Kejonuma Dam is a prefectural dam located in Osaki, Miyagi Prefecture. It is managed by the Miyagi Prefectural Government’s River Division and the Osaki Regional Dam Management Office.
The dam was constructed on the Chojagawa River, part of the Kitakami River system, primarily to control flooding in the Tadashiri River basin. It also provides a stable water supply for agriculture and other local uses, making it an important part of the infrastructure supporting the region’s communities and farmland.
Today, the dam and surrounding Lake Kejonuma are also valued as a natural and recreational area. Visitors can enjoy seasonal scenery, observe wild birds, walk along the lakeshore, and discover the area’s connections with local history and folklore.
Before the dam was built, Kejonuma was a natural lake surrounded by a rich natural environment. The lake had long been familiar to local residents, but using its water for agriculture was dependent on weather conditions, making it difficult to guarantee a stable water supply.
At the same time, the Tadashiri River flows through a low-lying wetland area and had limited capacity to carry floodwater. The river repeatedly overflowed during periods of heavy rain, causing significant damage to the surrounding communities.
The region experienced particularly severe flooding following the Typhoon Kathleen in 1947, the Typhoon Ione in 1948, and heavy rainfall in September 1966. These disasters highlighted the need for better flood-control infrastructure and a more reliable agricultural water supply.
In response, Miyagi Prefecture developed river improvement projects for the Tadashiri River. The Kejonuma Dam construction project began in 1976 with two major objectives: regulating floodwaters and securing a stable supply of water for agriculture.
After approximately 20 years of construction, the dam was completed in 1995.
Kejonuma Dam is an earthfill dam with a height of approximately 24 meters. Its primary purpose is flood control, and it is classified as a government-subsidized flood-control dam.
One of its notable characteristics is that it makes use of an existing natural lake. Relatively large dams of this type are uncommon in Japan. Examples of other dams that utilize natural lakes include Yogoko Dam in Shiga Prefecture and Chuzendji Dam in Tochigi Prefecture.
The dam therefore represents an interesting example of how existing natural landscapes can be incorporated into modern water-management infrastructure.
The lakeshore has been developed as a park-like area, with trees such as Japanese red pine and chestnut growing around the water. The lake itself and its surrounding wetlands support a remarkable variety of aquatic and wetland plants.
Plants recorded in the area include water chestnut, pondweed, reeds, and Japanese iris. In total, approximately 783 plant species belonging to 126 families have been identified.
The changing vegetation gives the lakeshore a different appearance throughout the year. Spring greenery, summer flowers, autumn colors, and winter landscapes each offer a different reason to visit.
One of Lake Kejonuma’s most important natural attractions is its role as a stopover and wintering habitat for migratory birds.
During the colder months, species such as greater white-fronted geese, bean geese, whooper swans, and Baikal teals visit the lake. Birds of prey, including white-tailed eagles and Steller’s sea eagles, may also be seen in the area.
The abundance of waterbirds and the importance of the surrounding habitat led to the designation of the area as the Kejonuma Wildlife Protection Area on August 1, 2008. Later that year, on October 30, Kejonuma was designated as a Ramsar Site, recognizing its international importance as a wetland.
For visitors interested in wildlife, winter is an especially rewarding season, when large numbers of migratory birds gather on and around the lake.
The area around Kejonuma has been inhabited by people for a very long time. Archaeological remains found nearby include the Miyazawa Archaeological Site and the Kuchikibashi Yokoana Burial Mounds, providing evidence of the region’s long history.
The lake is therefore more than a natural landscape. It is also part of a cultural landscape shaped by generations of people who lived alongside the water.
Kejonuma is also associated with a number of local folk stories and legends. Among them is the Legend of Shoya-hime, which is traditionally connected with the origin of the name “Kejonuma.”
For travelers interested in Japanese folklore, these stories offer an additional way to appreciate the landscape. The legends passed down around the lake show how local communities have historically connected natural places with stories, beliefs, and traditions.
An iris garden is located along the lakeshore, and in early summer the area comes alive with colorful Japanese irises. The flowers create an attractive contrast with the surrounding greenery and water.
Kejonuma is also known as a cherry blossom viewing destination. In spring, cherry trees around the lake come into bloom, attracting visitors who enjoy walking and seasonal flower viewing.
Picnic areas are also available in the surrounding area, making the lakeshore a pleasant place for families and visitors who want to take a break while enjoying the scenery.
Kejonuma is conveniently located near the Chojahara Service Area Smart Interchange on the Tohoku Expressway. It can also be reached from the Furukawa Interchange, approximately 9 kilometers away.
The Chojahara Service Area itself offers views toward Lake Kejonuma, making it a convenient place to appreciate the landscape during a road trip through Miyagi.
Osaki, Miyagi Prefecture, Japan
Kejonuma can be enjoyed throughout the year, with each season offering a different experience.
Spring: Cherry blossoms provide colorful scenery around the lakeshore.
Early summer: Japanese irises bloom in the lakeside iris garden.
Autumn: The surrounding trees take on vibrant autumn colors.
Winter: Migratory birds gather at the lake, making this an excellent season for birdwatching.
Kejonuma Dam and Lake Kejonuma offer visitors an opportunity to experience several different aspects of Miyagi in one location. The dam demonstrates how water resources and flood control support local communities and agriculture, while the lake and surrounding wetlands provide important habitat for plants and migratory birds.
The archaeological remains and local legends add another layer to the landscape, revealing the long relationship between people and the natural environment.
Whether you visit during cherry blossom season, the iris season, the colorful autumn months, or the winter bird migration, Kejonuma provides a changing landscape throughout the year. It is a worthwhile destination for travelers who want to explore a quieter side of Miyagi while discovering the connections between nature, local history, culture, and everyday life.