Today, "shade balls" got their moment in the sun.

On Monday afternoon, the 20,000 black plastic balls tumbled down the slopes of Los Angeles Reservoir, joining 95,980,000 of their brethren already covering the surface of the water.

The final deployment of these shade balls was the last step in a $34.5 million water quality protection project aimed at preventing evaporation and algae growth in the reservoir.

The EPA mandates that all reservoirs be covered, but because tarps can be expensive and metal coverings can take too long to install, shade balls — at least in Los Angeles — are becoming a preferred method.

According to a 2008 Los Angeles Times article, the LA Department of Water and Power used the plastic shade balls in 2008 to cover the Ivanhoe Reservoir. In that case, the balls were installed not to block evaporation and algae but to prevent a harmful chemical reaction from taking place in the water.

"The water needs to be shaded because when sunlight mixes with the bromide and chlorine in Ivanhoe's water, the carcinogen bromate forms, said Pankaj Parekh, DWP's director for water quality compliance. Bromide is naturally present in groundwater and chlorine is used to kill bacteria, he said, but sunlight is the final ingredient in the potentially harmful mix."

In addition to Ivanhoe, the shade balls are currently covering two other LA reservoirs.

At the Los Angeles Reservoir, the 96 million, 4-inch-diameter balls bobbing on the surface of the water are expected to save more than 300 million gallons of water annually.

"This is a blend of how engineering really meets common sense," said LADWP General Manager Marcie Edwards. "We saved a lot of money; we did all the right things."

Each ball costs only 36 cents, making it a cheaper solution than alternatives such as dividing the reservoir into two parts with a dam and installing floating covers, which would cost more than $300 million.

According to a Bloomberg article, the balls are coated in chemicals to block UV light, are not degradable and are designed to last up to 25 years.

Speaking at the reservoir yesterday, Los Angeles Mayor Eric Garcetti said he was proud of his city's innovation.

"While it's meeting the minimum standards, we want to go beyond that and have the healthiest water so we've been spreading these balls everywhere," he said.

Meanwhile, the surreal photos and videos of the shiny, water-filled spheres slithering down the sides of the reservoir, coupled with the fact it's difficult to say "shade balls" with a straight face, turned the water-saving measure into Internet gold.

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