IGW-Desktop Tutorial 6c - Real-time, interactive mass balance analysis.

More details please go to https://www.magnet4water.com This video demonstrates the ease of using IGW-Desktop to perform a mass balance analysis in an interactive and real-time manner. The video illustrates how to add sources/sinks to a model in a step-by-step manner. The impact of each additional source/sink is displayed immediately in the mass balance visualization. The sources/sinks added are: prescribed head boundaries, such as rivers or creeks, two-way head-dependent flux boundaries, such as lakes and ponds, one-way head-dependent flux boundaries, such as drains, recharge to the aquifer and pumping from the aquifer. A transient model in which pumping rates change with time are also simulated to illustrate the impact on the mass balance and the resulting changes to the seepage area predicted by the model. The steps to create the model are outlined briefly: (1) Create a domain polygon covering the workspace extent and edit in Attributes Explorer • ‘Flow Properties’ tab - check ‘Conductivity’ box, assign constant K • ‘Elevations’ tab - check ‘ Top Elevation’ box, assign constant Top Elevation, and uncheck ‘Use as starting head’. Next, check ‘Bottom Elevation’, assign constant thickness (2) Create a polyline along the left edge of the model; Assign as ‘Two-way’ underneath ‘Head Dependent Flux’, and open polyline attributes table; assign a Riv stage of 5m for each section of the polyline (3) Create a polyline along the right edge of the model; assign as ‘Two-way’ underneath ‘Head Dependent Flux’, and use the ‘Creek’ designation from the pull-down-men; open polyline attributes table - use default values for Riv Stage (4) Select the domain polygon in Attributes Explorer, and check the ‘Zone Budget’ box at the bottom of the Attributes Explorer window. (5) Discretize and re-open Attributes Explorer; in the bottom-left window, check ‘Water Balance’ under ‘Zone 2’; Note the water balance chart that opens (6) Run the model; Note the mass balance terms that appear after the model has been solved. The River is a source to the model while the Creek is a sink (7) Click the ‘Reset Toolbar’ icon, then open AE • ‘Source and Sinks’ tab - ‘Prescribed Flux, check ‘Recharge’, assign a constant recharge (8) Discretize and run the model; note the new source term representing recharge in the mass balance chart. (9) Add a ‘lake’ polygon near the left edge of the model domain • Source and Sinks tab - Head-Dependent flux sub-tab, check ‘Two-way head-dependent flux’ and assign constant stage and a constant bottom elevation (10) Shallow discretization is needed to incorporate the lake. Run the model, and note the new flow patterns in and around the lake. Also note the lake as both a source and sink term in the aquifer water balance. (11) Add a ‘pond’ polygon near the left edge of the model domain • Source and Sinks tab - Head-Dependent flux sub-tab, check ‘Two-way head-dependent flux’, change designation to ‘Pond’ from the pull-down-menu • Assign a constant stage, (12) Discretize and run the model; note the pond as both a source and sink term in the water balance (13) Add a pumping well just to the left of the pond, perform a shallow discretization, and ruin the model. The well is represented in the updated mass balance chart as a sink (14) Add a ‘drain’ polygon near the right edge of the model domain. • Source and Sinks tab - Head-Dependent flux sub-tab, check ‘One-way head-dependent flux’, use the default settings (15) Discretize and run the model; the drain polygon is represented in the mass balance as a sink term. • In display options, check the ‘Seep Area’ box to show the grid cells in which seepage out from the aquifer to the surface occurs. (16) Add a well just to the left of the drain polygon. In AE, select ‘Pumping’ as the well type • Select ‘Transient…’, and open the transient option window • Uncheck ‘Random fluctuation’ and ‘Periodic fluctuation…’, then click ‘Edit’ • Change the ‘Recycle period’, and click ‘OK’ • Click ‘Redraw’, then click ‘OK’, and close AE (17) Click on the “clock” icon, and select a ‘Transient State’ model and use the default settings (18) Discretize and run the model. Note the changes to the Water Balance chart and the predicted seepage area as the model proceeds from one time-step to the next. There is also a ‘Stor’ term added to the water balance which represents the water released or taken from aquifer storage More details on IGW: please go to https://www.magnet4water.net/GW_home.aspx - Hydrosimulatics Inc. https://www.magnet4water.net