When Los Angeles Mayor Eric Garcetti, standing alongside several workers from the Department of Water and Power (LADWP), was photographed emptying a bag of “shade balls” into the Los Angeles Reservoir in August, he couldn’t have imagined how fast and how far the image would travel.

Within hours, it was everywhere: The Los Angeles Times wrote that a professor from the University of Southern California had reported seeing it on a Russian newscast in her hotel room in Moscow. It had its own hashtag, with one Twitter user quipping, “If you ever doubted that LA was the home to everything plastic ... #shadeballs.”

Indeed, there aren’t many people who haven’t already seen a video or photograph of the four-inch black plastic balls covering the Los Angeles Reservoir. The deployment in August marked the final phase of a unique and innovative in-house solution to covering the city’s open-air reservoirs. The project started in 2008, and today all four of the city’s reservoirs use shade balls, which protect L.A.’s drinking water by preventing sunlight-triggered chemical reactions, deterring birds and other wildlife, and protecting water from rain and wind-blown dust. The shade balls also reduce evaporation by 85 to 90 percent.

But now they’re coming off the surface of all but one of the reservoirs. The shade balls will be removed not only at Ivanhoe Reservoir, which is being taken out of service, but also from Elysian and Upper Stone Canyon reservoirs. Instead, they’re receiving floating covers, says Richard Harasick, LADWP’s director of water operations.

Federal rules mandate that all bodies of drinking water open to the air be covered. Floating covers provide more of a complete barrier from both sunlight and airborne contaminants, says Harasick. The shade balls will only remain at Los Angeles Reservoir, and that’s because it would be cost-prohibitive -- to the tune of $250 million -- to install a floating cover on the 175-acre reservoir, which holds a total of 3.3 billion gallons of water, enough water to fill the Rose Bowl five times. At 36 cents a pop, the 96 million plastic balls covering the surface have a lifespan of 10 years and require almost no maintenance aside from occasional rotation. In addition, Harasick adds, “we are experiencing cost savings in the reduced use of chlorine because the shade balls have reduced the amount of algae growth requiring treatment.” The LADWP also estimates they’ll see 300 million gallons in water savings with the shade balls.

The idea for L.A.’s shade balls came when a now-retired LADWP biologist learned about the application of “bird balls” in ponds along airfield runways. Airports have detention basins to collect stormwater runoff. As the ponds fill up, they attract birds. So airports float the balls on the ponds to keep the birds off.

The LADWP is the first utility to use the technology for water quality protection -- and it may end up being the only one. “There is a general interest around [using shade balls in other jurisdictions],” says Harasick. “However, LADWP has a special set of water quality issues that fit the use of shade balls likely not seen by many other water utilities.”

What sets Los Angeles apart for the effective use of shade balls is that the water in the city’s reservoirs contains naturally occurring bromide. Once chlorine, which is used for disinfection, is added and mixes with sunlight, bromate is formed. “Bromate is a suspected human carcinogen,” says Harasick. But “the use of shade balls removes sunlight from the equation and this chemical reaction that makes bromate cannot occur.”