Seems like you'd be much better off floating them on a lake. There was a project a few years ago to do this both for power and to reduce evaporative loss in reservoirs, but I don't know if anything has come of it.
Putting solar cells on top of (artificial) lakes not only decreases evaporation, but also cools the solar cells, making them more efficient.
It's technically easier to put things on land if possible.
https://www.veritasium.com/videos/2019/5/23/why-are-96000000...
This NatGeo article from 2015, https://www.nationalgeographic.com/news/2015/08/150812-shade... , notes for example that they kill algae and microorganisms, and inhibit water-fowl.
I'm almost certain they'd kill lake-born fish too, preventing growth of water-borne oxygenators (which also serve as a food source, and place for eg snails to live).
Whilst the purpose appears to be to prevent plant and animal life, at least in part, it's possible a stable eco-system might still survive; but it seems highly unlikely to me -- do you have something to show me I'm wrong in my assumption?
https://www.sciencealert.com/here-s-what-s-really-going-on-w...
The death tolls of historical urban outbreaks shows that you would MUCH rather drink the treated water.
If through your process of learning, you come up with an understanding of any situation, then you should form an opinion.
I don't mean to be rude but your question is easily answerable by reading the article I linked (and it's a short one). If you're not going to take the 30 seconds to respect my comment, I will show none to your uninformed opinion.
Though I'm not familiar with the specifics and details of this case (and have seen the Veritasium video describing the use), it's reasonable to assume that these treatments would be applied regardless, and the shade balls are an effective countermeasure.