In this case there's a desire to cover the canals anyway for evaporation reasons. There's a reason you see a lot of solar covered parking: once you're already building the structure to support a cover, it doesn't drive up the structure cost that much to make it racking for solar panels. So this kind of thing can produce a real cost savings, by installing solar in situations where the supporting structure is desirable for independent reasons.
Yeah, solar panels have become really cheap. I am looking into covering a flat roof with solar. The support structure (nothing super fancy) will probably turn out to be more expensive than the panels themselves.
