is a freshwater caldera lake in

Satsumasendai is a city located in Kagoshima Prefecture, Japan. The modern city of Satsumasendai was established on October 12, 2004, from the merger of the city of Sendai, the towns of Hiwaki, Iriki, Kedōin and Tōgō, and the Koshikijima Islands (whi ...

, Kagoshima Prefecture, Japan. It forms part of Imutaike Prefectural Natural Park. Its plant communities were designated a

Natural Monument of Japan To protect Japan's cultural heritage, the country's government selects through the Agency for Cultural Affairs important items and designates them as Cultural Properties under the Law for the Protection of Cultural Properties. Designated items ar ...

in 1921 and sixty hectares of wetlands were designated a Ramsar Site in 2005.

Geography

Imuta-ike is surrounded by mountains; Funamidake (), San-o-dake (), Katagi-yama (), Tōmigashiro (), Ī-moriyama (, known due to its beauty also as Imuta-fuji), and there is no incoming large river. The outgoing water flows into Sendai River and Hiwagi River. Imuta-ike is in the last stage of the lake-pond formation cycle and is shrinking with the deposition of

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

. The colour of the pond is brown, 14 on the

Forel-Ule scale The Forel-Ule scale is a method to estimate the color of bodies of water. The scale provides a visual estimate of the color of a body of water, and it is used in limnology and oceanography with the aim of measuring the water's transparency and ...

, and its pH is 6.8; the water of the pond contains organic substances.Masaaki Tanaka ''Nihon Koshoushi 2 '' 2004, University of Nagoya Press , There are many cherry trees around the pond. About one third of its area, to the northwest, is wetland; dotted by

floating islands A floating island is a mass of floating aquatic plants, mud, and peat ranging in thickness from several centimeters to a few meters. Floating islands are a common natural phenomenon that are found in many parts of the world. They exist less co ...

composed of

peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficient ...

. This is very rare in warm areas and the pond was designated a Natural Monument as the "peat forming vegetation of Imuta-ike" in 1921.

Biota

On the surface of the pond,

phragmites ''Phragmites'' () is a genus of four species of large perennial reed grasses found in wetlands throughout temperate and tropical regions of the world. Taxonomy The World Checklist of Selected Plant Families, maintained by Kew Garden in L ...

and

wild rice Wild rice, also called manoomin, Canada rice, Indian rice, or water oats, is any of four species of grasses that form the genus ''Zizania'', and the grain that can be harvested from them. The grain was historically gathered and eaten in both ...

grow thick and in the water, there are ''

brasenia ''Brasenia'', commonly known as ''watershield'', is a genus belonging to the family Cabombaceae, consisting of one species, ''Brasenia schreberi''. It is widely distributed in North America, the West Indies, northern South America (Venezuela, Gu ...

, nymphaea tetragona'',

water caltrop The water caltrop is any of three extant species of the genus ''Trapa'': ''Trapa natans'', ''Trapa bicornis'' and the endangered ''Trapa rossica''. It is also known as buffalo nut, bat nut, devil pod, ling gok ( Chinese: 菱角), ling nut, lin ko ...

. As for fish, species include ''Zacco platypus'' (),

Black bass Black is a color which results from the absence or complete absorption of visible light. It is an achromatic color, without hue, like white and grey. It is often used symbolically or figuratively to represent darkness. Black and white have o ...

, '' Carassius langsdorfii'' and ''

Oryzias latipes The Japanese rice fish (''Oryzias latipes''), also known as the medaka, is a member of genus ''Oryzias'' (ricefish), the only genus in the subfamily Oryziinae. This small (up to about ) native of East Asia is a denizen of rice paddies, marshes, ...

''. A rare dragonfly, ''

Libellula angelina ''Libellula angelina'', also known as bekko tombo, is a species of dragonfly in the family Libellulidae, native to China and Japan. It is under threat by rapid loss of the ponds and other small water bodies it uses as habitat, and is currently ...

'' is found, leading to the pond's selection as a Ramsar Site. 20090830 imutaike kagoshima-ken japan

History

Between 300,000 and 400,000 years ago, there were groups of

lava domes In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of erupti ...

, 4 km from east to west and 7 km from north to south. The centre of the domes was depressed forming a

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

. The lava dome formed Iimori-yama. The depression collected water and Imuta-ike was formed. Prior to the

Taishō era The was a period in the history of Japan dating from 30 July 1912 to 25 December 1926, coinciding with the reign of Emperor Taishō. The new emperor was a sickly man, which prompted the shift in political power from the old oligarchic group of ...

(1912–1926), Imuta-ike was known for the growth of common rushes (''

Juncus effusus ''Juncus effusus'', with the common names common rush or soft rush, is a perennial herbaceous flowering plant species in the rush family Juncaceae. In North America, the common name soft rush also refers to '' Juncus interior''. Distribution ' ...

''), the raw material for

tatami A is a type of mat used as a flooring material in traditional Japanese-style rooms. Tatamis are made in standard sizes, twice as long as wide, about 0.9 m by 1.8 m depending on the region. In martial arts, tatami are the floor used for traini ...

mats. In autumn, villagers used to cut and bundle rushes. Between 1741 and 1763, a 380-meter tunnel water lane was made at the eastern end of the pond, and 15 hectares of rice fields were made. In 1953, Imuta-ike was made a

Prefectural Natural Park and in Japan are places of scenic beauty designated for protection and sustainable usage by the Minister of the Environment under the of 1957. National Parks are designated and in principle managed by the Ministry of the Environment. Quasi-Na ...

References

{{Reflist

External links

Imuta-ike Ramsar Site
Landforms of Kagoshima Prefecture Ramsar sites in Japan Lakes of Japan Natural monuments of Japan Volcanic crater lakes

Geography

Biota

History

See also

References

External links