Shade balls — just add wa­ter

One year after dump­ing 96 mil­lion plas­tic balls over its reser­voir, Los An­ge­les has de­clared its shade-ball ex­per­i­ment a suc­cess. By slow­ing evap­o­ra­tion, the balls saved mil­lions of dol­lars. But there is a catch

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As the Cal­i­for­nia drought drags on, lo­cal politi­cians have re­sorted to in­creas­ingly cre­ative meth­ods to con­serve wa­ter. In Au­gust 2015, Los An­ge­les Mayor Eric Garcetti an­nounced that shade balls would be used to cover the 70-hectare Los An­ge­les reser­voir, call­ing them an in­ex­pen­sive al­ter­na­tive to the mas­sive plas­tic cov­ers that would have caused lo­gis­ti­cal prob­lems over such a large sur­face. By re­duc­ing evap­o­ra­tion by 85 to 90 per cent, the balls have saved an es­ti­mated 1.1 bil­lion litres of wa­ter over the last year.

HOW THEY WORK

Made from high-den­sity poly­eth­yl­ene, the black balls, 10 cen­time­tres in di­am­e­ter, are re­sis­tant to ul­tra­vi­o­let light and use the same plas­tic as many wa­ter pipes do. They work by “re­duc­ing the wa­ter sur­face area ex­posed to the sun, and by re­duc­ing the flow of wind above the wa­ter sur­face,” Amanda Par­sons, spokesper­son for Los An­ge­les Depart­ment of Wa­ter and Power (LADWP), said in an email. Be­cause wind blew many of the first balls off the wa­ter, each one now con­tains 200 grams of wa­ter to weigh it down.

CHEM­I­CAL RE­AC­TION

The Los An­ge­les Depart­ment of Wa­ter and Power didn’t orig­i­nally de­ploy shade balls to slow evap­o­ra­tion. In 2008, they were re­leased on the Ivan­hoe reser­voir to fight a dan­ger­ous chem­i­cal re­ac­tion that oc­curs when sun­light re­acts with nat­u­rally oc­cur­ring bro­mide and the chlo­rine added to the wa­ter to com­bat al­gae growth — creat­ing the car­cino­gen bro­mate. The balls were added to two other reser­voirs be­fore the L.A. reser­voir got them.

FOR THE BIRDS

The balls were orig­i­nally de­vel­oped for the min­ing in­dus­try to pre­vent birds from land­ing on toxic tail­ing ponds. Ea­ger to keep birds away from run­ways, where they can get sucked into jet en­gines and cause crashes, air­port au­thor­i­ties have also adopted the balls. While some air­ports em­ploy elec­tronic chirps to keep birds at a dis­tance, the shade balls have proven just as ef­fec­tive by cov­er­ing nearby ponds that at­tract mi­grat­ing birds. They’ve been used at Fairchild Air Force Base in Wash­ing­ton State and San Fran­cisco In­ter­na­tional Air­port, among oth­ers.

THE CATCH

New U.S. fed­eral drink­ing-wa­ter reg­u­la­tions ban open-air reser­voirs, and places like L.A. are scram­bling to meet the new rules. Be­cause the shade balls aren’t con­sid­ered an ac­cept­able cover, the LADWP is re­plac­ing them with im­per­me­able plas­tic sheets. But be­cause the L.A. reser­voir is too big to cover in a cost-ef­fec­tive man­ner, the shade balls will stay in­def­i­nitely, and au­thor­i­ties will treat the wa­ter on its way out of the reser­voir. The shade balls pulled from the other reser­voirs will be re­cy­cled.

Los An­ge­les Mayor Eric Garcetti dumps a bag of “Shade balls” into the L.A. reser­voir in Au­gust 2015.

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