Although it may seem off-script for a meizanologist to visit a museum dedicated to a lake, an exception has to be made here. As a geological phenomenon, Lake Biwa is remarkable not just for its size – the largest freshwater expanse in Japan – but for its age. Most lakes fill in quickly, yet Biwa-ko has endured for four million years, so that it sustains no fewer than sixty or so endemic plants and fish.
An exhibit in the endemic Lake Biwa Museum explains this longevity. The reconstructed site of a geological fault line shows how the lake’s rocky floor has kept sinking over time, at roughly a metre every thousand years. In addition, the lake has tended to migrate in a northerly direction.
I’m reminded of the folk tale that a Godzilla-like giant Daidarabotchi excavated Lake Biwa, all in a single night, and piled up Mt. Fuji from the left-over spoil-tip…
The folk tale has it right in one respect - the lake has a history that is every bit as epic as the mountain's. Back in the museum, a diorama takes us into the deep past, when elephants roamed through forests of metasequoia, and crocodiles lurked at their watering holes. The elephants dwindled in size over time, thus anticipating the art of bonsai by almost two million years.
One of these smaller elephants later caused a sensation. In 1804, when people discovered its fossilised bones on the lake’s western shore, they thought at first they’d found the remains of a dragon.
From geology, we move into historical times. In the feudal era, long barges known as maruko-bune plied the lake, moving as elegantly as a modern N700, if not quite as fast.
There’s also a typical lakeside house, set up as it was in 1964, when water came from a stream and the nightsoil went straight onto the vegetable patch. In his Japan Journals, Donald Richie recalls how this latter practice led in the late 1940s to what he wryly calls a reverse Occupation…
After an hour or so among the cultural exhibits, I decide to make shorter work of those on insect and plant life.
After gawking at a giant dragonfly, I follow the children who are tugging their parents in the direction of the museum’s famous aquarium.
Somehow I manage to miss an encounter with a giant catfish, one of the so-called lords of Lake Biwa. This one must have luck on its side too, having miraculously survived the collapse of its tank three years ago.
I miss the catfish because I’m distracted by a friendly seal, who seems to be inspecting his visitors as curiously as they are inspecting him. Surely he can’t be an endemic? No, the seal is a Russian émigré, imported from Baikal, presumably one of Biwa-ko's Twin Lakes. I hope he doesn't miss the depths and ice sheets of his native waters.
Intending patrons of this museum should note that there is only one bus an hour back to Kusatsu station. Before catching the next one, there's just time to stroll out onto the outdoor viewing platform. A brisk spring breeze is whipping up white-capped waves out on the lake.
Under the clear sky, I start to appreciate Lake Biwa's scale. It seems reasonable that scooping it out would leave you with a Mt. Fuji-sized spoil-tip. How sad then that the volumes don’t match. No, not at all – the savants have calculated that you’d need to dig out something like fifty* Lake Biwa basins to pile up just one 3,776 metre-high mountain. Now even for a Daidarabotchi, that sounds too much like hard work...
*Footnote: Or perhaps only thirty-seven Lake Biwa basins. In his Fujiyama: The Sacred Mountain of Japan (1924), the o-fuda expert and anthropologist Frederick Starr has this to say:-
The Japanese often claim that Mount Fuji was formed in a single night and that simultaneously with its elevation the basin of Lake Biwa was scooped out. Apparently the idea is that the material from the lake basin was thrust up into the mountain. The distance between the two mountain and lake is about one hundred and fifty miles.
Lake Biwa takes its name from its shape. The biwa is a musical instrument something like a guitar. The lake is contracted at the middle by a bending in of the shore lines. It is about 36 miles long, and 12 miles in greatest width.
So persistent is this notion of a relation between the lake and mountain that Professor Omori has seen fit to demolish it by a calculation. According to the popular notion there should be some equivalence of bulk between the mountain and the lake basin.
In Japanese measures Lake Biwa is 16 ri 9 cho 45 ken in length by 5 ri 26 cho 49 ken in greatest breadth; it covers an area of 44.5 square ri and has an average depth of 130.7 shaku; its volume is 20,956 cubic cho, or 0.449 cubic ri.
Mount Fuji rises to a height of 34.6 cho above the sea; it covers an area of about 68 square ri; considering it a regular cone, its volume will be 16.7 cubic ri. The volume of Mount Fuji then will be thirty-seven times that of the water in Lake Biwa.






















































