Let me guess, those balls are made of plastics (made in China), so they stay above the water line - surely with plasticizer and maybe even other stuff you don't want to drink/eat which will surely dissolve into the water over time. So they are trading a future with less water for a future with more or less poisonous water...

Simple question. Doesn't the black color of the balls encourage heating, which would lead to increased evaporation rates and a potential increase in algae growth?

Compared to white ping pong balls? I hope these have good UV resistance.

I thought the same thing surly mirror balls would be more effective

Not sure here but why not lily pads growing in the reservoir. They could provide shade naturally and produce other benefits while shading the pool without toxic plastic intervention and cost. Nature usually has the best solutions. I guess no one will make money on this so .....nevermind.

They are made in Glendora (suburb of Los Angeles) and are a food-safe plastic. What that exactly means? I dunno - but shouldn't be any worse than the crap that ends up in there from birds, wildlife, pollution, whatever. . . the water gets treated before it goes into supply.
Supposedly the black color doesn't hurt because the plastic doesn't conduct heat that much and since they're (mostly) hollow they act as an insulator. (there is a small amount of water in them to keep them from blowing away, evidently.)

50 million dollars to save enough water for 8,000 people for a year ... thats $6,250 per person ... couldn't they just buy water from Arizona cheaper ?
how about not releasing 50% of the water to save a baitfish ? maybe only release 45% ... would save enough water for millions of people for a year ...

what could possibly go wrong?

Black is better for UV stabilization in plastics so they will last longer. Either way I'd hate to be the person that has to clean this up when the time comes.

The number of balls needed to cover a reservoir is preposterous. These balls will deteriorate from the sunlight and violent wave action during storms. Their pieces will clog the aquifers and end up polluting the environment. This is another obviously very bad idea.