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Integrated surface-groundwater analysis considering groundwater use in Pyoseon region, Jeju island, Korea

Nam-Won Kim*, Il-Moon Chung*, Hanna Na*, Sangyeon Yoo **and Sung-Kee Yang***

* Korea Institute of Construction Technology** Saman Cooperation

*** Jeju National University

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Background & Purpose Integrated SWAT-MODFLOW Application to Pyoseon watershed Results of simulation Conclusion

Content

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Background

Jeju island is the region where the highest rainfall occurs in Korea

The average annual rainfall of the island is about 1,975mm which is the 1.5 times larger than the mean value of 1,283mm for the Korean mainland (Won, 2004).

However, the island has suffered from water shortages mainly due to lacking large perennial rivers and streams

Main water resources is groundwater

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BACKGROUND

The streams in jeju island

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Surface water condition

Most of streams in upper region of watersheds show dried characteristics by means of large portion of recharge which goes to the deep aquifer : no baseflow in the upper area of watershed (losing stream).

On the contrary, groundwater discharge is more and more increasing as approaching to the downstream near to sea.

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Hydrogeology

Jeju island is mainly consisted of volcanic rocks including highly permeable basalts.

Mean transmissivity of permeable formations : 2,008 m2/day (K-Water, 2003)

A number of production wells have been installed.

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The groundwater flow direction

Equipotential lines

GW flow

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Deep recharge and discharge

Precipitation

Inland GW

Jeju GW

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Surface water measurements : Very hard

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SWAT-MODFLOW

Overview

SWAT(Arnold, 1993; Arnold, 1995) is widely used long term runoff model.

SWAT’ groundwater model is a semi-distributed type and thus the distributed parameters such as hydraulic conductivity and output (groundwater level) distributions could not be represented.

The conventional groundwater flow analysis performed by MODFLOW(McDonald and Harbaugh, 1988) often overlooks the accuracy of the recharge rates.

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SWAT-MODFLOW

Integrated SWAT-MODFLOW model

Development of subroutine for exchanging characteristics between HRU(Hydrologic Response Unit) of SWAT and CELL of MODFLOW

On the basis of these stable platforms, the groundwater module in SWAT is replaced by MODFLOW

Then, SWAT-MODFLOW is capable of simulating spatial-temporal GW recharge and stream-aquifer interactions by RIVER package in MODFLOW

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SWAT-MODFLOW

* Kim et al., Development and application of the integrated SWAT-MODFLOW model, J. of Hydrology (2008)

Schematic diagram

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SWAT-MODFLOW Linking RECHARGE in MODFLOW with SWAT

7 7 7 7

7 7 7 7

7 7 7 7

7 5 5

5 55 556 6 6

6 6 6

6 6

64

4 4 4 4

4 4

4 4

4 4

44 913554

SWAT

MODFLOW

HRU별 대수층의 함양량 = 54+44+35+91

소유역의 HRU

소유역의 HRU

MODFLOW의 cell

HRU based recharge

HRU in small watershed

HRU in small watershed

Cell in MODFLOW

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SWAT-MODFLOW

1 m

5

5

4 4 3 3

1 0

-2

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SWAT

MODFLOW

SWAT의 하천

소유역

MODFLOW의 cell

MODFLOW의 하천

SWAT의 하천유입량 = 소유역 유출량 + 하천-대수층간 물교환량 = 소유역 유출량 + 23 하천-대수층간 물교환량 = 5+5+4+4+3+3+1+0-2

Stream inflow in SWAT =discharge in small watershed +SW & GW exchange(23)

Stream inflow in SWAT

Small watershed

Cell in MODFLOW

Stream in MODFLOW

Linking RIVER in MODFLOW with SWAT

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Pyoseon region

SeongPanAkSamdasu

Pumping Well

Jeju

GyoRae

SungSan

4th GyoRae Br.

SeongEup

ChunMi Br.

EomDeuRik Br.

AnJwaRiver

JinPyeongRiver

GaSiRiver

Song River

ChunMi River

Surface observation station

Weather observation station

Rain observation station

Groundwater Well

Study Area

River network

SeongPanAkSamdasu

Pumping Well

Jeju

GyoRae

SungSan

4th GyoRae Br.

SeongEup

ChunMi Br.

EomDeuRik Br.

AnJwaRiver

JinPyeongRiver

GaSiRiver

Song River

ChunMi River

Surface observation station

Weather observation station

Rain observation station

Groundwater Well

Study Area

River network

DEM

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LAND USE

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17

SOIL CLASS

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18

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Samdasu Pumping Well

Zone1

Zone2

LONGITUDINAL GROUNDWATER LEVEL

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PUMPING WELLS (N=198)

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CHB(Constant Head

Boundary)

No-flow Boundary

No-flow Boundary

K-Zone1K-Zone2

K-Zone3

Samdasu Pumping Well

AQUIFER ZONING / BOUNDARY CONDITION

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SURFACE RUNOFF SIMULATION (R2=0.65)

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SEPARATION of SW / GW

River bed

GroundwaterLosing stream

Gwlevel(El.m)

GW CALIBRATION

OBS.

CAL.

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140

150

160

170

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190

200

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/04

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/06

Time(days)

GW

leve

l(Gl,

m)

-3

2

7

12

17

22

27

Rec

harg

e(m

m)

GroundWater LevelRecharge

SIM. RECHARGE vs GW LEVEL (R=0.87)

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Re-100 - 3435 - 6869 - 102103 - 136137 - 170171 - 204205 - 238239 - 272273 - 306No Data

N

EW

S

DISTRIBUTED GW RECHARGE (OCT. AVE.)

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FDCs with various PUMPING scenarios

Q (Current rate) / 10Q / 20Q

: Low flow rate 0.18CMS -> 0.15CMS -> 0.10CMS reduces 17%, 45% respectively

0.01

0.1

1

10

100

1000

0% 7% 14% 21% 27% 34% 41% 48% 55% 62% 69% 75% 82% 89% 96%

Dis

char

ge (c

ms)

Probability

Pumping

Pumping (10)

Pumping (20)

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Water Budget change (3, 13 subwatersheds)

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Sustainable additional groundwater resources

10Q / 20Q reduces the groundwater to Sea

: secures 60Mm3 /1000Mm3

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GW level variations

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GW recovery in alluvial aquifer

10Q -> Stop : Prompt recovery

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10Q -> Stop : Slow recovery

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GW recovery in rock aquifer

GW Time series at a single cell (SWAT-K)

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GW level distribution (SWAT-K)

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CONCLUSION

Integrated SW-GW analysis in Jeju island is performed

Annual groundwater recharge rate in the Pyoseon basin is about 53%

Impact analysis due to increasing Q scenarios- Recorvery tests show that 10Q / 20Q

Sustainable additional GW resources in Jeju island could be secured

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Thank you

This work is financially supported by 21century Frontier Research Program(code 2-2-3).

Slide Number 1Slide Number 2 Background BACKGROUND Surface water condition � Hydrogeology�Slide Number 7 Deep recharge and discharge Surface water measurements : Very hard SWAT-MODFLOW SWAT-MODFLOW SWAT-MODFLOW SWAT-MODFLOW SWAT-MODFLOWPyoseon regionSlide Number 16Slide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21Slide Number 22Slide Number 23Slide Number 24Slide Number 25Slide Number 26Slide Number 27Slide Number 28Slide Number 29Slide Number 30Slide Number 31Slide Number 32Slide Number 33Slide Number 34 CONCLUSIONSlide Number 36