Imuta Pond (Imutaike) is a volcanic lake located in Imuta, Kedoin-cho, Satsumasendai City, Kagoshima Prefecture. Approximately one kilometer in diameter, the lake is surrounded by mountains and is known for its distinctive wetlands and floating islands.
In 1921, the area’s peat-forming plant communities were designated a National Natural Monument of Japan under the name “Peat-Forming Plant Communities of Imuta Pond.” In 2005, the pond was also registered as a wetland under the Ramsar Convention. These designations recognize the ecological importance of this unusual natural environment and the need to protect it.
Imuta Pond lies in a scenic mountain basin surrounded by several peaks. These include Mount Funamiyama, at 498.8 meters; Mount Sannō, at 491 meters; Mount Katashiro, at 508.8 meters; Mount Tōmiga-jō, at 477 meters; and Mount Iimori, at 432 meters. Mount Iimori is also known as Imuta Fuji because of its distinctive shape.
One unusual feature of the pond is that no major river flows into it. Instead, water leaves the lake from its eastern end and flows through the Ushirokawauchi River and the Hiwaki River before eventually reaching the Sendai River.
Imuta Pond is also in the late stage of the natural lake-formation cycle. Sediment gradually accumulates on the bottom, slowly filling the basin. This process makes the pond an interesting subject for geological study and raises questions about how its landscape may change over time.
The water of Imuta Pond has a distinctive brownish color. Its color is classified as No. 14 on the Ule water-color scale. The water has a pH of approximately 6.8 and contains a relatively high amount of organic matter, supporting a distinctive aquatic ecosystem.
Approximately one-third of the pond’s northwestern side is occupied by wetlands. Scattered across this area are floating islands formed from accumulated peat. These islands are particularly unusual because they display characteristics commonly associated with wetlands in colder climates, despite the pond’s location in a warm region of Japan.
Plants such as Nebikigusa, reeds, and soft rush contribute to the formation of peat. The process by which these plants accumulate and form peat is scientifically valuable, and it was one of the reasons the area was designated a National Natural Monument in 1921.
Imuta Pond supports a diverse range of plants and animals. Reeds, creeping reeds, and wild rice grow along the shore, while aquatic plants such as water shield, water lilies, and water chestnuts can be found in the water.
Fish living in the pond include pale chub, Japanese crucian carp, and medaka rice fish. Black bass have also been recorded in recent years. The freshwater mussel known as Dobugai is among the mollusks found here.
The pond is also known as a breeding ground for spot-billed ducks. Its wetland habitats are important for aquatic plants and waterbirds, as well as for the endangered damselfly species known as the Bekko Tombo, or yellow-winged darter.
Because of this biodiversity and the importance of its wetland ecosystem, Imuta Pond was registered as a Ramsar Convention wetland in 2005. This international designation recognizes the site as an important wetland that deserves long-term conservation.
Before the Taisho period, the area around Imuta Pond was known as a production center for rushes, or igusa, which were traditionally used to make tatami mats and other woven products.
Every autumn, local residents took part in a communal harvesting activity known as Igitori, during which villagers gathered to cut the rushes growing around the pond. This seasonal work was an important part of local life and was closely connected with the area’s agricultural activities.
Although only limited areas of farmland were available along the shore, farming and the harvesting of wetland plants formed an important part of the community’s livelihood.
In 1953, Imuta Pond was designated a Kagoshima Prefectural Natural Park. Development as a recreational and tourist destination subsequently progressed, with efforts made to balance the use of the area for visitors with the protection of its valuable natural environment.
A traditional legend tells of a male dragon and a female dragon who once lived happily together in Imuta Pond.
According to the story, the male dragon eventually went to live with the goddess of Lake Ōnamiike on the Kirishima mountain range. The female dragon was left behind at Imuta Pond. She continued to pray for the male dragon’s safety and prepared a portion of food for him every evening. Over time, the accumulated offerings are said to have formed Mount Iimori.
Another version of the legend says that the female dragon eventually set out to follow the male dragon to Lake Ōnamiike. However, she mistakenly emerged at nearby Sumiyoshi Pond instead.
These stories give the surrounding landscape a mysterious atmosphere and remain part of the area’s local folklore.
The Dragon God Festival, known as Ryūjin-sai, is rooted in the legend of the two dragons. According to local tradition, villagers began holding the festival in the hope of bringing the male and female dragons together again.
The festival continues as an important local cultural event, keeping the old legend alive and strengthening the connection between the community and the natural environment of Imuta Pond.
Imuta Pond was formed through volcanic activity associated with the Imuta Volcano, which occurred approximately 500,000 to 350,000 years ago.
During this period, a group of lava domes developed across an area approximately four kilometers from east to west and seven kilometers from north to south. Mount Iimori was formed last, blocking the eastern side of the basin. Water subsequently accumulated in the enclosed depression, creating the lake known today as Imuta Pond.
However, the precise geological process that created the basin has not been conclusively determined. It remains uncertain whether the landscape resulted from the collapse of a volcanic body or from a subsidence structure. This unresolved question adds to the pond’s geological significance.
One of the most important features of Imuta Pond is its peat-forming plant community. The vegetation and accumulated peat provide valuable evidence for understanding the processes through which plant material gradually becomes coal.
Aerial photographs taken in 1974 also document the characteristics of this plant community and its wetland environment. The area is especially interesting because it displays wetland features commonly found in colder climates, even though it is located in a relatively warm part of Japan.
The combination of floating peat islands, distinctive vegetation, and a complex ecosystem makes Imuta Pond valuable not only as a scenic destination but also as a site for ecological and geological research.
Imuta Pond is a distinctive natural destination where volcanic landscapes, wetlands, wildlife, and local traditions come together. Visitors can appreciate the mountain scenery, observe the unusual floating islands, and learn about the plants and animals that depend on this rare wetland environment.
The pond’s history is equally fascinating. Its traditional rush harvesting, the legend of the two dragons, and the continuing Dragon God Festival reveal the close relationship between local people and the surrounding landscape.
Recognized as both a National Natural Monument and a Ramsar Convention wetland, Imuta Pond is an important place for understanding and appreciating the natural heritage of Kagoshima Prefecture.