1. 1 Using SUB model to predict long-term land subsidence in Yunlin and Chiayi areas Presenter : Chiou-Shiang Hung Adviser : Chuen-Fa Ni Date : 2010/10/07

2. 2 Literature review Motivation Methodology Results Future work Outline

3. 3 Literature review Steep declines in water level were accompanied by high rates of land subsidence. (A.M. Wilson, S. Gorelick. 1996)

4. 4 Motivation The Choshui River alluvial fan consists of sand, silt and clay. (Hung Wei Jia et al. 2009)

5. 5 Model MODFLOW-2000 (Version 1.19.01, March 25 2010) SUB (Subsidence and Aquifer-System Compaction) Package

6. 6 Governing equation

7. 7 Kv is the vertical hydraulic conductivity. h is the hydraulic head. Ssk is the specific storage. t is time △ b is the change in thickness. Sskv is the inelastic specific storage. Sske is the elastic specific storage. bo is the initial thickness. △ h is the change in hydraulic head.

8. 8 Layers 1, 2 and 3 Initial Head = 0 1000 2000 STORAGE COEFFICIENT=0.1 STORAGE COEFFICIENT=6.56x10 –5 STORAGE COEFFICIENT=2.62x10 –4 Column Row 12345678910 9 8 7 6 5 4 3 2 1 0 -100 -150 -350 K = 20 [m/day] Vertical leakance value = 3x10 –6 /m T = 1000, 0.5 [m 2 /day] Vertical leakance value = 3x10 –6 /m T = 1000 [m 2 /day] 100 50 200 Layer 1 Layer 2 Layer 3 Conceptual model

9. 9 T( transmissivity )=1000 [m 2 /day] Conceptual model (Layer 2) T( transmissivity )=0.5 [m 2 /day]

10. 10 123456789 1 2 3 4 5 6 7 8 9 Discharge area (Layer 1) Recharge area (Layer 1) 02 KILOMETERS Pumping well (Layer 3) Conceptual model

11. 11 Results (Head) Layer 1

12. 12 Layer 2 Results (Head)

13. 13 Layer 3 Results (Head)

14. 14 Results Subsidence

15. 15 Future work Data collection Model calibration and verification

16. 16 Thanks for your attention