Environment

Could water-saving "shade balls" have a shady side?

Could water-saving "shade ball...
The shade balls getting dispersed into the LA Reservoir
The shade balls getting dispersed into the LA Reservoir
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The shade balls getting dispersed into the LA Reservoir
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The shade balls getting dispersed into the LA Reservoir
The shade balls getting dispersed into the LA Reservoir
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The shade balls getting dispersed into the LA Reservoir

Three years ago, the drought-stricken city of Los Angeles covered the surface of the LA Basin with 96 million shade-providing floating balls, in order to keep the water beneath from evaporating. Now, an international study suggests that the making of the plastic balls may have have used up more water than they saved.

The "shade balls" were left in place on the reservoir for approximately one and a half years, during the latter part of the 2011 - 2017 California drought. According to the study, they kept an estimated 1.7 million cubic meters (60 million cubic feet) of water from evaporating. Unfortunately, however, it is also estimated that production of the balls used up 2.9 million cubic meters of water (102 million cubic feet). This happened at locations where the oil and natural gas used to produce the plastic were refined, and where the electricity necessary for production was generated.

In order for the shade balls to save as much water as was used in manufacturing them, they would reportedly have to be left on the reservoir for at least two and a half years – and that's only if drought conditions persisted for the entire period.

Additionally, the study points out that the manufacturing process would have had other negative environmental costs, such as the generation of carbon emissions and water pollution.

"We are very good at quick technological fixes, but we often overlook the long-term and secondary impacts of our solutions," says study co-author Dr. Kaveh Madani, from Imperial College London. "This is how the engineering community has been solving problems; solving one problem somewhere and creating a new problem elsewhere … We are not suggesting that shade balls are bad and must not be used. We are just highlighting the fact that the environmental cost of shade balls must be considered together with their benefits."

The findings of the study, which also included scientists from MIT in the US and the University of Twente in the Netherlands, were recently published in the journal Nature Sustainability.

Source: Imperial College London

31 comments
Fairly Reasoner
They sound surprised.
Ben Chernicoff
They are completely missing the fact that they were most likely made somewhere that water was plentiful. The point wasn't to save a net amount of water nationally, it was to conserve water someplace it is scarce.
Paul Muad'Dib
Mistakes are part of progress.
Roger Garrett
It seems to me that the balls would have saved a lot more water from evaporation if they had been bright white or even silvery instead of black. The blackness of the balls no doubt absorbed a lot of solar energy, heating up the underlying water and making it evaporate even more.
I'd like to know if any experiments were done comparing different colored balls to see which would be most effective in retaining water in reservoirs.
b@man
I assume the balls are made somewhere else, and have a lifespan longer than one year...
physics314
Ben, respectfully, if the point hadn't been to generate net water savings, water could have simply been transported to CA, avoiding the plastic and manufacturing expense altogether. This seems to be a clear case of someone not doing an even basic back-of-the-envelope materials balance calculation.
john248
shouldn't the balls be white?
PaleDale
I'd say they were black to be UV resistant and also still be "food safe". Some plastics might be UV resistant but then leech chemicals into the water etc... A food safe plastic like PET in black would be the safest and cheapest option.
Deres
@PaleDale I have the contrary, that many black plastics are not safe. Some of them are black because they contain recycled plastics of various color, hidden in a black color. And with recycled plastics, it is hard to be sure no one contains any dangerous product.
zr2s10
First, like other said, they should have been white, to prevent evaporation due to added heat. Second, that water that was used to make the plastic doesn't just disappear into the ether... It gets either evaporated and rained down again, or dumped back into the water supply it came from.