According to the Ministry of Land, Infrastructure, Transport and Tourism of Japan (MLIT, 2022-a), Japan has a water supply coverage rate of over 98% and is one of the few countries (only 11 countries in the world, including Japan) where tap water is drinkable without modification due to its high water quality. Japan has approximately 660 billion m³ of precipitation, of which about 35% is evapotranspiration, and the remaining 430 billion m³ is the maximum amount of water resources available for use in the country. The total amount of water used for industrial, agricultural, domestic, and urban purposes peaked around 1995 (about 89 billion m³) and has been declining consistently since then (about 78.5 billion m³ in 2019). In fact, no major droughts have occurred since the summer drought of 1994, when extreme precipitation shortages and high temperatures persisted. The risk of frequent water shortages in Japan is not high, at least in the short term.
On the other hand, while the frequency of short-duration intense rainfall and heavy rainfall is increasing, the number of annual precipitation days is conversely decreasing, resulting in localized situations where water withdrawal is restricted. According to the Japan Meteorological Agency (JMA, 2023), the annual average temperature increase rate for Japan is 1.30°C per 100 years, which is higher than the world average, and the years in which Japan has recorded significantly higher temperatures have been concentrated since the 1990s. The JMA has monitored precipitation since the late 1970s at approximately 1,300 regional meteorological observatories nationwide. According to the statistics, the annual number of no-rainfall events has been increasing, while the annual frequency of extreme heavy rainfall events has approximately doubled since around 1980. JMA acknowledges that global warming may be responsible for this increase in the frequency and intensity of extreme rainfall. The increase in the number of days with no rainfall while the increase in the number of days with short-term, concentrated rainfall means that the risk of disaster-level conditions during periods of heavy rainfall and the risk of drought due to persistent drought conditions are increasing.
Damage caused by river floods and landslides in Japan has been increasing on a year-by-year basis. According to MLIT (2022-b), the highest damage in the past five years was about 2.2 trillion yen in 2019; the average damage from 2017 to 2021 was over 1 trillion yen, about 2.7 times the average from 2012 to 2016. Although this is a short-term comparison, flood damage appears to be increasing with climate change. The amount of damage caused by the Great East Japan Earthquake in 2011, which triggered the accident at the Fukushima Daiichi Nuclear Power Plant, was 16.9 trillion yen (Cabinet Office, 2011). The amount of flood damage may seem smaller when compared to the amount of damage caused by the earthquake. Still, given that an earthquake the size of the Great East Japan Earthquake is said to occur roughly once every 1,000 years, the damage caused by flooding, which exceeds 7 trillion yen over the ten years from 2012 to 2021, is not a scale that can be underestimated. Related human suffering should also be increasing.
Source: Ministry of Land, Infrastructure, Transport and Tourism (2022-b)
On the other hand, no specific events or research results have been identified regarding changes in groundwater levels associated with changes in daily precipitation and temporal precipitation trends due to climate change and the effects of rising sea levels or associated damage (National Institute for Environmental Studies, 2021).
In 2018, the Japanese government promulgated the Climate Change Adaptation Law. It formulated the Climate Change Adaptation Plan in order to enhance and strengthen adaptation measures in various sectors, such as agriculture and disaster prevention, as well as to develop an information base on climate change impacts and adaptation. According to the Climate Change Adaptation Plan, measures for water resources can be summarized as follows:
- water shortage
- Utilization of existing facilities (measures against aging, efficient operation of dams, etc.)
- Use of rainwater and recycled water (installation of hydrants at sewage treatment plants, use of treated sewage water in emergencies; international standardization of Japanese water reuse technology)
- Monitoring/promotion of surveys and research, provision of information, and dissemination of information
- flood disaster
- Review of flood control plans in light of climate change impacts, detailed disaster risk assessment through inundation simulations, etc.
- New flood control facilities, sewers, and other facilities
- Utilization of existing stock, such as strengthening the flood control function of existing dams and upgrading additional pipes and storage facilities for sewerage facilities
- Promote community development that considers disaster risk in coordination with community restructuring measures in light of declining population, etc.
- Promote the use of green infrastructure in watershed flood control, etc. (secure and improve rainwater storage and infiltration functions through flood control areas, etc., and conserve and restore ecosystem functions that contribute to disaster risk reduction)
The fact that no major droughts have occurred while temperatures have continued to rise and the temporal and regional variability of rainfall has increased may be due not only to the major trend of reduced water consumption but also to certain policy achievements by the Japanese government. The government has also focused on flood damage, which has been increasing in recent years. It has strengthened its response to climate change in cooperation with ministries, agencies, and local governments. The budget for water resources has decreased by about 2% from 3,165.9 billion yen in FY2021 to 3,104.4 billion yen in FY2022, but there will be an increasing need to increase this budget in the future.
Regarding overseas water issues, Japan has actively contributed to global water resource issues through the UN, NGOs, and bilateral cooperation. For example, Japan is the world’s top donor in terms of bilateral ODA performance in the water and sanitation sector (approximately US$1.26 billion (5-year average from 2015 to 2019, based on committed amount)), and has continued to provide comprehensive support in both soft and hard areas (MILT, 2022-a). As we previously reported (https://www.climatescorecard.org/2023/03/japans-agriculture-sector-contributed-47-of-global-agricultural-emissions-in-2021/ ), Japan has greatly increased food imports from overseas along with its postwar economic development, reducing agricultural production and CO2 emissions domestically while increasing them overseas. If Japan were to produce the food that Japan is currently importing domestically, the country would face water shortages. Changes in water supply and demand overseas will certainly impact Japan, and this impact is expected to grow in the future. The issues of climate change and water resources need to be addressed in combination with the issues of Japan’s current food and economic system.
This Post was submitted by Cli8mate Scorecard Japan Country Manager Kazuya Takeda.
- Cabinet Office (2011). 東日本大震災における被害額の推計(Estimated Damage from the Great East Japan Earthquake). https://www.bousai.go.jp/kaigirep/hakusho/h28/honbun/3b_6s_19_00.html
- Japan Meteorological Agency (2023). 気候変動監視レポート(Climate Change Monitoring Report 2022). https://www.data.jma.go.jp/cpdinfo/monitor/2022/pdf/ccmr2022_all.pdf
- MLIT (2022-a). 日本の水資源の現況(Current status of water resources in Japan). https://www.mlit.go.jp/mizukokudo/mizsei/content/001572566.pdf
- MLIT (2022-b). 令和3年の水害被害額は全国で約 3,700 億円(Flood damage in 2021 was approximately 370 billion yen nationwide). https://www.mlit.go.jp/report/press/content/001499495.pdf
- National Institute for Environmental Studies (2021). 気候変動適応計画(Climate Change Adaptation Plan). https://www.env.go.jp/content/000138042.pdf