Providing Shade to Protect Reservoirs

Posted by Chuck Harrell on Sep 14, 2015 11:00:00 AM

reserviorA few weeks ago the Internet was buzzing about a Californian reservoir’s use of ‘shade balls’ to prevent the evaporation of its precious water in the midst of one of the worst droughts in the state’s history. One of the reasons for this excitement was because of the fun video that was released with the press release and press conference and that it was California doing something kooky. 

But despite this being a new idea for this particular reservoir, this concept was first used in 2008 at the Ivanhoe Reservoir and then again in 2009 at the Elysian Reservoir and more recently at the Upper Stone Canyon Reservoir in 2012. 

So what exactly are they? Well they look like rather dull ball pool (pit) balls, however there are several differences.

  1. Quality, whereas nobody expects ball pit balls to last very long, these ‘shade balls’ are expected to be exposed to direct sunlight for up to 10 years before they split and breakup. Therefore they’re made from a high-density, food safe, BPA free and NSF certified polyethylene. This is the same material used in milk bottles.
  2. Color, these aren’t the brightly colored items that kids throw around. No, these are black. Black because it resists UV rays, prevents the production of algae and the carcinogen, Bromate and also stops the plastic leeching into the water.
  3. Size, at four inches or ten centimeters, they are bigger than the seven centimeters of ball pool balls and they weigh 245 grams when empty.
  4. Not waterproof, these are designed to partially fill with water so they are heavier and sit in, rather than on, the water. This means that during storms they are less likely to blow away.
  5. Heat Resistant, these balls aren’t going anywhere soon and they have to be able to withstand some pretty harsh temperatures, so shade balls have been designed to withstand temperatures from 120~180OC.

Now that 96 million of these balls are on the LA reservoir, what are they expected to do? If everything goes according to plan they will reduce evaporation by 90% and save 300 million gallons of water per year.

So on paper it looks great, they save money and prevent the build-up of carcinogens, but are there any problems? Despite digging around online the only person to issue an opinion is Professor Max Liboiron who published this article and wrote:

“The black additive [in the balls] is carbon black, which isn’t supposed to be harmful when it leaches, which is great. Yet even with this precaution, most plastics leach endocrine disrupting chemicals that interfere with animal and human hormone systems (Yang 2011). Some endocrine disruptors, like bisphenol A (BPA), break down in water after a few weeks or months. Some don’t. We don’t know what chemicals are in the Shade Balls, but they will leach, especially because the balls are in the hot sun and are meant to be left in the water over a long period (reports say 10 years). Most water treatment systems don’t take these kinds of chemicals out of the water.”

But since these are meant to be replaced after 10 years, is this really such a concern? Although not initially designed to prevent evaporation (the original use was the prevention of Bromate), these may well be an answer to reservoir evaporation around the world.

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