The is a river in the Kantō region of Japan. It is in length (the second longest in Japan after the Shinano) and has a drainage area of (the largest in Japan). It is nicknamed Bandō Tarō (); Bandō is an obsolete alias of the Kantō Region, and Tarō is a popular given name for an oldest son. It is regarded as one of the "Three Greatest Rivers" of Japan, the others being the Yoshino in Shikoku and the Chikugo in Kyūshū. Geography The source of the Tone River is at () () in the Echigo Mountains, which straddle the border between Gunma and Niigata Prefectures in Jōshin'etsu Kōgen National Park. The Tone gathers tributaries and pours into the Pacific Ocean at Cape Inubō, Choshi in Chiba Prefecture. Tributaries Major tributaries of the Tone River include the Agatsuma, Watarase, Kinu, Omoi, and the . The Edo River branches away from the river and flows into Tokyo Bay. History The Tone River was once known for its uncontrollable nature, and its route changed whenever floods occurred. It is hard to trace its ancient route, but it originally flowed into Tokyo Bay along the route of the present-day Edo River, and tributaries like the Watarase and Kinu had independent river systems. For the sake of water transportation and flood control, extensive construction began in the 17th century during the Tokugawa shogunate, when the Kantō region became the political center of Japan. The course of the river was significantly changed, and the present route of the river was determined during the Meiji period, with the assistance of Dutch civil engineer Anthonie Rouwenhorst Mulder. Its vast watershed is thus largely artificial. Two ships of the Imperial Japanese Navy were named after the river, one of World War I vintage and another from World War II, the lead ship of its class. Fukushima Daiichi nuclear disaster As a result of the Fukushima Daiichi nuclear disaster radioactive cesium concentrations of 110 becquerels per kilogram were found in silver crucian carp fish caught in the Tone River in April 2012. The river is from the Fukushima Daiichi Plant. Six fishery cooperatives and 10 towns along the river were asked to stop all shipments of fish caught in the Tone. Use The Tone River was an indispensable inland water link between the capitol at Edo, and later Tokyo, to the Pacific Ocean. It carried not only local products