Lake Biwa

Lake Biwa
from space
Coordinates	35°20′N 136°10′E / 35.333°N 136.167°E / 35.333; 136.167
Primary inflows	more than 400 small rivers
Primary outflows	Seta River
Catchment area	3174 km²
Basin countries	Japan
Ramsar Wetland
Designated:	10 June 1993

Max. length	63.49 km
Max. width	22.8 km
Surface area	670.4 km²
Max. depth	103.58 m
Water volume	27.5 km³
Residence time	5.5 years
Shore length¹	235.2 km
Surface elevation	85.6 m

Islands	3
Settlements	Hikone, Otsu, Nagahama, Takashima
¹ Shore length is not a well-defined measure.

Lake Biwa (琵琶湖, Biwa-ko^?, literally "Biwa Lake") is the largest freshwater lake in Japan, located in Shiga Prefecture (west-central Honshu), northeast of the former capital city of Kyoto. Because of its proximity to the ancient capital, references to Lake Biwa appear frequently in Japanese literature, particularly in poetry and in historical accounts of battles.

Name

The term of Biwako was established in the Edo Period. There are some theories about the origin of Biwako, but it was generally believed that a stringed instrument Biwa is related to Biwako. Kōsō, a learned monk of Enryaku-ji in the 14th century, referred to a clue of Biwako in his writing; "The lake is the Pure land of Benzaiten. Because she lives in the Chikubu Island and the shape of the lake is similar to Biwa, her favorite instrument."^[1]

The lake was formerly known as Awaumi (淡海^?, Freshwater Sea) or Chikatsu Awaumi (近淡海^?, Freshwater Sea Near Capital). Later Awaumi changed to modern Ōmi, an etymology of Ōmi Province. The lake is also called Nio no Umi (鳰の海^?, "Little Grebe Lake") in literature.

Area and use

The area of this lake is about 670 km². Small rivers drain from the surrounding mountains into Lake Biwa, and its main outlet is the Seta River, which later becomes the, Uji-kawa, combining with the Katsura and Kizu to become the Yodo River and flows into the Seto Inland Sea at Osaka Bay.

It serves as a reservoir for the cities of Kyoto and Ōtsu and is a valuable resource for nearby textile industries. It provides drinking water for about 15 million people in the Kansai region. Lake Biwa is a breeding ground for freshwater fish, including trout, and for the pearl culture industry.

The Lake Biwa Canal, built in the late 1890s and later expanded during the Taishō period played a role of great importance in the rekindling of Kyoto's industrial life, after a steep decline following the transfer of the capital to Tokyo.

Lake Biwa is home to many popular beaches along the north-western shore, in particular, for example, Shiga Beach and Omi-Maiko. The Mizunomori Water Botanical Garden and The Lake Biwa Museum in Kusatsu are also of interest.

The Lake Biwa Marathon takes place in Otsu, the city at the southern end of the lake annually since 1962.

Natural history

Lake Biwa is of tectonic origin and is one of the world's twenty oldest lakes, dating to almost 4 million years ago. This long uninterrupted age has allowed for a notably diverse ecosystem to evolve in the lake. Naturalists have documented about 1100 species in the lake, including 58 endemic species. Among these endemics are four fish species: Gnathopogon caerulescens (a cyprinid), Opsariichthys uncirostris (a cyprinid), Gymnogobius isaza (a goby), and Silurus biwaensis (a large silurid catfish). The Biwa trout is also endemic to the lake, but some maintain that it is a subspecies of the widespread masu salmon rather than a separate species. Lake Biwa is an important place for water birds. About 5,000 water birds visit Lake Biwa every year.

Recently the biodiversity of the lake has suffered greatly due to the invasion of foreign fish, the black bass and the bluegill. Bluegill were presented to the Emperor and later freed in the lake as a food source for other fish. Black bass were introduced as a sport fish. In July 2009, a largemouth bass weighing 22 pounds, 4 ounces (about 10.09 kg) was caught in the lake by Manabu Kurita. It has been officially certified by the International Game Fish Association (IGFA) to tie the largemouth bass world record held solely by George Perry for 77 years.

Environmental legislation

Various environmental laws cover Lake Biwa:

Eutrophication prevention

Legislation to prevent eutrophication 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 for the nitrogen and phosphorus levels for agricultural, industrial, and household water sources emptying into the lake. They also banned people from using and selling synthetic detergents which contain phosphorus.

Wetlands protection

The lake was designated as a UNESCO Ramsar Wetland (1993) in accordance with the Ramsar Convention. The object of this treaty is to protect and sensibly use internationally valuable wetlands. The Kushiro marsh (釧路湿原, Kushiro Shitsugen) in Japan is under this treaty now.

Conservation of Reed Vegetation Zones

Reed colonies on the shore form give Lake Biwa its characteristic scenery. The reeds play an important role in purifying water as well as 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 to have halved in size due to encroaching development. This Shiga Ordinance for the Conservation of Reed Vegetation Zones to protect, grow, and utilize the reed beds has been in force since 1992.