Free Groundwater Modelling Software — MODFLOW, ModelMuse and PHREEQC
Groundwater modelling is one of the few fields in engineering where free software is not the alternative — it is the standard. MODFLOW, the US Geological Survey's model, is the engine under almost every commercial product in the field. What you pay for in programs like Groundwater Vistas or Visual MODFLOW is mostly the interface. And an interface exists for free too.
The model itself
1. MODFLOW 6
A finite-volume groundwater flow model developed at the USGS and updated since the 1980s. It is built from packages: wells, rivers, recharge, drains, evapotranspiration from groundwater and more — each adding one process to the model. The sixth version added a solute transport model directly inside MODFLOW, and a package for variable-density flow — what you need to study seawater intrusion into a coastal aquifer.
What's missing: it has no interface. Input is text files, and output is binary files that need a tool to read.
2. ModelMuse
The USGS's own free graphical interface for MODFLOW. You draw the aquifer boundaries, define layers and hydraulic properties, place wells and rivers — and the program writes the input files and runs the model. It also supports other USGS models, such as SUTRA for variable-density flow.
What's missing: Windows only, and less polished than the commercial interfaces. But all the functionality is there.
MODFLOW 6
U.S. Geological Survey (USGS)
The world standard for groundwater flow and solute transport modelling, from the USGS.
Get it from the vendorModelMuse
U.S. Geological Survey (USGS)
The free graphical interface to MODFLOW — build the model with a mouse instead of text files.
Get it from the vendorGeochemistry
3. PHREEQC
When the question is not only where the water flows but what happens to it on the way: mineral dissolution and precipitation, saturation indices, mixing of water sources, ion exchange, and one-dimensional reactive transport. PHREEQC is the tool geochemists use worldwide, and its thermodynamic databases are the reference in the field. Very useful for water quality questions, pipe scaling and dilution when recharging an aquifer.
PHREEQC
U.S. Geological Survey (USGS)
Aqueous geochemical calculations — equilibrium, dissolution, precipitation and reactive transport.
Get it from the vendorWhere to find more
The USGS software catalogue gathers all of the survey's water and geology tools — SUTRA, MT3D-USGS, GSFLOW and more — with source code and documentation. Python users will also find FloPy there, a library that builds and runs MODFLOW models from a script, which is the better way to do sensitivity studies with hundreds of runs.
A practical workflow
Build the model in ModelMuse, run it in MODFLOW 6, and if there is a water quality question — check it in PHREEQC. Boundaries and layers can be prepared in QGIS from maps and boreholes. That is a complete professional workflow without a single licence.
The data is the expensive part
The software is free; the data is not. Water levels, pumping tests, hydraulic conductivity and geological sections — these set the quality of the model, and no software, free or commercial, replaces them. A good groundwater model is above all a model calibrated against measurements.