Tamagawa Josui

by Johannes Schonherr

Tamagawa Josui, Tokyo 玉川上水 東京

The Tamagawa Josui is a historic freshwater canal built in Edo times that originally ran from what is today Hamura city in western Tokyo to Yotsuya Okido, just east of today's Shinjuku Gyoen Park, a distance of 43 kilometers in total.

Though the canal as such is not in use anymore, almost the entire length of the historic canal has been turned into a public park and designated as a "Green Road". For the largest part, the part outside of urban Tokyo, the canal still carries water, is framed by trees and accompanied by a walkway.

The water, by then a mere trickle, disappears underground in Tokyo's Setagaya Ward. Still, the park continues to follow the old route of the canal all the way into Shinjuku. Even in the city and without water visible, the old canal route makes for an interesting history walk.

Tamagawa Josui at Fussa, Japan.
Tamagawa Josui at Fussa
Tamagawa Josui, Japan.
Tama River at the start of the Tamagawa Josui, Hamura, Tokyo

History / Background

When Edo, today's Tokyo, became the capital of Japan in the early years of the 1600's, at the beginning of the Edo Period, the city expanded rapidly.

The Tokugawa Shogunate, ruling Japan and itself based in Edo, needed to provide infrastructure for the new metropolis. That included secure freshwater supplies.

Clean drinking water straight from the mountains, as opposed to the salty sea water of the bay and the polluted water of the rivers flowing through the city, into which many households and businesses emptied their sewage.

The Kanda Canal, built at the beginning of the 1600's, was a first attempt by the Shogunate to alleviate the fresh water shortages. Though a success at first, it soon proved to be insufficient.

Therefore, in 1653, the Shogunate designed and greatly funded a new project: the Tamagawa Josui. Additional funds for the building of the canal were raised from the communities directly benefiting from the new canal. In addition to providing drinking water, the canal also provided irrigation water for farmers in the towns and villages along the canal. The canal was also intended to assist fire fighting along its route.

Amazingly, the Tokugawa authorities didn't hand the execution of the project to some well-connected bureaucrats but deemed two brothers, members of a humble farming family, to be the most suitable for the management of construction.

Tamagawa Josui, Japan.
Tamagawa Josui in Hamura, Tokyo
Tamagawa Josui, Japan.
Monument to the Tamagawa brothers, leaders of the construction of the canal, Hamura, Tokyo

Indeed, under the leadership of the pair of brothers, the digging of the canal went ahead in an unexpected speed. The brothers knew about canal building (as any rice farmer knows to a certain extent) and they knew how to motivate the workers: making clear to them that this was not some slave work in the service of a samurai overlord but a communal project benefitting everyone involved.

In record speed of just 8 months, the basic canal from Hamura to Yotsuya Okido was finished. All 43 kilometers of it. Working out the details, such as building the bridges, took longer of course, but the whole project was finished within 18 months.

Impressed, the Tokugawa Shogunate accorded special privileges to the brothers and considerably raised their social status. They were given a family name, Tamagawa, and the right to carry katana (Japanese swords), thus being elevated into the ranks of the bushi, the aristocratic warrior caste.

Tamagawa Josui, Japan.
Woodblock print of the Tamagawa Josui in Edo Times
Tamagawa Josui, Japan.
Tamagawa Josui in Fussa

Walking the Tamagawa Josui Today

The Tama River (Tamagawa) collects most of its waters from the clear streams of the mountains today comprising the Chichibu-Tama-Kai National Park. The Tama River is still a vital fresh water resource for Tokyo.

If you travel out to Hamura on the JR Ome Line, it's a short walk from Hamura Station to the starting point of the Tamagawa Josui. There, the freshwater canal is still in use today. As a vital Tokyo water supply route, it is seriously fenced in.

The Tama River is blocked, its waters are diverted into an overflow pool from which excess water can be released back into the river in the case of floods. In Hamura, the Tamagawa Josui starts as a veritable river of its own.

Tamagawa Josui, Japan.
Tamagawa Josui in Takanodai, Kodaira City, Tokyo
Tamagawa Josui, Japan.
Tamagawa Josui near Daitabashi Station, Setagaya, Tokyo

The scenery can be viewed from a park on a small river peninsula, featuring a monument to the Tamagawa brothers who led the construction of the original canal.

A few hundred meters down river is a water processing facility where most of the canal's water is diverted into underground pipes.

The underground pipes lead straight to the Sayamako and Tamako reservoirs in or near Tokorozawa, Saitama Prefecture where the water is stored and from where it is released according to demand into the Tokyo water supply system.

Beyond that crucial facility, the canal is still relatively wide and still fenced in to protect the cleanliness of the water.

A walkway follows the canal. It's a popular path with bicyclists as well. From Hamura and through Fussa City all the way to Tachikawa and beyond, you can walk or ride a bike along the canal.

The water level of the canal decreases steadily on the way but the route remains a stretch of wild green even when it crosses newly built residential areas.

Tamagawa Josui, Japan.
Tamagawa Josui south of Sasazuka Station, Tokyo
Tamagawa Josui, Japan.
Tamagawa Josui historic park, Nishihara, Shibuya, Tokyo

In northern Tachikawa, the canal passes by the intersecting train stations of the Seibu Haijima Line and the Tama Toshi Monorail. Both stations are named after the canal, though their English spelling is slightly different: the Seibu Haijima Line station is called Tamagawa Josui, the Tama Toshi Monorail Station Tamagawajosui. (In Japanese, the station names are identical.)

The canal then enters the city of Kodaira. In the Takenodai neighborhood of Kodaira, the canal flows closely by the Sewerage Museum which features a few exhibits, including vintage woodblocks prints, on the Tamagawa Josui.

Crossing Koganei City, the canal reaches Mitaka City where it traverses busy Mitaka Station through a tunnel. On the other side of Mitaka Station, the canal becomes visible again.

Tamagawa Josui, Japan.
Tamagawa Josui monument, Hatsudai, Shibuya, Tokyo
Tamagawa Josui, Japan.
Tamagawa Josui canal park in Shibuya. Street crossings are still marked as historic bridges

Tokyo Section

The Tamagawa Josui then passes through Inokashira Park, famous for housing the Ghibli Museum and for its large number of cherry trees, turning the park into a very popular sakura viewing destination in late March / early April.

Soon after entering Tokyo proper in Suginami Ward, the Tamagawa Josui disappears under the Chuo Expressway. It reappears as waterless "Green Road" Park between Kami Kitazawa Station and Shimotakaido Station (both on the Keio Line) north of National Route 20 (Koshu Kaido).

Close to Daitabashi Station of the Keio Line, south of Koshu Kaido road, the actual canal appears on the surface again. By now, it's a rather small stream, flanked by a narrow park. Passing by Sasazuka Station (Keio Line), the canal finally disappears underground a few hundred meters south of the station.

From now on, the route of the historic canal is marked only by a long, winding stretch of park.

Tamagawa Josui, Japan.
View from Tamagawa Josui canal park to Taichoji Temple and the high rises of Nishi Shinjuku. Yoyogi, Shibuya, Tokyo
Tamagawa Josui, Japan.
Aoi Dori close to Shinjuku Station, view westwards from the very end of the historic canal route

The park crosses into Shibuya Ward. In the ward's Hatagaya neighborhood, it passes by the Tokyo Fire Academy, offering good views to the training grounds of the Tokyo Fire Department, often crowded with firemen doing exercises in full gear.

The park passes through Shibuya Nishihara before running closely parallel to Koshu Kaido in Hatsudai. In Hatsudai, a monument celebrating the Tamagawa Josui seems to close off the canal route.

That's not the case, though. The canal route continues, just that past Hatsudai it is not a continuous park anymore.

Running closely parallel to Koshu Kaido on the southern side, the old canal route now partly serves as a sidewalk to Koshu Kaido, partly it has been turned into small streets. In some sections, it is still a sort of park, though.

When a street crosses the canal route, the crossing often features a symbolic bridge-style railing. Memorial markers spell out the names of the historical bridges even though today, no water is in sight anywhere.

The final stretch of the Tamagawa Josui canal route is Aoi Dori (Blue Street). Aoi Dori may be a nondescript back street but it certainly is built on historic ground.

Aoi Dori ends in front of a Toyota car rental outlet, with the south-west corner of Shinjuku Station visible to the left. That's the real end of the canal route as it can be walked today. Right behind the car rental outlet are the multiple tracks of Shinjuku Station. Beyond them, in the densely built up Shinjuku areas towards Yotsuya, the Tamagawa Josui doesn't seem to be marked anymore.

All parts of the Tamagawa Josui can easily be reached by train. Even walking a small section of it might translate into a fascinating discovery tour tracing ancient Tokyo history.

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