Shinano River

The Shinano River (信濃川, Shinano-gawa) is the longest river in Japan. Its name comes from the old name of the current Nagano prefecture; the inhabitants of the region, however, have habitually called it the Chikuma River (千曲川, Chikuma-gawa). It is 367 km long and its basin, with 11,900 km², is the third among the rivers in Japan.

The Chikuma has its source west of Mount Kobushi, which lies on the border between Saitama, Yamanashi, and Nagano prefectures. In its course towards the north-northwest it passes through the plains of Saku, Ueda and Nagano; in the latter is located the city of Nagano. Upon entering Niigata Prefecture, the river changes its name to "Shinano" and runs northeast. Passing the Tōkamachi plain, it ends up on the Echigo plain. Near the city of Niigata it empties into the Sea of Japan, in the section of the Sado Strait.

The Shinano River and its tributaries form many plains in its upper and middle reaches. These valleys have been inhabited since ancient times. The river was an important route of river transportation until well into the 19th century.

However, the Echigo Plain, the largest in the entire river basin, had been an exception, due to frequent flooding. Works for the control of the lower Shinano began in the 16th century and continued through the Edo period. Relative safety allowed Niigata to develop as a port city, although the flooding could not be completely stopped.

The most ambitious work began in 1908. In 1922 the Ōkōzu Waterway (大河津分水路, or Shinshinano River 新信濃川; shin means & #34;new"), which is a second outlet into the Sea of Japan. Construction work on the Sekiya Waterway (関屋分水路), a third drainage canal, began in 1964 and was completed in 1972. The Echigo Plain is today considered the best rice-growing area in all of Japan thanks to these works.