Ueno Dam is a hydroelectric power dam located in the uppermost reaches of the Kanna River, part of the Tone River system, in Ueno Village, Tano District, Gunma Prefecture.
Standing deep in the mountains and surrounded by rich natural scenery, the dam has an imposing 120-meter-high concrete structure. The reservoir created by the dam is known as Oku-Kanna Lake, where the surrounding mountains are reflected beautifully in the water throughout the seasons.
Together with Minami-Aiki Dam in Minami-Aiki Village, Nagano Prefecture, Ueno Dam plays an important role in the Kanna River Power Station, one of the world’s largest pumped-storage hydroelectric power facilities.
The site has two distinct attractions: the peaceful beauty of a mountain landscape and a remarkable example of advanced engineering that supports Japan’s electricity supply.
Ueno Dam is a hydroelectric power dam operated by TEPCO Renewable Power, Inc. It is a 120.0-meter-high gravity concrete dam.
It is the sixth-highest dam in the Tone River system and is also among the largest dams in Japan built exclusively for hydroelectric power generation.
The reservoir has an effective storage capacity of approximately 12.67 million tons, roughly comparable to that of Minami-Aiki Dam, the upper reservoir of the system.
The two dams have an elevation difference of approximately 653 meters. This enormous difference in elevation is utilized by the pumped-storage system, which was planned to generate up to 2.82 million kilowatts of electricity when fully developed. Some generating units are currently in operation.
Oku-Kanna Lake, the reservoir created by Ueno Dam, is a quiet mountain lake surrounded by the clear waters of the Kanna River and densely forested mountains.
The view from the dam site is particularly impressive, with the lake stretching toward the surrounding mountain ranges. On sunny days, the clear blue sky and calm water create a striking landscape.
Although the lake is artificial, its setting blends remarkably well with the surrounding natural environment, making it an attractive destination for visitors who enjoy mountain scenery and photography.
Connecting Ueno Dam and Minami-Aiki Dam is the Kanna River Power Station, constructed approximately 500 meters underground.
Pumped-storage hydroelectric power works by pumping water to the upper reservoir during periods of low electricity demand, such as at night. During periods of high demand, the water is released downward through turbines to generate electricity.
This system makes efficient use of electricity and helps maintain a stable power supply by allowing large amounts of generating capacity to respond to changes in demand.
Units 1 and 2 are currently in operation. If all six planned generating units are eventually completed, the facility is expected to become one of the largest pumped-storage power stations in the world.
Free guided tours are also available, providing opportunities to see the enormous underground spaces and power-generating equipment at close range. Tours can accommodate both individual visitors and organized groups or educational programs.
The Kanna River is an important tributary of the Tone River system. TEPCO identified the upper reaches of the Kanna River as a promising location for a major new power-generation project following the development of other pumped-storage facilities.
The resulting plan was an ambitious pumped-storage hydroelectric project spanning two separate river systems: the Tone River system and the Shinano River system.
As part of the project, Minami-Aiki Dam was constructed on the Shinano River side and Ueno Dam on the Tone River side.
Construction of the Kanna River Power Station began in 1995. The main body of Ueno Dam was completed in 2003, and both dams were completed in 2005.
To improve construction efficiency, Ueno Dam employed what is known as a rationalized construction method.
The main dam was built using the RCD method, a construction technique commonly used for large dams, while an extended layer method was used for the auxiliary dam.
The use of two different construction techniques within a single dam project is relatively unusual and represents one of the technically noteworthy aspects of Ueno Dam.
Because Ueno Dam was constructed in a remote mountain environment, protecting the surrounding ecosystem was an important consideration throughout the project.
Rare plants, including rhododendrons and Futaba-aoi, were transplanted, and efforts were made to restore vegetation disturbed during construction.
Strict standards were also established for the treatment of turbid water in order to protect water quality.
These environmental initiatives were recognized when the project obtained ISO 14001 certification, the international standard for environmental management systems, in 2002.
After the dam was completed, discharge facilities were installed to ensure that a necessary amount of water continues to flow downstream.
This helps maintain stable river conditions and reduces the impact of the dam on fisheries and the river ecosystem.
Ueno Dam can be viewed by visitors, with open areas provided on both sides of the dam.
It is also possible to walk down to the area directly below the dam, where visitors can appreciate the enormous scale of the structure from close range.
Walking along the surrounding paths provides opportunities to enjoy the clear waters of the Kanna River and the lush greenery of the mountain landscape.
Several attractions are located around the dam, including Hampei Hot Spring “Shioji no Yu,” the National Folk Toy Museum, and the Motoya Special Fishing Area.
Combining a visit to the dam with a relaxing hot spring bath or freshwater fishing offers an enjoyable way to experience the slower pace and natural beauty of a Japanese mountain village.
Ueno Dam Cards are available at the Ueno Village Industrial Information Center and Shioji no Yu.
Visitors can receive a card by presenting a photograph proving that they visited the dam. These collectible cards are particularly popular among dam enthusiasts in Japan.
From Shinmachi Station on the Takasaki Line or Gunma-Fujioka Station on the Hachikō Line, take a local bus to Shioji no Yu. The journey takes approximately three hours, followed by a walk of approximately 3 kilometers.
From the Shimonita Interchange on the Joshinetsu Expressway, a relatively convenient route is to travel via National Route 254 and then Gunma Prefectural Route 45.
Visitors approaching from Nagano Prefecture can travel via Budo Pass or Jikkoku Pass. These are mountain roads, however, so drivers should exercise particular caution.
Ueno Dam is much more than a hydroelectric facility. It represents an impressive combination of natural scenery and advanced civil engineering, forming part of a vast pumped-storage power project.
The tranquil waters of Oku-Kanna Lake, the enormous underground power-generation facilities, and the surrounding mountains create a unique destination where visitors can experience both Japan’s engineering achievements and its unspoiled natural environment.
When visiting Ueno Village in southwestern Gunma, consider including Ueno Dam and Oku-Kanna Lake in your itinerary to discover a fascinating side of Japan where energy infrastructure, mountain landscapes, and local life come together.