Arakawa River

The Arakawa (荒川, Ara-kawa) is a Japanese river in the Kantō region, in the central part of the island of Honshū. Its length is 173 km and the surface of its basin is 2,940 km². It is one of two large rivers in the Kantō Plain along with the Tone River, which runs through the eastern part of the plain. The megapolis of Tokyo is located at its mouth, which serves as a boundary between Edogawa and Kōtō, two of its 23 Special Neighborhoods.

Course

The source of the river, within Saitama Prefecture, is located northeast of Mount Kobushi (甲武信ヶ岳, Kobushi-ga-dake), a peak of 2,475 m s. n. m. on the border with the prefectures of Yamanashi to the south and Nagano to the west. The Arakawa runs from its source to the east, within the Chichibu-Tama-Kai natural park, to the Chichibu plain, then north to the Nagatoro valley, and again runs towards the east, to Yorii, on the Kantō plain. In Kumagaya the direction changes to the south. At Kawagoe, it joins its main tributary on the right, the Iruma. On the border of Saitama and Tokyo prefectures (in the Iwabuchi area of Kita Special Ward), just 5 m s. n. m., the river was diverted to the east to avoid continuous flooding of the center of the historic capital of Edo. The Sumida River, which starts from this point, is the old channel of the Arakawa and both flow into Tokyo Bay, east of the city.

In the upper reaches of the Arakawa and its headwater tributaries, there are several reservoirs to supply water to the metropolitan area: The Futase Dam creates the Chichibu Reservoir. The Urayama Dam creates the Sakura Reservoir. The recently constructed Takizawa Dam on the Nakatsu River is currently being dammed.

Main cities of your course

Tributaries

History

The Arakawa was, in historical times, a tributary of the Tone River until the Muromachi period (14th-16th centuries). Until then, its course continued southeast beyond Kumagaya and joined the Tone River at Yoshikawa, since at that time the Tone River flowed into Tokyo Bay. Parallel to the course of the Tone ran the Watarase River (currently a tributary of the Tone on the left), which also flowed into Tokyo Bay, following the course of what is now the Edo River. Between the Tone and the Watarase the Naka River was located. The lower course of the current Arakawa was then the bed of the Iruma River, currently one of its main tributaries on the right. The channels of the lower reaches of the Iruma River, the Arakawa, the Tonegawa, the Naka River and the Watarasegawa changed frequently and the waters went out of course. Farming in the southern Kantō Plain was very difficult due to flooding.

The rivers of the Kantō plain in the centuryXVI.

The rivers of the Kantō plain in the centuryXX..

This situation changed when the shogun Tokugawa Ieyasu settled on the city of Edo (today's Tokyo), the new capital of Japan at the beginning of the Edo period, at the beginning of the century XVII.

The shogunate of the Edo period promoted control of the rivers of the Kantō Plain, both to benefit from the cultivation of the land and the riverside transportation of goods. Tokugawa Ieyasu appointed Ina Tadatsugu (伊奈忠次) as Kantō Gundai (関東郡代, civil governor of rural Kantō). Tadatsugu and his clan's successors, such as Ina Tadaharu (伊奈忠治), oversaw numerous public works in multiple and complex stages to tame the rivers of the Kantō Plain.

In 1621 the Tone River first diverted its lower course to the bed of the Watarase River. Tadaharu divided the Tonegawa and the Arakawa in 1629, since then the Arakawa turns south at Kumagaya and has captured the Iruma River near the Nishi neighborhood in the urban district of Saitama. In 1641 the new middle course of the Tone (and old lower course of the Watarase) shifted slightly east into what is today's Edo River. Later, the Tone River changed its course to the Hitachi River and then to the Kinu River. These works created many small rivers as drains, and irrigation ditches for the rice fields. The new courses of the Ara, Tone and Edo were also used as water channels to transport goods from the rural districts. The ships transported agricultural goods from Tōhoku and Kantō to the capital, Edo, and vice versa with manufactured goods in the capital. The shogunate was very satisfied with the result of these hydraulic works.

The bed of the Arakawa in the vicinity of the capital Edo was, in the Edo period, the course of the current Sumida River (in turn, the final course of the historical Tone River), since it was as the inhabitants of Edo called the lower course of the Ara River. Many Edo literati and poets wrote about the Sumida River, but in reality they were referring to the Ara River by another name; At that time, the 'Sumida River' It had a larger channel than the current one. Floods were still frequent during that historical period. The shogunate left a part of the rural area surrounding Edo without protection of containment dikes so that the flood waters would overflow into that area and thus not breach the dikes and flood the city. Since the speed of the water during the flood was slow (having to be dispersed over a larger area), this strategy did not cost many human lives. The shogunate did not collect taxes and helped the inhabitants of the damaged area after each disaster.

The Arakawa and its tributary, the Shingashi River, were important for river transportation to and from Tokyo, until the development of the railway at the turn of the century XIX.

The current shape of the lower course of the Arakawa is the product of the Meiji era planning of the so-called 'Ara River Transfer Canal', which began construction in 1911 and was completed in 1930. Since then, the Arakawa was provided with a wide channel and a strong dam, taking advantage of the final stretch and mouth of the Naka River, which in turn was moved further east. The "Ara River Transfer Channel" It became the last stretch of the Ara River as it appears today since 1965. Since then, the previous final course abandoned by the Arakawa officially became the Sumida River.

The Arakawa, as the main river of the capital of Japan, is twinned with the Potomac River of the United States of America.