
LA is dumping millions of plastic balls into its reservoir to tackle the drought - chris-at
http://www.sciencealert.com/la-is-dumping-millions-of-small-plastic-balls-into-its-reservoir-to-tackle-the-drought?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencealert-latestnews+%28ScienceAlert-Latest%29
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tristanj
They're not dumping plastic balls in order to tackle the drought, they're
being dumped because the EPA mandated that all reservoirs be covered. Direct
sunlight will cause bromide and chlorine in the water to mix into bromate, a
known carcinogen, and the EPA wants to prevent buildup of this compound in the
drinking water supply. Covering the reservoir with a tarp is too expensive
(costing over $300 million) and plastic balls are a much cheaper option. The
evaporation reduction is a secondary benefit, not the primary one, and the
article title should reflect this.

There's much better coverage of this story here [1] and here [2].

[1] [http://www.npr.org/sections/thetwo-
way/2015/08/11/431670483/...](http://www.npr.org/sections/thetwo-
way/2015/08/11/431670483/la-rolls-out-water-saving-shade-balls)

[2] [http://news.nationalgeographic.com/2015/08/150812-shade-
ball...](http://news.nationalgeographic.com/2015/08/150812-shade-balls-los-
angeles-California-drought-water-environment/)

~~~
TeMPOraL
> _Covering the reservoir with a tarp is too expensive (costing over $300
> million) and plastic balls are a much cheaper option._

This is what I don't get in this story. How on Earth are plastic balls cheaper
than just covering the thing? One would think that a tarp would use less
material and be easier to manufacture than the equivalent number of plastic
balls.

EDIT: Thanks for all your answers. I guess the heatwaves we have right now in
Poland are negatively affecting my imagination :(.

~~~
gokhan
Will tarp be a single piece or multiple pieces? What's the weight of the tarp?
how do you make sure it's on the surface? Or do you need a support structure
to keep it above the surface (say a meter etc.)? Will it have holes to drain?
Will holes be sturdy enough in the long run? etc...

~~~
aquadrop
I was thinking why they use ball form instead of something sheet-like. E.g.
thin pancake - it will have same properties as the balls but will cover
surface more efficiently, if you count material.

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david-given
This may seem like a silly question, but...

Why on earth are you chlorinating the water _in the reservoir_? I've never
seen any other country that does that. Isn't it a really, really terrible
idea? Environmentally ghastly because you kill everything in the reservoir,
expensive due to chlorine loss, subject to side effects (like this one), and
ideally suited to breeding chlorine-resistant bacteria... not to mention
giving you nigh-undrinkable water!

I'm from the UK, and we chlorinate our water pretty heavily, but even we don't
do this.

(I now live in Switzerland. Water in Zürich is purified via activated carbon,
live biofilm and ozonation. The water which comes out of the tap is
unchlorinated and is better and more drinkable than most bottled mineral
water.)

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allendoerfer
I think the story sounds a bit ironic:

So you are essentially dumping objects made out of chemicals, you had to drill
wholes in the ocean ground to get, into a lake, because you found out that the
chemicals you dumped into it earlier kill you when the sun shines on them. You
also think that this might help you with the water shortage caused by
unsustainable use of resources.

To me this all sounds like we arrived at a local maximum here. This simply
cannot be the way to do this. Maybe we should start over.

~~~
Asbostos
But we protected ourselves from diseases with the chlorine. That's a massive
win. Then we discovered there's a new risk of disease with the bromate, so we
protect ourselves from that too. Isn't this basically how most technology
develops? We keep getting better and better off because of it.

~~~
legulere
There are countries that don't use chlorine: Switzerland, Austria, Germany,
Sweden, ... and they're regularly touted as having the best tap water quality
in the world.

~~~
moftz
Ozone purification is cheap but could allow for future contamination if there
is backflow or possibly a leak in the water mains. Chlorination prevents
anything from growing in the water from the filtration plant to your home.

One problem that major coastal cities have is that they collect water from
streams that have already been polluted and are on their way out to the ocean.
The US has a lot of these cities, 40% of the population occupy the coasts
which is only 10% of the country. The cities in the US that typically are
regarded as having the best tap water are midwestern cities, ones that do not
have a coastline and tend to get cleaner water from natural sources.
Switzerland, Austria, and Germany are exactly the same. They are very central
countries with nearby access to Alpine runoff water, the water they get is
pretty unmolested when compared to what the Potomac River supplies to
Washington DC.

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WalterBright
I wouldn't be surprised if the balls increased the evaporation rate, for the
simple reason that it will increase the surface area of the water (the balls
will rotate in the water, bringing wet surfaces up). Black balls will also
heat up more, causing more evaporation.

~~~
redcalx
> Black balls will also heat up more, causing more evaporation.

Question. Overall, is the heat absorption of the black balls greater than open
water? I imagine it's about the same, but perhaps the issue is that the balls
are concentrating the heat at the surface, and on the surface of the rotating
balls. So it does seem like the evaporation rate could well be higher.

I suppose it comes down to the mean rotation rate of the balls.

~~~
rdlecler1
Smart thinking. The balls could be slightly weighted to avoid this issue,
albeit this could mean the balls collect a rim of sludge more easily.

~~~
WalterBright
The weighting won't prevent them from sloshing around due to wave action and
getting the upper surfaces wet anyway.

~~~
SamReidHughes
They'd be fine. For example, the tops of these ducks are dry:

[https://i.imgur.com/RYyBMrf.jpg](https://i.imgur.com/RYyBMrf.jpg)

In a reservoir you're not going to get waves that manage to spin the weighted
side of the ball up any considerable amount, even if it's only slightly
weighted.

~~~
SamReidHughes
Actually maybe I'm talking out of my behind -- what if there was wind? Add
more weight then. Obviously a weighted oblate spheroid, like the ducks, would
definitely work.

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Bootvis
What I don't understand is that they dumped black balls in the reservoir. If
you want to keep the water cool to lessen evaporation wouldn't it make sense
to use white or reflecting balls so the water stays slightly cooler?

I would be glad to know why black balls are chosen.

~~~
cengizkrbck
black is best suitable color to deflect UV rays.

~~~
erikb
Now you just said the opposite of what intuition suggests without any
evidence, or even argument. Please elaborate and don't just heat up the
discussion!

~~~
Implicated
UV + Chlorine = Bromide

~~~
erikb
Does that look like an explanation to you? I don't see anything about black. I
don't see anything about white. I don't see anything about reflecting
materials. I see something from chemistry, maybe?

Customer: "Why should I buy the product?" Developer: "Here we had a problem
with the inheritance tree. We worked around it with a factory method."

------
aquadrop
Looks like 3d simulation example came to life :)

But seriously, why balls are used? They say it's cheap but 36 cents doesn't
look too cheap on the hundreds of millions scale. Wouldn't it be better to use
sheet-like form? It will be covering space more efficiently.

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ZeroGravitas
I wonder if floating solar PV was considered as an alternative/complementary
solution that might pay for itself over time:

[http://www.eastgreenenergy.co.uk/for-
business/products/float...](http://www.eastgreenenergy.co.uk/for-
business/products/floating-solar-pv/)

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erikb
Do they really need to invent that much? It's true that the current situation
is maybe the worst they ever faced. But there are a lot of places where water
is even more valuable as a resource. Are they also looking into what people in
the desert do to keep their water sources alive, etc?

~~~
martin-adams
I do wonder if it's a different set of challenges. The demand for water in
California is probably much greater, rather than adapting everyone's use to
the climate. So I suspect the innovation is to sustain the level of water
usage that isn't seen in the desert.

~~~
erikb
Hm, okay. I guess that's the American Way to approach such a problem.

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Bohahahaha
This chlorine everywhere in the US astonishes me. When visiting I'm not able
to drink (non bottled) Coke b/c of the bad and intense chlorine taste.

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abricot
"in which a total of 96 million balls have been poured"

"they're cheap (costing just 36 cents per unit)"

Is that really cheap, or is it just because it's in LA?

~~~
hkmurakami
As sibling poster [1] mentioned, the balls are cheaper (and probably last
longer) than the tarp alternative.

[1]
[https://news.ycombinator.com/item?id=10052777](https://news.ycombinator.com/item?id=10052777)

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rdlecler1
The article title is misleading. If we assume water price of $1000/acre-foot,
then they spending ~$30m today to save 10x$2m over the next ten years. Water
Davis are clearly a by-product benefit (as the article states) and the balls
are not being used to tackle drought.

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undersuit
10 Year lifetime? Just the lifespan of these plastic balls being beaten with
sunlight?

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utuxia
[http://imgur.com/JagJndf](http://imgur.com/JagJndf)

