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California uses light-blocking plastic balls to conserve water

Battling a record dry spell that has left reservoirs badly drained, the Las Virgenes County water district on the outskirts of Los Angeles has decided to fill its reservoir with hundreds of black plastic balls. The balls sit on top of the water and block the sunlight from hitting it, helping to reduce water evaporation as well as natural contamination and certain chemical reactions that could cause algae blooms in the reservoirs. Aug 13, 2015