This freshwater natural lake is not only Japan’s largest, it is also considered to be one of this planet’s oldest. Lake Biwa, or Biwa-ko, is believed to be about four to five million years old. It is also believed to have been the result of the massive earthquake that accompanied the creation of Mount Fuji. The lake was so named because its shape resembles that of the Chinese four stringed lute, the biwa.
About 500 brooks and rivers flowing out of the surrounding Ibuki, Suzuka, and Hira mountains feed the lake. The lake has avoided being choked with sediments that rivers carry into it because the bottom of the lake continues to subside due to geological forces. The only river to flow out of Lake Biwa is the Seta River which flows out the southern end of the lake near Otsu and Ishiyama-dera, later joining the Yodo River and flowing into Osaka Bay.
The watershed of Lake Biwa covers roughly 3,250 square kilometers. About 60 percent of this area is forested mountains, while 18 percent is devoted to agriculture and the balance in other uses such as urban and industrial development. Cities that line the shores of Lake Biwa include Hikone, Nagahama, and Otsu.
The lake is completely encompassed within Shiga prefecture, with its surface area of 674.4 square kilometers occupying one-sixth of the prefecture’s total area. The lake surface lies 83.3 meters above sea level but its deepest point is 104 meters below. Despite this, Lake Biwa is only the eighth deepest lake in Japan (the deepest, Lake Tazawa in Akita prefecture has a depth of 424 meters).
The depth of the water varies widely. The northern part of the lake has an average depth of 41 meters with many parts reaching 50 meters, but the southern part only has an average depth of 4 meters and has no water area that is over 10 meters deep. The circumference of the lake is 235.4 kilometers, with a maximum length of 63.5 kilometers and maximum width of 22.8 kilometers. Within these dimensions, the lake contains about 27.5 billion cubic meters, or 27.5 trillion liters, of water.
Lake Biwa is the home to over 595 species of animals and 491 species of plants, some not found anywhere else on earth. As Japan has grown as a thriving economy, the lake has faced many threats to its environment and ecology. The region’s communities, particularly fishing communities such as that of Okishima, have been dedicated in cooperating to deal with any pollution-oriented problems that have come from a wide variety of sources. For example, the use of agricultural chemicals became prohibited within six kilometers from the lake despite the urgent need to boost food production immediately after World War II. Also, around 1980, the Shiga prefectural government passed an ordinance regulating the sale and use of synthetic detergents despite considerable protests by industrial interests. Actions such as these reflect the wish of the region’s citizens to maintain and pass on a clean Lake Biwa with a quality of water that is two to three times higher than national standards. Despite this, problems do still arise, such as the presence of aggressive non-native fish such as the Black Bass that are upsetting the ecological balance (anglers are being actively encourage to eat the foreign species, and not through the small ones back), the constant risk of “red tide” and the shrinking population of fresh water pearl oysters. As an insurance measure, a small number of pearl oysters were removed from the lake recently and established in a lake (dam) west of Tokyo.
Historically, rice produced in regions facing the Sea of Japan were carried by ship through Lake Biwa to Kyoto and Osaka. In the Edo period (1603-1868), although the transportation of rice was switched to marine routes, various products from northern Japan were still brought to Kyoto and Osaka via the lake and as economy of the country continued to grow, water transport on Lake Biwa flourished benefiting the economies of the region. Today, Lake Biwa is used to irrigate farms, provide drinking water for 12 million people, and generate power for the Kyoto, Osaka and Kobe regions.
Every year several million visitors come to the Lake Biwa Quasi-National Park to enjoy the incredible beauty of the lake and its surroundings. Chikubu and Okishima are islands well-known for their picturesque views and are part of the Omi Hakkei (The Eight Scenic Views of Omi; Omi being the former name of the majority of the territories now forming Shiga Prefecture). Chikubu Island is also a famous pilgrimage destination since it is the home of Hougonji Temple and Tsukubusuma Shrine.
A number of cities border Lake Biwa that can act as a launchpad to the lake’s many activities. To reach Hikone, where a ferry can be taken to Chikubu Island, take a shinkansen train to Maibara and transfer to the JR Biwako Line for the 5-minute trip to JR Hikone Station.
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