GMS:MODFLOW-NWT

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MODFLOW
Pre-processing
MODFLOW Commands
Building a MODFLOW Model
Map to MODFLOW
Calibration
Packages Supported in GMS
Saving a MODFLOW Simulation
Importing MODFLOW Files
Unsupported MODFLOW Features
Post-processing
MODFLOW Display Options
MODFLOW Post-Processing Viewing Options
Reading a MODFLOW Simulation
Tutorials
MODFLOW Tutorials
Packages
Flow: BCF6, HUF, LPF, UPW
Solvers:

DE4, GMG, NWT, PCG,

PCGN, LMG, SIP, SOR,

SMS
Other:

BAS6, BFH, CHD1, CLN,

DRN1, DRT1, EVT1, ETS1,

GAGE, GHB1, GNC, HFB1,

HUF, LAK3, MNW1, MNW2,

OUT1, RCH1, RIV1, SFR2,

STR1, SUB1, SWI2, WEL1,

UZF1

Starting at GMS version 8.2, GMS supports MODFLOW-NWT. MODFLOW-NWT is a version of MODFLOW based on MODFLOW-2005 that provides a different formulation of the groundwater flow equation designed to solve models that are non-linear due to unconfined cells or non-linear boundary conditions.

Choosing MODFLOW Version

Choosing to use MODFLOW 2000, MODFLOW 2005, or MODFLOW-NWT is done in the MODFLOW Global Options Dialog. At any time you can switch from one to the other.

MODFLOW Global Option Dialog

Changes to MODFLOW 2005

Source code differences between MODFLOW 2005 and MODFLOW-NWT.

  1. UPW Package
  2. NWT Solver
  3. WEL Package
    • The WEL package was modified to add an option to decrease the pumping rate as the head drops below a user-specified percentage of cell thickness. The new option is called PHIRAMP.
  4. SFR Package
    • The SFR package is modified to avoid removing water from dry cells and to calculate derivatives for the Newton formulation.
  5. UZF Package
    • The UZF package is modified to avoid removing water from dry cells and to calculate derivatives for the Newton formulation.
  6. Other Packages
    • Poor input values for other packages can result in convergence failure. For example, an EVT extinction depth below the cell bottom elevation can result water being improperly removed from a dry cell.

MODFLOW-NWT Files

Here are tables of some of the available input and output files for MODFLOW-NWT. Note: MODFLOW will produce the LMT and HFF files even if transport is turned off.

  • For more information on these files see the manual
Required Input Files
Name Description
MFN MODFLOW Name File
GLO Global Listing File
DIS Discretization File
OC Process Output Control Option File
BA6 Basic Package Global Options File
Solver Package File
Name Description
DE4 Direct
GMG Geometric Multi-Grid
LMG Link Algebraic Multi-Grid
NWT Newton
PCG Preconditioned Conjugate-Gradient
SIP Strongly Implicit Procedure
Input Flow Package Files
Name Description
BCF Evapotranspiration Segments
HUF Evapotranspiration
LPF Layer Property Flow
UPW Unsaturated-Zone Flow
Optional Package Files
Name Description
ASP PEST Advanced Spacial Parameterization
CHD Time-Variant Specified-Head
DRN Drain
DRT Drain Return
EVT Evapotranspiration
ETS Evapotranspiration Segments
GAG Gage
GHB General Head Boundary
HFB Horizontal Flow Barrier
LAK Lake
RCH Recharge
RIV River
SFR Streamflow-Routing
STR Stream-Routing
SUB Subsidence
SWI Seawater Intrusion
UZF Unsaturated-Zone Flow
WEL Process Well
Observation Input Files
Name Description
OBS Main Observation Process Input
DROB Drain Observation
CHOB Constant-Head Flow Observation Input
Output Files
Name Description
MFS MODFLOW Super File
MFW GMS MODFLOW World File
MFR GMS MODFLOW Result Index File
PRJ Projection
CSV Cell Summary Comma Separated Value Excel
HFF Head and Flow File Link to MT3DMS
H5 Hierarchal Data Format (HDF5) Array & List Data
LMT Link Modular Transport (MT3DMS)
M2P MODFLOW Pest
PARAM Parameter Information
Output Results Files
Name Description
CCF Cell-to-Cell Aquifer Flow
CCF2 Cell-to-Cell Stream Reach Outflow
DRW Drawdown
GLO Global Listing
HED Head Output
OUT Output
Output Package Files
Name Description
MNW Multi-Node Well
MNW2 Multi-Node Well Version 2
MNWI Multi-Node Well Information
SWIBUD Seawater Intrusion Package Budget
SWIZETA Sewater Intrusion Package Zeta Surface
Output Data Exchange Files
Name Description
_W Weighted Residuals
_WW Weighted Equivalents & Weighted Observation
_WS Weighted Residuals and Simulated Equivalents
_R Unweighted Residuals
_OS Observed Values and Simulated Equivalents
_B Data Exchange File
_NM Weighted Residuals and Probability Plotting

External Links