Yes, you are seeing that right. There is a giant mass of black balls in the Los Angeles Reservoir, black balls reservoir if you will, and it’s got people scratching their heads.

Is this some kind of practical joke? Is it April 1st already? It seems almost too strange to be true, too surreal a sight to have any kind of legitimate cause. But believe it or not, these whimsical-looking things have been around longer than you think, and they actually have a pretty serious – and pretty practical – purpose.

This isn’t really about water conservation.

Many have assumed that these black spheres – called “shade” balls – must have something to do with saving water. It is, after all, a California reservoir and what is California known for other than drought? While Los Angeles Weekly reports that, yes, they do decrease the amount of water that evaporates out of the reservoir, that is not their primary function.

This is actually about clean drinking water.

As explained in Science Alert, something was going on in the water in L.A. that was jeopardizing its safety for the stomachs of California residents.

In order to understand what went wrong, there is some explaining to do. We are all aware that drinking water gets treated with certain chemicals so that it’s safe to consume. We use good chemicals to get rid of bad chemicals, and bacteria, and contaminants, right?

One of the chemicals used to do this is chlorine, something that is not harmful in small quantities. Along with chlorine, this L.A. reservoir also contained bromide, which is a natural substance we find in saltwater.

On their own, these substances wouldn’t have posed any problems. The trouble came when they were both put together and under a hot California sun.

You see, when chlorine and bromide combined are exposed to sunlight, they react to produce something called bromate. Bromate is most definitely bad in drinking water and is potentially a carcinogen. You can read all about its studied effects on the human body here. Spoiler alert: it’s not pretty.

California had to come up with a way to stop the bromate from forming, and stop it fast; the longer they waited, the more water that was wasted.

So what do the shade balls do?

Well, as you might have guessed, the small black balls protect against one factor in the bromate equation: the sun.

How do they work? It’s much simpler than you might have imagined. The balls are made out of high-density polyethylene, as told by The Toronto Star, and are resistant to ultra-violet light. Because many of them blew away in the wind on the first go-round, they also each contain 200 grams of water to keep them firmly on the surface of the reservoir. They bob together in a giant black mass and block most of the sun’s rays from reaching the water. And… that’s pretty much it. That is the extent of their impressive scientific powers and why the reservoir can be nicknamed the black balls reservoir.

Simple enough, huh? Sometimes the most basic of ideas prove to be the most effective.

Interestingly, they were originally created to stop birds from alighting on toxic tailing ponds in the mining industry, and this is another perk for the L.A. Reservoir. Birds aren’t able to land in the water, and fewer birds mean less unsanitary substances the birds bring with them!

This, along with the water they save, show that despite their simplicity they do serve multiple functions. And isn’t there beauty in simplicity, anyway?

Could it really be as good as it seems?

A simple, low-cost, and kind of cool solution that actually works? Is it too good to be true?

Well, there are some sources that have expressed concern about the black balls.

For one thing, Science Alert brings attention to the fact that the spheres actually require more water to manufacture than the amount of water that they save. This is pretty disappointing, even if water conservation is not their main purpose.

On top of that, the balls only last ten years, at which point they will have to be replaced. Despite the fact that they’re pretty easy and cheap to procure, it’s still a significant extra cost. There are millions of them, after all.

It doesn’t stop there. This focus on protecting the drinking water has also outshined the plants and animals that live in and around the reservoir. What kind of impact will the balls have on the ecosystem? Will fish, frogs, and turtles be able to continue living there? Will plants still grow beneath the surface? And what will the lack of birds in the area mean for surrounding plants and animals? These are all questions that weren’t fully looked into before they decided to go full steam ahead with the glistening black balls.

All of that said, it’s hard to argue with something that achieves its goal. They are effective at what they seek to do, which is not to conserve water, or to protect aquatic life, or even to look cool. It is to stop the sun. And without the sun, there is no longer the issue of bromate in California’s drinking water. It can even be called a brave and creative solution – but only for now. Only time will tell just how effective, healthy, and sustainable these shade balls truly are.

Until then, we can all enjoy the strange sight of the black balls reservoir.