Makes a lot of sense, cuts losses to the air and uses 'vacant land'. Still, a side to side bridging frame will be needed as well as potential support in the middle area - perhaps by cable?
There may also be other aqua culture aspects - fish? Fish pee will fertilize the iffigation water. This would depend on minimum water levels. Waste plant materials can also feed some breeds of fish, and agriculture makes this at certain seasons.
From the article it seems like the two systems work well together. I'd like to see more mixed infrastructure like this around me, but I'm sure there's logistics issues more complicated than "throw some solar panels in a highway median".
A readily available water source would also simplify setup of an auto-cleaning system.