when power generation is required, water is released from either upper reservoir back down to the power station and its generators. the power station is located underground and consists of transformer, valve gallery and generator hall caverns. from the chiotas reservoir, water is sent back through a long tunnel and when near the power plant, it splits into a system of penstocks which feed each of its eight pump-generators. water from the rovina is processed by a single generator. after the water is used for power generation, it is discharged into a long tail-race tunnel and into lago della piastra. both the tail-race and power plant intake are protected from water hammer by surge tanks. the drop in elevation between the upper reservoirs and the power plant afford the chiotas a maximum hydraulic head of and the rovina .