Acknowledgement

ReferencesConclusions

Hydrological ModelBackground

Climate change

❑ Hanasaki, N., Kanae, S., & Oki, T. (2006). A reservoir operation scheme for global river routing models. Journal of Hydrology, 327(1-2), 22–41.❑ Hanasaki, N., Kanae, S., Oki, T., Masuda, K., Motoya, K., Shirakawa, N., Shen, Y., & Tanaka, K. (2008a). An integrated model for the assessment of global water resources – Part 1: Model description and input meteorological forcing. Hydrology and Earth System Sciences, 12, 1007–

1025.❑ Hanasaki, N., Kanae, S., Oki, T., Masuda, K., Motoya, K., Shirakawa, N., Shen, Y., & Tanaka, K. (2008b). An integrated model for the assessment of global water resources – Part 2: Applications and assessments, Hydrology and Earth System Sciences, 12, 1027–1037.❑ Mateo, C. M., Hanasaki, N., Komori, D., Tanaka, K., Kiguchi, M., Champathong, A., Sukhapunnaphan, T., Yamazaki, D., & Oki, T. (2014). Assessing the impacts of reservoir operation to floodplain inundation by combining hydrological, reservoir management, and hydrodynamic

models. Water Resources Research, 50, 7245–7266.

Impact Assessment of Reservoir Operation for Potential Adaptation in the Upper Chao Phraya River BasinSaritha Padiyedath Gopalan* and Naota Hanasaki

Centre for Climate Change Adaptation, National Institute for Environmental Studies (NIES), JapanEmail*: pgsaritha@nies.go.jp

Reservoir operation is one of the most influential factors for flood mitigation under future climate change by controlling and storing the natural flow

Objectives of the Study

Results and Discussions

This study was carried out as a part of the research project ‘Advancing Co-Design of Integrated Strategies with Adaptation to Climate Change in Thailand (ADAP-T)’ funded by Japan Science and Technology Agency, Japan.

High temperature Heavy precipitation

Extreme events Sea level rise

DroughtFloods

z: Infiltration

hole height

I: Inflows from

other basins

O: Water intake

from basin

Q: River discharge

E: Evapotranspiration R: Rainfall

ql: Ground water

related loss

s: S

tora

ge

z: Infiltration

hole height

I: Inflows from

other basins

O: Water intake

from basin

Q: River discharge

E: Evapotranspiration R: Rainfall

ql: Ground water

related loss

s: S

tora

ge

Reservoir Operation

Releasing water during dry season Storing flood volume during wet season

On flood peak reduction

Analyze the effect of two largestexisting reservoirs of Bhumibol(13.5 BCM) and Sirikit (9.5 BCM)at Nakhon Sawan (catchmentarea: 109973 km2)

Analyze the effect of ahypothetical dam (1.18 BCM), atSukhothai (catchment area:12769 km2) and Nakhon Sawan

44

Wang

Ping Yom Nan

Nakhon Sawan

Bhumibol

Sirikit

Hypothetical dam

Sukhothai

Y6

1

2

RCP 6 scenario

H08 hydrological model

Baseline ➔(1990-1999)

Future ➔ (2090-2099)

H08 Global Hydrological Model

Land surface hydrology module

River routing module

Reservoir operation module

H08 Model Calibration and Validation

-20

0

20

40

60

80

100

120

Jan-90 Sep-92 Jun-95 Mar-98 Dec-00 Sep-03 Jun-06Dis

char

ge (

mm

/mo

n)

Time (month)

Observed Simulated

0

20

40

60

80

100

P6

7

P2

A

P7

A

P1

7

W1

C

Y20

Y1C

Y14 Y6

Y3A

Y16

Y17 Y5

N64 N

1

N12

A

N60

N22

N5A

N7A

N8A

N67 C

3

C7

A

Bhumi…

Siri

kit

NSE

(%

)

Stations

65.96%50.21%

Calibration at Nakhon Sawan for naturalized flow

Monthly NSE = 85.79%

Validation at 26 stationsMonthly NSE Daily NSE

3. Effect of climate change on discharge at Nakhon Sawan

0

1500

3000

4500

6000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecDis

char

ge (

m3/s

)

Month

Monthly average discharge

1990-1999 2090-2099

Increased wet season discharge & similar dry season discharge

1. Reproduction of baseline regulated discharge at Nakhon Sawan

Dry season Wet season

No dam simulation

35%

0

2000

4000

6000

1-Jan-90 27-Sep-92 24-Jun-95 20-Mar-98 14-Dec-00

Dis

char

ge (

m3/s

)

Baseline simulations

B-NR B-ER

0

3000

6000

9000

12000

1-Jan-90 27-Sep-92 24-Jun-95 20-Mar-98 15-Dec-00

Dis

char

ge (

m3/s

)

Future simulation

F-NR F-ER5.78 times higher

peak discharge than baseline

5. Impact of hypothetical reservoirs (HR) on discharge at Nakhon Sawan and Y6 stations

0

1000

2000

3000

4000

Jan-90 Sep-92 Jun-95 Mar-98 Dec-00 Sep-03 Jun-06

Dis

char

ge (

m3/s

)

Baseline regulated flow

Observed Simulated

Good hydrograph reproducibility

NSE = 71%

2. Impact of existing reservoirs on baseline discharge at Nakhon Sawan

0

10

20

30

40

50

60

0

1000

2000

3000

4000

5000

6000

1 2 3 4 5 6 7 8 9 10

Peak

red

uct

ion

rat

e (%

)

Dis

char

ge (

m3/s

)

Year

Annual peak discharge

B-NR B-ER B_RR

0

10

20

30

40

50

60

0

2000

4000

6000

8000

10000

12000

1 2 3 4 5 6 7 8 9 10

Peak

red

uct

ion

rat

e (%

)

Dis

char

ge (

m3/s

)

Year

Annual peak discharge

F-NR F-ER F_RR

4. Impact of existing reservoirs on future discharge at Nakhon Sawan

Considerable peak reduction

Low flow increase

Low flow increase

Peak reduction

21%

52%

12%

48%

Flood years

Flood year

0

500

1000

1500

2000

2500

3000

1-Jan-90 27-Sep-92 24-Jun-95 20-Mar-98 14-Dec-00

Dis

char

ge (

m3/s

)

Baseline simulation at Nakhon Sawan

B-ER B-HR

No low flow improvement

0

200

400

600

800

1000

1-Jan-90 27-Sep-92 24-Jun-95 20-Mar-98 14-Dec-00

Dis

char

ge (

m3/s

)

Baseline simulation at Y6 station

B-NR B-HR

Increased low flow

0

2000

4000

6000

8000

10000

1-Jan-90 27-Sep-92 24-Jun-95 20-Mar-98 15-Dec-00

Dis

char

ge (

m3/s

)

Future simulation at Nakhon Sawan

F-ER F-HR

Low or no impact of hypothetical reservoir at

Nakhon Sawan

0

500

1000

1500

1-Jan-90 27-Sep-92 24-Jun-95 20-Mar-98 15-Dec-00

Dis

char

ge (

m3/s

)

Future simulation at Y6 station

F-NR F-HR

7.68 times higher peak discharge than baseline

-5

0

5

10

15

0

2000

4000

6000

8000

10000

1 2 3 4 5 6 7 8 9 10

Peak

red

uct

ion

rat

e (%

)

Dis

char

ge (

m3/s

)

Year

Annual peak discharge at Nakhon Sawan

B-ER B-HR F-ER F-HR B-RR F-RR

Negligible impact

-10

0

10

20

30

40

50

0

400

800

1200

1600

1 2 3 4 5 6 7 8 9 10

Peak

red

uct

ion

rat

e (%

)

Dis

char

ge (

m3/s

)

Year

Annual peak discharge at Y6 station

B-NR B-HR F-NR F-HR B-RR F-RR

Substantialimpact

Negligible peak reduction

14% (max)

3% (min)

-3% (min)

5% (max)

Enormous reduction

Notable peak reduction

Slight reduction in peak flow and small increase

in low flow

42% (max)

15% (min)-3% (min)

35% (max)

❖The proposed hypothetical dam could reduce flood damage at the lower reaches of Yom River where flooding is regular

due to gentle slope, but not at Nakhon Sawan.

❖The changes in discharge due to climate change are larger than those achieved by the reservoir operations for the future

scenario even though the simulated discharge highly depends on which general circulation model was used as input.

Nak

ho

n

Saw

an

Existing reservoirs

Hypothetical reservoir

Substantial effect on peak reduction

Negligible effect on peak reduction Y

6 s

tati

on

Hyp

oth

etic

al

rese

rvo

ir

Sub

stan

tial

ef

fect

on

pe

ak

red

uct

ion

Due to large storage capacity

Due to small storage capacity

Hanasaki et al. (2008a; b)

Hanasaki et al. (2008a; b)

Hanasaki et al. (2006)Mateo et al. (2014)

Chao Phraya River Basin

Floods are common

Climate change and two existing dams ➔ How do the existing dams control the impacts of climate change? Climate change adaptation by building a new dam ➔ How does a new dam mitigate the impacts of climate change?

NR – No reservoir

B – Baseline

F – Future

ER – Existing reservoir RR – Reduction rate

NR – No reservoir ER – Existing reservoir RR – Reduction rate

B – Baseline

F – Future

B – Baseline B – Baseline

F – Future F – Future

HR – Hypothetical reservoir