Imaichi Dam

The Imaichi Dam (今市ダム) is a concrete gravity dam on the Togawa River located 4 km west of Nikkō in Tochigi Prefecture, Japan. The dam serves as the lower reservoir for the 1050 MW Imaichi Pumped Storage Power Station, while the Kuriyama Dam forms the upper. It is owned by TEPCO and was constructed between 1979 and 1986. The reservoir can store 9100000 m3 of water. Of that storage volume, 6200000 m3 can be used for power generation.

Imaichi Pumped Storage Power Station
The power plant operates using the pumped storage hydroelectric method. During periods of high electricity demand, water is sent from the upper Kuriyama Reservoir to the power plant which contains 3 x 350 MW Francis pump turbines. Water discharged from the power plant then enters the Imaichi Reservoir. When demand is low, the pump-generators reverse mode and pump water from the lower reservoir back up to the upper. The process repeats as needed.