Water supply and sanitation in Japan is characterized by numerous achievements and some challenges. The country has achieved universal access to water supply and sanitation, has one of the lowest levels of water distribution losses in the world, regularly exceeds its own strict standards for the quality of drinking water and treated waste water, uses an effective national system of performance benchmarking for water and sanitation utilities, makes extensive use of both advanced and appropriate technologies such as the jōkasō on-site sanitation system, and has pioneered the payment for ecosystem services before the term was even coined internationally. Some of the challenges are a decreasing population, declining investment, fiscal constraints, ageing facilities, an ageing workforce, a fragmentation of service provision among thousands of municipal utilities, and the vulnerability of parts of the country to droughts that are expected to become more frequent due to climate change.
Access and service quality Access to an improved water source is universal in Japan. 97% of the population receives piped water supply from public utilities and 3% receive water from their own wells or unregulated small systems, mainly in rural areas.Ministry of Health, Labor and Welfare:Coverage, retrieved on January 6, 2011
Access to improved sanitation is also universal, either through sewers or on-site sanitation. All collected waste water is treated at secondary-level treatment plants. All effluents discharged to closed or semi-closed water bodies, such as Tokyo Bay, Osaka Bay, or Lake Biwa, are further treated to tertiary level. This applies to about 15% of waste water. The effluent quality is remarkably good at 3–10 mg/L of BOD for secondary-level treatment, well below the national effluent standard of 20 mg/L.
Water resources and the use of water
Water resources and climate change While Japan is not a water-stressed country per se, water availability varies substantially between years, seasons and regions, leading to regular and serious water shortages. On average over the period 1971–2000, water resources in Japan stood at 420 km3 per year. This comes to 3,300 m3 per capita, which is below the global average. On the Pacific coast where most Japanese live, 70–80% of rainfall occurs during only four months, i.e. the summer monsoon from June to July and the typhoon season from August to September. On the coast of the Sea of Japan the winter monsoon brings heavy snowfall from December to February.Food and Agriculture Organization (FAO) Aquastat:Japan country profile, Chapter on climate and water resources, 1997, retrieved on January 6, 2011 National droughts occur about every 10 years in Japan, in addition to more frequent regional droughts. During the drought in 1994 the piped water supply of 16 million people had to be restricted. It is expected that the severity of droughts will increase because of climate change which will reduce the amount of water stored in the form of snow, increase evaporation from reservoirs and reduce rainfall.Ministry of Land, Infrastructure and Transport:Current state of water resources in Japan , ca. 2006, retrieved on January 6, 2011 Most of the water for domestic use comes from surface water. About 45% of the total comes from reservoirs regulated by dams, while 27% comes directly from rivers, 1% from lakes and 4% from river beds, totaling 77% from surface water. 23% of domestic water supply comes from groundwater, which is over-exploited in parts of the country.Ministry of Health, Labor and Welfare:Water Sources, retrieved on January 6, 2011
Water storage While there are more than 2,500 dams in Japan, their total storage is low because rivers are short and steep. Total active storage of all dams is only 20 km3, corresponding to less than the storage capacity of Hoover Dam.Ministry of Land, Infrastructure and Transport:Water Resources Development , ca. 2006, retrieved on January 6, 2011 In addition, lakes have an important storage function, and their water levels are regulated through weirs. The largest lake is Lake Biwa that provides drinking water to more than 15 million people in the Keihanshin (Kyoto-Osaka-Kobe) metropolitan region.
Water use
Annual water use is about 83.5 km3, or 20% of water availability, in an average year. However, there are large variations in the utilization rate between years and regions. For example, in the coastal part of the Kantō region that includes Tokyo, the utilization rate is over 90% in a dry year. In the relatively dry north of Kyushu it is more than 50%.Ministry of Land, Infrastructure and Transport:Water balance in Japan , ca. 2006, retrieved on January 6, 2011 Of the total use, 55.2 km3 was for agriculture, 16.2 km3 for domestic use and 12.1 km3 for industrial use. Despite the introduction of water-saving devices, domestic per capita use declined only slightly from 322 liters per capita per day in 2000 to 314 in 2004. Per capita water use thus is slightly lower than in the United States (371 liters in 2005) and more than twice as high as in Germany (122 liters in 2007) or in England (145 liters in 2009).
Water quality Although drinking water quality and the quality of wastewater discharged into open watercourses typically exceed national standards, water quality in rivers and lakes still does not meet environmental standards. For example, the attainment rate of environmental standards was 87% in 2005, but in lakes and marshes it was only 50%.Ministry of Land, Infrastructure and Transport:Issues on water resources , ca. 2006, retrieved on January 6, 2011
Infrastructure and technology
Water supply New water distribution pipes are typically made from ductile iron and service pipes from stainless steel. The share of pipes made of these materials increased from 40% for ductile iron and zero for stainless steel in 1980 to 100% for both in 2006. The change in pipe materials is credited as a major factor in reducing water losses to one of the world's lowest levels.Ministry of Health, Labor and Welfare:Waterworks technologies in Japan, retrieved on January 6, 2011 Water treatment is usually through rapid sand filtration (76%), while 20% of water utilities only disinfect water without additional treatment. Utilities increasingly adopt advanced water treatment methods such as activated carbon, ozone disinfection and air stripping.Ministry of Health, Labor and Welfare:Types of Treatment Plants, retrieved on January 6, 2011
Wastewater treatment and sanitation
Currently, Japan's methods of wastewater treatment include rural community sewers, wastewater facilities, and on-site treatment systems such as the Johkasou system to treat domestic wastewater.Motoyuki Mizuochi: Small-Scale Domestic Wastewater Treatment Technology in Japan, and the Possibility of Technological Transfer , Asian Environment Research Group, National Institute for Environmental Studies, Japan, retrieved on January 6, 2011 Larger wastewater facilities and sewer systems are generally used to treat wastewater in more urban areas with a larger population. Rural sewage systems are used to treat wastewater at smaller domestic wastewater treatment plants for a smaller population. Johkasou systems are on-site wastewater treatment systems tanks. They are used to treat the wastewater of a single household or to treat the wastewater of a small number of buildings in a more decentralized manner than a sewer system.
Concerning sewerage, out of 1,896 systems, 1,873 were separate sewer systems (between sanitary sewers and stormwater sewers) and only 23 were combined sewer systems. In 2002 about 75 million people were connected to sewers and 35 million people had their wastewater treated through small-scale wastewater treatment devices (johkasous). They are common in areas not connected to sewers, but also exist in areas connected to sewers. There is even a specific johkasous law that regulates their construction, installation, inspection and desludging. The system use different technologies and serve different size buildings, from single-family homes to high-rise buildings, public or commercial buildings. Treated water is then reused for toilet flushing, watering gardens, car washing or other purposes. Sludge from johkasous can be used as fertilizer. The government has a program to subsidize the installations.Hiroshi Ogawa:Domestic Wastewater Treatment by Johkasou Systems in Japan, retrieved on January 6, 2011 It has been attempted to transfer the technology to China and Indonesia.Motoyuki Mizuochi:Small-Scale Domestic Wastewater Treatment Technology in Japan, and the Possibility of Technological Transfer , Asian Environment Research Group, National Institute for Environmental Studies, Japan, retrieved on January 6, 2011
History
Water use in Japan developed in close association with the production of rice paddies from ancient times. After rice paddy cultivation was introduced, the construction of small irrigation ponds was started, and then, with expansion of the manorial system and later backed by efforts of warring feudal lords to maintain and increase rice production, the use of water from small and medium rivers expanded.
Prior to the Meiji period drinking water in Japan was fetched mainly from springs and traditional shallow wells. However, there were also some piped water supply systems using wooden pipes.
A storm drain associated with the Heijō Palace has been excavated, dating to the 8th century in the Nara period.8th-century drain found at palace remains in Nara supports building's link to ancient gov't
The first modern piped water system in Japan was completed in 1887 in the port city Yokohama, using surface water treated by a sand filter. By 1900, seven cities had piped water supply and by 1940 about one third of the population was connected to piped water systems. The incidence of water-borne diseases such as cholera, dysentery and typhoid remained high until after the Second World War when disinfection was introduced by the Americans and became mandatory in 1957. Through the increase of piped water supply, disinfection and sanitation the incidence of waterborne diseases dropped sharply during the 1960s and 70s.Ministry of Health, Labor and Welfare:Development of Modern Waterworks, retrieved on January 6, 2011
In the early 1960s, Tokyo faced a chronic water shortage and water supply to about 1 million households had to be cut around the time of the 1964 Summer Olympics. At the time, people used to call the city the "Tokyo Desert".
In 1961, a Water Resources Development Promotion Law was passed. On its basis over the next decade seven river basins with high growth in water needs were designated for water resources development and investments in dams, weirs and inter-basin transfers was undertaken on the basis of comprehensive development plans for each basin.Japan Water Agency:History , retrieved on January 6, 2011 During the 1970s and 80s numerous dams were thus built to provide storage to avoid future water scarcity and to supply the growing cities with sufficient water. However, the construction of some dams was substantially delayed. For example, construction of the dam forming what is today Lake Miyagase was begun in 1971, but for a number of reasons including the need to resettle 300 households, the dam was only completed in 2000.Global Architects Guide:Miyagase Dam, retrieved on January 6, 2011 Beginning in the 1960s investment in wastewater treatment was initiated. In 1993 the Environmental Law was passed and subsequently legislation was passed to protect the headwaters of rivers, thus gradually shifting from a curative approach to a preventative approach of water quality management.Ministry of Land, Infrastructure and Transport:Water Resources of Japan. History of Water Use , retrieved on January 6, 2011
Responsibility for water supply and sanitation
Policy and regulation