Water Resources Applications Software

Geochemical || Ground Water || Surface Water || General || Statistics & Graphics

Summary of mf2005-GWM


ABSTRACT
MF2005-GWM is a Ground-Water Management Process for the U.S. Geological Survey modular three-dimensional ground-water model, MODFLOW-2005. MF2005-GWM 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 MF2005-GWM: 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 MF2005-GWM, 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 MF2005-GWM 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 MF2005-GWM uses the Ground-Water 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.

HISTORY

Version 1.1 2009/06 – Reconstructed from MODFLOW-2005 Version 1.6.02. Added capability for placement of streamflow constraints when SFR package is used. Bug fix that caused code failure when equality summation constraints were imposed on binary variables. Bug fix to correct output for SLP runs. See ‘release.txt’ for more details.


Version 1.0.1 2008/08 - Reconstructed from MODFLOW-2005 Version 1.5.00. Bug fix that prevented use of LPF or HUF packages. Change to output to GWMWFILE so that well information is printed even when stress is zero. New feature to allow formatted output of response matrix under NS option. See 'release.txt' for details.


Version 1.0.0 2007/07/12 - Initial release, built from MODFLOW-2005 Version 1.3.01 and MF2K-GWM Version 1.1.1


    

PROCESSES
This version of MF2005-GWM includes the following processes:
GWF2 -- Ground-Water Flow Process
GWM1 -- Ground-Water Management Process
OBS2 -- Observation Process

PACKAGES
In addition to all of the packages included with Version 1.6.02 of MODFLOW-2005, this version of MF2005-GWM includes the following packages:
DCV2 -- Decision Variable Package
OBJ2 -- Objective Function Package
HDC2 -- Head Constraints Package
STC2 -- StreamFlow Constraints Package
SMC2 -- Summation Constraints Package
DCC2 -- Decision-Variable Constraints Package
RMS2 -- Response Matrix Solution Package
BAS2-GWM -- Basic Package for GWM


DOCUMENTATION

See MF2005_GWM page.