Quoted from: https://www.usgs.gov/software/surface-water-routing-swr-process-a-program-modeling-surface-water-flow-usgs-modular 

The Surface-Water Routing (SWR) Process was developed to accurately simulate stages, surface-water flows, and surface-water/groundwater interactions in areas where surface-water gradients are small and (or) there is significant management of surface water. A simplified form of the Saint-Venant equations was implemented in the SWR Process based on assumption requirement that it will be applied to continuous simulations (hourly to daily time steps) in support of water-resource planning activities. As a result, the SWR Process was not intended as a replacement for hydrodynamic models that solve the full Saint-Venant equations and

are applied to event simulations (sub-hourly time steps).

The SWR Process uses a flexible approach for simulating one- and two-dimensional routing of surface-water flow. The SWR Process is implicitly coupled to the Groundwater Flow Process in MODFLOW. Surface-water routing in SWR can be simulated using a diffusive-wave approximation of the vertically-integrated Saint-Venant equations and/or a simplified level-pool approach. SWR can account for surface-water flow controlled by backwater conditions caused by small water-surface gradients or surface-water control structures. A number of typical surface-water control structures (such as culverts, weirs, and pumps, for example) can be represented, and simple operational rules can be specified to manage surface-water stages and streamflow by moving water from one surface-water feature to another. The non-linear surface-water flow equations implemented in the SWR Process are solved using Newton methods and

direct or iterative solvers.

The SWR Process uses the familiar structure of MODFLOW-2005 and the MODFLOW concepts of "packages" and "processes" are retained. This permits versions of MODFLOW-NWT and MODFLOW-2005 that include the SWR Process to work with many of the MODFLOW-related software programs, such as MODPATH, ZONEBUDGET, and parameter estimation programs. MODFLOW-NWT and MODFLOW-2005 with the SWR Process are public domain computer programs. The source code and software are distributed free of charge by the USGS.

Download Current Version of SWR Process

The current release is SWR Process v.1.01.0, released October 17, 2012.

Note: SWR Process users are encouraged to use the version incorporated into MODFLOW-NWT, even if the features of MODFLOW-NWT are not required for a particular application.

• SWR Release Notes
• MODFLOW-NWT with the current SWR Process program, source code, user guides, and example problems
• SWR Process example problems for MODFLOW-NWT
• SWRPre - a simple preprocessor for creating SWR Process connectivity from an Esri polyline shapefile and a MODFLOW discretization (DIS) file is also included. SWRPre creates a data file that defines SWR Process reaches, reach groups, and reach connectivity. SWRPre also creates 1. an Esri polyline shapefile that contains the data contained in the SWR Process data file to validate the SWR Process network, and 2. an Esri polygon shapefile of the DIS file to validate the coordinate offset and rotation angle provided to the pre-processor.

Documentation for SWR Process

Hughes, J.D., Langevin, C.D., Chartier, K.L., and White, J.T., 2012, Documentation of the Surface-Water Routing (SWR1) Process for modeling surface-water flow with the U.S. Geological Survey Modular Ground-Water Model (MODFLOW-2005): U.S. Geological Survey Techniques and Methods, book 6, chap. A40 (Version 1.0), 113 p.

Programs Related to SWR Process

• MODFLOW-2005
• MODFLOW-NWT
• ModelMuse

Superseded SWR Process Versions

Note: these versions are no longer actively supported or maintained.

• MODFLOW-2005 Version 1.9 with the SWR Process Version 1.01.0 program, source code, user guides, and example problems. This distribution also includes the preprocessor SWRPre.