They're not dumping plastic balls in order to tackle the drought, they're being dumped because the EPA mandated that all reservoirs be covered. Direct sunlight will cause bromide and chlorine in the water to mix into bromate, a known carcinogen, and the EPA wants to prevent buildup of this compound in the drinking water supply. Covering the reservoir with a tarp is too expensive (costing over $300 million) and plastic balls are a much cheaper option. The evaporation reduction is a secondary benefit, not the primary one, and the article title should reflect this.
There's much better coverage of this story here [1] and here [2].
There's much better coverage of this story here [1] and here [2].
[1] http://www.npr.org/sections/thetwo-way/2015/08/11/431670483/...
[2] http://news.nationalgeographic.com/2015/08/150812-shade-ball...