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Online Guide to MODFLOW-NWT

Abbreviation in Name file



Lakes and streams can be designated as having gaging stations located on them. For each such designated lake or stream, the time and a variety of other information will be written to a separate output file after each time step (and each transport time increment)  to facilitate graphical postprocessing of the calculated data.


Merritt, M.L., and Konikow, L.F., 2000, Documentation of a Computer Program to Simulate Lake-Aquifer Interaction Using the MODFLOW Ground-Water Flow Model and the MOC3D Solute-Transport Model: U.S. Geological Survey Water-Resources Investigations Report 00-4167, 146 p.

Prudic, D.E., Konikow, L.F., and Banta, E.R., 2004, A new stream-flow routing (SFR1) package to simulate stream-aquifer interaction with MODFLOW-2000: U.S. Geological Survey Open-File Report 2004-1042, 95 p.

Niswonger, R.G. and Prudic, D.E., 2005, Documentation of the Streamflow-Routing (SFR2) Package to include unsaturated flow beneath streams--A modification to SFR1: U.S. Geological Survey Techniques and Methods, Book 6, Chap. A13, 47 p.




Related Packages

Lake (LAK) package

Streamflow-Routing (SFR) package

Supported in







Input Instructions

Stream Gaging (Monitoring) Station File (GAGE)

Cells of the model grid can be designated as “stream gaging station” locations. At each designated cell (or stream reach), the time, stage, streamflow out of that reach, the streambed seepage, unsaturated storage, change in unsaturated storage, and groundwater recharge will be written to a separate output file to facilitate model output evaluation and graphical post processing of the calculated data. Several options are available to print additional information. The input file for specifying gaging station locations is read if the file type (Ftype) “GAGE” is included in the MODFLOW name file. The output file will contain two header lines that provide relevant information (the text will be contained within quotes).

For each simulation, if GAGE Package is used:

Data Set 1

For each gaging station:

Data Set 2 must include exactly NUMGAGE lines (or records) of data. If NUMGAGE > 1, it is permissible to interleaf in Data Set 2 records for stream gaging stations (according to the format specified in the documentation for the Stream Package) with records for gages on lakes. Data lines (records) within Data Set 2 can be listed in any arbitrary order.

If the gage is on a lake

Data Set 2a


If the gage is on a stream

Data Set 2b


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