Over the last few days, the Los Angeles Department of Water and Power released 96 million black, plastic shade balls into a reservoir at the Van Norman Complex in Sylmar, which spread out in a thick layer covering every square inch of the 175-acre water surface. The 4 inch balls are weighted down with water inside to keep them in place. The balls protect the water against dust and rain, birds and wildlife, and chemical reactions caused by the sun. It is also expected to save about 300 million gallons of water from evaporating each year, enough to provide drinking water for 8,100 people for a full year.

Shade balls are also cost effective. Each ball cost only 36 cents, bringing down the entire cost of the project to less than $35 million. Covering the reservoir using traditional means would have cost the department $300 million. The balls last about 10 years, after which the Water Department expects them to be recycled and replaced.