Amagase Dam (天ヶ瀬ダム)

Located in Uji City in Kyoto Prefecture, Amagase Dam is on the Uji-gawa River, the common name of the middle reaches of the main stream of the Yodo-gawa River, which is known as a first-class river.

This is a ministry-controlled dam under the Kinki Regional Development Bureau of the Ministry of Land, Infrastructure and Transport, and it is the only dam built on the main stream of the Yodo-gawa River, one of the greatest rivers in western Japan. Measuring 73.0 meters in height, it is an arched dam of concrete, built as a specified multipurpose dam with the multiple aims of the flood control of the Uji-gawa River, supplying drinking water to Uji City, and the hydroelectric power generation of up to 598-thousand watts. There is a plan in place for a renewal project, featuring the construction of a bypass tunnel to extend the functions of the dam. The lake made as a result of the construction of the dam is named Lake Ho-o, and is an important tourist attraction in the Uji area along with Hoo-do Hall (the Phoenix Pavilion) of Byodo-in Temple.

History
The Yodo-gawa River is an extremely important water resource that runs through two of Japan's major cities, Osaka and Kyoto, and the utilization of its water and flood-control of the river have been regularly carried out from ancient times, but even so frequent floods repeatedly caused problems for rulers in those days.

Excessive logging after the War caused many floods across the country including at the Yodo-gawa River, where Typhoon 13 of the 1953 season broke the levees of the Uji-gawa River and inflicted serious damage to Uji City and the areas around the river. The fact that Typhoon 13 caused the greatest volume of flood water yet at the Yodo-gawa River made the Kinki Regional Construction Bureau of the Construction Ministry (the present Kinki Regional Development Bureau of Ministry of Land, Infrastructure and Transport) implement 'the Basic Plan to Repair the Yodo-gawa River System,' a drastic measure of flood control throughout the Yodo-gawa River area. The building of Amagase Dam was included in this plan. Among the many dams of the Yodo-gawa River System, this dam is the only dam and the first multipurpose dam built on the main stream of the Yodo-gawa River.

Measuring 73.0 meters in height, it is an arch type concrete dam of the 'concrete dome arch dam' type. Although this type is very hard to design, it is economically advanced because it uses less concrete than other types. This design was first applied to Tonoyama Dam (Hiki-gawa River), and later to major dams in Japan such as Kurobe Dam (Kurobe-gawa River).

Amagase Dam is a multipurpose dam not only for flood control and the supply of drinking water to the south of Kyoto Prefecture, but also for hydroelectric generation at Amagase Power Station, which was built to replace the power plant of Kansai Electric Power Co., INC. at Shizugawa Dam (Omine Dam: a concrete gravity dam of 31.2 meters in height) which was submerged as a result of the construction of Amagase Dam. This power plant and Kisenyama Power Station at Kisenyama Dam which was completed in 1970 generate power by pumped-storage hydroelectricity (permitted output: 466,000 kW).

The Dam as a Tourist Attraction

It is an "urban type" dam close to Uji City. Within as little as 2.3 km from this dam are Byodo-in Temple (a World Heritage Site), Uji-bashi Bridge, and Amagase Forest Park. Many tourists visit this dam by sightseeing bus, because it is close to Kyoto City, and from here Keiji Bypass provides easy access to Otsu City, Mt. Hiei, and Ishiyama-dera Temple. This dam is also popular among elementary school children in the Kansai region, who visit it on school excursions or social studies trips. The lake was named 'Lake Ho-o' in 1987, because it is close to Hoo-do Hall of Byodo-in Temple and the dam body looks like a ho-o (a phoenix) with its wings extended. It has also scenic spots of cherry blossoms and colored leaves.

The 'Renewal Plan of Amagase Dam' had been underway since 1989 to strengthen the functions of flood control and to build the biggest tailrace tunnel in Japan for a greater utilization of its water. However, the plan was reassessed in 2003 due to opposition movements and a decline in water demand. Although the Ministry of Land, Infrastructure and Transport intends to continue this project, the Yodo-gawa River System Committee has recommended to abandon the plan, so the project is considered to be unlikely to reach completion.