Solar has become so cheap that the bottleneck is the interconnection queue - utilites are overwhelmed by the amount of modelling that they have to do to ensure

Solar has become so cheap that the bottleneck is the interconnection queue - utilites are overwhelmed by the amount of modelling that they have to do to ensure the stability and capacity of the grid with the addition of more renewables. (There are a number of ways that they make this harder for themselves. These processes are very much not built for intermittency.) Hydropower plants are already permitted and connected generators. They are allowed to produce energy for sale onto the grid. From the utility's perspective, adding solar to a hydropower plant is the same as if there was a year with extra rainfall - the maximum (and reserve) power limits will still be adhered to, but more total energy will come from that single source. (Note that solar on the ground right next to the hydropower plant would have the same benefits without the additional costs of floating, but often hydropower plants are built in geographies that are more challenging for ground-mounted solar - they're either extremely hilly or built out.)