Los Angeles Mayor Eric Garcetti lets some shade balls fly. (Photo: City of Los Angeles)

It’s jet black, fist-sized and perfectly round, and it’s going to save California. Give it up for the shade ball.

Yesterday, the Los Angeles Shade Ball Cover Project rolled to a halt, rounding off years of work. With a shout of “shade balls away!” Los Angeles city officials overturned a row of sacks and sent 20,000 of the jet black objects cascading down into the Los Angeles Reservoir. The new recruits joined those from previous releases (which have been occurring weekly for over a year), and raised the total ball count to 96 million. They now blanket the entire surface of the 175-acre basin. 

An early round of LA Reservoir shade balls being released last year.

Each ball is the size of a large apple, and contains just enough water to help it cluster with its companions. Together, the ball shroud prevents damage from sunlight, dust, and errant birds, and keeps 300 million gallons of surface water from evaporating each year. Dr. Brian White, a biologist formerly with the Los Angeles Department of Water and Power, came up with the idea, which has since been deployed in several other cities.

Shade balls elsewhere in California, taking over the Las Virgenes reservoir.

The shade ball initiative aims to bring the LA Reservoir in line with new water quality mandates. The closest competing plan—bisecting the reservoir with a dam, and covering each side with a floating tarp—would have cost $300 million. The shade balls are made in LA and cost 36 cents each

Plus, they look like a cheerful horde of alien children tumbling pell-mell into the water. Have fun, guys!

Every day, we track down a fleeting wonder—something amazing that’s only happening right now. Have a tip for us? Tell us about it! Send your temporary miracles to cara@atlasobscura.com.