March 20, 2009March 20, 2009

Lead Specialist of Water Resources EngineeringLead Specialist of Water Resources Engineering

Japan Water AgencyJapan Water Agency 　（　（ JWA)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 3.2.3 in the 5th 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

-10

0

10

20

30

Temp.（℃ ）

0

100

200

300

400

Precipitation(mm)

1 2 3 4 5 6 7 8 9 10 11 12

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 JapanRivers 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: http://bluestyle.livedoor.biz/

Tokyo in 2008

9

0

100

200

300

400

500

600

0

20

40

60

80

100

120

140

1950 1960 1970 1980 1990 2000

-2

0

2

4

6

8

10

12

14Pop. (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 d

eep

wells b

egins

in va

rious

loca

tions

Cumulative ground subsidence (cm)

0

-50

-100

-150

-200

-250

-300

-350

-400

-450

-500

18

90

19

00

19

10

19

20

19

30

19

40

19

50

19

60

19

70

19

80

19

90

20

00

Groun

d su

bside

nce

is co

nfirm

ed

Indu

strial

Wat

er L

aw is

ena

cted

Indu

strial

Wat

er la

w is re

vised

and

Buil

ding

Wat

er L

aw is

ena

cted

Basic

Law fo

r Env

ironm

enta

l Poll

ution

is e

nacte

d

Guideli

nes f

or G

roun

d Sub

siden

ce P

reve

ntion

esta

blish

ed fo

r

C

hikug

o an

d Sag

a Plai

ns a

nd N

obi P

lain

Guideli

nes f

or M

easu

res t

o Pre

vent

Gro

und

Subsid

ence

,

e

tc. e

stabli

shed

for n

orth

ern

Kanto

Plai

n

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: http://www.ara.go.jp/arage/keisei/keisei02.html

1970

4.5m

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 2000Inomori-cho, Tenpaku-ku, Nagoya city in 2000

“Source: MLIT

12Flood 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 PopulationIn Japan

Agricultural Water

Source: National Land Agency

- 18681868- 19121912- 19261926- 19451945-unknown

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 ：　 2,999,712×103 m3

Total Supply Area ：　 1,225,882 ha

Number of Ponds and Dams ：63,591

Source: Ministry of Agriculture, Forestry and Fisheries, MAFF

Agricultural Water

1900

1910

1920

1930

1940

1950

1960

1970

1980

1990

1995

1883

1890

Transition of Water Supplied Population and Average Life ExpectancyW

ater

util

izat

ion

capa

city

of d

am (h

undr

ed th

ousa

nds

m3 )

Wat

er s

uppl

ied

popu

latio

n (te

n th

ousa

nds)

Dam water utilization capability of the water supply

Ave

rage

life

exp

ecta

ncy

(yea

rs)

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

0

1,000

2,000

3,000

4,000

5,000

6,000

0

500

1000

1500

2000

2500

3000

3500

4000

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

Tota

l Num

ber o

f Dam

s ('0

00)

Floo

d C

ontr

ol C

apac

ity (m

illio

n m

3)

Ann

ual D

eath

Tol

l by

Floo

ds (p

erso

n)

Number of Dams in J apanCapacity of Flood Control DamsDeath Toll by Floods

Data source:国交省水害統計、ダム年鑑(1999); Graphed by Imamura & Yoshida

Old RiverLaw mainly for flood control

RiverLaw for multi-purpose

objectives

New River Law inclusive of

environmment and ecology

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

1,1001,2001,3001,4001,5001,6001,7001,8001,9002,0002,100

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

( mm )

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: 2006-2055

• 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 m3/year > Japan’s domestic consumption of irrigation water: 59 billion m3/yearTotal import amount: 64 billion m3/year > Japan’s domestic consumption of irrigation water: 59 billion m3/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 CO2.

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

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