'Shade balls' protect water quality at Los Angeles Reservoir

Los Angeles Mayor Eric Garcetti this month released 20,000 ‘shade balls’ onto the surface of the Los Angeles Reservoir. The deployment marked the final phase of a $34.5 million initiative that involves the deployment of 96 million shade balls into the 71 ha reservoir, owned and managed by the Los Angeles Department of Water and Power (LADWP).

Retired LADWP biologist Dr Brian White was the first person to think of using shade balls for water quality. The in-house solution has been used in LADWP’s open-air reservoirs since 2008 to block sunlight, prevent chemical reactions and curtail algae blooms. The shade balls come with the added benefit of reducing evaporation off the reservoir surfaces by 85 to 90%.

Currently in place at Upper Stone, Elysian and Ivanhoe reservoirs, and now in LA, the small, black plastic balls will protect the city’s water quality by preventing sunlight-triggered chemical reactions, deterring wildlife and protecting water from rain and wind-blown dust. At $0.36 each, the shade balls require no construction, parts, labour or maintenance aside from occasional rotation.

An investment that brings the LA Reservoir into compliance with new federal water quality mandates, the shade balls are expected to save $250 million when compared to other comparable tools considered to meet that goal, such as splitting the reservoir into two with a bisecting dam and installing two floating covers. The shade balls will additionally prevent the annual loss to evaporation of about 1136 ML of water.

“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,” said council member Mitchell Englander. “In addition to cutting back on the need to chemically treat our water to prevent natural occurrences like algae, these shade balls are a cost-effective way to reduce evaporation each year by nearly 300 million gallons — enough to provide drinking water for 8100 people for a full year.”

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