Current State of Water Resources in Japan

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Freshwater Resources
  • Amount of water on the earth:
    Approximately 1,400 million km3
    • Seawater and so on: 97.5%
      (approx. 1,300 million km3)
    • Freshwater: 2.5%
      (approx. 35 million km3)
      • Glaciers and so on: 1.74%
        (approx. 24 million km3)
      • Groundwater: 0.76%
        (approx. 11 million km3)
      • Rivers/Lakes and marshes: 0.01%
        (approx. 0.1 million km3)
  1. Annual precipitation in Japan is approximately 1,718 mm, roughly two times as much as the world average of about 810 mm.
  2. Annual precipitation per capita is approximately 5,100 m3 in Japan, roughly 1/3 of the world average of about 16,800 m3.
Existing Amount of Water Resources (Amount of Precipitation less Amount of Evaporation/Transpiration)
  1. Amount of precipitation in an average year in Japan is approximately 650 billion m3. After deducting about 230 billion m3 lost in evaporation/transpiration, the existing amount of water resources is roughly 420 billion m3 (65% of precipitation).
  2. The existing amount of water resources in Japan in a year of low rainfall occurring about once in 10 years is approximately 280 billion m3.
  3. Amount of water resources per capita in Japan (approximately 3,300 m3) is less than half of that in the world (about 7,800 m3).
Amount of Water Used
  1. Annual use of water in Japan (amount of water intake) is approximately 83.5 billion m3 in total which can be broken down into approximately 16.2 billion m3 for domestic use, 12.1 billion m3 for industrial use, and 55.2 billion m3 for agricultural use.
  2. Average amount of use per capita per day for domestic purposes is approximately 314 liters (132 liters in Asia; 428 liters in North America; 280 liters in Europe; and 63 liters in Africa).
  3. Annual amount of use of groundwater is approximately 10.8 billion m3 in total, (roughly 12% of the whole amount of water used) which can be broken down into approximately 3.7 billion m3 for domestic use, 3.8 billion m3 for industrial use, and 3.3 billion m3 for agricultural use.
  4. The total amount of domestic production and import of mineral water increased by 13 times from that in 1990 to approximately 2.3 billion liters (in 2006). The price is about 550-fold of tap water.
Developed Amount of Water
  1. The amount of water resources developed through construction of dams and so forth is 11.9 billion m3 for tap water (approx.73% of the amount of water used) and 5.9 billion m3 for industrial water (approx.49% of the amount of water used).
  2. The amount of unstable water intake (amount available only when river water is affluent, because water resources development facilities to serve as reservoirs are not yet completed) for urban water (domestic water + industrial water) in the metropolitan area (coastal area of Kanto) is 820 million m3, accounting for about 15% of the total amount of water used.
Crisis-related Information
Water Shortages
  1. After the water shortage during the Tokyo Olympics (1964), a large-scale water shortage has occurred about once in 10 years.
  2. Recently, the nationwide water shortage in 1994 affected about 16 million people due to troubles in tap water supply, while causing damage to agriculture with product losses of roughly 140 billion yen.
Global Warming
  1. The average temperature rose by about 0.74 ℃ during the 20th century globally, and by roughly 1.06 ℃ in Japan. According to IPCC, it is forecast to rise by 1.1~6.4 ℃ from 1990 to 2100.
  2. The amount of precipitation in Japan during the 20th century was on a decreasing trend when viewed in the long term (decrease of around 90 mm over the past 100 years.) There is a growing tendency for the difference in precipitation between high and low rainfall years (The precipitation in the years of low rainfall decreased by approximately 300 mm in the past 100 years).
  3. In view of these tendencies, we should assume the possibility of frequent occurrence of extremely low rainfall, decrease in snowfall, and earlier thaw.

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