GMS:DE4 Package

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MODFLOW
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Reading a MODFLOW Simulation
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

The DE4 package or Direct Solver is one of the solvers available for MODFLOW. It requires reading in a DE4 file. The MODFLOW DE4 Solver package dialog will show the variables in the DE4 file. The DE4 Solver is available through the ZONEBUDGET tutorial, in the MODFLOW Global basic package select DE4. Variables include:

  • Comments (Text) – Allows up to 199 characters.
  • Maximum number of iterations (ITMX) – Per time step. Enter 1 for no interations.
  • Maximum number of upper equations (MXUP) – Impacts the amount of memory used by the package. Prints the actual number of equations in the upper part when the package runs.
  • Maximum number of lower equations (MXLOW) – Impacts the amount of memory used by the package. Prints the actual number of equations in the lower part when the package runs.
  • Maximum bandwidth (MXBW) – Impacts the amount of memory used by the package. Prints the actual band width plus 1 when the package runs.
  • Frequency of change of coefficients in [A] (IFREQ) – Affects the efficiency of solution. Can be 1,2, or 3.
  • 1 = The flow equations are linear and that coefficients of simulated head for all stress terms are constant for all stress periods.
  • 2 = The flow equations are linear, but coefficients of simulated head for some stress terms may change at the start of each stress period.
  • 3 = A nonlinear flow equation is being solved, which means that some terms in [A] depend on simulated head.
  • Print flag for convergence information per time step (MUTD4) – Can be 0, 1, or 2.
  • 0 = The number of iterations in the time step and the maximum head change each iteration are printed.
  • 1 = Only the number of iterations in the time step is printed.
  • 2 = No information is printed.
  • Head change multiplier (ACCL) – Normally this value is 1. A value greater than 1 may be useful for improving the rate of convergence when using external iteration to solve nonlinear problems.
  • Head change closure criterion (HCLOSE) – Not used if not iterating, but a value must always be specified.
  • Interval for time step printing (IPRD4) – Not used if not iterating, but a value must always be specified.
The MODFLOW DE4 Solver package dialog.

DE4 File Format

FOR EACH SIMULATION
 0.  [#Text]
 1.  ITMX   MXUP   MXLOW   MXBW
 2.  IFREQ  MUTD4  ACCL    HCLOSE   IPRD4 

Item 0 is optional—“#” must be in column 1. Item 0 can be repeated multiple times.

See Also