Ⅰ. Status of Korea’s Water Resources

Ⅱ. Climate Change and Extreme Floods

Ⅲ. Securing Dam Safety

IV. Summary

Climate Change, Extreme Floods, and Dam Safety in Korea

Kwon, Do-Youp, Vice-Minister,

Ministry of Land, Transport and Maritime Affairs,

Republic of Korea

Agenda

Ⅰ. Status of Korea’s Water Resources

• Korean Peninsula : 222,135 ㎢(South Korea: 100,000 ㎢ / forest lands: 65.7%/ farmland: 21.9%/ urban area 5.2%, others:10% as of 1988 )

• Around 70% of Korea’s territory is mountains (∴ Vulnerable to floods)

• Most rivers flow into the West and South Sea

Location and Topography

Precipitation

Status of Water Resources

Total Water Resources (124.0)Total Water Resources (124.0)

Total water use (33.7)Total water use (33.7)

Streamflow (72.3)Streamflow (72.3) Loss (51.7)Loss (51.7)

Rainy season(52.2)

Rainy season(52.2)

Dry season(20.1)

Dry season(20.1)

Runoff to Ocean (38.6)Runoff to

Ocean (38.6) River (12.3) River (12.3) Reservoir (17.7) Reservoir (17.7) Groundwater (3.7) Groundwater (3.7)

Units : billion m3/yr

Source : Long-term Master Plan of Water Resources (Korea, ’06.7.)

II. Climate Change and Extreme Floods

Temperature increased by 0.6℃ during the past 140 years (global aver.)

→ The Korean average increased by around 1.5℃

•온•도

•편•차

•-1.5

•-1.0

•-0.5

•0.0

•0.5

•1.0

•1.5

•2.0

• Tem

per

atu

re v

aria

tio

ns

(°C

)

•1954 •1964 •1974 •1984 •1994

•Time (year)

Global Warming

RegionChanging forest

(temperate zones ⇒subtropical zones)

Vegeta-tion

South (temperate) 34.99%

Middle west(temperate)

16.18%

Middle east(temperate)

 3.16%

North (frigid zone)  3.11%

Fish East and west Sea Subtropical

※ Source : KEI (Korea Environment Institute, 2003)

Changing Climatic Zones

• Past: Monsoon → Now: Subtropical Climate (Changes expected in vegetation, fish stocks, ecosystem)

• Climate for 20% of territory will change by 2100

Northern Area

Middle easternArea

Middle WesternArea

Southern Area

• Abnormal climate caused changes in precipitation patterns for the past 20 years

Ex) Annual Precipitation: 7%↑( 1,166 mm → 1,247 mm ) Rainy Days: 14%↓(124.9 days/yr → 107.4 days/yr) Intensity: 18%↑(10 mm/d → 11.8 mm/d )

• Risk management against floods, droughts, and dam destruction is crucial

Abnormal Climate

Number of days with precipitationNumber of day with precipitation (larger than 80mm/day)

(b) Total Precipitation

1100

1150

1200

1250

1300

1920-29

1930-39

1940-49

1950-59

1960-69

1970-79

1980-89

1990-99

Year

mm

연 강수량Annual Precipitation

Increasing Severity of Rainfall

• Changes in annual precipitation and number of annual typhoon is not outstanding.

• However, the number of days with heavy rainfall (100 mm per day and above) rose by 1.5-fold during the past 10 years (222 times →325 times)

100~110 110~120 120~130 130~140 140~150 150↑Rainfall intensity (mm/day)

1992~2001 1971~1980mm/day

Changes in Rainfall Intensity

Rapid increase of damages

• Damage in 2000’s up 4.5 times (900 M $/yr) compared to 70’s~80’s

• 4.1 B$ in 2002

• Casualty was halved during same period

• Decreasing flooded area but rapid increase of the damage per unit flooded area (7 times up compared to 70’s~80’s) due to excessive urbanization along the river

Changes is Flood Damage Patterns

CasualtyDamage

Flooded area Damages per unit flooded area

year year

yearyear

Example of flood damages

Yeoncheon hydropower plant collapse- In 1996 due to heavy rain- 700mm in 3 days, daily max. 400mm

Levee failure in Pyeongchang river- In 2006 hit by typhoon “Bilis”

- Hourly max. 88mm

III. Securing Dam Safety

Dams in Korea

• Present: Total of 18,000 dams

15 Multi-purpose / 14 Water supply / Others (Irrigation, etc.)

→ Water Supply (17.7 bil.m3/yr), Flood Control (2.8 bil.m3)

• Under construction (~ 2012) 5 Multi-purpose dams

→ Water Supply (95 mil. m3/yr), Flood Control (360 mil. m3)

• Future (~2016)Build 7 small dams and rehabilitate 2 agricultural dams

→ Water Supply (760 M m3/yr)

Total Storage Capacity: 12.9 billion m3

∴Dams are essential in Korea

Roles of Dams in Korea

Estuary barrage(13%)

Irrigation dam(9%)

Single purpose dam(5%)

Dam(52.5%)

Stream(36.5%)

Groundwater(11%)

Total Water use:33.7 billion m3

47.2% of drinking water68.3% of (drinking +industrial water)

Accounts for 80.1% of total flood control capacity

Multipurpose dam(73%)

Extreme Floods

Recently, PMP surged in dam basins compared to the former designed value due to Climate Change → Max. 132% ↑ in multi-purpose dam basin

632→810mm(Soyanggang dam), 424→561mm(Imha dam)

Max. 317% ↑ in water supply purpose dam basin

241→715mm(Yeongcheon dam), 272→863mm(Angae dam)

New daily rainfall record (547→870.5mm/day, 2002.8)

(Units : million ㎥ /yr)

Flood

We must secure the

Hydrological Stability of Dams

against extreme flood

History of Flood Control Capacity

Enhancement Project

• 2002.8 : Typhoon “RUSA” (4.1bil.$ loss, 207 killed)

• 2003.4 : 『 Flood disaster Prevention and Countermeasure Plan 』 (The Office for Government Policy Coordination)

• 2003.4 : Presidential Directive (Cabinet Council) → Securing Dam stability against extreme flood

• 2003~ : Launched 『 Flood Control Capacity Enhancement Project 』

Structural Reinforcement Project for hydrological stability

(Auxiliary / emergency spillway construction)

• Total 23 dams (2003~2015, 1.3 b$) → 6 completed, 6 under construction, 11 planning

• Types of measures

- Spilling capacity ↑ (New, additional or enlarged spillways) - Dam storage ↑ (Parapet wall)

(ex1) Types of reinforcement

<highten><expansion>

<Yeongchon dam><Soyanggang dam>

Type1. Tunnel spillway Type2. Open channel spillway

Type3. Watergate Type4. Parapet wall

(ex2) Very large scale Waterway Tunnel

Soyanggang Dam

Two tunnels in rowProject cost : 0.16 b$D:14m × L:1,280mQ = 6,700m3/s

Imha Dam

Dae-am Dam

Three tunnels in a rowProject cost : 150 M$D:15m × L:420mQ = 8,215m3/s

Two tunnels in a rowProject cost : 40 M$D:10m × L:429mQ = 1,633m3/s

IV. Summary

• Precipitation has been continuously increasing in Korea due to climate change, causing massive damages.

• Dams play a critical role in Korea but are threatened by increasingly frequent and severe floods.

• Thus, to secure hydrological stability of dams, the Korean Government launched “Flood Control Capacity Enhancement Project” from 2003 which has been successful so far.

Thank you