Groundwater modelling software looks like a long list of products and is really two engines with a ring of interfaces around them. Most packages build, run and display models in MODFLOW, the US Geological Survey code, which is free. The main exception is FEFLOW, a separate finite element code from DHI. Choosing well is mostly about which interface your team can work in quickly, and whether the problem needs anything MODFLOW cannot do.
What is the best groundwater modelling software?
For most groundwater flow studies the best starting point is MODFLOW 6, because it is free, it is the version the USGS develops, and regulators and reviewers in most countries accept it without argument. The paid packages earn their price on workflow: building grids from GIS data, managing calibration, and producing figures a client can read. They do not compute a different answer from the same model.
The exception is a problem MODFLOW handles awkwardly, such as heavily faulted or fractured geology that needs a flexible mesh. That is where FEFLOW is worth its licence, as we set out in FEFLOW vs MODFLOW.
Is MODFLOW free?
Yes. MODFLOW 6 is public domain in the United States and released under CC0 worldwide, and version 6.8.1 came out in September 2026. It brings the older MODFLOW-2005, NWT and LGR versions together in one program, and it now covers more than flow: solute transport (GWT), heat transport (GWE, since 2024) and particle tracking (PRT). Its Buoyancy package handles variable density flow, the work SEAWAT used to do.
Two limits worth knowing: each transport model carries one solute, so several contaminants mean several transport models, and particle tracking does not yet work on fully unstructured grids. We cover the transport side in groundwater contamination modeling software compared.
Do I need to pay for an interface?
Not always. Two free tools are enough for many projects:
- ModelMuse, also from the USGS, is a free graphical interface for MODFLOW 6, the older MODFLOW versions, MODPATH and SUTRA, with PEST support. It is less polished than the paid packages and converts some older packages only partly when moving a model to MODFLOW 6.
- FloPy is a free Python package for building, running and reading MODFLOW models in code. It suits teams that rerun models often, because a script can be checked, versioned and repeated, which a sequence of clicks cannot.
The paid interfaces are worth it when the team is not comfortable in code, when the model is large, or when the client expects a familiar commercial package.
GMS, Visual MODFLOW Flex and Groundwater Vistas
- GMS, from Aquaveo, supports MODFLOW 2000 through MODFLOW 6, MT3DMS, RT3D, MODPATH, PEST and FEMWATER, with SEAWAT as an add-on. It is sold as a perpetual licence with annual maintenance, and a free Community Edition handles small models of up to 5,000 cells. Smart Bhujal is an authorised Aquaveo reseller in India, so read this entry with that in mind.
- Visual MODFLOW Flex, from Waterloo Hydrogeologic (part of Nova Metrix), bundles MODFLOW 6 with particle tracking, MODFLOW-USG Transport, MT3D-USGS and MODPATH 7. It is strong on building a conceptual model first and generating the grid from it.
- Groundwater Vistas, from Environmental Simulations Inc, supports MODFLOW, MT3D and MODPATH, with long standing PEST calibration support. Version 9 was released in 2024. It is popular with consultants who calibrate heavily.
All three drive the same MODFLOW engine. Ask for a trial, build a small piece of your actual site in each, and pick the one your team is fastest in.
When FEFLOW is the right choice
FEFLOW, from DHI, is a finite element code for flow, mass and heat transport in saturated and unsaturated ground. Its flexible mesh follows faults, thin layers and irregular boundaries closely, and it is strong on density driven flow such as seawater intrusion and on geothermal heat problems. It is sold as a subscription, and a free viewer mode lets a reviewer open a model without a licence. For a regional water balance in simple layered aquifers it is usually more than the problem needs.
The tools around the model
- PEST and PEST++ calibrate a model against observed heads and flows and estimate the uncertainty in its predictions. PEST++ is open source from the USGS. A model without calibration and an uncertainty range is a drawing, not evidence.
- Leapfrog, from Seequent (owned by Bentley), builds 3D geological models and exports grids to MODFLOW and FEFLOW. It earns its cost where the geology is complex and drilling data is plentiful.
- iMOD, from Deltares, is a set of open source tools for building large MODFLOW 6 models, common in the Netherlands.
How to choose
Work down the list. Is it a flow or water balance study in layered aquifers? MODFLOW 6, with ModelMuse or FloPy if the budget is tight and a paid interface if the team needs one. Is the geology faulted or fractured, or is density or heat the question? Look at FEFLOW. Is the model going to a regulator or reviewer who works in one package? Use that package. Will the model be rerun every year as new data arrives? Build it in FloPy, so the rerun is a script and not a week of clicking.
Licence terms in this market change, so confirm the current position with each developer before a project depends on it.
What actually determines the answer
Groundwater models are decided by their data. Aquifer properties from a handful of pumping tests, recharge estimated rather than measured, and water levels from wells nobody has surveyed will give a confident wrong answer in every package above. The monitoring network and the calibration deserve more of the budget than the choice of software.
Smart Bhujal builds groundwater models in MODFLOW, GMS and FEFLOW, set out on our groundwater modeling services page. Where the model has to become something a water manager uses every season, it becomes a water digital twin.