Numerical Prediction of Safe. Yield and Land Subsidence in Bangkok Aquifers System N P R U & U N I K

Transcription

1 umerical rediction of Safe Yield and Land Subsidence in Aquifers System Asst.rof.Dr.-ng.HATCHAASA ALA 1 rof.dr.rer.natmafed OCH 2 esearch Center of Water esources and Disaster Mitigation management, akhon athom ajabhat niversity, Thailand riverine_eng@yahoo.com 2 Department of Geohydraulics and Engineering Hydrology, niversity of assel, Germany

2 Content of resentation ational Study Area Model mplementation Flow Model Calibration Land Subsidence Model Calibration Determination of Safe Yield based on Land Subsidence Constraints Summary

3 ational Coastal Aquifers System interbedded alluvial and marine sediment Overdraft Heavily Lowering iezometric Head-> Seawater nstrusion and Land Subsidence (California, Tokyo, Jarkata etc.)

4 ational amkamhang niversity in 2004

5 ational Lorphensri, 2013

6 ational Lorphensri, 2013

7 ational n SA, more than 44,000 km 2 in 45 states subsidence caused by aquifer-system compaction and others 80% of land subsidence is owing to groundwater pumping The subsurface unit that is mainly contributed to the land subsidence is the confining unit and interbeds.

8 ational nteraction between groundwater and landsubsidence

9 ational Terzaghi (1925), 1-D consolidation neglect horizontal strains and stress gradient

10 ational BS1 (nterbed Storage ackage), Leake and rudic, 1991 SB (Subsidence and Aquifer System Compaction), Hoffmann, Leake, Galloway, Wilson, 2003.

11 ational Safe Yield? Hydraulics Solute Transport Land Subsidence

12 Study Area 3D Geological Map echarge (Sanford and Buapeng, 1996): rofile of Aquifers System a. nsignificant amount of recharge occurs at the center of this plain b. Main recharge exists at the basin flank of aquifer

13 Model mplementation Conceptual Model

14 Model mplementation Conceptual Model

15 Misfit error (MS) (m) Model mplementation Grid Discretization x x1000 Grid size 500x500 Grid sizes = 500x500 m. in and its vicinity and 1 x 1 km. in area which out of and its vicinity

16 Model mplementation Aquifer Basin Lower Chao hraya Modeled Layers 16 Model Domain (km 2 ) 27,325 Grid Size (m 2 ) 500 x x 1000

17 Model mplementation

18 Model mplementation

19 Model mplementation 3-D Groundwater Model of Lower Chao hraya Aquifers

20 Flow Model Calibration Steady-State Calibration initial head (2001) Observation wells = 189 wells Quantitative Assessment: Scattered lot Qualitative Assessment: iezometric head distribution atio of MS/regional head difference < 5% Transient Calibration Water level data: Observation wells = 233 wells Quantitative Assessment: Scattered lot Qualitative Assessment: Historical lot atio of MS/regional head difference < 5%

21 Flow Model Calibration

22 Flow Model Calibration

23 Flow Model Calibration

24 Flow Model Calibration

25 Flow Model Calibration Set of Calibrated arameters Layer x, y (m/d) z (m/d) 1 clay 4x10-2 4x aquifer 5x x Confining unit 3x x hra radaeng aquifer 3x x Confining unit 1x x akhorn Luang Aquifer 5x x Confining unit 1x x onthaburi Aquifer 1x x

26 Flow Model Calibration Set of Calibrated arameters Layer x, y (m/d) z (m/d) 9 Confining Layer 7x x10-2 7x x Sam hok Aquifer 1x x Confining Layer 7x x10-2 7x x hraya Thai Aquifer 1x x Confining Layer 1.8x x x x Thonburi Aquifer 1x x Confining Layer 2x x aknam Aquifer 1x x

27 Flow Model Calibration

28 Flow Model Calibration

29 Flow Model Calibration Set of Calibrated arameters Layer Ss (1/m) Sy 1 clay aquifer 4.8 x x hra radaeng aquifer 1.1 x x akhorn Luang Aquifer 1.2 x x onthaburi Aquifer 5.45 x x Sam hok Aquifer 1 x x Sam hok Aquifer 1.35 x x Thonburi Aquifer 1.15 x x aknam Aquifer 1.65 x x

30 Land Subsidence Model Calibration

31 Land Subsidence Model Calibration

32 Land Subsidence Model Calibration

33 Determination of Safe Yield based on Land Subsidence Constraints Safe Yield Definition: iezometric Head Constraint Salinity Constraint Land Subsidence Constraint eep pizometric head no lower than - 30 meters from ground Allow the chloride concentration in present freshwater area no more than 600 mg/l Allow the land subsidence rate no more than 1 cm/year

34 Determination of Safe Yield based on Land Subsidence Constraints Zoning in Amphoewised

35 Determination of Safe Yield based on Land Subsidence Constraints Zoning in Amphoewised

36 Determination of Safe Yield based on Land Subsidence Constraints DG 2011 rovince Safe Yield Ayutthaya 261,698 onthaburi 28,137 athumthani 152,000 akhonpathom 62,920 86,547 Samutsakhon 39,945 Samutprakan 56,428 total 687,675

37 Determination of Safe Yield based on Land Subsidence Constraints

38 Determination of Safe Yield based on Land Subsidence Constraints

39 Determination of Safe Yield based on Land Subsidence Constraints

40 Thank you very much indeed for DG support and your attention