Well, it’s certainly better than solar-freakin-roadways, but any time a “put solar on [thing]” project is proposed, it’s important to consider the relative cost and complexity of doing that instead of just building [thing] normally and putting a ground mount solar installation nearby. In this case, it seems like the primary benefits of putting solar on canals are:

1. Conserves water by reducing evaporation from the canals.
2. Increases efficiency and possibly lifetime of the panels by keeping them a bit cooler
3. Doesn’t require developing new land in areas where a canal is already present.

Water conservation could be achieved by a shade structure without solar panels attached. That would presumably also be cheaper to build and require less maintenance. I’d be interested to see numbers for the efficiency and lifetime claims. It’s well known that solar panels run better when they’re kept cool, but I question whether the effect is large enough to outweigh the downsides. As for land use, that’s absolutely true in areas where land is in demand, but most of these installations seem to be in remote areas with plenty of unused space on all sides.

Not a terrible idea overall, but I’m not convinced that the cost/benefit pencils out unless you assign a lot of value to being able to claim that your solar installation is “innovative” compared to all the others.