This Graphic Shows How Plastic Balls Are Saving L.A. From Drought

The city of Los Angeles has dumped millions of small black balls into the city’s reservoirs in an effort to protect the city’s water supply.

The “shade balls” are intended to maintain good water quality and protect against evaporation. It’s one solution to the state of California’s record-breaking drought, and could save the city millions in both water and costs. “As the drought continues, it has never been more important to focus on innovative ways to maintain the highest quality drinking water for our 4 million residents, Los Angeles City Council Mitchell Englander said in a statement.

But how do they work? Take a look at the graphic below and find out: