Miyagase Dam (Kanagawa Prefecture) Complete Guide: Charm and Tourism Information of the Kanto Region’s Largest Dam
What is Miyagase Dam?
Miyagase Dam is a gravity concrete dam constructed on the Nakatsu River, a tributary of the Sagami River system, a first-class river flowing through the center of Kanagawa Prefecture. Located in a vast area spanning three municipalities—Hanbara in Aikawa Town, Aikawa District; Aoyama in Midori Ward, Sagamihara City; and Miyagase in Kiyokawa Village, Aikawa District—it was completed in December 2000 (Heisei 12).
At approximately 50km from central Tokyo and about 40km from the urban areas of Yokohama and Kawasaki, it is the largest dam in the Kanto region, surrounded by abundant natural environments, and plays an important role in both flood control and water utilization. The formed dam lake is named “Miyagase Lake” and has been selected as one of the “100 Best Dam Lakes.”
Scale and Characteristics of Miyagase Dam
Overwhelming Scale
Miyagase Dam has a dam height of 156.0 meters, making it the second-highest gravity concrete dam in Japan. What is particularly noteworthy is that the dam body volume is 2.06 million cubic meters, making it the largest among gravity concrete dams in the country.
Major Specifications
- Dam Height: 156.0m
- Dam Crest Length: 375.0m
- Dam Body Volume: 2.06 million m³ (Japan’s largest gravity concrete dam)
- Total Storage Capacity: Approximately 193 million m³
- Effective Storage Capacity: Approximately 183 million m³
- Water Surface Area: Approximately 4.6 km²
- Type: Gravity concrete dam
- Operating Agency: Kanto Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism
With a total storage capacity of approximately 200 million tons, it functions as a key source for securing water resources in the Kanto region, significantly contributing to water supply for Kanagawa Prefecture and the entire Kanto region.
History and Transition of Miyagase Dam
Beginning of the Plan
The history of Miyagase Dam began in 1969 (Showa 44) when the Ministry of Construction (now the Ministry of Land, Infrastructure, Transport and Tourism) announced the “Miyagase Dam Construction Plan.” Following this announcement, preliminary surveys for dam construction were initiated, and in 1971 (Showa 46), two years later, it officially started as a multipurpose dam project.
Construction Process
At that time, with rapid economic growth, population increase and urbanization in the Kanto region caused water demand to surge dramatically. Simultaneously, the Sagami River basin frequently experienced flood damage, and the need for a large-scale dam became increasingly evident from both flood control and water utilization perspectives.
The long period of 31 years from plan announcement to completion was due to difficulties in compensation negotiations with local residents. Many settlements were to be submerged by dam construction, and negotiations regarding resident relocation and livelihood reconstruction proved extremely difficult.
Completion and Opening
Overcoming various difficulties, Miyagase Dam was completed in December 2000 (Heisei 12). Under the catchphrase “A Gift to the 21st Century,” its completion at the timing of the new millennium held symbolic significance. The total project cost reached approximately 400 billion yen, making it one of Japan’s largest dam construction projects in history.
Purposes and Roles of Miyagase Dam
Flood Control Function
One of the most important purposes of Miyagase Dam is flood adjustment. The Sagami River basin has experienced numerous floods in the past, causing catastrophic damage especially during typhoons and torrential rains. Miyagase Dam plays a role in temporarily storing water during floods and regulating flow to downstream areas, mitigating flood damage.
A flood adjustment capacity of approximately 60 million m³ is secured, significantly improving safety in the downstream Sagami River basin. As extreme rainfall becomes more severe due to recent climate change, it functions as important disaster prevention infrastructure.
Water Supply Function
Miyagase Dam supplies tap water and industrial water throughout a wide area of Kanagawa Prefecture. By supplying tap water to major cities including Yokohama, Kawasaki, and Yokosuka, it supports the lives of approximately 4 million people.
In the Sagami River system, three dams—Miyagase Dam, Sagami Dam, and Shiroyama Dam—conduct “comprehensive water management” in coordination, achieving efficient water resource management. This water supply network allows stable water supply to be maintained even during drought periods.
Power Generation Function
Miyagase Dam also generates hydroelectric power. Water released from the dam enables maximum power generation of 24,200kW, contributing to clean energy supply.
Compensation and Regional Impact
Submerged Areas and Relocation
With dam construction, many settlements, centered around the Miyagase district, were submerged. Approximately 300 households and about 1,000 residents were forced to relocate, resulting in the loss of long-established community connections in the region.
The submerged areas included historic shrines, temples, schools, and shops, creating not only issues of housing relocation but also challenges regarding the succession of regional culture and history.
Compensation Negotiation Process
Compensation negotiations became full-scale from the 1970s, involving prolonged discussions between residents and project operators on multifaceted issues including securing relocation sites, guaranteeing livelihood reconstruction, and spiritual compensation.
Ultimately, a comprehensive compensation package including residential land development at relocation sites, relocation expense compensation, and livelihood reconstruction support was agreed upon, with relocation proceeding in stages. Additionally, efforts were made to preserve records of submerged areas and erect memorials, implementing initiatives to pass regional history to future generations.
Transition to Regional Revitalization
Following dam completion, tourism development was actively promoted from a regional revitalization perspective. To revitalize the lost regional economy, the dam itself was utilized as a tourism resource, and various facilities were developed in the surrounding area to create new regional appeal.
Miyagase Dam as a Tourism Destination
Tourist Spillway: A Spectacular Water Show
The main attraction of Miyagase Dam is the regularly held tourist spillway. Implemented on Wednesdays, the second and fourth Fridays, and the second Sunday of each month (April–November), a massive 30 cubic meters of water per second is released.
With a discharge duration of 6 minutes, two white streams of water flow down the dam wall amid a thunderous “Gogoooo” sound—truly spectacular. When the released water strikes the riverbed, water spray rises like smoke, and on clear days, a beautiful rainbow often appears.
The spillway times are 11:00 AM and 2:00 PM twice daily (with seasonal variations), making it a popular event attracting many tourists.
Three Distinctive Areas
The area around Miyagase Lake is divided into three distinctive regions.
Dam Site and Prefectural Aikawa Park Area
This area offers close views of the dam itself, with the Prefectural Aikawa Park located adjacent. The park includes Adventure Forest, Fluffy Dome, and the Water and Energy Hall, making it popular with families with children. Facilities for learning about dam structure and function are available, allowing for educational tourism experiences.
From Aikawa No. 1 Park below the dam, one can enjoy the powerful sight of looking up at the dam’s body.
Miyagase Lakeshore Area
This area features the large suspension bridge “Mizu-no-Sato Grand Suspension Bridge” with a length of 315 meters at a height of approximately 70 meters above the lake surface. From the suspension bridge, one can overlook the majestic scenery of Miyagase Lake.
The large fountain “Fairy of the Rainbow” reaching 30 meters in height is also popular, with sprayed water creating rainbows—a fantastical sight. In winter, a giant Christmas tree exceeding 30 meters in height is illuminated, making the area one of the Kanto region’s premier illumination spots attracting many visitors.
Torii-hara Area
The lakeside slope is planted with Dodan azaleas, creating beautiful scenery as they turn brilliant red in autumn. Nature walking trails are well-maintained, allowing enjoyment of nature throughout the seasons.
Leisure Facilities
At Miyagase Lake, visitors can enjoy canoeing and boating (with some area restrictions). Camping grounds and barbecue areas are also developed along the lakeshore, making it a popular base for outdoor leisure.
A sightseeing boat “Mii-ya” also operates, allowing visitors to view the dam and surrounding nature from the lake.
Access Information
Public Transportation Access
To Dam Site and Prefectural Aikawa Park
- About 60 minutes by Kanagawa Chuo Bus “Miyagase” bound from Odakyu Line “Motosu Atsugi Station,” get off at “Aikawa Ohashi,” approximately 15-minute walk
- About 60 minutes by Kanagawa Chuo Bus “Miyagase” bound via “Migi” from JR Yokohama Line, Sagami Line, and Keio Line “Hashimoto Station”
To Miyagase Lakeshore Area
- About 60 minutes by Kanagawa Chuo Bus “Miyagase” bound from Odakyu Line “Motosugu Atsugi Station,” get off at the terminal
Automobile Access
- Approximately 40 minutes from “Atsugi IC” on Tomei Expressway (via National Route 412)
- Approximately 30 minutes from “Sagamihara IC” on the Kensodo
- Approximately 30 minutes from “Sagamiko East IC” on the Chuo Expressway
Parking facilities are available at each area, with approximately 500 spaces at Aikawa Park and approximately 1,000 spaces in the Miyagase Lakeshore area. Early arrival is recommended as congestion is expected on spillway event days, during autumn foliage season, and during the illumination period.
Miyagase Dam Through the Four Seasons
Spring (March–May)
During cherry blossom season, surrounding mountains are tinted in soft pink. Aikawa Park features approximately 40 varieties and approximately 4,000 cherry blossoms, making it a popular flower-viewing spot. During the fresh green season, vivid greenery reflects on the lake surface, creating beautiful scenery.
Summer (June–August)
With higher elevation and cooler temperatures than urban areas, it serves comfortably as a summer retreat. The period also sees frequent tourist spillways, with water spray providing refreshing relief. The optimal season for enjoying lakeside camping and barbecue.
Autumn (September–November)
The spectacular season when fall foliage colors the Torii-hara area’s Dodan azaleas and surrounding mountains. Particularly beautiful from late October to early November, the contrast between red and yellow-tinted mountains and the blue lake surface is breathtaking.
Winter (December–February)
In December, the giant Christmas tree illumination is lit, creating a fantastical atmosphere. Decorated with approximately 10,000 LED lights, the tree exceeding 30 meters in height boasts one of the largest scales in the Kanto region.
Winter air clarity provides crisp views of the dam and surrounding mountains, ideal for photography.
Works Featuring Miyagase Dam
Miyagase Dam, with its grand scale and convenient access from the Kanto region, has been used as a filming location for numerous movies, dramas, anime, and other productions.
In special effects works, the power of its enormous structure is utilized, often serving as the backdrop for action scenes and climactic moments. In anime productions, it may be depicted as a background, sometimes becoming a pilgrimage destination.
While specific titles are numerous, the dam’s majestic landscape plays an important role in giving narratives a unique atmosphere.
Nearby Facilities and Dining
Water and Energy Hall
An educational facility where visitors can learn about the dam’s role and hydroelectric power generation mechanisms. Through models and video, the dam’s construction history and importance of water resources can be understood clearly. Admission is free and ideal for children’s learning.
Miyagase Dam Incline
A cable car-style transport connecting the upper and lower sections of the dam, covering a height difference of approximately 120 meters in about 3 minutes. During the ride, visitors can enjoy spectacular views of Miyagase Lake.
Regional Cuisine
Restaurants and food stands using local ingredients are scattered throughout the area. Particularly, “Miyagase Dam Curry” is a popular menu item featuring rice and curry shaped like a dam.
Fresh local vegetables, mountain vegetables, and Sagami River sweetfish dishes can also be enjoyed. The Miyagase Lakeshore area has abundant souvenir shops where dam merchandise and regional specialty products can be purchased.
Viewing Tips and Precautions
Best Time to Visit the Dam
It is recommended to plan your visit to coincide with spillway event dates, which can be confirmed on the official website. Arrive about 30 minutes before spillway begins to secure a good viewing position.
Clothing and Items
The dam area has higher elevation and cooler temperatures than lowland areas, requiring seasonally appropriate clothing. Pay special attention to cold protection in winter. Walking shoes are essential if you plan to use the walking trails.
When viewing the tourist spillway, water spray may splash, so consider waterproof protection for cameras and electronic devices.
Photography Spots
- Aikawa No. 1 Park below the dam: powerful angle looking up at the body
- Mizu-no-Sato Grand Suspension Bridge: panoramic views overlooking Miyagase Lake
- Dam crest: views looking downstream from atop the dam
- Aikawa Park observation deck: commanding views of the dam and Miyagase Lake
Present and Future of Miyagase Dam
Water Level and Operations
Miyagase Dam’s water level status is published in real-time on the official website of the Sagami River System Broad-Area Dam Management Office of the Kanto Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism. Water levels fluctuate with rainfall and season, but recent climate change has altered rainfall patterns, increasing the importance of appropriate water resource management.
During drought periods, coordinated operations with Sagami Dam and Shiroyama Dam continue efforts to maintain stable water supply as much as possible.
Environmental Conservation Efforts
Around the dam lake, active natural environment conservation activities are conducted. Through forest management, rare species protection, and water quality monitoring, efforts are made to maintain a rich natural environment.
Additionally, habitat restoration projects for fauna and flora affected by dam construction are underway, with ecosystem recovery being pursued.
Coexistence with the Community
More than 20 years after dam completion, Miyagase Dam has become established as a regional symbol. Various events are held throughout the year, making it a venue for interaction between local residents and tourists.
Continuous regional development efforts are being made in cooperation with local municipalities, including tourism promotion, educational program provision, and contribution to the regional economy with the dam as the core.
Summary
Miyagase Dam, boasting the Kanto region’s largest scale as a gravity concrete dam, plays an important role in both flood control and water utilization. Its overwhelming scale—with a dam height of 156 meters and body volume of 2.06 million cubic meters—represents the culmination of Japanese dam engineering technology.
Completed after 31 years of effort and the dedication of many people, this dam functions not merely as infrastructure but also as a major tourism destination attracting over 1 million annual visitors. With attractions including the power of the tourist spillway, beautiful scenery throughout the seasons, and well-developed leisure facilities, Miyagase Dam’s multifaceted charm continues to captivate. As a “Gift to the 21st Century,” it will undoubtedly continue to be cherished by many people.
Taking advantage of its location approximately one hour from central Tokyo, please consider visiting as a destination for weekend outings or family vacations. The grand dam and abundant nature will surely provide an unforgettable experience.
