Why have 96million balls been released into a reservoir?

There is something about dumping 96million balls into a reservoir to block out the sun that seems very old school.

But it’s actually a new technology – and a very cheap and effective one at that – that is being used in Los Angeles to protect water quality.

The city just released the last batch of around 20,000 ‘shade balls’ onto the 175-acre surface of the LA Reservoir to prevent sunlight-triggered chemical reactions, deter birds and other wildlife and protect water from rain and wind-blown dust.

The shade balls cost $34.5million (£22million), or $0.36 (£0.23) each, and are expected to save $250million (£160million). Splitting the reservoir into two with a dam and installing floating covers were considered as alternatives, but either of these would have cost in excess of $300million (£192.5million).

The balls cost $0.36 each (Picture: REX Shutterstock)

The shade balls require no construction, parts, labour or maintenance aside from occasional rotation.

‘In the midst of California’s historic drought, it takes bold ingenuity to maximize my goals for water conservation,’ said Mayor Eric Garcetti.

‘This effort by LADWP is emblematic of the kind of the creative thinking we need to meet those challenges.’

The reservoir holds 3.3billion gallons of water – enough to supply Los Angeles for up to three weeks.

Metro