Online Guide to MODFLOW-NWT

Table 2. Suggested input values for the NWT input file

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Table 2. Suggested input values for the NWT input file

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Table 2. Suggested input values for the NWT input file

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[Dashes (–) indicate that values are not applicable]

Input variable name

Default values

Range

Iteration Control

HEADTOL

1×10-4 (L)*

–

FLUXTOL

500 (L3/T)*

–

MAXITEROUT

100

10–2,000

Dry Cell Tolerance

THICKFACT

0.00001

1×10-6-1

NWT Options

LINMETH

1

1 or 2

IPRNWT

0

0 or 2

IBOTAV

0**

0 or 1

Under relaxation Input

 

Model Complexity

 

 

Simple

Moderate

Complex

 

DBDTHETA

0.97

0.90

0.85

0–1

DBDKAPPA

0.0001

0.00001

0.00001

0–1

DBDGAMMA

0.0

0.0

0.0

0–1

MOMFACT

0.0

0.1

0.1

0–1

Residual Control

 

Model Complexity

 

 

Simple

Moderate

Complex

 

BACKFLAG

0***

0

1

0 or 1

MAXBACKITER

20

20

50

1–100

BACKTOL

1.5

1.1

1.1

1–2

BACKREDUCE

0.97

0.9

0.7

0.05–0.99

Linear Solution Control and Options for GMRES

 

Model Complexity

 

 

Simple

Moderate

Complex

 

MAXITINNER

50

50

50

25–1,000

ILUMETHOD

2

2

2

1 or 2

LEVFILL

1

1

1

5–10 for ILUMETHOD=1

0–2 for ILUMETHOD=2

STOPTOL

1×10-10

1×10-10

1×10-10

1×10-8-1×10-12

MSDR

5

10

15

5–20

Linear Solution Control and Options for χMD

 

Model Complexity

 

 

Simple

Moderate

Complex

 

IACL

1

1

2

0,1, or 2

NORDER

0

0

0

0,1, or 2

LEVEL

1

1

15

1–10

NORTH

5

10

1

4-10 for Orthomin

2 otherwise

IREDSYS

1

1

1

0 or 1

RRCTOLS

0.0

0.0

0.0

0–0.0001

IDROPTOL

1

1

1

0 or 1

EPSRN

5×10-3

5×10-3

1×10-3

5×10-5-1×10-3

HCLOSEXMD

1×10-3

1×10-3

1×10-4

1×10-3-1×10-5

MXITERXMD

50

100

200

25–1,000

*These values are dependent on the units specified in the MODFLOW-2005 discretization input file. Values given are for units of meters and days.

**The optimal value for IBOTAV is problem specific. Values of 0 and 1 should be tested for each problem.

***BACKFLAG should be set to 0 (residual control set to inactive) unless there are convergence problems. “OPTIONS” must be set to “SPECIFIED” if the residual control option is used.