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close this bookWater for Urban Areas (UNU, 2000, 243 p.)
close this folder2. Water management in Metropolitan Tokyo
close this folderHistory of waterworks in Tokyo
View the documentEarly water supply systems
View the documentOpening of modern waterworks
View the documentThe Ogouchi Dam project
View the documentWar damage and the increase in water leakage
View the documentSerious water shortage in 1964
View the documentDevelopment of water resources in the upper Tone River basin

Early water supply systems

During the sixteenth and seventeenth centuries, the city of Edo was already equipped with comprehensive water supply systems that did not exist even in Europe. This was one foundation of the prosperity of Edo that has lasted for nearly 300 years. In 1590, Tokugawa Ieyasu ordered Okubo Fujigoro to draw up a master plan for a water supply system, and, based on this master plan, part of the Kanda Canal was completed. In 1654, the Tama River Canal, with a length of 43 km, was completed by using the Tama River, running west of Edo. It became possible to supply water continuously to the centre of the Edo area and its vicinity. These excellent water systems were based on what one might call classical technologies. They depended not on pumps but on the skilful use of gravity flow, and the water was not sterilized. A rough chronological table of waterworks in Tokyo is shown in table 2.1.

Table 2.1 History of waterworks in Tokyo


Tokugawa Ieyasu, founder of the Edo Shogunate, commissioned Okubo Fujigoro to carry out a survey and draw up a master plan; partial completion of the Kanda Canal


Completion of the Tamagawa Canal


Yodobashi Purification Plant started operating


Facilities badly damaged in the Great Kanto earthquake


Sakai Purification Plant started operating


Completion of Kanamachi Purification Plant


Completion of Yamaguchi Reservoir


Construction of Ogouchi Dam started


Facilities devastated in World War II


Completion of Ogouchi Dam (Tama River system)


Nagasawa Purification Plant started operating


Higashi-Murayama Purification Plant started operating


Great water shortage in the Tama River system; water distribution cut by max.50%


Abolition of Yodobashi Purification Plant because of the Shinjuku Suburbanization Plan


Asaka Purification Plant started operating


Completion of Yagisawa Dam (Tone River system)


Completion of Shimokubo Dam (Tone River system)

Completion of Tone Diversion Weir and Musashi Canal


Ozaku Purification Plant started operating

Intake stopped from Tamagawa Purification Plant


Completion of Tone Estuary Barrage


Misono Purification Plant started operating


Completion of Kusaki Dam (Tone River system)


Misato Purification Plant started operating


Completion of Naramata Dam (Tone River system)


Completion of 1st Stage of Advanced Water Purification Treatment Facility in Kanamachi Purification Plant

Completion of Tamagawa Cold Water Countermeasure Facility

Source: Bureau of Waterworks (1994).

Opening of modern waterworks

Fig. 2.1 Developments in Tokyo's water service, 1900-1995 (Source: Bureau of Waterworks, 1994)

Along with the opening of the country, the Japanese government imported advanced waterworks technologies developed in Western Europe. Beginning in 1887, modern waterworks were constructed under the supervision of William Palmer, an Englishman, in Yokohama, which had a large settlement of foreigners. The Yodobashi Purification Plant started operating in 1898. At the beginning, it was capable of supplying only 166,800 m3 of water per day to 80,000 people. However, as the population increased and the potable water service spread, the waterworks kept on growing. Private sector systems and nearby villages and towns were absorbed. Developments in Tokyo's water service are shown in figure 2.1; the growth in the average daily water supply is shown in figure 2.2.

These figures demonstrate the remarkable expansion of the water supply system. The process of expansion was not smooth, however. Some of the difficulties were the Kanto earthquake on 1 September 1923, World War II, and in particular the destruction of waterworks by air raids towards the end of the war, and then slow recovery. Furthermore, serious water shortages in the Tama River in 1940, flood damage in the eastern areas of Tokyo caused by Typhoon Katherine in 1947, and another serious water shortage caused by low precipitation on the Tama River Upper Basin in the summer of 1964 affected the management of the Tokyo water service.

The reconstruction of the water service facilities that had been completely destroyed by the earthquake of 1923 not only employed earthquake-resistant structures, but also involved the construction of new reserve water systems, changing from steam pumps to electric pumps at the Yodobashi Purification Plant, the carrying out of land readjustment for urban renewal, and major modifications to and expansion of water service networks. As a result of the unusual water shortages in the Tama River in 1940, water supply sources were reinforced, new wells were constructed, neighbouring water systems were connected, and emergency measures for water supply were completed.

Fig. 2.2 Growth in the average daily water supply volume, 1900-1995 (Source: Bureau of Waterworks, 1994)

The Ogouchi Dam project

As a drastic measure to cope with the rapid increase in population, the Tokyo City Waterworks Bureau decided to go ahead with the Ogouchi Dam project. At 149 m, the dam height was, as a dam for the exclusive use of the water service, the highest in the world at the time, and it was an epoch-making undertaking considering that the highest dam in Japan at the time was the Komaki Dam, at 79 m. The water volume of the reservoir (later named Lake Okutama) created by the Ogouchi Dam was approximately 180 million m3. However, construction did not commence until 1938, because the acquisition of water rights in the lower basin of the river ran into difficulties. Moreover, construction had to be discontinued during World War II because of a shortage of labour and materials.

After the war, construction of the dam recommenced in 1948, and it was completed in 1957. The water supply capability of the Tokyo waterworks immediately expanded. Within a year, the Nagasawa Purification Plant, intended for bringing water from the Sagami River to Tokyo, was completed. This was built in Kawasaki City in Kanagawa Prefecture, which is next to Tokyo. The ceding of the water supply to Tokyo began in 1959. Also in 1957 the Waterworks Laws were decreed. The promotion of the water service was a significant policy throughout the Japan.

War damage and the increase in water leakage

World War II not only interrupted construction of the Ogouchi Dam, but caused great damage to the waterworks facilities. Air raids became ever more intense over all Japanese cities from 1944 and were heavily concentrated on Tokyo in particular; its waterworks facilities were completely devastated. From August 1945, with the end of the war, reconstruction of the war-damaged waterworks facilities began. Since losses of water from water pipes in Tokyo had been considerable as a result of the war damage and poor maintenance, the repair of water leaks became the main challenge.

Table 2.2 Trends in Tokyo's water leakage rate, 1915-1995


Rate (%)































Source: 1950-1995 – Bureau of Waterworks, Annual Report on Waterworks in Tokyo, Tokyo Metropolitan Government.

Changes in the rate of water leakage since 1915 are shown in table 2.2. The leakage rate had been over 20 per cent since 1930, but in 1945 - at the end of the war - it had rocketed to approximately 80 percent. Though it fell to 68 per cent by 1946, the water supply system was jokingly called the "waterworks colander." Specialists in the Metropolitan Government were employed to find the points of leakage and to deal with the problem. They succeeded in at last bringing the rate down to 22 per cent in 1955. This rate was still quite high. As a result of continued efforts, it fell to 10.6 per cent in 1993. Since the annual distribution of water in 1993 was 1,700 million m3, a leakage rate of 10.6 per cent meant that the volume of leakage was 170 million m3 annually, an amount equivalent to the total pondage of the Ogouchi Dam. However, since most of the points of leakage were not in the main pipes, but in the very great number of final distribution pipes, it was not easy either to locate or to deal with the problem; it required time and labour. It took many years to get the rate down to 10 per cent, and ceaseless efforts must continue to be made in the future.

Serious water shortage in 1964

From around 1957, when the Ogouchi Dam was completed, the population of Tokyo started to increase rapidly. This was a time of transition from a period of urban population concentration to a period of high economic growth. The population increase and the rise in living standards resulted in an inevitable increase in the consumption of potable water and the volume of water used for various city activities. For that reason, the annual increase in the water service in Tokyo reached approximately 300,000 m3.

In 1963/64, during this period of rapid increase in demand for water services, there was little precipitation in the upper basin of the Tama River, the upstream region of the Ogouchi Dam. In particular, precipitation during May and July of 1964, the rainy season, was extremely low. At this time, the sources of water for Tokyo consisted of the Tama River system, including the Ogouchi Dam (about 60 per cent), the Edo River (about 20 per cent), the Sagami River (about 10 per cent), and underground water and other sources (about 10 per cent). Dams along the upper basin of the Tone River, such as the Yagisawa Dam, were under construction, and others were still in the planning stage, so water from these areas was not yet supplying the water service system to serve the citizens of Tokyo. The lack of precipitation in the upper basin of the Tama River system lasted from June until 20 August 1964, and the pondage of Ogouchi Dam, which was 180 million m3 at its maximum, fell to as little as 2 million m3. This was a decisive blow to Tokyo's water supply. The Tokyo Waterworks Bureau had to impose severe restrictions on the use of water. Areas in the highlands of Tokyo went whole days with no water. Water tankers of the Self Defence Forces were mobilized every day, and citizens had to wait in line with buckets for their share.

The Olympic Games, held for the first time in Asia, were to open on 10 October 1964. A construction rush had been under way in Tokyo for hotels, metropolitan expressways, the Tokaido Shinkansen, and subways. Construction sites and newly built hotels were also suffering from the shortage of water.

Because the dams along the upper basin of the Tone River were not yet completed, the construction schedule for the Musashi Canal (a man-made channel connecting the Tone River and the Ara River) was accelerated. As part of the total water system carrying water to Tokyo, it succeeded in achieving a temporary supply of water by 20 August. Luckily, toward the end of August, normal precipitation for the season fell in the upper Tama River basin, and restrictions on water use were gradually lifted. The Olympic Games went ahead without any water-related fears.

Development of water resources in the upper Tone River basin

Development of the water resources of the upper basin of the Tone River system to serve Tokyo had been proposed to Tokyo City Council in 1926. Concrete discussions in the Council started in 1936, but it was not until after World War II that the actual plans were approved for execution. In March 1963, a plan to bring water from the Tone River to Tokyo was decreed by the Cabinet as the "Water Utilization Plan of Tone River Systems." Based on the plan, the development of water sources has become a part of the National Water Resource Development Plan, and many of its projects have been executed by the Water Resources Development Public Corporation that was established in 1962. The Tokyo Metropolitan Government was to take partial financial responsibility for the costs of the water supply, including industrial water, by way of multi-purpose dams. The Akigase Intake Weir and Asaka Canal had been built as emergency measures during the "Tokyo Water Famine" of 1964 as described earlier. The Musashi Canal was also constructed by the Public Corporation. Thus it became possible to get water from the Tone River systems when there was some spare volume, until the completion of dams in the upper basin of the river. Water from the upper Tone River basin was planned to flow through the Musashi Canal, via Tone Oseki (Tone Grand Diversion Weir), to the Ara River, with purification occurring at the Asaka Purification Plant, and sent from there to Tokyo by way of water pipes. The Asaka Purification Plant was completed in 1966. (Prior to that, in 1965, the Yodobashi Purification Plant, which had played an important role as the largest plant in Tokyo, ceased to exist. The site occupied by the plant was taken over for the development of the Shinjuku Suburbanization Plan, and became a town of high-rise buildings, such as the Tokyo Metropolitan Government Centre, hotels, and offices.)

The volume of water supplied to Tokyo increased by 1,200,000 m3/day after construction of the Asaka Purification Plant (900,000 m3/ day) and the Higashi-Murayama Purification Plant (300, 000 m3/ day). All planned construction was completed by 1968, including the Yagisawa Dam in the upper basin of the Tone River in August 1967 and the Shimokubo Dam in the basin of the Kanna River, a branch of the Tone River, in November 1968. As a result, the volume of water supplied to Tokyo increased dramatically. Furthermore, the Tone River water resource development projects were completed one by one, and after 1965 the water supply operation expanded to serve not only the urban areas of Tokyo but also Tama districts. Construction of the Tone Estuary Barrage was completed in 1971 and dams in the basin of the Watarase River, the Kinu River, etc. and expansion of the Asaka Purification Plant were undertaken in the 1960s and 1970s.

Since the 1970s, however, it has become increasingly difficult to get agreement on dam-site areas. Difficulties in balancing water demands in the future have been anticipated. The Tokyo Waterworks Bureau made a public announcement in 1973 on "Statements Concerning Water Conservation" and, for the first time, appealed to citizens regarding the need for control over water demand and the saving of water. At about the same time, the state government began to propose a "water conservation conscious society." Furthermore, the 1973 "Act of Special Measures for Reservoir Areas," a measure to cope with the difficult situation of upstream reservoir areas, was passed by the Diet. Great progress has been made, by making a differentiation from money compensation-type measures. This was one of the turning points in the history of dam construction policy.

Criticisms about dam construction were originally based on the shortcomings of the measures for the reservoir areas of the upstream basin. Eventually, the effect of dam construction upon the environment has begun to be taken into account, with the cost of environmental measures being added on. The cost of construction has thus risen considerably. Although the Yanba Dam and other dams along the Agatsuma River (a branch of the Tone River) are already on the government's construction list, potential dam sites are in general decreasing and it is gradually becoming difficult to secure future water resources for Tokyo by means only of dams.

Tokyo's waterworks, having experienced a century of many complications, have fulfilled their mission well. Now there are new problems: environmental problems such as pollution of water at intake points on rivers, etc., further upgrading of service to inhabitants, and earthquake measures.