Why Los Angeles Reservoirs Are Covered With Black Plastic Balls

On August 13, Los Angeles Mayor Eric Garcetti along with officials from the water department watched as the last 20,000 "shade balls" rolled their way into the city's largest in-basin water reservoir. The release marked the final phase of the project that involved covering the 175-acre lake with 96-million four-inch black plastic balls. Their purpose? To provide shade and improve water quality.

According to experts, the ball cover will keep the water from being contaminated by wildlife and dust and also help reduce sunlight-triggered chemical reactions. The latter is of particular importance for Los Angeles. That's because its reservoirs contain a large amount of a naturally occurring chemical called bromide. While safe on its own, it reacts with the chlorine (used to disinfect water) and the sun's ultra-violet rays to form bromate, which is believed to be dangerous to humans.

The half-pound shade balls that are filled with eight ounces of water to keep them in place, help block the UV rays and also prevent algae build-up in the water. This means that they not only stop the chemical reaction from occurring, but also, alleviate the need to treat the water with chlorine. According to Marty Adams, the Water District's Senior Assistant General Manager, in addition to the health benefits, this will also save the city almost $28,000 USD each month.

An added bonus? The shade balls will prevent the loss of about 300 million gallons of water through evaporation, annually. Given that the city residents used 136 billion gallons just in the month of June, it is by no means a large amount, but for water-starved California, every drop counts.

At a total cost of $34.5 million USD ( $0.36 cents a ball), the cover was not cheap. But according to Los Angeles Department of Water and Power (LADWP) officials, it was a bargain compared to the alternative - A conventional floating cover that would have set the city back $300 million USD. Additionally, this low-tech solution that will protect the water for a decade, required no assembly, cost little to implement and requires no maintenance aside from occasional rotating.

The shade balls which have been in use at other Los Angeles reservoirs since 2008, are the brainchild of Dr. Brian White. The now retired LADWP biologist was inspired after noticing the effectiveness of a similar product on water puddles along airfield runways to keep birds away.

This is not the only initiative the city is taking to ensure clean water for its residents. They are also building an indoor reservoir to replace existing storage and working to complete a $100 million USD Ultraviolet water treatment facility. Now if they could only get some rain, life would be perfect, at least for the residents of Los Angeles!

Resources: gizmodo.com, vox.com, scpr.org,weather.com,space109.com.