TONE RIVER

Japanese Tone-gawa, major river of the Kanto Plain, Honshu, Japan. It rises in the volcanic area of northwestern Kanto chiho (region), about 35 miles (56 km) north of Maebashi in Gumma ken (prefecture). The river flows for 200 miles (320 km) south and southeast through the centre of the Kanto Plain to enter the Pacific Ocean at Choshi in Chiba ken, near Cape Inubo. It was once known as Bando Taro, the principal river of Japan in the Bando (now Kanto) region. No other river in Japan has been so modified by human activity. Its entire length has been embanked with dikes, and the course itself often has been altered. The most notable alteration was completed in 1654, when the lower course was diverted from draining into Tokyo Bay and channeled into its present outlet. The Tone River and its tributaries and distributaries are navigable for small boats. The river system formed a major transportation network in the Kanto Plain, giving rise to many small port towns. In competition with road and rail transport, most of the townssuch as Sawara, Sekiyado, Noda, and Nagareyamalost their function as ports. The Tone River is an indispensable source of water for irrigation throughout its populous drainage basin. Since 1950, dams have been constructed on its headwaters to produce hydroelectricity and to form reservoirs to supply water to the Keihin Industrial Zone.