History and Development
The development of Naramata Dam can be traced back to the Revised Tone River Improvement Plan of 1949 and the Basic Plan for Water Resources Development in the Tone River System of 1962.
Based on these plans, a series of dams and water-control facilities were constructed throughout the Tone River basin, including Yagisawa Dam, Fujiwara Dam, Shimokubo Dam, Sonohara Dam, Aimata Dam, Kusaki Dam, and the Watarase Retarding Basin.
However, as the population of the Tokyo metropolitan area increased and industrial areas expanded, demand for water continued to grow. At the same time, improvements in agricultural technology and the expansion of farmland across the Kanto Plain increased the need for agricultural water.
In response to these growing demands, the Water Resources Development Public Corporation revised part of the Basic Plan for Water Resources Development in the Tone River System. Construction of the multipurpose dam on the Naramata River began in 1973, and Naramata Dam was completed in 1990.
Functions and Purposes of Naramata Dam
Naramata Dam serves several important purposes. These include flood control, maintaining water levels for various water uses, agricultural irrigation in eastern Boso Peninsula, municipal and industrial water supply for the Tokyo metropolitan area and Gunma Prefecture, and hydroelectric power generation.
The prefectural hydroelectric power facility has an authorized output of 12,800 kW, contributing to the region’s supply of renewable electricity.
Structure of the Dam
Naramata Dam is a central impervious-core rockfill dam. It has a height of 158 meters, making it the tallest dam in the Tone River system.
A dam known as Kurihara River Dam, planned with a height of 160 meters, was ultimately not constructed. As a result, Naramata Dam became the highest completed dam in the Tone River system.
Among completed rockfill dams in Japan, Naramata Dam is also one of the tallest, following Takase Dam at 176 meters and Tokuyama Dam at 161 meters.
Scenery and Attractions Around Naramata Dam
The construction of Naramata Dam resulted in changes to the water-control facilities downstream. The former Naramata Dam was renamed Sugata Dam.
The surrounding area offers numerous attractions for visitors interested in dams and mountain scenery. Because several large dams are concentrated in the northern Minakami area, the region is particularly suitable for a dam tour.
Dam Tour from Lake Dogen
From Lake Dogen, the reservoir created by Sugata Dam, visitors can travel toward Yunokoya Onsen. Following the lakeside road eventually leads to Naramata Dam.
The area around Yagisawa Dam, Sugata Dam, Fujiwara Dam, and Naramata Dam contains several major water-control facilities within a relatively compact area, making it possible to enjoy a scenic tour of the dams while exploring the mountains of Minakami.
Dam Exhibition Facilities
Naramata Dam is open to visitors, and a dam information facility called Hilltop Naramata is located on the left bank.
The facility provides information about the history, structure, and functions of Naramata Dam, helping visitors understand how the dam contributes to flood prevention and water resource management.
Snowmelt Discharge
One of the most impressive seasonal sights occurs during the snowmelt season. As snow accumulated in the surrounding mountains begins to melt, water is discharged through the spillway on the left bank of the dam.
The powerful flow of snowmelt water against the backdrop of the surrounding mountains creates a spectacular landscape and is one of the highlights of visiting Naramata Dam in spring.
Enjoying the Four Seasons
The scenery around Naramata Dam changes throughout the year.
Spring
Spring brings melting snow from the surrounding mountains. The resulting water discharge can create a particularly dramatic view of the dam and its spillway.
Summer
In summer, the surrounding mountains are covered in fresh green foliage. The contrast between the deep green forests, blue sky, and expansive reservoir creates beautiful scenery.
Autumn
Autumn is an especially attractive season for sightseeing. The mountains surrounding the reservoir are covered in vivid red, orange, and golden foliage, creating a spectacular landscape around the dam.
Winter
During winter, snow covers the surrounding mountains and forests. The quiet, snowy landscape offers a completely different atmosphere from the warmer months.
A Major Water Resource Supporting the Kanto Region
Naramata Dam is more than a sightseeing destination. It is an important piece of infrastructure supporting the lives and industries of people across the Kanto region.
Its functions include flood control, agricultural water supply, municipal water, industrial water, and hydroelectric power generation. At the same time, its enormous structure and surrounding mountain scenery make it an impressive destination for visitors.
A Dam Where Engineering Meets Mountain Nature
Naramata Dam offers an unusual combination of large-scale civil engineering and beautiful natural scenery. Visitors can learn about the history and role of the dam while enjoying the forests, mountains, and reservoir of Minakami.
With its dramatic scale, seasonal scenery, and proximity to other major dams and hot spring resorts, Naramata Dam is a worthwhile stop for anyone exploring the Minakami and Okutone area of Gunma.