The article describes artificial reservoirs as the water body of choice, which are less complex (partly because they already destroyed the ecosystem that was there) than naturally forming lakes, and has the added benefit of reducing solar driven evaporation in the same vein as this[0]

[0]https://www.youtube.com/watch?v=uxPdPpi5W4o

This seems to be most important part. It could be beneficial as prevents evaporation and warming. LA reservoir even has floating balls for this https://www.nationalgeographic.com/science/article/150812-sh...

All local impacts have to be weighed against the global impact of CO2 emissions.

It's an area of open research, but especially if it doesn't cover 100% of the water body it's fairly benign: https://www.sciencedirect.com/science/article/pii/S136403212...

For instance, birds perch on the panels, turtles loaf on the floats, fish hide from predators under them. It changes the water body, but not in a way that would be different from, say, trees that have fallen halfway into the water and are shading part of the surface.

If you space them out enough you wouldn’t have huge areas of no sun. It would emulate an ecosystem of water under shade trees. Shade actually attracts a lot of biodiversity.

Including canals, which the author disclaimed for some reason. Here at least they have all kinds of aquatic and bird life.