seems reasonable as far as space utilization and reducing evaporation. I'm sure that there will be other unappreciated consequences mostly related to biology, e.g. algal/fungal/mosses and other growths and recolonization effects. I'd bet that the back sides of the panels act as condensers which might create other problems. Humans being human, i also think vandalization will be a huge and eventually fatal problem.
It's being done already in India and seems to be working fine. The reason for doing it in India may be different as farmland is in much shorter supply there compare to water. There is no shortage of sunny hills in central CA where the canals are so shading the water to conserve water is perhaps a valid idea. Would love to see how they estimate the amount of water saved due to less evaporation. That versus putting solar panels on the ground and using excess electricity to desalinate.
News 
Market Data 
Discover 
