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MODFLOW-NWT: a Newton Formulation for MODFLOW-2005
Overview of MODFLOW-NWT
The USGS MODFLOW-NWT is a Newton-Raphson formulation for MODFLOW-2005 to improve solution of unconfined groundwater-flow problems. MODFLOW-NWT is a standalone program that is intended for solving problems involving drying and rewetting nonlinearities of the unconfined groundwater-flow equation.
MODFLOW-NWT must be used with the Upstream-Weighting (UPW) Package for calculating intercell conductances in a different manner than is done in the Block-Centered Flow (BCF), Layer Property Flow (LPF), or Hydrogeologic-Unit Flow (HUF) Packages. Flow-property input for the UPW Package is designed based on the LPF Package and material-property input is identical to that for the LPF Package except that the rewetting and vertical-conductance correction options of the LPF Package are not available with the UPW Package. Input files constructed for the LPF Package can be used with slight modification as input for the UPW Package.
The NWT linearization approach generates an asymmetric matrix, which is different from the standard MODFLOW formulation that generates a symmetric matrix. Because all linear solvers presently available for use with MODFLOW-2005 solve only symmetric matrices, MODFLOW-NWT includes two previously developed asymmetric matrix-solver options. The matrix-solver options include a generalized-minimum-residual (GMRES) Solver and an Orthomin / stabilized conjugate-gradient (CGSTAB) Solver.
MODFLOW-NWT is described in the documentation report by Niswonger and others (2011). The Surface-Water Routing (SWR1) and Seawater Intrusion (SWI2) Packages, which are included with MODFLOW-NWT are documented in Hughes and others (2012) and Bakker and others (2013), respectively.
MODFLOW-NWT Information and Downloads
Note: Users are encouraged to read the documents that are provided in the 'doc' directory of this software distribution.
Documentation of MODFLOW-NWT
Example USGS Applications of MODFLOW-NWT
Feinstein, D.T., Fienen, M.N., Kennedy, J.L., Buchwald, C.A., and Greenwood, M.M., 2012, Development and application of a groundwater/surface-water flow model using MODFLOW-NWT for the Upper Fox River Basin, southeastern Wisconsin: U.S. Geological Survey Scientific Investigations Report 2012-5108, 124 p.
Davis, K.W., and Putnam, L.D., 2013, Conceptual and numerical models of groundwater flow in the Ogallala aquifer in Gregory and Tripp Counties, South Dakota, water years 1985-2009: U.S. Geological Survey Scientific Investigations Report 2013-5069, 82 p.
Eggleston, J.R., Carlson, C.S., Fairchild, G.M., and Zarriello, P.J., 2012, Simulation of groundwater and surface-water interaction and effects of pumping in a complex glacial-sediment aquifer, east central Massachusetts: U.S. Geological Survey Scientific Investigations Report 2012-5172, 48 p.
Morway, E.D., Gates, T.K., Niswonger, R.G., 2013, Appraising options to reduce shallow groundwater tables and enhance flow conditions over regional scales in an irrigated alluvial aquifer system: Journal of Hydrology, v. 495, pp. 216-237.
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, v. 48, 20 p.
Point of Contact
Support is provided for correcting bugs and clarification of how MODFLOW-NWT is intended to work. Only limited assistance can be provided for applying MODFLOW-NWT to specific problems by contacting the points of contact listed below:
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
Please refer to the USGS Software User Rights Notice for complete use, copyright, and distribution information. The USGS provides no warranty, expressed or implied, as to the correctness of the furnished software or the suitability for any purpose. The software has been tested, but as with any complex software, there could be undetected errors. Users who find errors are requested to report them to the USGS.
References to non-USGS products, trade names, and (or) services are provided for information purposes only and do not constitute endorsement or warranty, express or implied, by the USGS, U.S. Department of Interior, or U.S. Government, as to their suitability, content, usefulness, functioning, completeness, or accuracy.
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