Lake Biwa (Japanese:琵琶湖,Hepburn:Biwa-ko) is the largestfreshwaterlake in Japan. It is located entirely withinShiga Prefecture (west-centralHonshu), northeast of the former capital city ofKyoto.[3] Lake Biwa is anancient lake, over 4 million years old.[1] It is estimated to be the 13th oldest lake in the world.[4] Because of its proximity to the country's historical capitalKyoto, references to Lake Biwa appear frequently in Japanese literature, particularly in poetry and in historical accounts of battles.
The nameBiwa-ko was established in theEdo period. There are various theories about the origin of the nameBiwa-ko, but it is generally believed to be so named because of the resemblance of its shape to that of a stringed instrument called thebiwa, and indeed, they use the samekanji:琵琶 (biwa). Kōsō, a learnedmonk ofEnryaku-ji in the 14th century, gave a clue to the origin of the nameBiwa-ko in his writing: "The lake is thePure Land of the goddessBenzaiten because she lives onChikubu Island and the shape of the lake is similar to that of thebiwa, her favorite instrument."[5]
The lake was formerly known asAumi (淡海, Freshwater Sea) orChikatsu Awa-umi (近淡海, Freshwater Sea Near [the Capital]). The current pronunciation of this word has becomeŌmi, as in the name ofŌmi Province. The lake is also calledNio no Umi (鳰の海, "Little Grebe Lake") in literature.
The area of this lake is about 670 km2 (260 sq mi).[6] Small rivers drain from the surrounding mountains into Lake Biwa. Its main outlet is the Seta, which later becomes the Uji, combining with the Katsura and Kizu to become theYodo River, which flows into theSeto Inland Sea atOsaka Bay.
It serves as a reservoir for the cities ofKyoto andŌtsu and is a valuable resource for nearby textile industries. It provides drinking water for about 15 million people in theKansai region. Lake Biwa is a breeding ground for freshwater fish, includingtrout, and for thepearl culture industry.
TheLake Biwa Canal, built in the late 1890s and later expanded during theTaishō era, played a crucial role in the revival of Kyoto's industrial life after a steep decline following the transfer of the capital to Tokyo.
Thegiant Lake Biwa catfish is the largest predatory fish in the lake and is found nowhere else.
Lake Biwa is oftectonic origin and is one of the world'soldest lakes, dating to at least 4 million years ago (mid-Pliocene).[1] This long, uninterrupted period has allowed for a notably diverseecosystem to evolve in the lake. Naturalists have documented more than 1000 species andsubspecies in the lake, including about sixtyendemics.[1] Lake Biwa is an essential place forwater birds. About 5,000 waterbirds visit Biwa every year.
“At that time, we had not experienced any serious invasive species problems and bluegill did not look dangerous according to its feeding habits, not being a fiercepiscivore,” says Nakai Katsuki,[b] a Japanese research scientist at theLake Biwa Museum who has studied invasive North American fish species in Japan’sShiga Prefecture since 1989.[11]
The Awazu site, a submerged shellmidden, is an importantarchaeological site of theJōmon period. It goes back to the beginning of theInitial Jōmon period (c. 9300 BCE). It lies near the southern end of Lake Biwa, close toŌtsu, at a depth of two to three meters from the bottom.[12]
The site shows the use of plant and animal food resources by theJōmon people. It also highlights the significance of nut consumption during this period.
Awazu Midden 3 is dated to theMiddle Jōmon (3520–2470 BCE). An abundance ofhorse chestnuts were uncovered here (about 40% of their total estimated diet). This indicates that by this later period, a sophisticated processing technology had been mastered to remove the harmfultannic acid and make this food safe for consumption.[13]
At the prefectural level, the Eutrophication Control Ordinance was enacted in 1979. It was intended to control industrial pollution from the use of syntheticdetergents by companies and residents alike, following a successful citizens' campaign known as the Soap Movement, which had emerged from women's consumer groups earlier in the 1970s.[14]
Legislation to preventeutrophication was enacted in 1981 and first enforced on July 1, 1982; therefore, this day is called "Lake Biwa Day (びわ湖の日,Biwako no Hi)". The legislation established standards fornitrogen andphosphorus levels in agricultural, industrial, and household water sources that empty into the lake. They also banned the use and sale of synthetic detergents containing phosphorus.
The lake was designated as aUNESCO Ramsar Wetland (1993) in accordance with theRamsar Convention.[15] The object of this treaty is to protect and sensibly use internationally valuablewetlands. The Kushiro marsh (釧路湿原,Kushiro Shitsugen) in Japan is under this treaty now.
Reed colonies on the shore give Lake Biwa its characteristic scenery. The reeds play an essential role in purifying water and providing habitat for birds and fish. At one time, there were large areas of reeds along the shores of Lake Biwa, which local government surveys recently found had halved in size due to encroaching development. This Shiga Ordinance for the Conservation of Reed Vegetation Zones, which protects, grows, and utilizes reed beds, has been in force since 1992.
^abcdKawanabe, H.; Nishino, M.; and Maehata, M., editors (2012).Lake Biwa: Interactions between Nature and People. pp 119-120.ISBN978-94-007-1783-1
^Segers, H.; and Martens, K; editors (2005).The Diversity of Aquatic Ecosystems. p. 46. Developments in Hydrobiology. Aquatic Biodiversity.ISBN1-4020-3745-7
^abElliott, Christian (January 11, 2022)."The prince, the mayor, and the U.S. fish that ate Japan".National Geographic. Archived fromthe original on March 30, 2023. RetrievedJuly 15, 2025.When Crown Prince Akihito visited Chicago on October 3, 1960, his sole request was to visit Shedd Aquarium. Then Mayor Richard J. Daley, an avid angler, presented the prince with a gift that he scooped with a net from one of the tanks himself: 18 bluegills, the official Illinois state fish. The 26-year-old future emperor was already a passionate ichthyologist, and he planned to stock the exotic fish in the moat surrounding his palace, according to accounts in theChicago Tribune at the time. At windy Chicago O'Hare International Airport the next day with Princess Michiko, Akihito bid the city farewell, carrying a gift that he couldn't have imagined would cause a decades-long ecological crisis in his homeland. In the intervening six decades, the bluegills became an invasive, species-destroying nightmare, crowding Japanese freshwater lakes and rivers and destroying native fish biodiversity, says Kenji Saitoh, a researcher at the country's Fisheries Resources and Education Agency. Fortunately, science has marched on in 60 years. Now, Japanese geneticists are experimenting with the gene-editing wizardry of CRISPR to sterilize invasive bluegills. If the initiative succeeds, wildlife managers could use the same technique to rid the U.S. of invasive aquatic species such as Asian carp. In Japan, the public is ambivalent toward bluegills and wary of genetic efforts to curb them, and it's easy to see why. The 60-year history of bluegill in Japan is a cautionary tale about human intervention on all sides. The invasion begins When he arrived home after his 1960 U.S. tour, Akihito asked Japan's national Agency of Fisheries to breed the 15 captive bluegills that survived the trans-Pacific journey, in hopes of releasing them into the wild as a new game fish, nicknamed the "prince fish" in his honor. In 1966, the bluegills' offspring were deposited into Lake Ippeki-ko outside Ito City in Japan's Shizuoka Prefecture. Three years later, a stone monument was placed on the shore to celebrate the successful introduction of the prince fish. More bluegills were released into freshwater ecosystems across Japan. "At that time, we had not experienced any serious invasive species problems, and bluegill did not look dangerous according to its feeding habits, not being a fierce piscivore," says Nakai Katsuki, a Japanese research scientist at the Lake Biwa Museum who has studied invasive North American fish species in Japan's Shiga Prefecture since 1989.
