Map-Based Groundwater Simulation Model

Zichuan Ye, David R. Maidment, Daene C. McKinney
Center for Research in Water Resources
The University of Texas at Austin
ye@nile.crwr.utexas.edu

Table of contents

  • 1. Model Installation
  • 2. Model Description

    1. Model Installation

    To run the installation program, insert the Disk marked GFlowSim into drive a: and from C:\ prompt, type in:

    Where C:\ is the target drive on which the program will be installed. If the program is to be insta lled onto D:\users, then you should first move yourself to D:\users\ directory and from D:\users\ prompt, type in:A:GMSETUP D:\USERSUnder default situation, GMSETUP program will copy the files onto C:\ drive and put all the project related files/coverages into C:\GFMAP directory. If the directory does not exist, the setup program will create the directory. Upon a successful installation, the setup program will clean up all the unnecessary files it creates. If the programs are installed into C:\GFMAP, a user can immediatly start ArcView to load the project GFMAP.APR that contains the map-based groundwater flow simulation model. If the model programs are installed into a directory other than C:\GFMAP,e.g. D:\USERS\GFMAP, the user will need to load START.APR project. START.APR will prompt for the user to enter the path to the directory where GFMAP.APR project is located. START.APR will then correct the path for GFMAP.APR and load the project. The START.APR is acquired from ESRI with some minor modification to fit the project needs.

    2. Model Description

    2.1. GENERAL DESCRIPTION

    This groundwater flow simulation model (GFlowSim) is designed using ArcView's GIS capability and it's Avenue object-oriented programming language so that all three elements of a simulation model:equations, maps, and data sets are integrated. The model design is based on the similar concept described on the map-based surface flow simulation model. In general, the map-based groundwater model is construncted by applying the continuity equation to the cell or subwatershed polygons and applying Darcy's law on the boundaries of the cells. During the simulation, the program first loop through the line feature attribute tables (LFTAB) of the boundary line theme to compute mass flux across each boundary line by applying Darcy's law on each line. For each polygon, a memory variable is created to accumulate the flux coming into the polygon. program is then loop through the poly feature attribute table (PFTAB) to compute water level changes based on the continuity equation. This process is then repeated for each time step until the final time step is reached (unsteady state) or until solution converges (steady state). The grid of this map-based groundwater simulation model can be of both regular and irregular shapes. It can therefore take the shapes of subwatersheds as its simulation mesh so that the integration of surface/subsurface flow model can be simplified.

    Listed below are the tasks this map-based simulation model is designed to accomplish:

    To verify the concept and ensure the programming correctness, this map-based model is applied to solve the problem of groundwater flow in a phreatic aquifer with accretion [bear, 1979] and the model results match those of theoretical solution. The problem assumes two parallel rivers of 50 km apart, cuts into a phreatic aquifer and can act as line sources/sinks of the aquifer. The river levels and quifer water level are initially at 50 m elevation. The aquifer has impermeable boundaries on north and south sides. It has also an impermeable bed at elevation 0 m.(See Figure 1.) This problem is used as the example problem on the application submited. This groundwater model has been tested on Unix SunOS, Alpha-Machines, Windows3.1, and Windows 95 under both ArcView 2.1 and ArcView 3.0 Beta, and the model has worked properly under all the situations tested.

    Figure 1. The view containing the map-based groundwater simulation model

    2.2. The maps of the groundwater simulation model

    List below are the base maps upon which the map-based groundwater simulation model is constructed.

    2.3. MODEL'S GRAPHICAL USER INTERFACE

    The graphical interface of the simulation model (GFlowSim) is designed to facilitate a userŐs access of the model and model related programs. A user can use these graphical interfaces to activate the simulation model, modify the model conditions, display and analyze modeling results. This section describes the functions and programs assoicated with each user interface.

    2.3.1. View Menu

    One menu section, GFwModel is added to the standard view menu GUI provided by the ArcView. GFwModel menu is created to run the groundwater flow simulation model and its related programs. GFwModel contains seven menu items and these items are divided into the simulation model and preprocessor sections. The functions of the menu items contained in each section are described below, with the title of the program it activates put in [ ].

    2.3.2. View Button Bar

    One button is added to the standard view button bar GUI provided by the ArcView. The function and programs associated with this button are explained below.

    - Pen, writes selected or all the scripts contained in the project's SEd to a designated location of a disk [wrtfiles.utl].

    2.3.3. View Tool Bar

    Two buttons are added to the standard view button bar GUI provided by the ArcView. The functions and programs associated with these buttons are explained below.

    - Execute, runs all the programs available to SEd of the project [Main.utl - associated with apply event]. When the tool is selected, the program, Main.utl is loaded and activated when mouse is clicked at the cursor sensitive area of the active view. The last program run by the Main.utl is the default program to be run. If the user wants to run other programs, select NO option, and a pop-up menu will appear with a list of programs for the user to choice. The selected program will then run. with the cursor position taken into consideration.

    - AlingBottom, plots flow vectors on groundwater simulation cell's boundaries or plot time series of head(t), dh(t), spr(t), pmp(t), etc., of a cell at a user selected location. Programs associated with click and apply events are described below.

    2.4. MODEL PROGRAMS

    This map-based surface flow simulation model contains a total of 25 programs. Some of these programs are the essential programs for model construction and model simulation, and some of these programs are written to speed up routine spatial data processing. The descriptions of these programs are given in Section 2.4. of readme file of SFlowSim model.

    2.5. PERFORMING GROUNDWATER SIMULATION TASKS UNDER GFLOWSIM

    This section gives a brief description of the procedures to perform tasks using GFlowSim, the map-based ground flow simulation model.

    2.5.1. Groundwater Flow Simulation

    The procedure activate GFLOWSIM to simulate groundwater flow is, from ViewMenuBar, GFwModel -> GFlowSim . After the program started, you will be presented with a a multiple input table containing the model control parameters. These parameters are

    2.5.2. Plot Simulation Results

    To plot the model simulation results, click from the ViewToolBar, and follow the instructions given by the program.2.5.3. Chang Modeling Conditions One of the advantage of using map-based groundwater simulation model is that it is easy to modify the model simulation conditions. This section describe how, in general, this could be done. Tables 1, and 2 show the attributes of line and polygon objects used for the groundwater flow simulation model. The modeling conditions can be modified by changing the values of the attribute assoicated with the line and polygon attributes. Both the utility programs contained in this simulation model and ArcView's database management programs can be used for this purpose.