Lake Ozenuma is one of the most iconic natural landscapes in Oze, stretching across Katashina Village in Gunma Prefecture and Hinoemata Village in Fukushima Prefecture. Located at an elevation of approximately 1,660 meters, the lake covers about 1.81 square kilometers and has a circumference of approximately 9 kilometers.
Surrounded by mountains and highland marshes, Lake Ozenuma offers beautiful scenery that changes dramatically with the seasons. Its tranquil waters and pristine surroundings have long attracted hikers, photographers, and nature enthusiasts.
The lake is also part of the headwaters of the Tadami River and, together with the Oze Marsh, plays an important role in the region’s natural water system.
Lake Ozenuma is believed to be a volcanic dam lake formed by volcanic activity. Approximately 10,000 years ago, lava released during an eruption of Mount Hiuchigatake blocked the flow of the Numajiri River, creating the lake.
This geological history has had a major influence on the natural environment of the entire Oze region. Oze originally had a basin-like landscape, where sediment and plant material accumulated over thousands of years to form extensive wetlands.
Around Lake Ozenuma, visitors can observe the gradual transition between open water and highland marshland. This makes the area particularly valuable not only as a scenic destination but also as a site of scientific and ecological interest.
Lake Ozenuma is located within the Special Protection Zone of Oze National Park, where strict conservation measures are in place to protect the area’s fragile ecosystem.
The Oze area was originally part of Nikko National Park before becoming an independent national park in 2007. In 2005, Oze Marsh and Lake Ozenuma were also registered as a Ramsar Wetland, recognizing their international importance as a valuable wetland environment.
Oze is also well known for its “Take Your Trash Home” campaign. This approach to environmental conservation is regarded as an important part of the history of Japan’s nature conservation movement. The cooperation of every visitor helps preserve this fragile landscape for future generations.
On the eastern shore of Lake Ozenuma stands the Ozenuma Visitor Center, an important information facility for exploring the natural environment of Oze.
Visitors can learn about the formation of Oze and its diverse plants and animals through exhibitions, videos, and other educational displays. Staff members are available to provide useful information about hiking conditions, walking routes, and the natural environment before visitors set out.
The exhibits include animal pelts, such as those of Asian black bears and Japanese serows, as well as a computer-generated video explaining how the Oze landscape was formed.
Renovated in 2021, the visitor center uses plenty of wood to create a warm, welcoming atmosphere that blends naturally with the surrounding environment.
Oze is sometimes described as a “treasure house of plants”, with more than 900 species of plants growing throughout the region.
In spring, the wetlands become covered with beautiful Asian skunk cabbage, while summer brings colorful alpine plants, including Nikko kisuge daylilies and watasuge cotton grass. These seasonal displays are among the highlights of a visit to Oze.
The region is also home to a diverse range of wildlife. Mammals include Asian black bears, Japanese serows, and stoats, while more than 160 species of birds have been recorded. Numerous insects, amphibians, and other organisms also inhabit the area.
These plants and animals interact with one another as part of a complex ecosystem, helping maintain the unique natural environment of Oze.
The scenery around Lake Ozenuma changes significantly throughout the year. In spring, the melting snow gives way to blooming Asian skunk cabbage, creating one of the region’s most distinctive seasonal sights.
From early summer through summer, colorful alpine plants bring the wetlands to life. In autumn, the grasses of the marsh turn golden and reddish brown, creating an expansive landscape of autumn colors.
During winter, the area is covered in deep snow and experiences severe mountain conditions, making it inaccessible to ordinary visitors. The snow, however, plays an important ecological role by protecting vegetation and helping sustain new life for the following spring.
Lake Ozenuma cannot be reached directly by car. Visitors must enter the area from one of the trailheads and continue on foot.
One of the main approaches is a route of approximately 7 kilometers from Oshimizu. Another popular route is approximately 2.8 kilometers from Numayama Pass. Shuttle buses can be used for part of the journey, making access to the area more convenient.
Wooden boardwalks have been installed throughout the wetlands, allowing visitors to enjoy the scenery while minimizing damage to the fragile vegetation.
Walking outside the designated boardwalks is prohibited as part of the area’s strict conservation measures. Visitors are asked to remain on the marked paths and follow local guidelines to help protect the ecosystem.
Lake Ozenuma is one of Japan’s outstanding natural scenic destinations, where magnificent mountain landscapes coexist with a delicate and highly protected ecosystem.
The appeal of Ozenuma goes beyond its beautiful scenery. Its volcanic origins, diverse wildlife, seasonal landscapes, and long history of environmental conservation provide visitors with opportunities to learn about the natural world as well as enjoy it.
When visiting Lake Ozenuma, it is important to respect the natural environment and follow all conservation rules. By doing so, travelers can enjoy the extraordinary beauty of Oze while helping ensure that this precious landscape continues to be protected for future generations.