What’s the Purpose of Shade Balls?

shade-ballsIf you’ve ever been to Los Angeles, you may have seen a ton of little plastic balls floating on top of their water reservoirs. There are millions of them! So many that from far away, they look more like a blacktop than a gigantic and wet ball pit.

But before diving in face first, consider that these balls actually serve a very important purpose. Reservoirs, like the ones in Los Angeles store the city’s drinkable and potable water. But Federal law says that they can’t just leave this water exposed to the open air. When the EPA enacted this mandate in 2006, it was responding to an outbreak of cryptosporidiosis, a stomach illness contracted from drinking contaminated water, namely from reservoirs. But cryptosporidiosis is not the only side effect of exposed reservoirs.

But cryptosporidiosis is not the only side effect of exposed reservoirs. Uncovered water can be pooped in by birds, or just get dirty from dust and dirt settling on top. In the aftermath of 9/11, a lot of people were concerned that open reservoirs would be targeted by terrorists – like the enemy would fly by on a plane and drop in toxic chemicals, infecting entire populations.

But Batman-based terror attacks aside, the biggest concern when it came to exposed drinking water, at least for LA County, was a chemical reaction that occurs when the water interacts with sunlight.

LA’s reservoirs contain a small amount of chlorine as a disinfectant. In direct sunlight, when chlorine combines with a natural element found in groundwater, bromide, it creates a chemical called “bromate”. Bromate sucks to ingest, and can cause stomach pain, nausea, and in high doses, serious damage to the kidneys and nervous system.

Sunlight can also lead to algae growth, which isn’t harmful in itself. But when algae breaks down and the organic components mix with chlorine, it creates byproducts, which have been associated with birth defects and even certain cancers.

So, LA county needed to cover up their reservoirs. And they considered a few ways of doing it. The most logical solutions were to build a huge roof, or use a massive tarp. But these alternatives were going to be really expensive. Like, $300 million dollars expensive. That’s like three-quarters of the average cost to launch a damn space shuttle.

So instead, LA County went with “shade balls”. The idea was pretty simple: 96 million 4-inch diameter plastic balls would float on the reservoir, preventing evaporation and protecting the water from harmful airborne pollutants. The balls were also coated with a black carbon colorant that repels ultraviolet light, which can cause plastics and other materials to degrade. This chemical coating is intended to protect them for up to 25 years.

Thankfully, shade balls are also economical. Each ball costs just 36 cents, representing a total savings of roughly $250 million dollars for LA County. This is all fairly new. In fact, LA is the first county to use shade balls for this purpose. But they’re getting a lot of attention, especially as a way to mitigate the effects of this never-ending drought. The Los Angeles Reservoir’s shade balls are expected to prevent roughly 300 million gallons of water from evaporating every year.

Could shade balls be the future of environmental protection?

Let us know down below in the comments section below!


  1. I would like to use the above image for a book I’m working on (scientific). Please advise.

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