MODFLOW is the modular hydrologic model developed by the USGS and widely considered an international standard for simulating and predicting groundwater conditions and groundwater/surface-water interactions.
IGW-NET provides the user with the option to use MODFLOW to solve the finite difference equations resulting from discretization of the conceptual model.
MODFLOW solver inputs and options are enabled interactively so the user should move across the tabs making selections and changes as desired.
Versions
-> Packages
-> Solvers
-> Inner Loop
-> Outer Loop If no changes are made default values will be used.
Note: MODFLOW boundary condition packages integrated with the IGW-NET platform include:
- Constant Head (CHD)
- Recharge (RCH)
- Well (WEL)
- Drain (DRN)
- Evapotranspiration (EVT)
- General Head Boundary(GHB)
- Drain (DRN)
- River (RIV)
Future integration planned for the additional packages:
- Lake (LAK)
- Stream Flow (SFR)
Versions
Depending on the MODFLOW version chosen there may be one or two flow packages from which to choose and one or more matrix solvers.
Support is provided for:
- MODFLOW-6 (Current Core Version)
- MODFLOW-USG
- MODFLOW-NWT
- MODFLOW-2005
- MODFLOW-2000
Packages (Groundwater Flow)
The MODFLOW groundwater flow packages define aquifer properties and give the user control over flow schemes and calculation options.
Solvers
Every MODFLOW model must include one solver packages that is used to solve the groundwater flow equations. Each version of MODFLOW has different solver options.
Inner Loop
Most MODFLOW solvers use iteration to quickly solve the equations needed to calculate groundwater levels across the model domain.
The inner (or linear) loop is where the solvers solve the linear equations (terms dependent on groundwater level are held constant). If a given solver uses inner iteration, the uses can control the ways in which a matrix is preconditioned prior to solving, choose linear acceleration schemes, and specify the closure criteria that determine when a solution is sufficient and the loop can be exited.
Outer Loop
The Outer (or nonlinear/Picard) loop is where the solvers solve the nonlinear equations and terms dependent on groundwater level are calculated. If a given solver uses outer iteration, the uses can control solution relaxation and damping, choose nonlinear acceleration, and specify the closure criteria that determine when a solution is sufficient and the loop can be exited.