Tomodachi Autumn 2015


Sumida River Renaissance

Tokyo Brings a Famous Waterway Back to Life

 The Sumida River, though only 23.5 kilometers (about 15 miles) long, f lows through a densely populated area of central Tokyo, with about 3 million people living in its basin, and it is one of the capital’s most famous waterways. Until around the mid-twentieth century it was the habitat for fish and other aquatic life, and people gathered on its banks for recreation. But as the result of urban development during the rapid-growth years of the 1950s and 1960s, it became polluted and ceased to be an attraction.
 Tokyo Metropolitan Government (TMG) has responded with a variety of measures to revive the river. To improve the quality of the water, the metropolitan authorities first moved to strengthen controls on wastewater from factories and homes, a major cause of the river’s pollution. TMG was at the time undertaking a comprehensive set of measures to tackle the pollution resulting from urbanization, and it adopted an ordinance imposing a set of standards stricter than those mandated under national legislation. It applied administrative guidance through on-site inspections of factories and worked together with business operators to improve the quality of factory wastewater with initiatives including training sessions for businesses.
 Also, the selection of Tokyo in 1959 as the site of the 1964 Olympics provided impetus for a major increase in the share of households connected to the sewer system. The extension of the sewer system was accompanied by the introduction of advanced treatment methods and other moves to improve the quality of water released from wastewater treatment plants. Through these efforts, Tokyo achieved a substantial advance in its handling of wastewater from homes.
 Alongside measures to cut off the sources of pollution, TMG moved to clean up the already-polluted water in the Sumida River. The polluted water was diluted by linking the Sumida to the Tone and Arakawa Rivers by artificial channels and causing cleaner water to flow in. The construction of these linking waterways drew on the water-control technology that Japan has built up over the centuries.
 The metropolitan authorities also conducted dredging to remove earth, sand, and sludge from the riverbed. Dredging operations were started in 1958 and continue to this day, but the three dredging projects undertaken in the first 10 years were especially large-scale, showing TMG’s strong determination to revive the river. Thanks to these many efforts, the water quality improved greatly, and by 1978 there were visible signs that aquatic life forms were returning to the river.
 Now that the water is cleaner, people are once again gathering along the Sumida River. Popular seasonal events like the summer fireworks display and the annual So-Kei Regatta between Waseda and Keio Universities, which had been canceled while the river was badly polluted, are being held again. Work has also progressed on constructing areas where people can enjoy the river at close hand, such as the Sumida Terrace riverside walkway and the Sumida Park Open Café coffee shops, part of TMG’s “Sumida River Renaissance” project aimed at enlivening the area.
 Formerly a target of despair as a “river of death,” the Sumida River is once again a popular waterway full of life. The half century of work on its revival has been a pioneering example of river improvement in Asia. How about coming to see for yourself?

During the Edo period (seventeenth through midnineteenth centuries), the Sumida River was a key artery in the system of water transportation that supported people’s lives, and it was also a popular spot for boat rides, fireworks, and other types of recreation, serving as the theme for color prints, songs, and literary works. In today’s Tokyo, this river has once again become the habitat for many types of fish, insects, and plants.

From Annual Report on the Environment in Japan,
1982: Abridged and Illustrated for Easy Understanding.
A view of the Sumida River from around 1967: Wastewater from factories and homes had caused water quality to deteriorate sharply.

Thanks to improved sewer system coverage and dredging, the water quality has improved, allowing seagulls and fish like gobies to return.

Sewer System Coverage and Water Quality, Sumida River Water System


In the early 1960s the pollution of the Sumida River was at its worst, with biochemical oxygen demand as high as 63 milligrams per liter (mg/l). But since the mid-1980s the figure has been below 10 mg/l. And as pollution has declined, the river’s popularity has recovered.
BOD (biochemical oxygen demand)
BOD is an indicator of the degree of water pollution. It indicates the quantity
of oxygen required by aerobic organisms to oxidize and break down organic
materials (pollutants) in the water over a certain period of time. Higher values
indicate greater pollution.

Water buses now ply the Sumida, and regular events are staged on the river, which has become a recreational spot for residents and visitors.