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Water Software > Groundwater Software > MODFLOW and Related Programs > GSFLOW

GSFLOW: coupled groundwater and surface-water flow model

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) and the USGS Modular Groundwater Flow Model (MODFLOW 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 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.

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.

GSFLOW Information and Downloads

[ Image: Cover of software documentation report. ]

Software Downloads

The current release of GSFLOW is version 1.2.2, February 23, 2018. Users are encouraged to read the documents that are provided in the 'doc' directory of this software distribution.

Documentation of GSFLOW

How to Cite

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

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.

Software/Code Citation for GSFLOW v. 1.2.2

Regan, R.S., Niswonger, R.G., Markstrom, S.L., Maples, S.R., and Barlow, P.M., 2018, GSFLOW version 1.2.2: Coupled Groundwater and Surface-water FLOW model: U.S. Geological Survey Software Release, 23 February 2018,

Example USGS Applications of GSFLOW

Albano, C.M., Dettinger, M.D., McCarthy, M.I., Welborn, T.L., and Cox, D.A., 2015, Use of a hypothetical winter-storm disaster scenario to identify vulnerabilities, mitigation options, and science needs in the greater Lake Tahoe, Reno, and Carson City region, USA: Natural Hazards [Link exits the USGS web site], vol 79, 22 p., DOI 10.1007/s11069-015-2003-4.

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.,

Carroll, R. W., Huntington, J. L., Snyder, K. A., Niswonger, R., Morton, C., and Stringham, T. K., 2016, Evaluating mountain meadow groundwater response to Pinyon‐Juniper and temperature in a Great Basin watershed: Ecohydrology,

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 [Link exits the USGS web site]: 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 [Link exits the USGS web site]: Water Resources Research, vol. 48, W11524, doi: 10.1029/2012WR012319.

Mejia, J.F., Huntington, Justin, Hatchett, Benjamin, Koracin, Darko, and Niswonger, R.G., 2012, Linking global climate models to an integrated hydrologic model: Using an individual station downscaling approach [1.2MB PDF] [Link exits the USGS web site]: Journal of Contemporary Water Research and Education, issue 147, p. 17-27.

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 or

Tanvir Hassan, S.M., Lubczynski, M.W., Niswonger, R G., and Su, Z., 2014, Surface-groundwater interactions in hard rocks in Sardon Catchment of Western Spain: an integrated modeling approach: Journal of Hydrology, doi: 10.1016/j.jhydrol.2014.05.026. 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.,

A complete list of publications discussing GSFLOW is also available.

Conference Proceedings

Huntington, J.L., Niswonger, R.G., Rajagopal, S., Zhang, Y., Gardner, M., Morton, C.G., Reeves, D.M., McGraw, D., and Pohll, G.M., 2013, Integrated hydrologic modeling of Lake Tahoe and Martis Valley mountain block and alluvial systems, Nevada and California [380KB PDF] [Link exits the USGS web site]: Golden, CO, MODFLOW and More 2013 Conference Proceedings, 5 pp.

Markstrom, S. L., Regan, R. S., Niswonger, R. G., Prudic, D. E., and Viger, R. J., 2006, GSFLOW -- A basin-scale model for coupled simulation of ground-water and surface-water flow -- Part A. Concepts for modeling surface-water flow with the US Geological Survey Precipitation-Runoff Modeling System, in Proceedings of the 3rd Federal Interagency Hydrologic Modeling Conference, Reno, NV, April 2-6, 2006: Reston, VA, Subcommittee on Hydrology, Advisory Committee on Water Information, 8 p. Available online at

Niswonger, R. G., Prudic, D. E., Markstrom, S. L., Regan, R. S., and Viger, R.J., 2006, GSFLOW -- A basin-scale model for coupled simulation of ground-water and surface-water flow -- Part B. Concepts for modeling saturated and unsaturated subsurface flow with the U.S. Geological Survey modular ground-water flow model, in Proceedings of the 3rd Federal Interagency Hydrologic Modeling Conference, Reno, NV, April 2-6, 2006: Reston, VA, Subcommittee on Hydrology, Advisory Committee on Water Information, 8 p. Available online at

Walker, J. F., Hunt, R. J., Markstrom, S. L., Hay, L. E., and Doherty, J., 2008, Using a coupled groundwater/surface-water model to predict climate-change impacts to lakes in the Trout Lake Watershed, Northern Wisconsin, in The third Interagency Conference on Research in the Watersheds: Estes Park, CO. Available online at


Training Materials

The USGS Modeling of Watershed Systems (MOWS) group has supplemental training and instructional materials available from a 2009 USGS GSFLOW training course:

Research Seminar

Richard Niswonger presented a GSFLOW talk at the USGS Menlo Park Water Resources Research Seminar Series in January 2015:

Point of Contact

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 by contacting GSFLOW Help or contacting the Office of Groundwater:

U.S. Geological Survey
Office of Groundwater
411 National Center
12201 Sunrise Valley Drive
Reston, VA 20192

Related USGS Software Resources

USGS computer programs related to GSFLOW include the following:

Other USGS Groundwater Software

The USGS develops groundwater, water-quality, surface-water, and other water-resources software for use by the USGS in fulfilling its mission. Most of this software is available online for download at no charge.

Disclaimers and Notices

This software has been approved for release by the U.S. Geological Survey (USGS). Although the software has been subjected to rigorous review, the USGS reserves the right to update the software as needed pursuant to further analysis and review. No warranty, expressed or implied, is made by the USGS or the U.S. Government as to the functionality of the software and related material nor shall the fact of release constitute any such warranty. Furthermore, the software is released on condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from its authorized or unauthorized use. Also refer to the USGS Water Resources Software User Rights Notice for complete use, copyright, and distribution information.

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

See also, USGS policy on linking to non-Federal web sites.

Software License and Purchase Information

This software is a product of the U.S. Geological Survey, which is part of the U.S. Government.


This software is freely distributed. There is no fee to download and (or) use this software.


Users do not need a license or permission from the USGS to use this software. Users can download and install as many copies of the software as they need.

Public Domain:

As a work of the United States Government, this USGS product is in the public domain within the United States. You can copy, modify, distribute, and perform the work, even for commercial purposes, all without asking permission. Additionally, USGS waives copyright and related rights in the work worldwide through CC0 1.0 Universal Public Domain Dedication ( [Link exits USGS]).

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