Japan Navigator

What is the largest river in Japan? If you don’t know the answer to that question, it does not necessarily mean that your geography of the Land of the Rising Sun is weak. Japan is full of rivers, but in contrast to Mt Fuji among mountains, none is of world-shattering format.

The largest river in Japan is the Shinano River (367 km; drainage basin 11,900 sq km) which flows through Nagano and Niigata Prefectures. Interestingly, in Nagano it is called Chikuma River - and it is a typically Japanese phenomenon that parts of rivers have different names. The Shinano (as we will call it here) starts at Mt Kobushigatake on the border of Saitama, Yamanashi and Nagano, flows NW and meets the Sai River at Kawanakajima, the site of a series of famous 15th c. battles. It then passes through the Saku, Ueda, Nagano, Iiyama and Tokamachi basins and finally empties into the Sea of Japan at Niigata City. It has 280 tributaries and its water is used for irrigation, industry, electric power and drinking water. The river used to cause many floods in the downstream area, so in 1922 the Okozu Diversion canal was built to drain superfluous water off to the ocean.

Number two is the Tone River (322 km; drainage basin 16,840 sq.km) which flows through the Kanto region and was nicknamed Bando Taro, the “eldest son of the Bando (= Kanto) area.” It has its start at Mt Ominakami (in the Echigo mountains in the Joshin’etsu Kogen National Park) on the border of Gunma and Niigata and enters the Kanto Plain at Maebashi, the capital of Gunma. The Tone finally pours into the Pacific at Choshi City in Chiba. The Edo River branches away to flow into Tokyo Bay. Other tributaries include the Watarase, Kinu, Omoi and Kokai rivers. Once known for its uncontrollable nature and frequent flooding, over the centuries, the route has changed drastically - in the past, it flowed into Tokyo Bay. Until the advent of the railway in the late 19th century, it also was an important transport route. Today the river has several dams to supply water for the more than 30 million inhabitants of the Tokyo metropolitan area.

In third place comes the Ishikari River (268 km; drainage basin 14,330 sq km), to no surprise in Hokkaido which after all has lots of space for large rivers. The river rises from Mt Ishikari in Daisetsuzan National Park and flows through Asahikawa and Sapporo, to empty into the Sea of Japan in Ishikari Bay. The name was derived from the Ainu word for “winding river,” as it once meandered through the Ishikari plain. The Ishikari Plain is one of the most productive farmlands in Hokkaido. A famous scenic spot is the Sounkyo Gorge on its upper reaches.