11

SemiSemi--coupling of a surfacecoupling of a surface-- and and

groundwater model togroundwater model to

investigate surface and investigate surface and

groundwater interactionsgroundwater interactions

in the Upper Great Chao Phraya Plain of in the Upper Great Chao Phraya Plain of

ThailandThailand

01.04.2010 @ University of Hong Kong

22

Contents

•• IntroductionIntroduction

•• Application to the study areaApplication to the study area

•• Coupling resultsCoupling results

•• Interactions of SW Interactions of SW -- GWGW

33

�� IntroductionIntroduction

Irrigation canal

GW pump

Shallow GW well

44

ModelsModels

�� SWATSWAT

�� MODFLOWMODFLOW

Saturated Zone

Unsaturated Zone

Overview of the couplingIntroduction

t

hSW

z

hK

zy

hK

yx

hK

xszzyyxx

∂

∂=−

∂

∂

∂

∂+

∂

∂

∂

∂+

∂

∂

∂

∂

( ) 2

a

a

e

SIP

IPP

+−

−=

1,2,

2,1,2,1,

22storedstored

outoutininVV

qqt

qqt −=

+⋅∆−

+⋅∆

Variable Storage

SCS, CN

Darcy’s Law

•• Develop Develop a coupling processa coupling process between SW and GW between SW and GW models to understand their interactionsmodels to understand their interactions

•• Apply the coupled model to analyst Apply the coupled model to analyst water balancewater balance and and hydrological components hydrological components between SW and GW in between SW and GW in study areastudy area

Functions in c

oupling

5

Coupling componentsModel coupling

Surface

SWAT

Soil

MODFLOW

Percolation

RechargeAquifer

∆t = 1 month (coupling)

Qriv HrivHaq

SWAT

MODFLOW

SWAT

( )aqrivrivriv

HHCQ −=

Checking parameters :

Streamflow (discharge) and GW Level

6

16

9

5

7

11

SW

GW

River-interaction

6

13

16

4

19

3

20

9

1

2

8

10

12

5

14

18

15

7

21

22

11

17

streamlines

Coupling dimensions (spatial)Model coupling

6

13

16

4

19

3

20

9

1

2

8

10

12

5

14

18

15

7

21

22

11

17

GW

Infiltration

SW

16

16

19

3

20

9

8

15

7

11

17

Subbasin polygon

Subbasin block

SpaceDimension

SpaceDimension

river package

7

Coupling dimensions (temporal)Model coupling

Data exchang

e

data exchang

e

SW model (daily time step)

GW model (monthly time step)

TimeDimension

iterations

8

Coupling of parameters

•Surface Recharge(one-way)•Streamflow-GW interaction(two-way)

99

�� Application to study areaApplication to study area

1010

Study area: OverviewApplication

Southeast Asia

Thailand

Ping river

Yom riverNan river

Chao Phraya river

Sakae Krang river

study area

alluvial aquifers

covers 9 provinces northern of Thailand

1111

#Y

#Y

#Y

#Y

6

13

16

4

19

3

20

9

1

2

8

10

12

5

14

18

15

7

21

22

11

17

Mathematical modelApplication

SW GW

C.2

Y.14

P.7A

N.12A

22 Subbasins,4 main-stream 2 layers,666 grid-cells

1212

Water balance: : Hydrological compoentsApplication

Coupling

Annual hydrological components (mm)

SW

GW

1313

Water balance : : RatiosApplication

10-year average

Coupled components

1414

น�ําท่ารายเดือน ที�สถานี C2

0

2000

4000

6000

8000

10000

12000

0419

9307

1993

1019

9301

1994

0419

9407

1994

1019

9401

1995

0419

9507

1995

1019

9501

1996

0419

9607

1996

1019

9601

1997

0419

9707

1997

1019

9701

1998

0419

9807

1998

1019

9801

1999

0419

9907

1999

1019

9901

2000

0420

0007

2000

1020

0001

2001

0420

0107

2001

1020

0101

2002

0420

0207

2002

1020

0201

2003

น�ําท่

า (ล้าน

ลบ.ม./เดือน)

Observed Data

Uncoupled (SWAT)

Coupled (SWAT + MODFLOW)

SW results : StreamflowCoupling results

Streamflow at outlet

Flow (million m

3/m

onth)

151534

35

36

37

38

39

40

41

42

43

44

04-2536 04-2537 04-2538 04-2539 04-2540 04-2541 04-2542 04-2543 04-2544 04-2545 04-2546

ระดับน�ําใต้ดิน (ม.รทก.)

Coupled (MODFLOW)

Coupled (SWAT + MODFLOW)

GWW results : water levelsPCP-20

30

31

32

33

34

35

36

37

38

39

40

04-2536 04-2537 04-2538 03-2539 03-2540 03-2541 03-2542 03-2543 03-2544 03-2545 03-2546

ระดับน�ําใต้ดิน (ม.รทก.)

Uncoupled (MODFLOW)

Coupled (MODFLOW + SWAT)

Observed well

Coupling results

inner gw basin

dense pumping

1616

�� SWSW--GW interactions (results)GW interactions (results)

1717

นํ าท่ารายเดอืน ที�สถาน ีC2

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

011996 021996 031996 041996 051996 061996 071996 081996 091996 101996 111996 121996 011997 021997 031997

นํ าทา่ (ล

า้น ลบ.ม

./เดอืน)

Observed Data

Uncoupled (SWAT)

Coupled (SWAT + MODFLOW)

ปรมิาณการเตมินํ าในแอง่นํ าใตด้นิจากผวิดนิ

0

5

10

15

20

25

30

35

40

45

50

Wet Dry

2539

ปรมิาณน

ํ/ารายฤด

กูาล-แลง้/ฝน

(มม.)

Coupled SWAT+MODFLOW

MODFLOW

Coupled results: Seasonal effectsCoupled results: Seasonal effectsPCP-20

33

34

35

36

37

38

39

01-2539 02-2539 03-2539 04-2539 05-2539 06-2539 07-2539 08-2539 09-2539 10-2539 11-2539 12-2539 01-2540 02-2540 03-2540

ระดบันํ าใต้ดิน (ม.รทก.)

Uncoupled (MODFLOW)

Coupled (MODFLOW + SWAT)

ปรมิาณการเตมินํ าในแอง่นํ าใตด้นิจากลํานํ า-80

-70

-60

-50

-40

-30

-20

-10

0

10

Wet Dry

2539

ปรมิาณน

ํ/ารายฤด

กูาล-แล้ง/ฝ

น (มม.)

Coupled SWAT+MODFLOWMODFLOWSWAT

Streamflow GW Level

River Recharge Surface Recharge

Wet Dry Wet Dry

Results

48 billion m3

Difference of uncoupling and coupling

Wet Dry

Wet Dry

~0

1818

Movement of water between SW and GWMovement of water between SW and GW

ปรมิาณการเตมินํ าในแอง่นํ าใตด้นิ

-30

.0

-20

.0

-10

.0

0.0

10.0

20.0

30.0

40.0

50.0

Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry

2536 2537 2538 2539 2540 2541 2542 2543 2544 2545

ปริมาณน

ํ/ารายฤดกูาล-แล้ง/ฝน (มม.)

เติมจากแม่นํ/า

เติมจากผิวดิน

++ Into groundwater

-- Into rivers

Results

Total for 10 years + 21.5 billion cubic meters- 6.1 billion cubic meters

Raise 1.5 billion m3

In 10 years

1993 2002Recharge from river

Recharge from surface

1919

-7%

1%

19%

10%

0%

7% 7%

18%

8%

30%

7%

15%

8%

17%

5%

17%

8%

17%

6%

8%

-10

%

-5%

0%

5%

10%

15%

20%

25%

30%

35%

Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry

2536 2537 2538 2539 2540 2541 2542 2543 2544 2545

ความผดิพลาดเฉลี�ยสมัพัทธ์

0

5,000

10,000

15,000

20,000

25,000

ปริมาณ

นํ าท่า (ล้าน ลบ.ม.)

ความคลาดเคลือนลดลง

ปรมิาณนํ�าท่า

Situation 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

wet

average

dry

drought

SW results : Water situation effect

Results

1993 2002

Less calculation error

Streamflow

Streamflow(m

illion m

3)

Less of prediction error (%

)

2020

Conclusions

••EvaluationEvaluation

The semiThe semi--coupling of MODFLOW and SWAT improves coupling of MODFLOW and SWAT improves

the individual results of the GW and SW simulations by the individual results of the GW and SW simulations by

2%2%--20% better with regard to the uncoupled 20% better with regard to the uncoupled

models, models, especially in the dryespecially in the dry--seasonseason

•Uncoupled vs coupled results

ParametersImproved by coupling (less prediction error)

Whole year Wet DryDry

Streamflow 11.5% 7.5% 16.7%

GW Level 2.3% 0.55% 2.9%

2121

Questions & AnswersQuestions & Answers