March 20, 2009 Lead Specialist of Water Resources Engineering Japan Water Agency （ JWA) Michio OTA Roles of Dams for the Future in Japan Japan Commission on Large Dams Japan Commission on Large Dams (JCOLD) Topic 3.2 Session in the 5 th World Water Forum

Contents 1. Condition of Water Affairs in Japan 2. Roles of Dams up to the present in Japan 3. Roles of Dams for the Future in Japan 4. Roles of Dams for the Future in the World with regard to Food Security

Contents 1. Condition of Water Affairs in Japan

Rivers and Precipitation in Japan Tokyo Temp. （℃）（℃） Precipitation (mm) Source: Ministry of Land, Infrastructure, Transport and Tourism, MLIT Annual mean rainfall: 1,700mm

Distance from river mouse (km) Elevation (m) Comparison of Riverbed Gradients Rivers in Japan Rivers in Continents Source: MLIT

Feature of Rivers in Japan is, - huge difference in the condition between flooding time and normal time - the water flow out soon after the flooding time Tone River Kiso River Yodo River Thems River Danube River Mississippi River Source ： MLIT, Annual Report of Flow Rate （ 1984 ～ 1993 ）

7 Tokyo after the war in 1945 Source: Prof. Tuneaki Yoshida, Tokyo Univercity

Source: Tokyo in 2008

Pop. (Million) GDP (Trillion YEN) DGP growth rate (%) Population GDP Periods according to the Change of Economic Condition Source: MLIT

Serious Water Shortage in Metropolitan Area Supply trough Water Tank Truck

11 Pollution in Urban River Smelled badly and no fish In 1960s to early 1970s

Digging of deep wells begins in various locations Cumulative ground subsidence (cm) Ground subsidence is confirmed Industrial Water Law is enacted Industrial Water law is revised and Building Water Law is enacted Basic Law for Environmental Pollution is enacted Guidelines for Ground Subsidence Prevention established for Chikugo and Saga Plains and Nobi Plain Guidelines for Measures to Prevent Ground Subsidence, etc. established for northern Kanto Plain Minamiuonuma (Yokawa, Muika Town, Niigata Prefecture) Chikugo / Saga Plains (Yokote, Shiroishi Town, Saga Prefecture) Kanto Plain (Higashiowa, Washinomiya Town, Saitama Prefecture ) Nobi Plain (Hakke, Nagashima Town, Mie Prefecture) Niigata Plain (Sakai, Niigata City, Niigata Prefecture) Osaka Plain (Hyakushima, Nishiyodogawa Ward, Osaka) Kanto Plain (Kameido, Koto Ward, Tokyo) Changes Over Time in Ground Subsidence Source: m 0 m GL

Tokyo area hit by Kathleen Typhoon in 1947 Flood Disaster Source: MLIT

Normal condition Struck by the disaster Inomori-cho, Tenpaku-ku, Nagoya city in 2000 “Source: MLIT 12 Flood Disaster

Contents 2. Roles of Dams up to the present in Japan

Manno-Ike Pond: Presented by Manno-Ike Land Improvement District Change of Farm Land Area and Population In Japan Agricultural Water Source: National Land Agency

２４％ ９％ ３％ ７％ ４７％ １０％ Percentage of Active Storage Capacity of Irrigation Ponds and Dams in Japan (a supply area of 2 ha or more) Total Active Capacity ： 2,999,712×10 3 m 3 Total Supply Area ： 1,225,882 ha Number of Ponds and Dams ： 63,591 Source: Ministry of Agriculture, Forestry and Fisheries, MAFF Agricultural Water

Transition of Water Supplied Population and Average Life Expectancy Water utilization capacity of dam (hundred thousands m 3 ) Water supplied population (ten thousands) Dam water utilization capability of the water supply Average life expectancy (years) Average life expectancy Water supplied population 18 Domestic Water Source: MLIT

Energy for Water Source: Electric Power Civil Engineering Association Changes of Electric Power Production at the Early Stage

Energy for Water Comparison of Electric Power Source

Flood Control: Mitigation of Flood Disasters in Japan 21 Flood Control

Japan has around 2,800 dams which heights are over 15m. Dams have played a critical role for Japanese socioeconomic development based on increase of food production, supply of electric power, development of water for domestic and industrial use and improvement of safety level of flood control especially in large cities.

Contents 3. Roles of Dams for the Future in Japan

Annual Precipitation Average rainfall trend In Japan Variability Variability of extreme events is increasing due to climate change Climate Change Source: MLIT

Estimation of the snow depth at 100 years from now Because of the global warming, at 100 years from now, it is predicted that there will be almost no snow in West Japan At the Sea of Japan side, it is predicted that the area which has the greatest snow depth of 100cm or more will be narrowed drastically Distribution map of greatest snow depth in cooling season legend less than 1cm from 1cm to less than 5cm from 5cm to less than 10cm from 10cm to less than 20cm from 20cm to less than 50cm from 50cm to less than 100cm from 100cm to less than 150cm 150cm and more Source: “Estimation of change of snow under global environmental change” Inoue Satoshi, Yokohama Kotaro, National Institute for Agro-Environmental Sciences 4 legend less than 1cm from 1cm to less than 5cm from 5cm to less than 10cm from 10cm to less than 20cm from 20cm to less than 50cm from 50cm to less than 100cm from 100cm to less than 150cm 150cm and more Present 100 years later Climate Change

Changes in water supply capacity of the Kiso River System.

Source: National Institute of Population and Social Security Research in Japan Population Projections for Japan:

Japan indirectly uses other countries’ water resources through the import of foods etc The trend in trade will also have impact on the future water demand and supply in Japan Japan’s total import amount of virtual water Source: Calculation of the research group of Oki assistance professor at Institute of Industrial Science, University of Tokyo, based on the demand and supply of foods etc. Total import amount: 64 billion m 3 /year > Japan’s domestic consumption of irrigation water: 59 billion m 3 /year 7 Virtual water poured in Japan by import item (billion m3/year ) Corn Soybean Wheat Rice Barley Beef Pork Chicken Milk and dairy products Industrial products Others Virtual Water Self-sufficiency rate in food is 40%

Contents 4. Roles of Dams for the Future in the World with regard to Food Security

Predictions of the future world population and grain production Source: Water Resources Dept. MLIT

1. Secure Food Production in Japan Japan should increase more food production domestically and ensure stable supplies of food in the future. A stable supply of irrigation water must be ensured by storing unstable river flow with irrigation ponds and dams. 2.Water for Energy in Japan Japan should have a policy to restrict emission of CO 2. Hydropower is a clean and 100% domestically produced recyclable energy in Japan. Dams for hydropower generation will contribute to the above. Conclusion

3. Climate Change Adaptation in the view of Dams in Japan Abnormal phenomena of heavy rain and serious drought et al. will be caused by global warming and make a greater impact on water supply in the future. Using Dams is one of the effective climate change adaptations. However, new dams will not being smoothly constructed in Japan, thus the burden on existing dams will continue to rise. The priority issues are redeveloping existing dams and reorganizing of existing dams to optimize their operations. Conclusion

4. Roles of Dams for the Future in the World with regard to Food Security Need of world grain production in the near future will increase demand for agricultural water. Further expansion of cultivated land and improvement of deteriorated farmland including overgrazing of grassland, land of salt accumulation caused by excessive pumping of grand water and so must be done especially in developing countries. These factors will increase the need for development of new water resources to supply irrigation water.

Tama River around 1970 Photo: Environment Bureau, Tokyo Metropolitan Government Thank you for your kind attention