Amagase Dam
Encyclopedia
The is an arch dam
Arch dam
An arch dam is a type of dam that is curved and commonly built with concrete. The arch dam is a structure that is designed to curve upstream so that the force of the water against it, known as hydrostatic pressure, presses against the arch, compressing and strengthening the structure as it pushes...

 on the Uji River just upstream from Uji City
Uji, Kyoto
is a city on the southern outskirts of the city of Kyoto, in Kyoto Prefecture, Japan. Founded on March 1, 1951, Uji is located between the two ancient capitals of Nara and Kyoto. The city sits on the Uji River, which has its source in Lake Biwa. As of April 1, 2008, Uji has an estimated population...

 in Kyoto Prefecture
Kyoto Prefecture
is a prefecture of Japan located in the Kansai region of the island of Honshu. The capital is the city of Kyoto.- History :Until the Meiji Restoration, the area of Kyoto prefecture was known as Yamashiro....

, 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
Kansai Electric Power Company
, also known as , is an electric utility with its operational area of Kansai region, Japan . The company is regarded as one of the leading companies in Kansai, as well as a leader of the Japanese electric power industry....

.

Design

The dam is a 73 m (240 ft) tall, 254 m (833 ft) long variable-radius arch type with structural volume of 162000 cubic metre. The dam withholds a reservoir called of 26280000 cubic metre of which 20000000 cubic metre is active or "useful" storage. It has a surface area of 1.9 km² (0.733594101325817 sq mi).

The dam's spillway
Spillway
A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically being the river that was dammed. In the UK they may be known as overflow channels. Spillways release floods so that the water does not overtop and damage or even destroy...

 consists of four 4.36 m (14 ft) x 10 m (33 ft) floodgate
Floodgate
Floodgates are adjustable gates used to control water flow in flood barriers, reservoir, river, stream, or levee systems. They may be designed to set spillway crest heights in dams, to adjust flow rates in sluices and canals, or they may be designed to stop water flow entirely as part of a levee or...

s 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 (12 ft) x 4.7 m (15 ft) 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°53′42"N 135°51′13"E that is 91 m (299 ft) high, 255 m (837 ft) long and has a crest width of 11 m (36 ft). The dam also has structural volume of 2338000 cubic metre and withholds a reservoir of 7227000 cubic metre of which 5408000 cubic metre is active storage. From the upper reservoir, water can be released back down to the power station 34°53′30"N 135°51′34"E where the two 233 MW reversible Francis turbine
Francis turbine
The Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, Massachusetts. It is an inward-flow reaction turbine that combines radial and axial flow concepts....

 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 (971 ft) above sea level while it is 78.5 m (258 ft) ASL in the lower reservoir. This affords the power station an effective hydraulic head
Hydraulic head
Hydraulic head or piezometric head is a specific measurement of water pressure above a geodetic datum. It is usually measured as a water surface elevation, expressed in units of length, at the entrance of a piezometer...

 of 219.35 m (720 ft). 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.
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