MODFLOW 6 Flow#

This page groups scientific reading for flow/modflow6.

Use this path when the study needs MODFLOW 6 package semantics, runtime DISV-style unstructured support, XT3D method choices, or downstream transport/modflow6gwt compatibility.

What Is Repeated From The Common MODFLOW Part#

flow/modflow6 still uses the common MODFLOW-family contract:

  • hydraulic head is the primary groundwater-flow state;

  • recharge, wells, storage, imposed heads, and drainage are normalized by the HydroModPy Flow layer before backend assembly;

  • stress periods carry the time discretization seen by the backend;

  • package semantics must be documented before interpreting a result;

  • comparison against another backend requires checking mesh, vertical representation, forcing aggregation, and boundary-condition mapping.

This repetition is intentional. The MODFLOW 6 page should be readable without first opening the MODFLOW-NWT page.

MODFLOW 6 Specifics#

Topic

MODFLOW 6 interpretation

Process pair

flow/modflow6.

Backend family

MODFLOW 6 GWF.

Grid support

Structured support and runtime DISV-style triangular support where enabled by the workflow.

Package vocabulary

Modern MODFLOW 6 package stack for flow, storage, recharge, boundary conditions, and outputs.

Irregular-mesh option

XT3D can matter on irregular DISV-style meshes.

Active drainage outputs

DRN budgets are post-processed to positive outflow_drain and routed to accumulation_flux when the run exposes a usable solver mesh.

Downstream transport

Preferred path for transport/modflow6gwt.

Focused Reading#

Typical Use Cases#

Use flow/modflow6 when:

  • the study needs modern MODFLOW 6 package semantics;

  • the mesh may be irregular or DISV-style;

  • XT3D behavior is part of the numerical-method question;

  • downstream concentration transport should use MODFLOW 6 GWT;

  • simulated drainage activation or active-network diagnostics should be inspected from persisted result fields;

  • the run is part of a controlled comparison against MODFLOW-NWT or Boussinesq.

Be explicit when:

  • reproducing a legacy MODFLOW-NWT study;

  • comparing structured and irregular supports;

  • changing XT3D;

  • comparing raw cell outputs against collapsed profiles or observations.

Surface-Seepage Example Path#

When flow/modflow6 is used for drainage activation or simulated active network diagnostics, read the evidence in this order:

  1. Conceptual Model to decide whether the case is a stream boundary, seepage/drainage operator, or post-solve active network question.

  2. Simulated Active Network to check the MODFLOW 6 output contract: raw DRN budget is normalized to positive outflow_drain, then routed to accumulation_flux, then displayed as simulated_active_network when the mesh is plottable.

  3. Nancon K-Sweep Results for a real-basin MODFLOW 6 example where active-network overlap is compared against the observed reference hydrographic network.

  4. Worked Examples for the exact commands and files to open.

  5. Status And Limitations for the current distinction between implemented result fields, demonstrated examples, and future contracts such as a persisted hydrographic_network_simulated_active vector role.

This is the example path that demonstrates the MODFLOW 6 work. It is stronger than only showing a head map because it follows the full interpretation chain: head, local seepage or drain outflow, routed network signal, and validation overlay.

Scientific Checklist#

Decision point

What to document

Grid support

Structured grid or runtime DISV-style mesh.

XT3D

Whether modflow6.runtime.mf6_enable_xt3d is enabled, disabled, or auto-resolved.

Package envelope

Which MODFLOW 6 packages are assembled for recharge, wells, storage, boundary conditions, and outputs.

Comparison target

Whether the run is compared to MODFLOW-NWT, Boussinesq, an analytical case, or field observations.

Transport coupling

Whether the flow run must feed transport/modflow6gwt.

Active drainage diagnostics

Whether outflow_drain, accumulation_flux, and simulated_active_network are interpreted as local drainage, routed network signal, or thresholded display mask.

Minimal Plan Shape#

[[simulation.process]]
id = "flow_main"
type = "flow"
solvers = ["modflow6"]

[solver]
backend = { backend = "modflow6" }

Minimal Process Interpretation#

The short TOML shape above means:

  • one flow process is requested;

  • the selected solver name is modflow6;

  • HydroModPy resolves common Flow inputs to MODFLOW 6 packages;

  • the final scientific interpretation depends on package choices, grid support, stress periods, and output diagnostics.