IGW-Desktop Tutorial 13: Data-enabled groundwater modeling (China).

This video illustrates the use of IGW-Desktop to create a Google Maps-based, “one-click” data-enabled model in China. Google Maps is used to zoom and pan to the area to be modeled, and the user selects and draws a box in the area of interest. In one click, the box drawn in the GIS environment is converted to a model in the IGW environment. Since this model is for China, the only existing dataset that can be used for the model is the DEM (which defines the topography). All other parameters-such as the hydraulic conductivity of the model area, the aquifer’s bottom elevation, and the recharge rate-are assumed to be constant and are assigned by the user. The model is discretized and run to show the hydraulic head contours and flow directions. The model results are also plotted in cross-section view. The model created here is a preliminary model that can be improved upon by the user with additional data.
The steps to create the model are outlined briefly:
(1) In the Google Map interface, enter ‘Chengdu, China’ in the search bar. A flag will appear in the Google Map display indicating the location of this city.
(2) Increase the “zoom level” to 8 to focus the display to Chengdu. Adjust the “zoom” level until the appropriate map area is displayed for use in an IGW model.
(3) When the area of interest is centered and completely contained within the display, click on the ‘Capture GE map’ icon to create a map for IGW. The user may choose from the available UTM coordinate grids available for China.
• Enter a ‘3’ in the input box of the prompt that appears to use the 3 degree UTM zone rather than the 6 degree.
• Additionally, an appropriate projection system is suggested, although the user may import a system of their choice. Answer ‘Yes’ to the prompt to apply the suggest projection system, and use the original map resolution.
(4) The map will be automatically opened in the GIS layer explorer. Click on the ‘Draw a rectangle for IGW’ icon and draw a rectangle to define the modeling extent to be used in the IGW main window.
(5) Click on the ‘Extract/Import model features from GIS to IGW’ icon and the IGW main window appears with an “import data” window. Click ‘Ok’ to import the rectangle into IGW with the map layer as the model basemap.
(6) Select the domain polygon and edit its properties in Attributes Explorer
• In the ‘Flow Properties’ tab, check ‘Conductivity’, and assign a constant value of 15m/day.
• In the ‘Elevatoins’ tab, check ‘Top Elevation’, and select ‘Raster’ and ensure that ‘DEM from IGW server’ is selected. Check ‘Bottom Elevation…’, and enter a constant bottom aquifer elevation of 310m
• In the ‘Head dependent flux’ sub-tab, check ‘One-way head-dependent’ flux, and select ‘Top Elevation’ as the drain elevation. In the ‘Prescribed flux’ sub-tab, check ‘Recharge’ and input a constant recharge of 10 cm/year across the model domain.
(7) Increase the model grid resolution and discretize the model.
(8) Run the model, and edit the velocity vectors in the display. Open the ‘Velocity Draw Option’ window and increase the grid separation between displayed velocity vectors. Also, ensure that the ‘Seep Area’ box is checked. Note the easily discernable head contours and flow directions. Also note that the grid cells exhibiting seepage to the land surface are heighted in blue.
(9) Draw a cross-section through the center of the model, and note the gradual decrease in hydraulic head from the northwest to the southeast as shown in the ‘Profiles Display’ window
• Check the ‘Top Elevation’ box to display the land surface profile alone the cross-section. Note the abrupt rise and fall of land surface, which was visible in the Google Earth display seen earlier in this example.

- Hydrosimulatics Inc.