Ryujin Lake and the Legend of Izumi Kotaro
The name Ryujin Lake reflects the long-standing connection between this area and the legend of Izumi Kotaro. Along the lakeshore stands a bronze statue depicting a dragon and a boy riding on its back, bringing the legendary story to life for visitors.
According to the traditional tale, Izumi Kotaro was a boy who helped develop the Azumino region together with his dragon mother. The story has been passed down as an important part of the area’s cultural heritage and later inspired Ryū no Ko Taro, a children’s story written by Miyoko Matsutani.
The story also became familiar to audiences throughout Japan through the popular television program まんが日本昔ばなし, which featured traditional Japanese folktales in animated form. At Omachi Dam, the combination of the lake, mountains, and dragon-and-boy monument creates a distinctive atmosphere where local nature and folklore meet.
The Role and Structure of Omachi Dam
Flood Control and Water Resources
One of Omachi Dam’s primary purposes is to regulate flooding along the Takase River. It also provides water for public use and supports the stable management of water resources in the surrounding region. These functions make the dam an important part of everyday life as well as a striking landmark in the mountain landscape.
Hydroelectric Power Generation
Immediately below the dam is the Omachi Power Station, operated by Tokyo Electric Power Company. Water released from the upstream Nanakura Dam through the Nakanosawa Power Station is regulated at Omachi Dam before being supplied to the Omachi Power Station for electricity generation.
This system, known as reverse regulation, helps maintain a stable flow of water downstream while allowing hydroelectric power to be generated efficiently. The dam therefore serves both as a major piece of energy infrastructure and as part of the broader water-management system of the Takase River.
The Takase River and Its Mountain Waters
The Takase River originates in the Northern Alps near Mount Yari, which rises to 3,180 meters. With a drainage basin of approximately 445 square kilometers and a river course extending about 56 kilometers, it is one of the characteristic mountain rivers of northern Nagano.
Approximately 25 kilometers downstream from Omachi Dam, the Takase River joins the Sai River. The water then flows into the Chikuma River and eventually becomes known as the Shinano River after entering Niigata Prefecture before reaching the Sea of Japan. Together, this river system forms one of the major waterways connecting the mountains of Nagano with the Sea of Japan.
The upper Takase River receives considerable precipitation, averaging around 1,700 millimeters a year. Rain during the rainy season and typhoon season, as well as heavy winter precipitation in the surrounding mountains, contributes to the river’s abundant flow and rapid current.
The Scenic Takase Gorge
The upper reaches of the Takase River around Omachi Dam are known as Takase Gorge. Three major dams—Omachi Dam, Nanakura Dam, and Takase Dam—are located along this mountain valley, creating a remarkable landscape where large-scale engineering structures stand alongside rugged mountains and forests.
The area is particularly beautiful in autumn. From the dam and surrounding viewpoints, visitors can see colorful forests spread across the steep valley, creating a dramatic contrast with the massive concrete structure and the deep blue-green waters of the reservoir. The usual peak season for autumn foliage is from mid-October to early November.
The nearby Kuzu Hot Spring area adds another dimension to the experience, allowing visitors to combine mountain scenery with the relaxing atmosphere of traditional Japanese hot springs.
Nature, Legends, and Mountain Scenery
Omachi Dam is more than a flood-control and power facility. Its surroundings offer a memorable combination of natural scenery, engineering, and regional folklore. The imposing dam wall provides a sense of scale, while the bronze monument beside Ryujin Lake introduces visitors to one of the area’s best-known traditional stories.
Throughout the year, the landscape changes dramatically. Fresh greenery spreads across the mountains in spring, summer brings lush forests and clear mountain air, autumn transforms the gorge into a vivid tapestry of colors, and winter creates a quiet alpine atmosphere.
Walking and Exploring the Gorge
Walking routes around the Takase Gorge allow visitors to experience the mountain environment at a slower pace. Along the way, the scenery changes from the broad reservoir to steep valleys, waterfalls, bridges, and forested slopes.
Nearby attractions include Fudōzawa Suspension Bridge and Nigorizawa Waterfall, both of which offer opportunities to appreciate the rugged character of the gorge. Nigorizawa Waterfall is especially striking when surrounded by autumn foliage, making it a popular location for photography.
Hot Springs and Mountain Adventures
For visitors who want to explore deeper into the mountains, Yumata Onsen lies farther upstream. The secluded hot spring area is also used as a base for mountain routes toward peaks such as Mount Yari and Mount Noguchigoro.
The journey from Omachi Dam to Yumata Onsen takes approximately two and a half hours on foot, making it suitable for travelers who enjoy longer walks and mountain scenery. Combining a visit to the dam with a hot spring or hiking excursion offers a deeper experience of the Northern Alps landscape.
A Place Where Infrastructure and Folklore Meet
Omachi Dam and Ryujin Lake offer a distinctive way to experience the mountains of Nagano. The dam was created to protect communities and manage water and energy resources, while the surrounding landscape preserves dramatic scenery and stories rooted in local tradition.
For travelers, the attraction lies in this unusual combination. A massive dam rises above a mountain valley, emerald-colored water stretches toward the Northern Alps, and the legend of a dragon mother and her son adds a sense of mystery to the lakeshore.
Whether visiting for the spectacular autumn colors, exploring the Takase Gorge, learning about hydroelectric power, or discovering the local folklore behind Ryujin Lake, Omachi Dam provides an opportunity to see a different side of Nagano’s mountain country.