Home Stories The 96 Million Black Balls In LA’s Reservoir Aren’t There Only To...

The 96 Million Black Balls In LA’s Reservoir Aren’t There Only To Save Water


96 million black plastic “shade balls” are covering the LA reservoir. Why? As it is reported, these plastic balls are used to stop evaporation from water storages. But apparently, they have another idea in mind as they are also doing something different.

Derek Muller, in a new Veritasium episode, investigates the whole story behind these black balls. “It looks absurd,” Muller laughs in the video. “It’s like we’re in the world’s biggest ball pit.”

However, in spite of their purpose of saving water, the balls were not put in the water to reduce evaporation. The main problem lies in the natural substance bromide that exists in saltwater.

Bromide is harmless when it exists on its own, but when it gets in contact with the reservoir and goes through an ozone treatment with the LA’s drinking water it forms a compound called bromate that is a carcinogen substance.

The LA Department of Water and Power believed they had the bromate levels under control, but this carcinogen continued spiking anytime there was water in the reservoir. As they discovered, when chlorine and bromide interact with sunlight its reaction produces even more bromate than when it interacts with ozone.

The solution? Black plastic balls. These balls are typically used around airports to stop birds from perching in nearby water and are also very effective at keeping sunlight out which is also good because it keeps the water below the reservoir cooler.

“So for all of these reasons, shade balls reduce evaporation by 80 to 90 percent,” Derek explains. “That’s pretty significant for a dry climate like Los Angeles.”

Mary Wright