What kind of lake is Lake Biwa?

Let us give you a tour of its size and origin, its plants and animals, and its importance to the people living near it.

The lake is so broad that a boat sailing out into Lake Biwa will eventually disappear beyond the horizon.Just like the ocean, Lake Biwa reminds us of the spherical nature of planet on which we live.The lake’s shores are widely varied. The North shore where the mountains protrude close to the lake has some rocky areas and inlets, whereas the East shore has sandy beaches. The south shore, however, is somewhat developed, as that is where the city touches the lake.Lake Biwa area is approximately 670km 2.While lake shore measures 235km in circumference, the actual road around the lake is 200km long, and a bicycle trip around it would probably take two days. At its deepest, the lake is about 104m deep. North to South, it is about 60km long, and East to West, it is 20km wide. The lake holds about 27.5 billion tons of water—enough water for 14.5 million people, the total population of the Yodo River valley, to use for 11 years.

▲View of Lake Biwa (Lake Biwa Museum, courtesy of Shigehumi Kanao)

Shiga Prefecture is surrounded by Mt. Ibuki, Mt. Suzuka, and the Hira mountains, which are all higher than 1000m, and in the center is Lake Biwa. Rain falls on these mountains and their surroundings and flows to collect in Lake Biwa via both large and small rivers. The catchment of this lake is 96%, meaning almost all the water from the Prefecture finds its way in to the lake.

Topography of Shiga Prefecture(Lake Biwa Guidebook)

Lake Biwa has an ancient history. About 4 million years ago, a shallow, narrow lake (Lake Ohyamada) appeared where what is today Iga City in Mie Prefecture. With repeated fault movements that caused land collapses and upheavals, that lake gradually changed shape and shifted to where it is now. The Lake Biwa we see today formed at least 400,000 years ago.

On average, lakes disappear within 10,000 years of forming due soil sedimentation. It is quite rare to find one as old as 100,000 years. There are only 20 lakes in the world that are more than 100,000 years old with their unique endemic species and environments, and Lake Biwa is the only one of these special lakes in Japan.

Since the ancient Lake Biwa formed 4 million years ago and the current Lake Biwa has existed for at least 400,000 years, life has had enough time to evolve into unique endemic species. There are more than 1700 species living in and around Lake Biwa, and more than 60 of these are endemic, found nowhere else on earth.

▲Lake Biwa creatures circle of life

There are many swimming areas on Lake Biwa, such as Miyagahama, which is one of the best 88 swimming spots in Japan. People also enjoy lake sports, such as yachting, canoeing, etc. Approximately 700,000 people visit the lake every year to enjoy swimming and playing in the fresh water.The road surrounding the lake is mostly flat, and many people enjoy “Biwaichi”, cycling or walking around the whole lake, to enjoy its size and vistas.

▲Miyagahama swimming area (Omihachiman City)