FloPy is a Python package for developing, running, and post-processing models that are part of the MODFLOW family of codes. FloPy includes support for MODFLOW-2000, MODFLOW-2005, MODFLOW-NWT, and MODFLOW-USG. Other supported MODFLOW-based models include MODPATH (version 6), MT3DMS and SEAWAT. If you think you have found a bug in FloPy, or if you would like to suggest an improvement or enhanceme...

The nonhorizontal-model-layer (NHML) grid system is more accurate than the horizontal-model-layer grid system to describe groundwater flow in an unconfined sloping aquifer on the basis of MODFLOW-2000. However, the finite-difference scheme of NHML was based on the Dupuit-Forchheimer assumption that the streamlines were horizontal, which was acceptable for slope less than 0.10. In this study, we...

The accuracy with which MODFLOW simulates surface water-groundwater interaction is examined for connected and disconnected losing streams. We compare the effect of different vertical and horizontal discretization within MODFLOW and also compare MODFLOW simulations with those produced by HydroGeoSphere. HydroGeoSphere is able to simulate both saturated and unsaturated flow, as well as surface wa...

As a widely used groundwater flow model, MODFLOW offers a set of packages to simulate hydrologic stresses, inflows and outflows, to a groundwater system. Specifically, MODFLOW lacks a general method to process areally distributed recharge and discharge to groundwater. One solution would be to create a new package for MODFLOW. Alternatively, it is also possible to make the best use of existing c...

Prior to using MODFLOW, students need experience with simpler codes that provide “hands-on” experience setting up boundary and initial conditions, coding simple solution algorithms, and handling numerical errors. The best way to do this is using spreadsheet models; faculty no longer can expect students to know a common computer language, but students are familiar with spreadsheets. Many aspects...

Accurate representation of groundwater-surface water interactions is critical to modeling low river flow periods in riparian environments in the semi-arid southwestern United States. A link between the objectoriented decision support model RiverWare and MODFLOW was developed to incorporate critical features such as riparian evapotranspiration, localized variations in seepage rates, irrigation r...

Introduction The development and application of ground-water models has been an important component of USGS hydrologic investigations since the early 1970s. During the past 35 years, the USGS has developed a wide range of computer models to simulate saturated and unsaturated subsurface flow, solute transport, and chemical reactions. The most widely used of these programs is the MODFLOW model, w...

MOC3D is a general-purpose computer model developed by the U.S. Geological Survey (USGS) for simulation of three-dimensional solute transport in ground water (Konikow and others, 1996). The model is an update to the widely used USGS two-dimensional solutetransport model (MOC) and is implemented as an optional “package” for the ground-water flow model MODFLOW (Harbaugh and McDonald, 1996). Direc...

This paper presents an approach for coupling MODFLOW and MT3DMS for the simulation of variable-density ground water flow. MODFLOW routines were modified to solve a variable-density form of the ground water flow equation in which the density terms are calculated using an equation of state and the simulated MT3DMS solute concentrations. Changes to the MODFLOW and MT3DMS input files were kept to a...

In order to simulate large-scale ground water flow problems more efficiently with MODFLOW, the OpenMP programming paradigm was used to parallelize the preconditioned conjugate-gradient (PCG) solver with in this study. Incremental parallelization, the significant advantage supported by OpenMP on a shared-memory computer, made the solver transit to a parallel program smoothly one block of code at...