I think that in case of PVs in arid areas we will observe a very beneficial correlation between PVs energy yield and energy demand for AC (as you said). In my opinion they have a huge potential to shave the peak load. Take a look for example at a recent paper by Sebastian Sterl et al., (http://iopscience.iop.org/article/10.1088/1748-9326/aad8f6/meta) where they proposed a new index for assessing solar-wind hybrids operation and discussed it in case of West Africa countries.
When it comes to coupling PVs with another sources I can recommend you some papers by Bo Ming and myself where analysis was performed for PV-hydropower hybrid systems.
Although I don't know how huge is the potential of hydropower in "arid regions". However, this is an interesting research direction. We (@Bartłomiej Ciapała) addressed this issue in our recently published in Solar Energy paper, where we have analysed the PV-hydrpower operation also from the water retention perspective.