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GSFLOW: Coupled Groundwater and Surface-Water Flow Model

March 17, 2023

Overview of GSFLOW

GSFLOW is a coupled Groundwater and Surface-water FLOW model based on the integration of the USGS Precipitation-Runoff Modeling System (PRMS-V) and the USGS Modular Groundwater Flow Model (MODFLOW-2005 and MODFLOW-NWT). GSFLOW was developed to simulate coupled groundwater/surface-water flow in one or more watersheds by simultaneously simulating flow across the land surface, within subsurface saturated and unsaturated materials, and within streams and lakes. Climate data consisting of measured or estimated precipitation, air temperature, and solar radiation, as well as groundwater stresses (such as withdrawals) and boundary conditions are the driving factors for a GSFLOW simulation.

GSFLOW screenshot showing hydraulic conductivity values used in ground-water model, Sagehen Creek watershed near Truckee, CA
GSFLOW screenshot showing hydraulic conductivity values used in groundwater model, Sagehen Creek watershed near Truckee, CA.

GSFLOW operates on a daily time step. In addition to the MODFLOW variable-length stress period used to specify changes in stress or boundary conditions, GSFLOW uses internal daily stress periods for adding recharge to the water table and calculating flows to streams and lakes. Specified stream inflow over boundaries, internal stream-diversion flow rates, and groundwater-pumping flow rates can be specified using time-series input files that allow these stresses to vary during each time step. 

GSFLOW can be used to evaluate the effects of such factors as land-use change, climate variability, and groundwater withdrawals on surface and subsurface flow for watersheds that range from a few square kilometers to several thousand square kilometers, and for time periods that range from months to several decades.


Download Current Version of GSFLOW

Version 2.3.0 release has a major bug. Use version 2.2.1 instead.

Support is provided for correcting bugs and clarification of how GSFLOW is intended to work. Only limited assistance can be provided for applying GSFLOW to specific problems.

Download Previous Versions of GSFLOW

Version 2.2.1 (Released February 24, 2022)
Version 2.2 (Released March 11, 2021)
Version 2.1 (Released March 4, 2020)
Version 2.0 (Released May 30, 2018)

Documentation for GSFLOW

GSFLOW is documented in the following report:

Markstrom, S.L., Niswonger, R.G., Regan, R.S., Prudic, D.E., and Barlow, P.M., 2008, GSFLOW-Coupled Ground-water and Surface-water FLOW model based on the integration of the Precipitation-Runoff Modeling System (PRMS) and the Modular Ground-Water Flow Model (MODFLOW-2005): U.S. Geological Survey Techniques and Methods 6-D1, 240 p.,

Tools for developing GSFLOW input files:

Gardner, M. A., Morton, C. G., Huntington, J. L., Niswonger, R. G., and Henson, W. R., 2018, Input data processing tools for the integrated hydrologic model GSFLOW: Environmental Modelling & Software, v. 109, p. 41-53.

Documentation for saving GSFLOW results and restarting simulations:

Regan, R.S., Niswonger, R.G., Markstrom, S.L., and Barlow, P.M., 2015, Documentation of a restart option for the U.S. Geological Survey coupled groundwater and surface-water flow (GSFLOW) model: U.S. Geological Survey Techniques and Methods, book 6, chap. D3, 19 p.

Additional documentation can be found in the 'doc' subdirectory in the GSFLOW distribution and in the Summary of GSFLOW, including release history [1 MB PDF]. Users are encouraged to read the documents that are provided in the 'doc' directory of this software distribution.


Programs Related to GSFLOW

Guidance for determining applicability of the USGS GSFLOW and OWHM models for hydrologic simulation and analysis


Find MODFLOW-Related Software

Visit the MODFLOW and Related Programs page for a list of MODFLOW-related software.


How to Cite GSFLOW

This USGS software has two citations associated with it.

  1. The report citation is for the original report or article documenting the underlying theory, methods, instructions, and (or) applications at the time the initial version of the software was released. This digital object identifier (DOI) is for the report.
  2. The software release citation is for the software/code itself (now referred to by USGS as a "Software Release") and references a specific version of the code and associated release date. This DOI links to the code.

In instances where an author is citing use of this software, it would be appropriate to cite both the report documenting the code and the specific software release version that was used.

Report Citation for GSFLOW Shown Above

Software/Code Citation for GSFLOW

Regan, R.S. and Niswonger, R.G., 2021, GSFLOW version 2.2.0: Coupled Groundwater and Surface-water FLOW model: U.S. Geological Survey Software Release, 18 February 2021.


Example USGS Applications of GSFLOW

Allander, K.K., Niswonger, R.N., and Jeton, A.E., 2014, Simulation of the Lower Walker River Basin hydrologic system, west-central Nevada, Using PRMS and MODFLOW models: U.S. Geological Survey Scientific Investigations Report 2014-5190, 93 p.,

Ely, D.M., and Kahle, S.C., 2012, Simulation of groundwater and surface-water resources and evaluation of water-management alternatives for the Chamokane Creek basin, Stevens County, Washington: U.S. Geological Survey Scientific Investigations Report 2012-5224, 74 p.

Essaid, H.I., and Hill, B.R., 2014, Watershed-scale modeling of streamflow change in incised montane meadows  : Water Resources Research, vol. 50, pp. 2657-2678, doi:10.1002/2013WR014420. 

Fulton, J.W., Risser, D.W., Regan, R.S., Walker, J.F., Hunt, R.J., Niswonger, R.G., Hoffman, S.A., and Markstrom, S.L., 2015, Water-budgets and recharge-area simulations for the Spring Creek and Nittany Creek Basins and parts of the Spruce Creek Basin, Centre and Huntingdon Counties, Pennsylvania, Water Years 2000-06: U.S. Geological Survey Scientific Investigations Report 2015-5073, 86 p,

Gannett, M.W., Lite, K.E., Jr., Risley, J.C., Pischel, E.M., and La Marche, J.L., 2017, Simulation of groundwater and surface-water flow in the upper Deschutes Basin, Oregon: U.S. Geological Survey Scientific Investigations Report 2017-5097, 68 p.,

Hunt, R.J., Walker, J.F., Selbig, W.R., Westenbroek, S.M., and Regan, R.S., 2013, Simulation of climate-change effects on streamflow, lake water budgets, and stream temperature using GSFLOW and SNTEMP, Trout Lake Watershed, Wisconsin: U.S. Geological Survey Scientific Investigations Report 2013-5159, 118 p.

Hunt, R.J., Westenbroek, S.M., Walker, J.F., Selbig, W.R., Regan, R.S., Leaf, A.T., and Saad, D.A., 2016, Simulation of climate change effects on streamflow, groundwater, and stream temperature using GSFLOW and SNTEMP in the Black Earth Creek Watershed, Wisconsin: U.S. Geological Survey Scientific Investigations Report 2016-5091, 117 p.,

Huntington, J.L., and Niswonger, R.G., 2012, Role of surface-water and groundwater interactions on projected summertime streamflow in snow dominated regions: An integrated modeling approach  : Water Resources Research, vol. 48, W11524, doi: 10.1029/2012WR012319. 

Niswonger, R.G., Allander, K.K., and Jeton, A.E., 2014, Collaborative modelling and integrated decision support system analysis of a developed terminal lake basin: Journal of Hydrology, doi: 10.1016/j.jhydrol.2014.05.043. Available online at

Woolfenden, L.R., and Nishikawa, Tracy, eds., 2014, Simulation of groundwater and surface-water resources of the Santa Rosa Plain watershed, Sonoma County, California: U.S. Geological Survey Scientific Investigations Report 2014-5052, 258 p.,



Publication Year 2023
Title GSFLOW: Coupled Groundwater and Surface-Water Flow Model
Product Type Software Release
Record Source USGS Digital Object Identifier Catalog