Tutorial 7. Water Table and Bedrock Surface

Transcription

1 Tutorial 7 Water Table and Bedrock Surface Table of Contents Objective. 1 Step-by-Step Procedure... 2 Section 1 Data Input. 2 Step 1: Open Adaptive Groundwater Input (.agw) File. 2 Step 2: Assign Material Zone Properties with High-Resolution Vertical Layering.. 2 Step 3: Define Bedrock Surface and Water Table. 6 Step 4: Interpolate Bedrock Surface and Water Table Elevation Data.. 7 Step 5: Import ASCII Data and Interpolate 8 Step 6: View Contour Maps of Bedrock Surface and Water Table... 8 Step 7: Inspect Material Zones Created by Bedrock Surface and Water Table. 9 Step 8: Define Material Zone Properties 11 Section 2 Simulation Results Visualization.. 12 Step 1: View Hydraulic Conductivity Distribution 12 Step 2: View Cross-Section (x-z) Flood Contour Map of Hydraulic Conductivity Step 3: Show Groundwater Pathline.. 13 Step 4: View Hydraulic Conductivity Values by Cell 14 Step 5: View Hydraulic Head Distribution 16 Step 6: View Cross-Section Line Contour Plot (x-z) of Hydraulic Head.. 16 Step 7: View Plan-View Contour Map of Solute Concentration 19 Step 8: Cross-Section (x-z) Flood Map of Concentration.. 19 Step 9: View Monitoring Point Data.. 20 Objective Illustrate the incorporation of saturated thickness variations caused by a bedrock unit (i.e., lower confining unit) and water table (i.e., unconfined aquifer) using the high-resolution material zone layer capability of the program. This capability is also utilized in Tutorial 8 to develop a highresolution representation of a thin regional clay layer separating two sand units. The completed Adaptive Groundwater input files for this tutorial are included in the Tutorial_7 subdirectory of the tutorials directory under the Adaptive_Groundwater program folder: 1

2 C:\Adaptive_Groundwater\Tutorials\Tutorial_7\Tutorial_7_Completed.agw Because Tutorial 7 builds upon the input data and boundary conditions for Tutorial 1, you can refer to this first tutorial for illustrations of basic input data preparation (e.g., grid design, basic boundary condition specification, time step control, etc.). The completed Tutorial 7 project files are provided to you as a reference (you can check the completed input data if you have questions while working through the tutorial). Many output times are also provided so that you can view the variations of hydraulic heads and solute concentrations over a long time period. As discussed below, you will work with a separate set of project files. This tutorial is divided into two sections. The first part covers input data preparation. Section 2 illustrates the generation of various visualizations of the simulation results for this tutorial. Step-by-Step Procedure Section 1 Data Input Step 1 - Open Adaptive Groundwater Input (.agw) File Go to File > Open in the main menu to open the file Tutorial_7_Start.agw that is stored in the following subdirectory: C:\Adaptive_Groundwater\Tutorials\Tutorial_7 The Base Grid is initially displayed on the screen. We will first convert the material zones in this example from the default course layering (10 Base Grid layers in this problem) to a highresolution material-zone model with 160 total material layers (16 layers per Base Grid layer based on the AMR refinement factor of 2 and a total of 5 levels in the AMR mesh). Second, we will import ASCII files containing (x, y, Elevation) data that define the bedrock surface and the water table configuration. Step 2 Assign Material Zone Properties with High-Resolution Vertical Layering In the main menu select Porous Media Zones > Assign Zones > Window and the Assign Porous Media Zones dialog pops up (Figure 1). Note: the material zone layer refinement can also be performed using the Porous Media Zones > Assign Zones > Polygon or Porous Media Zones > Assign Zones > Cell options. 2

3 Figure 1 In the Assign Zones dialog click on the Change button located next to the No. of Material Zone Layers field (Figure 1), and the Select No. of Material Zone Layers child dialog appears (Figure 2). 3

4 Figure 2 In the child dialog select 160 for the number of material zone layers and click on OK. The information dialog in Figure 3 is displayed. Click on Yes and continue. 4

5 Figure 3 Figure 4 is a cross-sectional view of the newly-created material zone layering (40x vertical exaggeration). Note 1 : The computational mesh still contains only 10 layers in the Base Grid (AMR Level 1). The examples below will illustrate how the refined material layering is handled during a simulation with multiple levels of grid refinement. Note 2 : For the grid used in this tutorial (5 levels; IREFINE=2; 10 Base Grid layers) the maximum number of layers in the multi-level AMR mesh would be 160 (i.e., the highest level of refinement would extend over the entire aquifer thickness in some plan-view section of the aquifer). Note 3 : In this example, appropriate vertical and horizontal material-property (e.g., K) averaging is performed in cells located on coarser AMR refinement levels 1-4 (see simulation results in Section 2). Note 4 : We could have chosen 320 material layers if we were considering the future use of a finer AMR mesh (i.e., IREFINE=4). However, the 320 material layers would be a factor of two finer (i.e., z-dir. thickness) than the Level 5 cells for this tutorial. As a result, material-property averaging would also have to be performed on Level 5. 5

6 Figure 4 Step 3 Define Bedrock Surface and Water Table Close the Assign Porous Media Zones dialog. The next step is to define the locations of the water table and bedrock surface using the Porous Media Zones > K zones based on Stratigraphy option in the main menu. The water table is treated as a geologic contact separating the aquifer from an overlying impermeable (i.e., vadose) zone. The second geologic contact is the bedrock surface. In the main menu select the Porous Media Zones > K zones based on Stratigraphy option. The information dialog in Figure 5 appears; click on the OK button and continue. 6

7 Figure 5 Step 4 Interpolate Bedrock Surface and Water Table Elevation Data In the 2D Kriging Dialog (Figure 6) select the Interpolate Geologic Contact Elevations button. The default kriging parameter values in the dialog are OK for this tutorial. The warning message in Figure 7 appears. You can read the Help discussion for the kriging dialog for more information. Basically, the Figure 7 message is alerting you to the fact that (i) with this option you are replacing any material zones you have defined with new ones based on interpolated geologic contact surfaces; (ii) for N c geologic contacts a total of N c + 1 geohydrologic units are created (numbered in sequence from the bottom of the aquifer); and (iii) edit the material zone database when finished to set the material properties for your new geohydrologic units. Therefore, due to item (i) you may want to save an extra copy of your Adaptive Groundwater project files under a different name before proceeding. Figure 6 7

8 Figure 7 Step 5 Import ASCII Data and Interpolate Select Yes on the Figure 7 information dialog and the file open dialog shown in Figure 8 appears. Load the ASCII file that contains the bedrock and water table data, which is included in the Tutorial_7 subdirectory: C:\Adaptive_Groundwater\Tutorials\Tutorial_7\XYZ_WaterTable_Bedrock.txt After opening this file the two-dimensional kriging of the contact surfaces is automatically performed by the program, and a flood contour map of the bedrock surface (Contact Surface 1) is drawn (Figure 9). Step 6 View Contour Maps of Bedrock Surface and Water Table You can view either the water table boundary (Contact Surface 2) or the bedrock surface (Contact Surface 1) by changing the Contact Surface No. in the kriging dialog (Figure 6). 8

9 Figure 8 Step 7 Inspect Material Zones Created by Bedrock Surface and Water Table Interpolation Close the Geologic Contact dialog. In the main menu select Porous Media Zones > Inspect/Edit to view the three geohydrologic units you created: bedrock, aquifer, and the zone above the water table. Figure 10 is an x-z cross-section of the three material zones using a 40x vertical exaggeration. Note that the program creates additional material zones in the database if an adequate number of zones (e.g., three in this example) do not exist before importing the geologic contacts. 9

10 Figure 9 10

11 Figure 10 Step 8 Define Material Zone Properties In the main menu select Porous Media Zones > Edit Database and edit the properties of the three material zones. Figure 11 shows the parameter values used for this tutorial. The bedrock unit and the region above the water table are considered to be impervious relative to the sand aquifer. Make sure to save your database entries ( Save Data ) before exiting. Note: For this tutorial the linear hydraulic head boundary conditions at the left- and right-hand sides of the aquifer were re-set to 55 m and 45 m, respectively, using the Boundary Conditions > Hydraulic Head > Aquifer Boundaries option in the main menu. These B.C. s mimic a confined aquifer that becomes unconfined at about the midpoint of the regional flow field and, therefore, are consistent with the water table configuration (Figure 10). 11

12 Figure 11 Section 2 Simulation Results Visualization In this section we show how to create various two-dimensional plots of the simulation results for Tutorial 7. You can use either the supplied Tutorial_7_Completed project files or your working copy of the Adaptive Groundwater files for this tutorial: Tutorial_7_Start.agw. It does not matter if you have made new runs with shorter simulation times than those shown here; select whatever output time that you want. Step 1 View Hydraulic Conductivity Distribution In the main menu select Output > z-dir. Hydraulic Conductivity and the View Simulation Results dialog appears (Figure 12). A plan-view flood map of K z through the middle of the aquifer is automatically generated. Click the Go To button at the top of the dialog to pop up a child dialog with available output times; click on t = 10,000 days and select OK in the Go to Output Time dialog. You may also use the + / - buttons to toggle through the output times. 12

13 Figure 12 Step 2 View Cross-Section (x-z) Flood Contour Map of Hydraulic Conductivity To display the cross-sectional view in Figure 13, click on the X-Z Slice (Row) button in the lower left hand corner (red circle in Figure 2), and then select the row of cells (i.e., x-z slice) with y = m. You can also select View > Change View Plane in the main menu. When you first switch to the cross-section view, you will want to add vertical exaggeration (e.g., VE = 10-20) by going to View > Vertical Exaggeration in the main menu. Note that the contours for hydraulic conductivity plots are logarithmically distributed (select Contour Options in View Simulation Results dialog). Figure 14 highlights the exponent format for the contour legend. Step 3 Show Groundwater Pathline Select the Pathlines tab in the Contour Parameters and Overlays dialog to turn on the groundwater pathlines (Figure 15). If you wish to use any of these display options later, click on the Save Plot Format button at the bottom of the View Simulation Results dialog (Figure 12). 13

14 In all plots you can Zoom In, Zoom Last, or Translate the view by clicking one of the icons in the upper-left corner of the display (Figure 13) or by making the appropriate selection under View in the main menu. Zoom in to get a close-up view of the groundwater pathlines above the bedrock surface (Figure 16). Figure 13 Step 4 View Hydraulic Conductivity Values by Cell By moving the mouse cursor over grid cells in the cross-section view you can view the K values in the small left-hand side window. In coarser-level cells (i.e., AMR Levels 1-4 in this example) the program uses linear averaging for horizontal K and computes a harmonic mean in the vertical direction. An example calculation of mean K values is presented in Tutorial 8. 14

15 Figure 14 Figure 15 15

16 Figure 16 Step 5 View Hydraulic Head Distribution In the main menu select Output > Hydraulic Head and a plan-view flood map through the middle of the aquifer is automatically generated. Under Plot and Contour Types you see that 2D (i.e., two-dimensional) plots are the default. Change the Contour Type to lines. Step 6 View Cross-Section Line Contour Plot (x-z) of Hydraulic Head Generate the cross-sectional view in Figure 17 by clicking on the X-Z Slice (Row) button in the lower left hand corner (red circle in Figure 2), and then select a row of cells (i.e., x-z slice) through the middle of the aquifer. Alternatively, select View > Change View Plane in the main 16

17 menu. When you first switch to the cross-section view, you will want to add vertical exaggeration (e.g., VE = 10-20) by going to View > Vertical Exaggeration in the main menu. You can also use the slice plane Go To button (Figure 12) to change the view-plane, or the row no. +/- buttons. Further, you can view an animation of the different slices by changing the Animation Type to Row (J-plane) and clicking the Start Animation button. Select the Vectors tab in the Contour Parameters and Overlays dialog (Figure 18) and zoom in to display the pore velocity vectors in the x-z cross-section (Figure 19). You can vary the vector length [V Length (%)] and reduce the number of plotted vectors by changing the Vector Indices Skip parameters to values greater than one (Figure 18). Figure 17 17

18 Figure 18 Figure 19 18

19 Step 7 View Plan-View Contour Map of Solute Concentration Close the View Simulation Results dialog for hydraulic head output and on the main menu select Output > Solute Concentration to generate a plan-view flood map of the plume (Figure 20). By default the program initially selects an x-y slice through the highest concentration zone and the last simulation time. Figure 20 is a t = 10,000 day snapshot; use the slice plane Go To button (Figure 12) to change the view-plane elevation to z = m The contour range is 0-1 mg/l with 20 intervals. Figure 20 Step 8 Cross-Section (x-z) Flood Map of Concentration To display the cross-sectional view in Figure 21 (with vertical exaggeration), click on the X-Z Slice (Row) button in the lower left hand corner (red circle in Figure 2), and then select a row of cells (i.e., x-z slice) through the center of the plume (e.g., y = 829 m). 19

20 Figure 21 Step 9 View Monitoring Point Data While in a plan or cross-section view, single click on any, or all, of the four monitoring point symbols to pop up a separate dialog containing graph(s) of the simulated concentration or hydraulic head versus time at these locations (Figure 22). 20

21 Figure 22 21