This is the subheading from a Nature comment piece last week:
Covering 10% of the world’s hydropower reservoirs with ‘floatovoltaics’ would install as much electrical capacity as is currently available for fossil-fuel power plants. But the environmental and social impacts must be assessed.There is mention of the benefits:
Placing solar arrays on reservoirs could have many advantages. The arrays are simply conventional solar panels installed on floats that are anchored through mooring lines. Proximity to water tends to keep them cool, making floating panels about 5% more efficient than land-based ones7. Arrays shield the surface from the sun and might reduce evaporation, retaining water for hydropower, drinking and irrigation8. Hydropower reservoirs already have the grid infrastructure for conveying electricity to consumers, reducing transmission costs. Pairing solar with pumped-storage hydropower could address the twin challenges of providing energy when sunlight is weak and storing it as potential energy in reservoirs when solar-power production is high9.
I've been saying this for some time....