Some more context around this news article about Mount Baldy placing these 4" plastic balls into their snowmaking reservoir
Basically, this company Xavier C- http://www.reduceskiareareservoirevaporation.com - makes these floating plastic balls. They just dump them into the reservoir and they apparently reduce evaporation by 90%. The Mt. Baldy CEO says evaporation costs them something like $120k a year so if they can reduce it 90%, that's pretty significant.