Los Angeles once used 96 million plastic balls to fight drought, creating a hidden cost

In 2015, millions of black plastic balls rolled across the surface of a reservoir in Los Angeles, creating an image that quickly travelled far beyond California. The 96 million shade balls were placed on the water during a severe drought, with a practical purpose: reducing evaporation while also helping protect drinking water from sunlight-related chemical reactions. At first glance, the idea appeared straightforward: cover the reservoir, block the sun and keep more water in the system. But there was another part of the calculation that was harder to see. The plastic balls themselves required water to manufacture. A 2018 study examined that hidden water use and found that the environmental equation was more complicated than the reservoir alone suggested.Why Los Angeles covered its reservoir with plastic ballsThe shade balls were not introduced simply as a way of dealing with evaporation. Los Angeles had already been using them before the spectacular 2015 deployment, beginning in 2008.One of their purposes was to keep sunlight from triggering chemical reactions in treated reservoir water. Sunlight can contribute to the formation of bromate when it interacts with naturally occurring ...