Tama River, Tokyo

Why you should experience Tama River in Tokyo, Japan.

Tama River is a pastoral corridor where Futako-Tamagawa's historic crossing, broad floodplain, suburban growth and enduring relationship with western Tokyo's mountain watershed unfold along one of the capital's great waterways.

Running through Futako-Tamagawa between Setagaya and Kawasaki, the river descends from Mount Kasatori in the Chichibu Mountains before traveling approximately 138 kilometers toward Tokyo Bay, forming much of the boundary between Tokyo and Kanagawa along its lower reaches. Around Futako-Tamagawa, expansive river terraces and gravel bars create an abrupt opening in the dense metropolitan fabric, with the Tokyu Den-en-toshi and Oimachi lines crossing beside Futako Bridge. Levees, playing fields and riverside paths occupy the floodplain, preserving substantial open ground along a watercourse historically associated with ferries, agriculture, gravel extraction and the expansion of western suburbs. The result is a river corridor where the geography of the Kanto region remains strikingly visible within metropolitan Tokyo.

What you should know about Tama River.

Tama River is best known for carrying water from a 1,953-square-kilometer basin through a 138-kilometer course whose importance to Edo and Tokyo expanded dramatically after the seventeenth century. Tokugawa Ieyasu entered Edo in 1590 and ordered Koizumi Jidayu to undertake major irrigation works across the Tama River lowlands, producing the Rokugo irrigation system on the northern bank and Nikaryo irrigation system on the southern bank during the early Edo period. Another engineering campaign began in 1653 under brothers Shoemon and Seiemon to channel Tama River water from Hamura toward the growing capital. The resulting Tamagawa Josui opened in 1654, extending roughly 43 kilometers from Hamura to Yotsuya Okido and supplying Edo with drinking water through a gravity-fed system. Population growth and industrialization increased demand during the Meiji and Taisho eras, leading Tokyo to complete Murayama Reservoir in 1927 and Yamaguchi Reservoir in 1934 as new storage infrastructure tied to the Tama River system. Ogouchi Reservoir followed in 1957 after decades of planning and construction, creating Lake Okutama and adding approximately 185 million cubic meters of storage to the metropolitan water network.

Flood control produced another consequential chapter after repeated inundation exposed the difficulty of containing a large river beside expanding suburbs. The national government began direct improvement works on the Lower Tama River in 1918, launching a program of levee construction, channel work and flood management across the increasingly urbanized basin. The river entered a new environmental era during the postwar decades as rapid population growth and industrial discharge severely degraded water quality, with biochemical oxygen demand at Chofu Weir reaching its worst annual value in 1970. Expansion of sewerage and wastewater treatment subsequently drove a sustained recovery, and ayu populations returned in substantial numbers to reaches where pollution had once restricted aquatic life. A 2001 national river-improvement plan established a long-term approach spanning flood control, water use and environmental restoration across the basin. Contemporary management combines levees, reservoirs, weirs, habitat protection and extensive public river space, carrying a waterway once engineered principally for irrigation and urban supply into a far broader metropolitan role.

How to fold Tama River into your trip.

Tama River works as the anchor for a daytime exploration tracing prehistoric settlement, Japanese folk architecture and modern artistic patronage through the wooded terraces above the river.

Begin at Todoroki Valley, where the Yazawa River cut into the Musashino plateau to create a steep green ravine extending through southern Setagaya near the Tama River terraces. Archaeological remains surrounding the valley include the Todoroki Valley No. 3 horizontal tomb, part of a burial complex dating from the late Kofun period and preserving evidence of settlement in the district centuries before Edo. Continue west to Seikado Bunko Art Museum, founded from the collection assembled by Mitsubishi's second president Yanosuke Iwasaki and expanded by his son Koyata Iwasaki. The collection encompasses approximately 200,000 classical books and 6,500 works of East Asian art, including National Treasures and Important Cultural Properties gathered through the Iwasaki family's scholarly patronage. Conclude at Gotoh Museum, opened in 1960 to house the collection of Tokyu founder Keita Gotoh. Architect Isoya Yoshida designed the museum beside a garden assembled from the former residential properties of prominent figures including Prince Nashimoto Morimasa, and the collection includes the National Treasure Tale of Genji Illustrated Scrolls. The progression moves from ancient burial grounds above the river through the Iwasaki family's preservation of East Asian scholarship and onward to Keita Gotoh and Isoya Yoshida's union of collecting, architecture and garden design, revealing successive cultural layers across the terraces overlooking Tama River.

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