To improve the quality of the water, 96 million balls now float upon the Los Angeles reservoir. Here they are going in, like a deranged live-action performance of one of those cheapo cgi educational videos on YouTube with vast oceans of balls and 100 million views. All it needs now is a text-to-speech bot announcing "BLACK COLORED BALLS".
The first time I heard about shade balls the claim was they reduce evaporation. But it turns out this isn't the reason they were introduced. Huge thanks to LADWP for arranging this special tour for me. Next time let's put the GoPro on the submersible! The balls are made of high density polyethylene (HDPE) which is less dense than water so they float on the surface of the reservoir even if they break apart. They are 10cm (4 inches) in diameter and contain about 210ml of water. So the main reason they are on the reservoir is to block sunlight from entering the water and triggering a chemical reaction that turns harmless bromide into carcinogenic bromate. This effect occurs with prolonged exposure to bromate so regulators insist that levels be kept below 10 microgram per liter on average over a 12 month period.