Shade balls — just add water
One year after dumping 96 million plastic balls over its reservoir, Los Angeles has declared its shade-ball experiment a success. By slowing evaporation, the balls saved millions of dollars. But there is a catch
As the California drought drags on, local politicians have resorted to increasingly creative methods to conserve water. In August 2015, Los Angeles Mayor Eric Garcetti announced that shade balls would be used to cover the 70-hectare Los Angeles reservoir, calling them an inexpensive alternative to the massive plastic covers that would have caused logistical problems over such a large surface. By reducing evaporation by 85 to 90 per cent, the balls have saved an estimated 1.1 billion litres of water over the last year.
HOW THEY WORK
Made from high-density polyethylene, the black balls, 10 centimetres in diameter, are resistant to ultraviolet light and use the same plastic as many water pipes do. They work by “reducing the water surface area exposed to the sun, and by reducing the flow of wind above the water surface,” Amanda Parsons, spokesperson for Los Angeles Department of Water and Power (LADWP), said in an email. Because wind blew many of the first balls off the water, each one now contains 200 grams of water to weigh it down.
CHEMICAL REACTION
The Los Angeles Department of Water and Power didn’t originally deploy shade balls to slow evaporation. In 2008, they were released on the Ivanhoe reservoir to fight a dangerous chemical reaction that occurs when sunlight reacts with naturally occurring bromide and the chlorine added to the water to combat algae growth — creating the carcinogen bromate. The balls were added to two other reservoirs before the L.A. reservoir got them.
FOR THE BIRDS
The balls were originally developed for the mining industry to prevent birds from landing on toxic tailing ponds. Eager to keep birds away from runways, where they can get sucked into jet engines and cause crashes, airport authorities have also adopted the balls. While some airports employ electronic chirps to keep birds at a distance, the shade balls have proven just as effective by covering nearby ponds that attract migrating birds. They’ve been used at Fairchild Air Force Base in Washington State and San Francisco International Airport, among others.
THE CATCH
New U.S. federal drinking-water regulations ban open-air reservoirs, and places like L.A. are scrambling to meet the new rules. Because the shade balls aren’t considered an acceptable cover, the LADWP is replacing them with impermeable plastic sheets. But because the L.A. reservoir is too big to cover in a cost-effective manner, the shade balls will stay indefinitely, and authorities will treat the water on its way out of the reservoir. The shade balls pulled from the other reservoirs will be recycled.