NAMEmodbrnch - MODFLOW/BRANCH coupled flow modelABSTRACTSurface- and ground-water interactions can be simulated by the coupled BRANCH and USGS modular, three-dimensional, finite- difference ground-water flow (MODFLOW-96) models, referred to as MODBRNCH. MODFLOW-96 simulates steady and nonsteady flow in an irregularly shaped flow system in which aquifer layers can be confined, unconfined, or a combination of confined and unconfined. BRANCH simulates steady or unsteady flow in a single open-channel reach (branch) or throughout a system of branches (network) connected in a dendritic or looped pattern by solving the one- dimensional equations of continuity and momentum for the river flow. Channel-aquifer flows are leakage through a confining layer or riverbed. Computation of this leakage in the ground-water and surface-water systems allows these processes to be coupled for simulation purposes.METHODThe ground-water flow equation is solved using the finite-difference approximation. The BRANCH model uses a weighted four-point, implicit, finite-difference approximation of the unsteady-flow equations. A leakage term has been added to the equations in the BRANCH model and was coupled through the leakage quantity to the MODFLOW-96 model.HISTORYVersion 3.7 1997/06/05 - Use name file to designate input and output file names. Updated to be compatible with MODFLOW-96 version 3.1 and BRANCH version 4.3. Version 3.6 1995/11/09 - First version available on World Wide Web. Coupled with MODFLOW version 2.5 and BRANCH version 4.0.DATA REQUIREMENTSIn order to use MODFLOW, initial conditions, hydraulic properties, and stresses must be specified for every model cell in the finite- difference grid. BRANCH input data consist of channel geometry and initial flow conditions defined at all cross-section locations and boundary conditions defined at channel extremities. Refer to input specifications instructions for the MODFLOW-96 and BRANCH models for specific details.OUTPUT OPTIONSPrimary ground-water computational output is head, which can be written to the listing file or into a separate file. Other output includes the complete listing of all input data, drawdown, and budget data. Budget data are printed as a summary in the listing file, and detailed budget data for all model cells can be written into a separate file. Time series of computed surface-water flow results can be directly output in tabular or graphical form at all, or selected, cross- section locations. Tabular output options include discrete flow results at every time step or iteration; daily summaries of minimum, maximum, and average flow conditions; monthly flow-volume summaries; or river-mile locations of injected particles. Digital or line- printer graphical options include hydrograph plots of computed water levels or discharges or comparative plots of computed results versus measured data. Output results can be either in metric or inch-pound units.SYSTEM REQUIREMENTSMODBRANCH is written in Fortran 77 with the following extensions: use of integer*2 declarations, use of include files, variable names longer than 6 characters, use of mixed case, and reference to compiler-dependent system date and time routines. To compile MODBRANCH the BRANCH and MODFLOW-96 software and LIBUTL utility library are required. LIBUTL includes software/user, software/computer, software/data base, and software/graphics interaction routines. MODBRANCH graphics (from the BRANCH model) are coded using CalComp graphics calls. The LIBUTL software provides graphics libraries to convert CalComp graphic references to Graphical Kernel System (GKS) library references and Interactive Software Services's INTERACTER library references. MODBRANCH memory requirements depend on array dimensioning parameters found in the dimens.cmn include file and modflw96.f source file. The memory requirements can be tailored to suit application needs and computer system memory constraints by modifying the parameters in these files and then recompiling the code. Generally, the program is easily adapted to most computer systems that have access to one of the mentioned graphics libraries. The code has been used on UNIX-based computers and DOS-based 386 or greater computers having a math coprocessor and 8 mb of memory.DOCUMENTATIONSwain, E.D., and Wexler, E.J., 1996, A coupled surface-water and ground-water flow model (MODBRNCH) for simulation of stream- aquifer interaction: U.S. Geological Survey Techniques of Water- Resources Investigations, book 6, chap. A6, 125 p. Swain, E.D., 1992, Incorporating hydraulic structures in an open- channel model: Proceedings, 1992 National Hydraulic Engineering Conference, American Society of Civil Engineers, New York, N.Y., p. 1118-1123.RELATED DOCUMENTATIONBRANCH Schaffranek, R.W., 1987, Flow model for open-channel reach or network: U.S. Geological Survey Professional Paper 1384, 12 p. Schaffranek, R.W., Baltzer, R.A., and Goldberg, D.E., 1981, A model for simulation of flow in singular and interconnected channels: U.S. Geological Survey Techniques of Water-Resources Investigations, book 7, chap. C3, 110 p. Latest version enhancements and additions to the BRANCH model are documented and maintained in a file included in the software distribution. The latest model version is downward compatible with the original documentation: MODFLOW The basic model is documented in: Harbaugh, A.W., and McDonald, M.G., 1996, User's documentation for MODFLOW-96, an update to the U.S. Geological Survey modular finite-difference ground-water flow model: U.S. Geological Survey Open-File Report 96-485, 56 p. Harbaugh, A.W., and McDonald, M.G., 1996, Programmer's documentation for MODFLOW-96, an update to the U.S. Geological Survey modular finite-difference ground-water flow model: U.S. Geological Survey Open-File Report 96-486, 220 p. McDonald, M.G., and Harbaugh, A.W., 1988, A modular three- dimensional finite-difference ground-water flow model: U.S. Geological Survey Techniques of Water-Resources Investigations, book 6, chap. A1, 586 p. GENERAL Harbaugh, A.W., 1990, A simple contouring program for gridded data: U.S. Geological Survey Open-File Report 90-144, 37 p. Regan, R.S., and Schaffranek, R.W., 1985, A computer program for analyzing channel geometry: U.S. Geological Survey Water- Resources Investigations Report 85-4335, 49 p. Regan, R.S., Schaffranek, R.W., and Baltzer, R.A., 1996, Time- Dependent Data System (TDDS)--An interactive program to assemble, manage, and appraise input data and numerical output of flow/transport simulation models: U.S. Geological Survey Water- Resources Investigations Report 96-4143, 104 p. Sanders, C.L., 1995, The use of three-parameter rating table lookup programs, RDRAT and PARM3, in hydraulic flow models: U.S. Geological Survey Water-Resources Investigations Report 95-4090, 18 p.TRAININGModeling of Ground-Water Flow Using Finite-Difference Methods (GW2096TC), offered annually at the USGS National Training Center. Advanced Modeling of Ground-Water Flow (GW3099TC), offered annually at the USGS National Training Center. Ground-Water/Surface-Water Relationships (ID2015TC), offered annually at the USGS National Training Center. Implementation and Calibration of Unsteady Open-Channel Flow Transport Models (SW3091TC), offered annually at the USGS National Training Center.CONTACTSOperation: U.S. Geological Survey Eric Swain 9100 NW 36 Street, Suite 107 Miami, FL 33178 edswain@usgs.gov Distribution: U.S. Geological Survey Hydrologic Analysis Software Support Program 437 National Center Reston, VA 20192 h2osoft@usgs.gov Official versions of U.S. Geological Survey water-resources analysis software are available for electronic retrieval via the World Wide Web (WWW) at: http://water.usgs.gov/software/ and via anonymous File Transfer Protocol (FTP) from: water.usgs.gov (path: /pub/software). The WWW page and anonymous FTP directory from which the MODBRNCH software can be retrieved are, respectively: http://water.usgs.gov/software/modbrnch.html --and-- /pub/software/surface_water/modbrnchSEE ALSObranch(1) - One-dimensional Branch-network flow model cgap(1) - Channel Geometry Analysis Program contour(1) - A contouring program for gridded data libutl(1) - Utility libraries for simulation models modflow(1) - Modular three-dimensional ground-water flow model Modflowp(1) - Parameter-estimation version of the modular model modpath(1) - Particle-tracking postprocessor program for the modular three-dimensional finite-difference ground-water flow model tdds(1) - Time-Dependent Data System wdm(1) - Watershed Data Management system

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