We have a plant like that here in CA, called the Helms project. 2 lakes, one uphill from another, connected by a tunnel through a mountain. During peak load periods, water is released down the tunnel and through turbines. When loads are lower, water is pumped back uphill to the upper lake, using... power from Diablo Canyon!. Funny how when they want RELIABLE power, they turn to the nukes again and again. I suppose that wind power could be used, if enough was out there. They could re-open the Altamont setup (it’s dead because it kills birds) and use the Pacheco Pass wind turbines also.