How to Choose the Right MODFLOW Packages for Your Groundwater Model

Selecting the right MODFLOW packages isn’t just a technical step—it’s the foundation for an efficient, reliable groundwater model. Whether you're simulating recharge, stream interaction, or complex boundary conditions, GMS gives you the tools to tailor your model with precision. In this guide, we break down the essential MODFLOW packages and show you how to choose the best combination for your specific hydrogeologic scenario—so you can model smarter, not harder.

Groundwater Modeling System (GMS) builds accurate and efficient groundwater simulations using MODFLOW packages. MODFLOW is a highly modular package system that simulates specific physical processes such as recharge, pumping, evapotranspiration, and stream interactions. 

This guide explains key MODFLOW packages and how to choose the ones that best meet your groundwater modeling objectives. 

Basic (BAS) Package

The BAS package is the foundation of every model and defines the active and inactive cells and initial heads. This is always required and sets up the computational domain. 

Layer Property Flow (LPF) or Block-Centered Flow (BCF) Packages

Use these packages when modeling confined/unconfined aquifers with homogeneous or layered hydrogeology. These packages define aquifer properties such as hydraulic conductivity and layer properties. 

• Choose the BCF package when defining aquifer cell properties directly. 

• Choose the LPF package when defining aquifer cell properties directly or through the use of parameters. 

Well (WEL) Package 

Use when modeling wells, remediation systems, or water supply infrastructure. The WEL package simulates pumping or injection wells, and can assign time-varying flow rates and control stress periods. 

Recharge (RCH) Package 

Use this package when recharge is a significant part of the water balance of the aquifer. The RCH package lets you apply spatially and temporally varying recharge from precipitation, irrigation, or return flow. 

River (RIV) and Streamflow Routing (SFR2) Packages

Use one of these packages when modeling the impact of rivers, streamflow, or watershed connectivity. 

• Choose the RIV package when modeling simple river-aquifer exchange. 

• Choose the SFR2 package when modeling more complex river-aquifer interactions like gaining/losing streams, flow routing, or streambed conductance. 

Drain (DRIN) and General Head Boundary (GHB) Packages

Use these packages when modeling boundary conditions that vary with head. 

• Choose DRN when modeling features such as drainage canals or seepage. 

• Choose GHB when modeling constant-head boundaries such as lakes or adjacent aquifers. 

Conclusion

Choosing the right MODFLOW packages is just the beginning. With GMS, you have access to a full suite of tools designed to streamline model setup, calibration, and visualization.GMS allows you to quickly add and remove packages with ease, giving you greater control over your groundwater project.

Make use of all of the MODFLOW packages by downloading GMS today!