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Lake Inba
印旛沼 (Japanese)
LocationChiba Prefecture, Japan
Lake Inba is located in Chiba Prefecture
Lake Inba
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Location of Lake Inba within Chiba Prefecture
Lake Inba is located in Kanto Area
Lake Inba
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Location of Lake Inba within Kanto region
Lake Inba is located in Japan
Lake Inba
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Location of Lake Inba within Japan
Coordinates35°46′37.5″N 140°13′55.2″E / 35.777083°N 140.232000°E / 35.777083; 140.232000
TypePolder
River sources
Catchment area494 square kilometres (191 sq mi)
Basin countriesJapan
Max. depth
  • 4.8 metres (16 ft) (north)
  • 2.9 metres (9 ft 6 in) (west)
Water volume19,700,000 cubic metres (700,000,000 cu ft)
Islands0
Sections/sub-basins
  • North Lake Inba (北印旛沼, Kita Inba-numa)
  • West Lake Inba (西印旛沼, Nishi Inba-numa)
  • Inba Cutoff Canal (印旛捷水路, Inba Shōsuiro)
Settlements
References[1][2]
Location
Map
Map
Interactive map of Lake Inba

Lake Inba (印旛沼, Inba-numa) is a man-made polder lake consisting of northern and western sections connected by a canal and located in Inba Tega Prefectural Natural Park in the Tone River basin in Chiba Prefecture, Japan. It is the largest lake in the prefecture. It was formed from remnants of the Katori Sea after the Tone River was diverted.

It is a popular location for outdoor activities, including fishing, bicycling, and birding, and is home to numerous species of plants, birds, and other wildlife. The National Museum of Japanese History is located on the grounds of the ruins of Sakura Castle, southwest of the lake. It is easily accessible through a number of train and bus services.

The lake is also variously known as Lake Imba, Lake Imbanuma, Inbanuma, and Imbanuma.

Geography and history

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Lake Inba is located in Inba Tega Prefectural Natural Park, and is the largest lake in Chiba Prefecture, with an original surface area of 25.8 square kilometres (10.0 mi2).[2][3] It is a man-made lake created by the natural damming of a small valley, and it is the largest lake in Chiba Prefecture. The lake is within the Shimōsa Plateau, which covers most of northern part of the prefecture. After multiple land reclamation projects, similar to those carried out on Lake Teganuma, its surface area was significantly reduced to about 13.1 square kilometres (5.1 mi2),[4] before being further reduced to 9.43 square kilometres (3.64 mi2).

About 1000 years ago, the Tone River flowed into what is now Tokyo Bay, and the area where Lake Inba is now located was part of the inland Katori Sea and was called Inbaura (印旛浦).[2] As part of a large project to control flooding in the Tokyo area during the Edo Period, the river's course was diverted to flow into the Pacific Ocean, with its mouth now at Chōshi.[2] The Katori Sea was slowly filled in and the remaining water and land desalinated, and a large swampy area that eventually drained into Tokyo Bay was created.[2]

Lake Inba was a large, swampy area containing a W-shaped lake of about 25.8 square kilometres (10.0 mi2) until the 1930s.[2] A project completed in 1949 reduced the surface area of the lake almost in half, and split the lake into northern and western sections connected by the Inba Cutoff Canal (印旛捷水路, Inba Shōsuiro).[2][3] The Inba Cutoff Canal is listed as one of the top 100 canals in Japan.[5] The northern section reaches depths of 4.8 metres (16 ft), while the western section is shallower at about 2.9 metres (9 ft 6 in) maximum depth.[1] A reclamation project completed from 1963 to 1969 developed additional water resources, improved area rice fields, and better managed flooding.[6] The lake contains no islands.

Due to population increases in the area during the 1970s, nutrient runoff into the lake began causing blue-green algae blooms, an increase in water chestnut growth, and municipal water odors. Various education programs and better handling of wastewater have reduced these issues.[6]

The lake spans multiple municipalities, including the cities of Inzai, Narita, Sakura, and Yachiyo, and the town of Sakae.[2][7] The drainage basin, which spans 494 square kilometres (191 sq mi), includes these municipalities as well as the cities of Chiba, Funabashi, Kamagaya, Yotsukaidō, Yachimata, Shiroi, and Tomisato, and the town of Shisui.[2] The population found within the lake's basin is about 794,000 as of 2020.[2]

There are numerous rivers that empty into Lake Inba. These include the Nagato River, Kashima River, Moroto River, Takasaki River, Teguri River, Kanzaki River, Kannō River, and Shin River. The lake holds a water volume of about 19,700,000 cubic metres (700,000,000 cu ft), and each year supplies about 34,831,000 cubic metres (45,557,000 cu yd) of potable water, 47,368,000 cubic metres (61,955,000 cu yd) of water for industrial uses, and 76,876,000 cubic metres (100,550,000 cu yd) for agricultural uses.[2]

Flora and fauna

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Lake Inba supports a variety of plants and animals in the lake and its surrounding environs. Major plants found there include the hornwort, common reed, Japanese reed, the water snowflake, various eelgrasses, the fringed water lily, Carolina fanwort, Manchurian wild rice, water chestnut, pondweeds such as potamogeton wrightii and potamogeton lucens, western waterweed, the lesser bullrush, spiny water nymph, trapa incisa, various members of the water caltrop genus, hydrocharis dubia, and the lotus.[6][8] A number of species of phytoplankton are also found in the lake, including microcystis, cyclotella, and chlamydomonas.[6]

Fish found in the lake include the common carp, the Japanese bitterling, tamoroko, pond loach, pond smelt, Japanese halfbeak, icefish, Japanese eel, kawahigai, hasu, oikawa, mugitsuku, Chinese false grudgeon, and various types of Crucian carps and gobies.[6]

Inba Lake is a popular birding destination due to many birds frequenting the lake and the surrounding wetlands. Birds found there include yellow, Eurasian, and Schrenk's bitterns (though the latter is very rare), Oriental reed warblers, ducks such as the falcated and Baikal teals and the smew, Japanese green pheasants, Siberian meadow buntings, Japanese buzzards, kestrels, sparrowhawks, and eastern marsh harriers.[8] A single great white pelican has been living at the lake since the early 2000s.[8]

Recreation and access

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The lake features relatively-flat bicycle paths along most of the shoreline, including the main canal, and bicycles can be rented.[9][10] The cycling path continues for a few kilometers along the Shin River off the western section, and along the western shore of the northern section up to the Sakano Water Gate on the Nagato River. It is also a popular fishing and birding destination.[3][9][10]

The National Museum of Japanese History is located on the grounds of the ruins of Sakura Castle, southeast of the western section of the lake in Sakura. The castle ruins are 20th on Japan's Top 100 Castles list by the Japan Castle Foundation.[11] A Dutch windmill and fields of tulips are located next to the lake.[10]

There are no toilet facilities at the lake.[8]

Transportation

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Narita International Airport is located about 11.3 kilometres (7.0 mi) southeast of Lake Inba. The Higashi-Kantō Expressway, a limited-access toll road, runs east-west and then northeast several kilometers south (and then east) of the lake. The lake is accessible from the Tomisato, Narita, Shisui, and Sakura Interchanges.

The following railway stations are within about 6 kilometres (3.7 mi) of Lake Inba (listed by line, then by distance):

All stations on the looping Yamaman Yūkarigaoka Line are near the west end of the west section of the lake.[15]

Surrounding area

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See also

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References

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  1. ^ a b 調査実施湖沼一覧 [List of Surveyed Lakes] (in Japanese). Geospatial Information Authority of Japan. 2019. Archived from the original on 19 September 2025. Retrieved 19 September 2025.
  2. ^ a b c d e f g h i j k 印旛沼の概要 [Inba-numa Overview] (in Japanese). 印旛沼水質保全協議会. 2020. Archived from the original on 19 September 2025. Retrieved 19 September 2025.
  3. ^ a b c d "Lake Imbanuma". Japan Travel by Navitime. Retrieved 21 October 2025.{{cite web}}: CS1 maint: url-status (link)
  4. ^ "Inbanuma". Encyclopedia of Japan. Tokyo: Shogakukan. 2012. OCLC 56431036. Archived from the original on 25 August 2007. Retrieved 21 July 2012.
  5. ^ 疏水百選 [Top 100 Canals] (in Japanese). 全国土地改良事業団体連合会 (National Federation of Land Improvement Associations). Archived from the original on 19 September 2025. Retrieved 19 September 2025.
  6. ^ a b c d e "Inba-Numa (Lake Inba)". International Lake Environment Committee Foundation. Archived from the original on 19 September 2025. Retrieved 19 September 2025.
  7. ^ 平成26年全国都道府県市区町村別面積調 [2014 National Area Survey by Prefecture, City, Ward, and Municipality] (PDF) (in Japanese). Geospatial Information Authority of Japan. 2014. p. 97. Archived (PDF) from the original on 24 August 2025. Retrieved 19 September 2025.
  8. ^ a b c d e f g h Brazil, Mark; Cook, Chris (5 June 2021). "Chiba Prefecture". Japan Nature Guides. Archived from the original on 14 June 2025. Retrieved 21 October 2025.
  9. ^ a b "Lake Inbanuma". Chiba Prefectural Tourism & Local Products Association. Archived from the original on 19 September 2025. Retrieved 19 September 2025.
  10. ^ a b c d e "Lake Inba". Live Japan. Archived from the original on 19 July 2025. Retrieved 21 October 2025.
  11. ^ 日本１００名城 [Japan 100 Famous Castles] (in Japanese). Japan Castle Foundation. Archived from the original on 23 September 2025. Retrieved 23 September 2025.
  12. ^ "Lake Inbanuma". Chiba Prefectural Tourism & Local Products Association. 17 March 2025. Archived from the original on 16 July 2025. Retrieved 21 October 2025.
  13. ^ 印旛日医大地区の紹介 [Introduction to the Greater Inba Area] (in Japanese). 千葉ほくそうパルケ. 3 June 2025. Archived from the original on 21 October 2025. Retrieved 21 October 2025.
  14. ^ 印旛沼公園 [Inbanuma Park] (PDF) (in Japanese). 印旛土木事務所 (Inba Civil Engineering Office). Archived (PDF) from the original on 23 April 2025. Retrieved 21 October 2025.
  15. ^ 林新二郎 (Hayashi Shinjirō) (July 2011). 都市計画の視点から見た中量軌道システム「山万ユーカリが丘線」 [Medium-Capacity Rail System from an Urban Planning Perspective: "Yamaman Yukarigaoka Line"] (PDF) (in Japanese). Civil Engineering Consultant. Archived (PDF) from the original on 14 April 2023. Retrieved 21 October 2025.
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