Amagase Dam

The Amagase Dam (天ヶ瀬ダム) is an arch dam on the Uji River just upstream from Uji, Kyoto Prefecture, Japan. The main purpose of the dam is flood control but it supports a hydroelectric power station and creates the lower reservoir for the Kisenyama Pumped Storage Plant. The dam itself serves a 92 MW power station while the pumped-storage power station upstream has a 466 MW capacity. Construction on the dam began in 1955 and it was complete in 1964. The pumped-storage power station became operational in 1970. Both plants are owned by Kansai Electric Power Company.

Design
The dam is a 73 m tall, 254 m long variable-radius arch type with structural volume of 162000 m3. The dam withholds a reservoir called Lake Hōō (鳳凰湖) of 26280000 m3 of which 20000000 m3 is active or "useful" storage. It has a surface area of 1.9 km2.

The dam's spillway consists of four 4.36 m x 10 m floodgates on its crest with a maximum discharge capacity of 680 m3/s. In the middle of the dam body, there are three 3.6 m x 4.7 m gate-controlled orifice openings with a maximum discharge of 1110 m3/s. The dam's power station has a 92 MW installed capacity and a discharge capacity of 186 m3/s.

Kisenyama Pumped Storage Plant


Using Lake Hōō as the lower reservoir, water is pumped up to the upper reservoir via two pump-generators. The upper reservoir is created by a rock-fill dam 34.895°N, 135.85361°W that is 91 m high, 255 m long and has a crest width of 11 m. The dam also has structural volume of 2338000 m3 and withholds a reservoir of 7227000 m3 of which 5408000 m3 is active storage. From the upper reservoir, water can be released back down to the power station 34.89167°N, 135.85944°W where the two 233 MW reversible Francis turbine pump-generators use it for power production.

This process can be repeated and generation usually occurs during peak usage periods. The high water level at the upper reservoir is 296 m above sea level while it is 78.5 m ASL in the lower reservoir. This affords the power station an effective hydraulic head of 219.35 m. Its discharge capacity is 248 m3/s. The first generator of the pumped-storage power station was operational in January 1970, and the second in July of that year. It has a maximum output of 466 MW.