Hiyoshi Dam (日吉ダム)

Located in around Hiyoshicho-naka, Nantan City, Kyoto Prefecture (formerly Hiyoshi-cho, Funai-gun), Hiyoshi Dam is built over the middle reaches of the Katsura-gawa River which is one of the subsidiary streams of the Yodo-gawa River.

The Development of the Katsura-gawa River
The major project of the improvement of the Yodo-gawa River System started after Typhoon Thirteen of 1953 caused massive damage to the Yodo-gawa River area for the first time after the Second World War. The Economic Stabilization Agency made the 'Revised River Improvement Plan' in 1949, and based on which the 'Revised the Yodo-gawa River System Basic Plan' was decided in 1954, in which the building of multipurpose dams was planned for the first time to control floods. Based on this plan, the Setagawa-araizeki Barrage was upgraded, and Amagase Dam over the Yodo-gawa River, Takayama Dam (initially Tsukigase Dam) over the Nabari-gawa River, and Muro Dam (initially Udagawa Dam) over the Uda-gawa River were built.

In 1962, for the Yodo-gawa River System, the 'Yodo-gawa River System Water Resources Development Basic Plan' was created based on the 'Water Resources Development Promotion Law' in order to cope with pressing water demands due to the growing population in the Kansai region. In accordance with that, Water Resources Development Public Corporation (now Japan Water Agency) planned and built Shorenji Dam over the Shorenji-gawa River, and Nunome Dam over the Nunome-gawa River. In the course of the comprehensive development of the Yodo-gawa River System, in relation to the Katsura-gawa River which is a main subsidiary stream as important as the Yodo-gawa River and the Kizu-gawa River, a plan to build a dam at a place close to the boundary of the then Sonobe-cho and Hiyoshi-cho (Kyoto Prefecture) based on the 'Revised Yodo-gawa River System Basic Plan' emerged in 1961.

This dam plan, originally called 'Miyamura Dam,' developed to be the subsequent Hiyoshi Dam Project.

History
Although Hozu-kyo Valley around the middle reaches of the Katsura-gawa River (this part of the river is also called the Hozu-gawa River) is a major sightseeing spot that attracts many tourists for river rafting and the scenic beauty of Mt. Arashi, this valley had serious problems in terms of flood control. Hozu-kyo valley is so narrow that it inhibits the flow of flood water caused by heavy rain and easily inundates Kameoka City and Funai-gun County upstream, acting as a natural flood control basin. This situation is very similar to the relationship between Tenryu-kyo valley of the Tenryu-gawa River and Iida City, and likewise floods have caused damage to Kameoka Basin many times over the centuries. Building barrages and dredging the river bed had only a limited effect, and it was almost impossible to improve the river further because of compensation issues, while there were growing calls for fundamental flood control measures, and demand for water was rapidly increasing due to the rapid growth of the population in the Kansai region.

In 1971, the Construction Ministry (now Ministry of Land, Infrastructure and Transport Kinki Regional Development Bureau) devised the 'Yodo-gawa River System Construction Implementation Basic Plan,' and revised flood water estimates for the first time since the Isewan (Ise Bay) Typhoon. So in order to achieve better flood control, the building of Hinachi Dam (over the Nabari-gawa River) was planned and flood control using dams was also demanded for the Katsura-gawa area.
Hiyoshi Dam was incorporated in this basic plan as a major dam project, but at that time it was named 'Miyamura Dam.'
The Water Resources Development Public Corporation revised the 'Yodo-gawa River System Construction Implementation Basic Plan' and it was planned to construct the dam as a multipurpose dam based on the 'Water Resources Development Public Corporation Law' the same year.

The Lake bottom Concert(湖底コンサート)by Kosetsu MINAMI was staged just before the lake was filled with water.

It is a concrete gravity dam of 70.4 m in height. It was completed in 1997, twenty-five years after the announcement of the plan to construct it, with the following purposes; flood control, the description of specifications and purposes of dams in Japan (maintaining the current flow of the Katsura-gawa River, and protecting the natural river environment), and the supply of drinking water to Osaka City, Kyoto City, Kobe City, Nishinomiya City, and Ashiya City.

Success in Revitalizing the Town
Because 188 households in Hiyoshi-cho were to be submerged through the building of this dam, the residents formed 'Hiyoshi Dam Taisakukyogikai Amawaka Domei' (Amawaka Association, Hiyoshi Dam Opposition Movement) in 1961 when the plan to build 'Miyamura Dam' was announced, and they staged an uncompromising opposition movement against the plan involving people of the whole town for twenty-four years until September 1984 when the compensation negotiations were settled. The negotiation finally reached settlement based on the following conditions: (1) the designation of this dam for Chapter Nine of the Act on Special Measures concerning Measures Related to Water Resources Areas, (2) raising the share of national subsidy for compensation, and (3) the implementation of comprehensive measures for regional economic development.

As a result, the Water Resources Development Public Corporation used the dam from the early stages of construction to help the people of Hiyoshi-cho with regional economic development. In 1994, when it was still under construction, regarding dams and dam lakes as essential for regional development, the Construction Ministry promoted the policy of 'Dams Friendly and Open to the Regions' in the aim of making dams contribute to regional economic development by actively opening them to the public and by promoting them as tourist attractions. Hiyoshi Dam being the first to be designated for the measures, systematic and wide spread development of the neighborhood was carried out in cooperation with Hiyoshi-cho and other organizations. At the downstream side of the dam, they constructed a hot spring facility 'Springs Hiyoshi,' which is equipped with hot springs, a swimming pool, and a gymnasium, and planted grass over a wide area to create a park with a camp site. They also built Hiyoshi-cho Kyodoshiryokan (Hiyoshi-cho Town Folk Museum) and Kyoto Fumin no Mori (Kyoto Prefectural Citizen's Forest) in the area, and the dam lake, Lake Amawakako, became popular as the best spot for fishing in the north of the Kansai region, with a reciprocal effect of creating an extensive outdoor pleasure spot including Ono Dam and Wachi Dam which had long been famous in the country for bass fishing, and the Yura-gawa River which provided a course for the canoe competition at Kyoto Kokutai (National Sports Festival) in 1963. A walking trail around the dam lake was made fit for hiking, marathons and jogging. This dam is also popular with people in neighboring cities, because its access roads are maintained in a better condition than other dams, and it is close to major arterial roads such as Sonobe Interchange of National Route 9, Kyoto Longitudinal Expressway, National Route 372, and National Route 477.

Thus, as a result of the cooperation of the administrators of the dam and the residents who had sacrificed their lands for the dam and for regional development, the area around Hiyoshi Dam grew to be a major leisure area for the people of Kyoto Prefecture, and it is now an established sightseeing spot in Tanba region. It makes an economically significant contribution to the area, because a growing number of tourists visit Michi no Eki (a roadside rest site with a market of local products aimed at tourists) and other commercial facilities on their way to this dam. The research of the Ministry of Land, Infrastructure and Transport on the number of yearly visitors to dams under the direct control of the ministry and under the Japan Water Agency shows 870,000 people visit this dam per year, second to Gosho Dam in Iwate Prefecture (the Shizukuishi-gawa River of Kitakami-gawa River System, Ministry of Land, Infrastructure and Transport Tohoku Regional Bureau). This is a rare example of success as a public facility that many citizens use, whereas many useless public facilities are seen as a problem across the country.

This dam was on a postage stamp in 1998 after it was completed. Other dams that were once on postage stamps are all major large dams in Japan: Sakuma Dam (the Tenryu-gawa River), Ogochi Dam (the Tama-gawa River), Kurobe Dam (the Kurobe-gawa River), and Nukui Dam (the Takiyama-gawa River).

Lake Amawakako

The man-made lake of the Hiyoshi Dam was named 'Amawakako' (Lake Amawakako) after the name of the area that went under water. In 2005, Hiyoshi-cho Town successfully recommended this lake to be included in 'Selected 100 Dam Lakes' by the Water Resources Environment Technology Center. Many athletes in and out of the prefecture come to compete in 'Hiyoshi Dam Marathon' on the lakeside road every April. Also, every June, many motor sports fans visit the area to see 'Kyoto Nantan Rally,' the all Japan rally championships.

One of the Best Fishing Spots in the Kansai Region

Lake Amawakako is famous for being one of the best fishing spots in the Kansai region. Anglers for black bass visit this lake in large numbers both on weekends and weekdays, because both Ono Dam and Wachi Dam which are in the area have long been famous in the country for bass fishing. Because black bass had been released in the lake created by Segi Dam upstream, many big fish of ranker size have been caught since Hiyoshi Dam was completed. It is very popular with bass anglers, because it has a variety of fishing points and is a good size where it is possible to cover all the points in a day.

There is a rental shop for fishing boats equipped with an electric trolling motor, and it acts as a base for bass fishing tournaments several times a year.

Also, since it is located in a suburban area, it is often used as a site where professional bass anglers are filmed, and often appears on TV, in specialized fishing magazines, and in fishing newspapers.

Because its good location and popularity produce a high revenue from fishing fees, it exists in harmony with the local fisheries cooperative association.

Japanese Giant Salamander

The water quality was proved to be maintained at a high level by the fact that a Japanese giant salamander, which is designated as a special national treasure and also as an endangered species, was discovered here in 2006.

Segi Dam

Segi Dam, the next dam upstream, was built to serve as a exclusively hydroelectric power plant for Kansai Electric Power Co., Inc. in 1951. Its body is a concrete gravity dam of 35.5 m in height. More than eighty percent of the dam went under water after the construction of Hiyoshi Dam, and all the gates installed on the dam were removed. As it is not completely under water, it still serves in the generation of power as a overflow dam. It is therefore different to the case of Shizugawa Dam that was completely submerged after the construction of Amagase Dam.

A rare example of a dam that still maintains its function even with more than a half of it under water is Numamoto Dam (also known as Tsukui Dam) which is over the main stream of the Sagami-gawa River, and although more than half of its body is under the water of Lake Tsukuiko created following the construction of Shiroyama Dam downstream, it still functions today.