DSD-INT 2017 The unsaturated zone MetaSWAP-package, recent developments - Van Walsum
Transcript of DSD-INT 2017 The unsaturated zone MetaSWAP-package, recent developments - Van Walsum
- 1. The unsaturated zone MetaSWAP-package Recent developments Paul van Walsum Wageningen Environmental Research
- 2. Overview 1. Introduction 2. MetaSWAP concept for the unsaturated zone 3. Coupling to salinity model TRANSOL 4. Coupling to crop growth model 5. Conclusions 2
- 3. Introduction Why MetaSWAP? Simple MODFLOW packages for unsaturated zone: EVT, ETS extinction function for capillary rise; soil water dynamics ? UZF1 kinematic wave for infiltration; capillary rise ? Advanced MODFLOW packages: VSF/REF1 Richards Equation Flow ; computation time ? 3
- 4. MetaSWAP Water balance of 1D-Richards equation: : moisture content (m3 m-3) q : vertical flux (m d-1) : source term (m3 m3 d-1) 4 + =
- 5. MetaSWAP Water balance of Richards equation: : moisture content (m3 m-3) q : vertical flux (m d-1) : source term (m3 m3 d-1) Solution procedure in two steps: Generate steady state profiles, store in database Combining steady state profiles with water balance during simulation coupled to groundwater model 5 + =
- 6. MetaSWAP Steady state profiles: detailed vertical resolution 6 q (mm d-1 ) 1 0 -1 -2 -5 m 3 m -3 0.00 0.30 0.32 0.34 0.36 0.38 0.40 0.42 z (m) -2.0 -1.5 -1.0 -0.5 0.0 root zone h T > 0 I > 0
- 7. Metafunction for the vertical flux q 7 q(pr,h): pr : mean pressure head root zone h : groundwater level
- 8. Aggregation boxes for water balances Subgrid computational method 8 Aggregation box 1 (root zone) Aggregation box 2 Swap compartments Aggregation box 3 Aggregation box 4
- 9. p (m) -0.8 -0.6 -0.4 -0.2 0.0 z (m) -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 4 d3 dt = 2 d box 1 (root zone) box 2 box 3 9 q (mm d-1) qtot (mm) Simulation of percolation: comparison with SWAP Infiltration = 16 mm/d
- 10. Coupling to MODFLOW Two possible options for balances: System Control volumes volume 10 Groundwater Unsaturated zone Unsaturated zone Groundwater
- 11. Coupling to MODFLOW Balance equation for communal control volume Implementation with Control volume dynamic storage coefficient (sc1) (hn ho) = (qmsw + qmod) t 11 Unsaturated zone Groundwater
- 12. Verification of coupling MODFLOW-MetaSWAP Comparison MODFLOW-MetaSWAP with SWAP MODFLOW-dummy : only drainage flux 12 -2,5 -2 -1,5 -1 -0,5 0 3655 4020 4385 4750 SWAP MF-MSW h (m) Model N (mm/j ETact (mm/j) R (mm/j) SWAP 809 484 325 MF-MSW_1d 809 485 324
- 13. Coupling to salinity model TRANSOL Dynamic mixing cell model of solute transport Analytic integration of time steps Vertical resolution same as Richards model Aggregation box 1 (root zone) Aggregation box 2 Swap compartments p(m) -0.8 -0.6 -0.4 -0.2 0.0 z (m) -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 4 d3 dt = 2 d box 1 (root zone) box 2 box 3
- 14. TRANSOL dispersion, verfication with SWAP-CD Numerical dispersion Ldis,num=0.5*z For z = 5 cm Ldis,num=2.5 cm Equivalent to SWAP Ldis,num = 0.5*z = 0.5*1 cm Ldis,CD = 2 cm Ldis,tot = 0.5 + 2 = 2.5 cm
- 15. Coupling to crop growth model WOFOST Simulation of production based on assimilation Feedback to hydrologic model with dynamic crop parameters canopy resistance
- 16. Computational performance
- 17. Conclusions MetaSWAP, the pros: fast (10-50X SWAP) emulator of Richards model water balance and groundwater dynamics stable and efficient coupling to MODFLOW Limitations: hill slope situations (1D instead of 2D) deep groundwater when timing of infiltration front is critical (cf. UZF1) 17
- 18. Questions ? 18