No real particular reason why it shouldn't work if there is more than enough solar and wind power operating there to keep the reservoirs full and provide power to the consumers at the same time.Whether it works or not depends on the size and height of the reservoirs relative to the supply and demand. There can be supply gaps and shortages of several days to a week coinciding with high demand - in the regular grid there are usually provisions for 3-6 months of backup available for worst case considerations, such as war or natural disaster that disrupts fuel supply. 22,000 olympic size swimming pools is 22,000 x 2,500 m3 = 55 billion kilos of water.24h x 300 MW converts to 26 terajoules of potential energy and by the simple equation e=mgh we see that 55 billion kilos needs to be lifted up by a mere 48 meters. Twice that if you account for efficiency and evaporation. That's a normal run-of-the-river hydroelectric plant with a rather large 15 sq-km lake behind it.
