IGW-Desktop Tutorial 7a - Interactive hierarchical groundwater modeling

This video demonstrates the use of IGW-Desktop to create a hierarchical groundwater model in a real-time manner. A watershed with a large-capacity pumping well is modeled at a coarse resolution. A monitoring well is placed near the pumping well to measure the drawdown due to the pumping. First, only one model is used to simulate this watershed. The monitoring well shows significant drawdown due to pumping. However, the distance between the pumping well and monitoring well is smaller than the grid resolution of the regional model. To better resolve the dynamics near the well, a “patch” or child model is interactively added in the area of interest and simulated. The drawdown predicted by the child model is seen to be smaller than that predicted by the regional model. To further resolve the drawdown cone near the pumping well, another patch is added within the existing patch. The drawdown curves from the three models of increasing resolutions are compared. The steps to create the model are outlined briefly: (1) Select the pre-made domain polygon to edit the aquifer properties • ‘Flow Properties’ tab - check ‘Conductivity’ box, assign constant K • ‘Elevations’ tab - check ‘ Top Elevation’ box, assign a constant Top Elevation, and uncheck ‘Use as starting head’. Next, check ‘Bottom Elevation’, and assign constant bottom elevation • ‘Source and Sinks’ tab - ‘Prescribed Flux’ sub tab, check ‘Recharge’, assign a constant recharge (2) Select the lake polygon in the top-left portion of the model domain • ‘Source and Sinks’ tab - ‘Head-dependent flux’ sub tab, check ‘Two-way head-dependent flux’, use the default values for lake stage, bottom elevation and leakance (3) Add a pumping well next to the lake by using the ‘Vertex Coordinates’ input box at the bottom of the IGW main window; edit in Attributes Explorer • Assign as a ‘pumping’ well, and select ‘Transient’; open the transient options window • Uncheck ‘Random fluctuation’ and ‘Periodic fluctuation…’, then click ‘Edit’ • Update the transient pumping data: o Delete all of the ‘Time’ cells other than 0 and 180 days; cell; then use the ‘Update’, ‘Delete’ and ‘Insert’ buttons to update the transient data so that there are prescribed pumping rates for each of the four pumping intervals spanning 0 to 3650 days. (4) And a monitoring well next to the pumping well by using the ‘Vertex Coordinates” input box. In Attributes Explorer, select the newly added well and select ‘None’ for source/sink type, then check the ‘Monitoring Head and Concentration’ box under ‘Monitoring Well’. (5) Discretize the model (6) Open Attributes Explorer; in the bottom-left window, check ‘Head/Conc’ under the monitoring well; Note the head hydrograph that opens as a result (7) Run the model. Note the changing flow patterns in the plan view and the dynamic head hydrograph (8) Stop the model, and create a “patch”, or child, model around the lake and pumping well using the ‘Create Submodel’ icon - create the sub-model in the same fashion that one uses for creating polygons. Edit in Attributes Explorer • Select ‘Model 2-1’, and use the default grid size and default Parent/Child Grid Ratio. Note that the patch model grid size is half of the parent grid size. • Click on the ‘unit boxes’ to display the values in different unit systems • Go to the ‘Down/Upscaling’ tab and ensure that the ‘Prescribed head’ boundary condition is selected under ‘Downscaling from parent’. Upscaling from the child to parent model is also available, but not used in this example (9) Discretize the model. Note the new child (sub-model) window that appears (10) Open Attributes Explorer; in the bottom-left window, check ‘Head/Conc’ under the monitoring well in the ‘Model 2-1’ window tree. This will open a new Head Hydrograph window for the submodel (11) Run the model. Note the difference in the head hydrographs as the model proceeds. In particular, the drawdown simulated by the chilld model is less than that simulated by the parent model. (12) Stop the model, and add another patch within the existing patch. Use the default grid size of 50 m for the newly created patch model (Model 2-1-1) (13) Discretize the model. Note the new (sub-sub-model) window that appears. Display the Head Hydrograph for the sub-sub-model. (14) Run the model. Note the difference in the Head Hydrographs. The sub-sub-model predicts a drawdown between that simulated in the parent model and first child model. (15) Save the IGW model. More details on IGW: please go to https://www.magnet4water.net/GW_home.aspx - Hydrosimulatics Inc. https://www.magnet4water.net