harvesting

0:06:00.680,0:06:03.416
is to capture the water, clean the water

0:06:03.440,0:06:04.680
and get it underground.

0:06:05.520,0:06:08.536
And that's exactly[br]what the city of Los Angeles is doing

0:06:08.560,0:06:12.656
with a new project that they're building[br]in Burbank, California.

0:06:12.680,0:06:16.776
This figure here shows[br]the stormwater park that they're building

0:06:16.800,0:06:21.976
by hooking a series of stormwater[br]collection systems, or storm sewers,

0:06:22.000,0:06:25.576
and routing that water[br]into an abandoned gravel quarry.

0:06:25.600,0:06:27.496
The water that's captured in the quarry

0:06:27.520,0:06:30.296
is slowly passed[br]through a man-made wetland,

0:06:30.320,0:06:32.936
and then it goes[br]into that ball field there

0:06:32.960,0:06:34.896
and percolates into the ground,

0:06:34.920,0:06:37.280
recharging the drinking water[br]aquifer of the city.

0:06:37.960,0:06:40.976
And in the process[br]of passing through the wetland

0:06:41.000,0:06:42.776
and percolating through the ground,

0:06:42.800,0:06:46.296
the water encounters microbes[br]that live on the surfaces of the plants

0:06:46.320,0:06:47.896
and the surfaces of the soil,

0:06:47.920,0:06:49.400
and that purifies the water.

0:06:50.160,0:06:52.536
And if the water's[br]still not clean enough to drink

0:06:52.560,0:06:55.256
after it's been through[br]this natural treatment process,

0:06:55.280,0:06:56.616
the city can treat it again

0:06:56.640,0:06:59.216
when they pump if back out[br]of the groundwater aquifers

0:06:59.240,0:07:01.320
before they deliver it to people to drink.

0:07:02.440,0:07:06.816
The second tap that we need to open up[br]to solve our urban water problem

0:07:06.840,0:07:08.296
will flow with the wastewater

0:07:08.320,0:07:10.480
that comes out[br]of our sewage treatment plants.

0:07:11.360,0:07:14.837
Now, many of you are probably familiar[br]with the concept of recycled water.

0:07:14.861,0:07:16.736
You've probably seen signs like this

0:07:16.760,0:07:20.016
that tell you that the shrubbery[br]and the highway median

0:07:20.040,0:07:21.536
and the local golf course

0:07:21.560,0:07:23.416
is being watered with water

0:07:23.440,0:07:25.720
that used to be[br]in a sewage treatment plant.

0:07:26.400,0:07:29.336
We've been doing this[br]for a couple of decades now.

0:07:29.360,0:07:31.376
But what we're learning[br]from our experience

0:07:31.400,0:07:35.496
is that this approach is much more[br]expensive that we expected it to be.

0:07:35.520,0:07:38.616
Because once we build[br]the first few water recycling systems

0:07:38.640,0:07:40.416
close to the sewage treatment plant,

0:07:40.440,0:07:42.679
we have to build longer[br]and longer pipe networks

0:07:42.703,0:07:44.863
to get that water to where it needs to go.

0:07:45.600,0:07:48.400
And that becomes prohibitive[br]in terms of cost.

0:07:49.000,0:07:50.216
What we're finding is

0:07:50.240,0:07:54.256
that a much more cost-effective[br]and practical way of recycling wastewater

0:07:54.280,0:07:56.856
is to turn treated wastewater[br]into drinking water

0:07:56.880,0:07:58.400
through a two-step process.

0:07:59.080,0:08:02.216
In the first step in this process[br]we pressurize the water

0:08:02.240,0:08:04.976
and pass it through[br]a reverse osmosis membrane:

0:08:05.000,0:08:07.416
a thin, permeable plastic membrane

0:08:07.440,0:08:09.976
that allows water molecules[br]to pass through

0:08:10.000,0:08:14.776
but traps and retains the salts,[br]the viruses and the organic chemicals

0:08:14.800,0:08:16.720
that might be present in the wastewater.

0:08:17.520,0:08:19.456
In the second step in the process,

0:08:19.480,0:08:21.976
we add a small amount of hydrogen peroxide

0:08:22.000,0:08:24.696
and shine ultraviolet light on the water.

0:08:24.720,0:08:27.616
The ultraviolet light[br]cleaves the hydrogen peroxide

0:08:27.640,0:08:30.776
into two parts that are called[br]hydroxyl radicals,

0:08:30.800,0:08:34.895
and these hydroxyl radicals[br]are very potent forms of oxygen

0:08:34.919,0:08:37.320
that break down most organic chemicals.

0:08:38.120,0:08:41.176
After the water's been[br]through this two-stage process,

0:08:41.200,0:08:42.816
it's safe to drink.

0:08:42.840,0:08:44.096
I know,

0:08:44.120,0:08:46.696
I've been studying recycled water

0:08:46.720,0:08:50.136
using every measurement technique[br]known to modern science

0:08:50.160,0:08:51.600
for the past 15 years.

0:08:52.320,0:08:53.736
We've detected some chemicals

0:08:53.760,0:08:56.336
that can make it through[br]the first step in the process,

0:08:56.360,0:08:58.360
but by the time we get to the second step,

0:08:58.384,0:09:00.296
the advanced oxidation process,

0:09:00.320,0:09:02.736
we rarely see any chemicals present.

0:09:02.760,0:09:06.936
And that's in stark contrast[br]to the taken-for-granted water supplies

0:09:06.960,0:09:08.840
that we regularly drink all the time.

0:09:10.040,0:09:12.416
There's another way we can recycle water.

0:09:12.440,0:09:15.536
This is an engineered treatment wetland[br]that we recently built

0:09:15.560,0:09:18.336
on the Santa Ana River[br]in Southern California.

0:09:18.360,0:09:22.456
The treatment wetland receives water[br]from a part of the Santa Ana River

0:09:22.480,0:09:26.096
that in the summertime consists[br]almost entirely of wastewater effluent

0:09:26.120,0:09:29.136
from cities like Riverside[br]and San Bernardino.

0:09:29.160,0:09:31.216
The water comes[br]into our treatment wetland,

0:09:31.240,0:09:33.576
it's exposed to sunlight and algae

0:09:33.600,0:09:36.096
and those break down[br]the organic chemicals,

0:09:36.120,0:09:39.656
remove the nutrients[br]and inactivate the waterborne pathogens.

0:09:39.680,0:09:42.136
The water gets put back[br]in the Santa Ana River,

0:09:42.160,0:09:44.056
it flows down to Anaheim,

0:09:44.080,0:09:47.336
gets taken out at Anaheim[br]and percolated into the ground,

0:09:47.360,0:09:50.016
and becomes the drinking water[br]of the city of Anaheim,

0:09:50.040,0:09:53.976
completing the trip[br]from the sewers of Riverside County

0:09:54.000,0:09:56.280
to the drinking water supply[br]of Orange County.

0:09:58.000,0:10:01.416
Now, you might think[br]that this idea of drinking wastewater

0:10:01.440,0:10:04.856
is some sort of futuristic fantasy[br]or not commonly done.

0:10:04.880,0:10:09.256
Well, in California, we already recycle[br]about 40 billion gallons a year

0:10:09.280,0:10:12.376
of wastewater through the two-stage[br]advanced treatment process

0:10:12.400,0:10:13.696
I was telling you about.

0:10:13.720,0:10:17.456
That's enough water to be[br]the supply of about a million people

0:10:17.480,0:10:19.240
if it were their sole water supply.

0:10:20.280,0:10:24.496
The third tap that we need to open up[br]will not be a tap at all,

0:10:24.520,0:10:26.136
it will be a kind of virtual tap,

0:10:26.160,0:10:29.256
it will be the water conservation[br]that we manage to do.

0:10:29.280,0:10:32.736
And the place where we need to think[br]about water conservation is outdoors

0:10:32.760,0:10:36.376
because in California[br]and other modern American cities,

0:10:36.400,0:10:38.800
about half of our water use[br]happens outdoors.

0:10:39.760,0:10:41.216
In the current drought,

0:10:41.240,0:10:42.816
we've seen that it's possible

0:10:42.840,0:10:45.816
to have our lawns survive[br]and our plants survive

0:10:45.840,0:10:47.736
with about half as much water.

0:10:47.760,0:10:50.776
So there's no need[br]to start painting concrete green

0:10:50.800,0:10:53.896
and putting in Astroturf[br]and buying cactuses.

0:10:53.920,0:10:58.136
We can have California-friendly[br]landscaping with soil moisture detectors

0:10:58.160,0:11:00.056
and smart irrigation controllers

0:11:00.080,0:11:02.520
and have beautiful[br]green landscapes in our cities.

0:11:03.760,0:11:06.776
The fourth and final water tap[br]that we need to open up

0:11:06.800,0:11:08.696
to solve our urban water problem

0:11:08.720,0:11:10.760
will flow with desalinated seawater.

0:11:11.360,0:11:15.336
Now, I know what you probably heard[br]people say about seawater desalination.

0:11:15.360,0:11:19.536
"It's a great thing to do if you have[br]lots of oil, not a lot of water

0:11:19.560,0:11:21.936
and you don't care about climate change."

0:11:21.960,0:11:26.296
Seawater desalination is energy-intensive[br]no matter how you slice it.

0:11:26.320,0:11:28.936
But that characterization[br]of seawater desalination

0:11:28.960,0:11:31.976
as being a nonstarter[br]is hopelessly out of date.

0:11:32.000,0:11:34.776
We've made tremendous progress[br]in seawater desalination

0:11:34.800,0:11:36.040
in the past two decades.

0:11:36.920,0:11:38.576
This picture shows you

0:11:38.600,0:11:42.576
the largest seawater desalination plant[br]in the Western hemisphere

0:11:42.600,0:11:45.416
that's currently being built[br]north of San Diego.

0:11:45.440,0:11:47.696
Compared to the seawater[br]desalination plant

0:11:47.720,0:11:51.016
that was built in[br]Santa Barbara 25 years ago,

0:11:51.040,0:11:53.696
this treatment plant[br]will use about half the energy

0:11:53.720,0:11:55.240
to produce a gallon of water.

0:11:55.840,0:11:59.576
But just because seawater desalination[br]has become less energy-intensive,

0:11:59.600,0:12:02.839
doesn't mean we should start building[br]desalination plants everywhere.

0:12:02.863,0:12:04.599
Among the different choices we have,

0:12:04.623,0:12:06.736
it's probably the most energy-intensive

0:12:06.760,0:12:08.696
and potentially environmentally damaging

0:12:08.720,0:12:11.640
of the options to create[br]a local water supply.

0:12:12.560,0:12:13.776
So there it is.

0:12:13.800,0:12:15.576
With these four sources of water,

0:12:15.600,0:12:18.920
we can move away[br]from our reliance on imported water.

0:12:19.680,0:12:24.176
Through reform in the way we landscape[br]our surfaces and our properties,

0:12:24.200,0:12:27.296
we can reduce outdoor water use[br]by about 50 percent,

0:12:27.320,0:12:30.776
thereby increasing [br]the water supply by 25 percent.

0:12:30.800,0:12:33.324
We can recycle the water[br]that makes it into the sewer,

0:12:33.348,0:12:36.428
thereby increasing[br]our water supply by 40 percent.

0:12:36.880,0:12:39.496
And we can make up the difference[br]through a combination

0:12:39.520,0:12:42.000
of stormwater harvesting[br]and seawater desalination.

0:12:43.280,0:12:47.096
So, let's create a water supply

0:12:47.120,0:12:50.776
that will be able[br]to withstand any of the challenges

0:12:50.800,0:12:53.376
that climate change throws at us[br]in the coming years.

0:12:53.400,0:12:56.736
Let's create a water supply[br]that uses local sources

0:12:56.760,0:13:00.800
and leaves more water[br]in the environment for fish and for food.

0:13:01.640,0:13:06.656
Let's create a water system that's[br]consistent with out environmental values.

0:13:06.680,0:13:10.136
And let's do it for our children[br]and our grandchildren

0:13:10.160,0:13:12.776
and let's tell them this is the system

0:13:12.800,0:13:15.136
that they have to[br]take care of in the future

0:13:15.160,0:13:19.096
because it's our last chance[br]to create a new kind of water system.

0:13:19.120,0:13:20.978
Thank you very much for your attention.

0:13:21.002,0:13:23.922
(Applause)