LA is dumping millions of plastic balls into its reservoir to tackle the drought

[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/...

[2] http://news.nationalgeographic.com/2015/08/150812-shade-ball...

[markyc]

doesn't the plastic + sunlight + heat combination release dangerous chemicals in the water?

also, why are they black, doesn't that attract more heat?

[DanBC]

Was the article edited after you read it?

> And the primary reason for deploying the hollow balls is more to protect the quality of the water rather than to simply stop it evaporating. In the reservoir water, the naturally occurring bromide was mixing with sunlight and chlorine (added to disinfect drinking water) to create dangerous levels of the the carcinogen bromate. Shade balls should stop that harmful chemical reaction from happening at a large scale, and of course by deflecting the Sun's rays, they also keep more of the water in liquid form.

[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 :(.

[marincounty]

Went to the second link, and got the real story. It was an isolated, rare problem. The EPA mandate makes sense. Only these three lakes had high levels of bromate in 2007? I was picturing my beloved lakes filled with plastic.

"reservoirs exposed to sunlight are now rare. The area's reservoirs -- Silver Lake, Ivanhoe and Elysian -- first registered elevated levels of bromate between June and October 2007.

But state health officials said the dangers were minimal because bromate poses a small cancer risk only after consumed daily over a lifetime."

[girvo]

The article says all of that:

> And the primary reason for deploying the hollow balls is more to protect the quality of the water rather than to simply stop it evaporating

[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.)

[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.

[icebraining]

Unless you have a better idea, I don't see how the criticism is useful.

[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.

[sauravt]

Not if the dye they are using to paint these balls is hydrophobic.

[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.

[throwaway_yy2Di]

According to a chemist on /r/askscience, the plastics probably contain carbon black [0] as a UV protectant. So it might not be deliberate.

    (/u/Platypuskeeper) Although I have not seen a specification of what
    the balls are made of, what I know from polymer chemistry is that the
    black is quite likely from carbon black (essentially soot), which is
    used as an additive/filler in polymers (e.g. tire rubber) for multiple
    reasons but not least UV protection. Carbon black is one of the most
    (if not the most) effective UV-protective additives, precisely because
    it absorbs the UV and prevents it from penetrating deeply into the
    plastic. Plastic without some UV protective additive would degrade
    pretty quickly in the California sun, not least HDPE which has pretty
    bad UV resistance.

https://www.reddit.com/r/askscience/comments/3gpu6x/why_are_...

[0] https://en.wikipedia.org/wiki/Carbon_black

[PhasmaFelis]

Black absorbs more light (and, yes, heat), which means less light penetrates through it to heat the water directly. If you block one bright light with a sheet of thin white plastic, and another with a sheet of thin black plastic, you'll see a lot more light shining through the former. And do remember that the primary purpose is to block UV, not heat, so you want maximum light absorption even if it means greater heat transfer.

Chrome-mirrored balls would certainly be even better, but the whole reason they're using plastic balls is because they're dirt cheap. If you have enough money to fill your reservoir with disco balls, you'd be better off just building a gigantic awning.

[thaumaturgy]

The primary purpose of these is not to slow down evaporation. In fact they have a negligible effect on the rate of evaporation.

Their primary purpose is to absorb the light spectra that drives chemical reactions in the treated water to prevent carcinogenic bromate from being formed.

Most of the reporting on this, including this article, is pretty bad, and causing a lot of laymen to ask questions like yours, because it doesn't make sense as described in the reporting.

[Bootvis]

Thanks for making a bit of sense of this!

[cengizkrbck]

black is best suitable color to deflect UV rays.

[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.

[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...

[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.

[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.

[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

[DonHopkins]

Since it's LA, they could have recycled millions of silicon breast implants instead of using plastic balls. ;)

[venomsnake]

Depends on the ball ... you need to use food grade plastic. And certifications and on and on and on ...

[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.

[undersuit]

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

[utuxia]

http://imgur.com/JagJndf