# GMS:DE4 Package

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Flow: |
BCF6, HUF, LPF, UPW |

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SMS |

Other: |
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.

## 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

- For more information on this solver, see page 84 of the USGS documentation.

GMS – Groundwater Modeling System | ||
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Aquaveo |

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