PHOTOGRAPH BY GENE BLEVINS, LA DAILY NEWS/ZUMA WIRE/CORBIS
You might have seen the stories going around about the LA Department of Water and Power putting almost 100 million black orbs, called “shade balls”, into its reservoir in Sylmar, CA. These balls floated out and are now covering the entirety of the water’s surface in a mesmerizing pattern reminiscent of a 5 Gum commercial. These spheres are designed to protect LA’s dwindling water supply from contamination, dangerous UV rays breaking down the disinfecting chlorine, and evaporation.
We thought this was awesome, but we also weren’t sure why the shade balls weren’t white. Granted, the colors shouldn’t matter for the contamination and UV issues, but it would seem to matter for the evaporation. Since, out of any color, black absorbs light the best, it should raise the temperature of the water and speed up the rate of evaporation.
We posited various ideas to each other, which became increasingly humorous yet unlikely: for example, perhaps local birds were attracted to white balls and would pick them up and fly them away, dropping them on unsuspecting Angelinos? Unsatisfied with our own answers, one of our contributors, Abbey Interrante, reached out to the LA Department of Water and Power with the question. Here is their response, coming from an employee named Albert Rodriguez:
"The shade balls used by LADWP are HDPE – high-density polyethylene and are approved for contact with drinking water by the National Science Foundation. They use the same material as one-gallon milk cartons. The carbon black is an added layer of UV protection from the sun. To have used other colors would have required dyes, which do leach into the water. The carbon black does not emit or leach any chemicals. The shade balls do eventually lose structural integrity and may split in half or fail at the seams after 10 years at which point they will be removed and fully recycled.
We have previously looked at the effect of the shade balls on temperature on both the water and the local climate. What we found was there is no effect in either case. It does not warm up the water or the air in any perceptible way. Rather they provide a 4-inch layer of thermal protection that keeps the water cool.
Water temperature is not a contributor to the issues of water quality. Those factors are natural occurring bromide in our source water, chlorine for disinfection, and sunlight.
LADWP has all but eliminated disinfection byproducts with our multi-barrier approach, which also includes UV treatment."
So there’s your answer! The balls basically come standard in black, and adding color would likely introduce chemicals into the water, which would be completely counterproductive let alone more expensive. Also, testing the black balls showed that the water temperature did not rise appreciably. It is likely that the material in this case matters more than the color, at least in the sense of evaporation rates.
This article has been adapted with permissions from Event Horizon Magazine