Water Resources Applications Software
Summary of GWM-2000
GWM-2000 is a Groundwater Management Process for the U.S. Geological Survey
modular three-dimensional groundwater model, MODFLOW-2000. GWM-2005 uses a
response-matrix approach to solve several types of linear, nonlinear, and
mixed-binary linear groundwater management formulations. Each management
formulation consists of a set of decision variables, an objective function,
and a set of constraints. Three types of decision variables are supported
by GWM-2000: flow-rate decision variables, which are withdrawal or injection
rates at well sites; external decision variables, which are sources or sinks
of water that are external to the flow model and do not directly affect the
state variables of the simulated groundwater system (heads, streamflows, and
so forth); and binary variables, which have values of 0 or 1 and are used to
define the status of flow-rate or external decision variables. Flow-rate
decision variables can represent wells that extend over one or more model
cells and be active during one or more model stress periods; external
variables also can be active during one or more stress periods. A single
objective function is supported by GWM-2000, which can be specified to either
minimize or maximize the weighted sum of the three types of decision
variables. Four types of constraints can be specified in a GWM-2000
formulation: upper and lower bounds on the flow-rate and external decision
variables; linear summations of the three types of decision variables;
hydraulic-head based constraints including drawdowns, head differences, and
head gradients; and streamflow and streamflow-depletion constraints.
The Response Matrix Solution (RMS) Package of GWM-2000 uses the Groundwater
Flow Process of MODFLOW to calculate the change in head at each constraint
location that results from a perturbation of a flow-rate variable; these
changes are used to calculate the response coefficients. For linear
management formulations, the resulting matrix of response coefficients is then
combined with other components of the linear management formulation to form a
complete linear formulation; the formulation is then solved by use of the
simplex algorithm, which is incorporated into the RMS Package. Nonlinear
formulations arise for simulated conditions that include water-table
(unconfined) aquifers or head-dependent boundary conditions (such as streams,
drains, or evapotranspiration from the water table). Nonlinear formulations
are solved by sequential linear programming; that is, repeated linearization
of the nonlinear features of the management problem. In this approach,
response coefficients are recalculated for each iteration of the solution
process. Mixed-binary linear (or mildly nonlinear) formulations are solved
by use of the branch and bound algorithm, which is also incorporated into
the RMS Package.
Version 1.1.4 2011/6 – correct bug that may affect problems with both binary
variables and external variables.
Version 1.1.3 2009/12 – MF2000-GWM is renamed GWM-2000.
Version 1.1.2 2009/06 – Bug fix that caused code failure when equality
summation constraints were imposed on binary variables. Bug fix to
correct output for SLP runs.
Version 1.1.1 2007/03 – Reconstructed from MODFLOW-2000 Version 1.17.02
so that the GMG solver can be used. Bug fixed that caused improper
reading of response matrix when both head and stream constraints are
Version 1.1 2006/08 – New features added to output the response
coefficients in a formatted file, the optimal values of the flow
variables in a file formatted similarly to a MODFLOW WEL file, the
solution at each iteration of the SLP algorithm, the status of
summation constraints and additional screen and file output reporting
on algorithm progress. Additional controls on SLP algorithm added.
Several minor clean-ups and improvements. Many of these features are
described in the online PDF called "GWM Addendum."
Version 1.0.3 2006/01/21 Correct a bug
that caused incorrect reading of flow process files when certain
combinations of variables are read using the parameter input
structure. Correct several bugs related to proper input when
non-zero base and/or reference flows are specified and when the
response matrix file is written or read. New features added to
SLP to check for dry cells at wells and to better control iterations.
Version 1.0.2 2005/09/24 Correct a
compiler setting in the Version 1.0.1 executable that prevented opening
of binary files. Add ability to comment lines in GWM file.
Several minor improvements to output.
Version 1.0.1 2005/07/29 Fix a bug that
caused incomplete checking for
feasibility of binary-only summation constraints. Fix an output
bug that caused improper reporting of range analysis for stream
depletion and drawdown constraints. Several minor improvements to
output appearance and input checking.
Version 1.0.0 2005/02 - Initial release, built from MODFLOW-2000
This version of MF2K-GWM includes the
GWF1 -- Ground-Water
GWM1 -- Ground-Water
SEN1 -- Limited
capability to read Sensitivity Process files
In addition to all of the packages included
with Version 1.13 of MODFLOW-2000, this version of MF2K-GWM includes
the following packages:
DCV1 -- Decision
OBJ1 -- Objective
HDC1 -- Head
STC1 -- StreamFlow
SMC1 -- Summation
Decision-Variable Constraints Package
RMS1 -- Response
Matrix Solution Package
BAS1-GWM -- Basic
Package for GWM
Ahlfeld, D.P., Barlow, P.M., and Mulligan, A.E., 2005, GWM-A
ground-water management process for the U.S. Geological Survey modular
ground-water model (MODFLOW-2000): U.S. Geological Survey Open-File
Report 2005-1072, 124 p.
Addendum to GWM, version 1.1.1: A new input requirement; new
capabilities added to increase output options; revised Supply sample
problem (supply2). – March 2007.
Barlow, P.M., 2005, Use of Simulation-Optimization Modeling to Assess
Regional Ground-Water Systems: U.S. Geological Survey Fact Sheet
2005-3095, 4 p.