A 140-Meter-High Gravity Concrete Dam
Kusaki Dam is a 140-meter-high gravity concrete dam and is one of the largest dams in the Tone River system. Its total storage capacity is approximately 60 million tons of water, making it an important water resource for the greater Tokyo metropolitan area.
The dam was completed in 1977. It was originally known as “Kambe Dam,” but the name was later changed to Kusaki Dam in response to a request from the local community.
The Important Roles of Kusaki Dam
Flood Control and River Management
During periods of heavy rainfall, Kusaki Dam stores large amounts of water and controls the flow released downstream. This helps reduce the risk of flooding and protect communities and farmland along the Watarase River.
The dam was designed with large-scale flood events in mind, including rainfall conditions comparable to those associated with the Typhoon Kathleen floods. Since its completion, it has played an important role in improving flood safety throughout the river basin.
Water Supply for the Tokyo Metropolitan Area
Kusaki Dam supplies water for municipal and industrial use to areas including Tokyo, Saitama, and Gunma. It also contributes to a stable supply of agricultural water, supporting farming communities in the surrounding region.
Together with Watarase Reservoir, also known as Lake Yanaka, Kusaki Dam forms part of the important network of water resources supporting the wider Tokyo metropolitan area.
Hydroelectric Power Generation
Water released from Kusaki Dam is also used for hydroelectric power generation. The Toho Power Station directly below the dam works together with other downstream facilities to generate electricity.
The combined facilities can produce up to approximately 61,000 kilowatts of electricity, giving the dam an additional role as a source of renewable energy.
Lake Kusaki – A Scenic Dam Reservoir
Lake Kusaki was selected as one of Japan’s “100 Best Dam Lakes” in 2005. The shoreline stretches for approximately 12.4 kilometers and offers beautiful scenery throughout the seasons.
In spring, cherry blossoms add color to the lakeside. Fresh green foliage dominates in early summer, while autumn brings vivid red and golden leaves. In winter, the clear air creates a different atmosphere, and on clear days visitors may be able to see the snow-covered mountains of the Nikko range.
The reflection of the distinctive red Kusaki Bridge on the surface of the lake is another memorable sight.
Outdoor Activities and Seasonal Events
Walking trails and observation points have been developed around the lake, making the area suitable for walking and hiking.
From spring through autumn, visitors can also enjoy water activities such as canoeing and stand-up paddleboarding (SUP). These activities offer a different way to appreciate the surrounding mountains and lake scenery.
Seasonal events are also held around Lake Kusaki. The Kusaki Lake Festival takes place in August, while a marathon event is held in September, bringing additional activity to the lakeside area.
The History Behind Kusaki Dam
Development and Flooding Along the Watarase River
The Watarase River basin has long been an important agricultural region. During the medieval period, it was associated with powerful local families such as the Nitta and Ashikaga clans. During the Edo period, agricultural development was promoted by feudal domains including the Tatebayashi Domain.
In the Meiji period, Kiryu’s silk and textile industries expanded, while copper mining developed in the Ashio area upstream. Population and economic activity in the river basin increased as a result.
However, the Watarase River repeatedly experienced severe flooding. At the same time, pollution associated with the Ashio Copper Mine caused serious environmental problems, affecting farmland and the lives of people living downstream.
Against this background, a comprehensive solution was sought that could address both flood control and water use. The construction of a multipurpose dam became an important part of this approach.
Construction as a Multipurpose Dam
After World War II, comprehensive flood-control planning for the Tone River system progressed. Kusaki Dam was constructed as part of these efforts, with full-scale construction beginning in 1967.
The project involved major engineering works as well as the relocation of residents and the rerouting of railway infrastructure. After approximately a decade of construction and preparation, the dam was completed in 1977.
The project involved significant challenges, but the facility eventually began operation with the cooperation and understanding of the local community.
Attractions Around Kusaki Dam
Tomihiro Museum
The Midori City Tomihiro Museum stands beside Lake Kusaki and displays works by poet and artist Tomihiro Hoshino.
His delicate watercolor paintings accompanied by poetic words are known for their gentle and reflective character. The museum offers visitors an opportunity to experience his art while enjoying the natural surroundings of the lake.
Children’s Songs Hometown Museum
The Children’s Songs Hometown Museum introduces the life and achievements of Wasaburo Ishihara, a lyricist known for Japanese children’s songs such as “Usagi to Kame” and “Kintaro.”
Through historical materials and video displays, visitors can learn about the development of Japanese children’s music and the cultural heritage associated with these familiar songs.
Ashio Copper Mine Ruins and Matsuki Gorge
Upstream from Kusaki Dam are the remains of the historic Ashio Copper Mine and the dramatic landscape of Matsuki Gorge.
The area around Ashio Erosion Control Dam has been developed for environmental and educational purposes, allowing visitors to learn about the region’s industrial history, environmental challenges, and efforts toward restoration.
Routes Toward Nikko and Takatsudo Gorge
National Route 122 provides a scenic driving route through the Ashio area toward Nikko. Travelers can continue toward Nikko’s famous World Heritage sites while enjoying the mountain scenery along the way.
Downstream, attractions include Takatsudo Gorge and Yabuzuka Onsen. The gorge is particularly attractive during the autumn foliage season.
How to Get to Kusaki Dam
By Car
By car, Kusaki Dam is approximately 70 minutes from the Kita-Kanto Expressway Ota-Yabuzuka Interchange and approximately 100 minutes from the Tohoku Expressway Sano-Fujioka Interchange.
By Public Transportation
From Kiryu Station on the JR Ryomo Line or Aioi Station on the Tobu Kiryu Line, transfer to the Watarase Keikoku Railway.
Get off at Konaka Station, then continue on foot or by local bus to reach the dam and surrounding attractions.
A Lakeside Destination Where Nature and History Meet
Kusaki Dam and Lake Kusaki combine an important piece of infrastructure with beautiful mountain scenery and a rich regional history. The dam helps protect communities from flooding, supplies water to the wider metropolitan area, and generates hydroelectric power, while the reservoir has become a place where visitors can enjoy nature and outdoor activities.
From cherry blossoms and fresh greenery to colorful autumn foliage and clear winter landscapes, each season offers a different view of Lake Kusaki. A visit provides an opportunity to discover the relationship between water, nature, industry, and the history of the Watarase River basin.