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Instructions for GSFLOW Model Input Preparation

1.      Overview

       1.1.   Purpose and Scope

       This report describes the input preparation process for GSFLOW, version 1.1, specifically, the creation of the PRMS Data File, the GSFLOW maps, the PRMS Parameter File, and the MODFLOW Input Files.

       These instructions are not the only way to prepare input for GSFLOW, but are intended to serve as a procedural guide. Clearly, any single step from the outline below, could involve (and may require) much more effort, study, and expertise from a GSFLOW modeler or modeling team. Anyone considering a GSFLOW modeling project is encouraged to work through this outline and complete the example problem to gain insight into what will be required to develop a full application.

       The USGS has corporate policies about the hardware and software tools which are made available to its employees and cooperators. These instructions reflect these policies and are not intended to endorse any particular trade, product, or firm. These instructions can (and have been) successfully carried out with many alternative hardware and software configureations.

       1.2.   Software Requirements

       The following software packages are required to prepare input for GSFLOW:
       1.3.   Hardware Requirements

       The following represents a minimum hardware configuration to prepare input for GSFLOW:
       1.4.   Download Example Problem Data Sets

       The data for the following example is available here.

These steps should be completed in order, as later steps may require maps or data produced in earlier steps.

2.      Making PRMS Data File

       2.1.   Create a PRMS Data File (for time series climate and stream flow data)
              2.1.1.     
Creating a PRMS Data File with the USGS Downsizer (available on USGS computers)
              2.1.2.      Creating a PRMS Data File with a text editor (non-USGS computers)
       2.2.  
Computation of Lapse Rates/Monthly Means using Excel
                  
3.      Making GSFLOW maps

       3.1.   Before Starting
       3.2.   DEM Reconditioning
       3.3.   Delineation of Spatial Modeling Features for GSFLOW
             3.3.1.      Natural Watershed Boundary
              3.3.2.      Generation of the Stream Segment map
              3.3.3.      Generation of the MODFLOW Grid Cell map (ArcMap Fishnet  method)
              3.3.4.      Generation of "Clipped" Model Domain and Active Cells Maps
              3.3.5.      Generation of PRMS HRU map
              3.3.6.      Generation of GSFLOW Gravity Reservoir (GVR) map

4.      Adding modeling attributes to the GSFLOW maps

       4.1.   HRU map
       4.2.   MODFLOW Grid Cell map
       4.3.   GVR map

5.      Making the PRMS Parameter File

       5.1.   Dimension sizes
       5.2.   Spatial parameters
       5.3.   Cascade parameters
       5.4.   Non-spatial parameters

6.      Making the MODFLOW Files

       6.1.   Create the MODFLOW Grid Cell map (ModelMuse method)
       6.2.   Select MODFLOW packages
       6.3.   Set MODFLOW Units and Other Options
       6.4.   Importing Shapefiles in ModelMuse
       6.5.   Set Stream Segment Information
       6.6.   Set Hydraulic Conductivity for Aquifers
       6.7.   Set Layer Top and Bottom Altitudes
       6.8.   Set Active Cells
       6.9.   Set All other Cell Property Data



Please note that some U.S. Geological Survey (USGS) information accessed through this page may be preliminary in nature and presented prior to final review and approval by the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the sole responsibility of the user.

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. For further information, please see the standard USGS Disclaimer.

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