1. Groundwater Modeling Study case : Central Plain of Thailand
December 16, 2009
Werapol Bejranonda
Department of Geohydraulics and Engineering Hydrology
University of Kassel, Germany

2. Contents Study Area / Groundwater hydro. Methodology
Groundwater Modeling
Application of the model

3. Research Objectives
Investigate use-patterns of conjunctive water between groundwater and surface water
in the upper central plain of Thailand
Estimate the impact of groundwater use via the use-patterns

4. Study Area GW Basins Geological Map of Thailand Upper Central GW Basin
of great central basin
Agricultural
Bangkok
(Capital)
*The first upper central
regional GW Model
Lower Central GW Basin
of great central basin
Industrial
Agricultural
Hydrogeological map of
upper central GW basin
GW Basins

5. Study Area Surface Water cover 5 main surface-water basins
Study Area Boundary
4 Main Streams
Yom Rive
Nan River
Ping River
Sakaekrang River
cover 5 main surface-water basins
Surface Water

6. Study Area Project study area covers 6 Provinces 47,000 km2 UTD SKT
PSL
KPP
PCT
47,000 km2
NKS
Project study area covers 6 Provinces

7. Existing Conjunctive Use
Irrigation area
Rainfed area
Personal GW pumps

8. Study flowchart

9. GW use ?? Field data collection (pumping behavior)
area
crops/year
season
pumping/crop
day/pumping
hours/day
irrigation
2.5
dry
6.0
2.6
19.3
wet
3.8
2.3
rainfed
2.0
6.5
3.1
22.0
2.1
16.0
pilot area
(irrigation)
5.4
4,9
20.4
3.5
4.5
23.8

10. Layer Classification
Flood Deposit & Low Terrain
High Terrain

11. Upper Layer (Semi-confined) Lower Layer (Confined)
GW Model
(MODFLOW)
2 Layers Conceptual Model
10 km.
Upper : 320 grids
Lower : 346 grids
10 km
Upper Layer (Semi-confined)
Lower Layer (Confined)

12. Upper Layer Lower Layer thickness 40-100 m. thickness 100-300 m.
Recent Flood Plain Deposits
Low Terrace Deposits
High Terrace Deposits
Rock
Upper Layer
thickness m.
Lower Layer
thickness m.

13. Calculation Method Steady Calibration : 2003
Transient Calibration :
Model Verification :
1.Steady State for Hydraulic Conductivity
1993
2.Transient State for Specific Storage
2003
2005
3.Verification

14. Calibration & Verification
Steady
Calculation
Average Error (m)
Root Mean Square Error(m)
Calibration (Steady)
-0.97
2.75
Calibration (Transient)
3.83
4.53
Verification
(Transient)
1.77
5.34
Transient

15. Observed
Simulation
(steady)
Groundwater Level in dry season of 2003

16. Surface Water Budget Situation

17. water demand : SW : GW (all in wet year)
Space Dimension
Aquifer types
pump yield
GW use
to demand
M3/hr
flood deposits
10-20
17%
Low terrace deposits
5-12 7%
high terrace deposits
1-10 2%
GW Use
Ratios
Basin
water demand : SW : GW
Irrigation area
rain-fed area
Ping
1 : 0.54 : 0.08
1 : 0.83 : 0.17
Yom
1 : 0.90 : 0.01
1 : 0.87 : 0.13
Nan
1 : 0.53 : 0.30
1 : 0.97 : 0.03
Chaophraya
1 : 1.00 : 0.02
1 : 0.99 : 0.01
Sakaekrang
1 : 0.83 : 0.01
all basins
1 : 0.62 : 0.17
1 : 0.93 : 0.07
Water
situation
water demand : SW : GW
(all in dry season)
Wet
1 : 0.49 : 0.27
Normal
1 : 0.32 : 0.36
Dry
1 : 0.47 : 0.52
Drought
1 : 0.63 : 0.68
Time Dimension
Irrigation condition
water demand : SW : GW (all in wet year)
rainy season
dry season
whole year
irrigation area
1 : 0.74 : 0.05
 1 : 0.50 : 0.29
1 : 0.66 : 0.13
rain-fed (no irrigation)
 1 : 0.98 : 0.02
1 : 0.54 : 0.46
1 : 0.94 : 0.06

18. Surface
and
Groundwater
Use
Conjunctive Use Patterns
Ratio of
Groundwater Use
to total water demand

19. Different GW Level from Calculation Approach

20. Application#1 : GW Level in pilot area GW yield awareness
Agricultural well yield
Simulated as
Drought year

21. Application#2 : Regional GW table
2005
Application#2 : Regional GW table
2018
Simulated groundwater table using conjunctive use ratio

22. Conclusions Groundwater use varies on deficit of surface water supply
Conjunctive use pattern significantly varies with surface water situation, season, aquifer characteristic and irrigation-rainfed area
Conjunctive use pattern is a key factor to estimate groundwater consumption and simulate groundwater-level fluctuation

23. References
Faculty of Engineering, Chulalongkorn University (2002), Groundwater Potential in Lower Central Part of Thailand.
Koontanakulvong, S. and Siriputtichaikul P. (2003), Groundwater Modeling In the North Part of the Lower Central Plain, Thailand, International Conference On Water and Environment, Bhopal, India, Vol.Ground Water Pollution No.19, pp
Panot (2000), Groundwater Modeling of Lower Central Part of Thailand.

24. Acknowledgement Department of Groundwater Resources
Royal Irrigation Department
Water Resources System Research Unit, Chulalongkorn University

25. Questions & Answers