Lake
Biwa is the largest lake and the greatest water resource in
Japan. It supplies municipal and industrial water to some 14
million residents around and downstream of the lake including
those in such megalopolises as Osaka, Kyoto and Kobe Cities.
The lake has a surface area of 670 km2 with a maximum depth
of 103.6 m. It comprises two basins; the large, deep and mesotrophic
North Basin and the small, shallow and eutrophic South Basin.
There are more than 450 rivers and streams flowing into the
lake, whereas there is only one natural outlet, the Seta River,
and there are two artificial canals supplying lake water to
Kyoto.
Lake Biwa is one of the "ancient lakes" in the world,
as are Lake Baikal in Russia and Lake Tanganyika in East Africa.
The Paleo Lake Biwa can be traced back to almost 4 million years
ago. The limnetic and terrestrial fossils have been found in
abundance from the Paleo Biwa Formation Group. The present Lake
Biwa is considered to be born some 400,000 years ago, and about
1,100 of animal and plant species have been recorded so far.
A total of 59 endemic species (51 species, 6 subspecies and
2 varieties) have been listed from the lake, of which nearly
a half (28 spp.) are molluscs and a quarter (12 spp.) are fishes.
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Lake
Biwa and the boundary of Shiga Prefecture