1Hypothetical Plumes — Fort Custer, Michigan
Step 1 — Load Parent Model and Create Submodel
Click 
to load and simulate the regional model from Tutorial 1. Add a submodel and apply 'Boundary Conditions from Parent Model' in the Default Model Input Parameters and Display Options Menu.
Step 2 — Add a Continuous Source (500 ppm)
Click 
the 'ZoneRect' and 'SaveShape' buttons to add a rectangular zone in the south-central portion of the model domain. Assign this as a continuous source of 500 ppm. A continuous source maintains a constant concentration over time — like an ongoing industrial discharge or a leaking storage tank that hasn't been removed. The resulting plume grows steadily downstream.
Step 3 — Add an Instantaneous Source (1500 ppm)
Click 
the 'ZonePoly' and 'SaveShape' buttons to add a zone in the south-eastern portion of the model domain. Assign this as an instantaneous source of 1500 ppm. An instantaneous source releases contamination once and then stops — like a one-time spill. The resulting plume moves downstream as a shrinking, diluting slug.
Step 4 — Add an Injection Well
Click 
the 'Well' button to add an injection well to the model domain (yellow dot). An injection well introduces contaminated water at a point — creating a radially expanding plume that is then carried downstream by the regional flow. This simulates scenarios like deep-well disposal or aquifer remediation injection.
Step 5 — Add a Monitoring Well
Place a monitoring well just beyond the continuous source, downstream in the flow direction. This well will record concentration over time — producing a breakthrough curve that shows when the plume arrives, how concentration builds, and whether it reaches a steady state.
Step 6 — Draw a Cross-Section
Click 
to draw a cross-section line through the continuous source and the downstream area. This will show the vertical structure of the plume — how deep contamination penetrates, whether it's confined to shallow layers, and how it interacts with the water table.
Step 7 — Submit for Simulation
Click to submit the model for simulation. IGW-NET solves the flow equations first, then uses the computed velocity field to drive contaminant transport. In real-time streaming mode, you'll see plumes evolving — spreading, migrating, and interacting with the flow field — as the equations solve.
Step 8 — View Cross-Section and Breakthrough Curve
Click 
the 'Analysis' button, then select 
'Display Charts' from the submenu. This opens analysis windows including the full cross-section view (showing the plume's vertical extent and migration) and the monitoring well breakthrough curve (showing concentration vs. time at the observation point). Together these reveal the complete story: where the plume is, how deep it goes, when it arrives, and how strong it is.
Step 9 — Save or Publish
Click 
to save or publish the model for future use.
Three Source Types — Three Plume Behaviors
Continuous source (500 ppm): Concentration is maintained at the source indefinitely. The plume grows steadily downstream, eventually reaching a quasi-steady-state shape where advection, dispersion, and (if present) decay balance each other. This represents ongoing contamination — leaking tanks, active industrial discharge, persistent PFAS sources.
Instantaneous source (1500 ppm): All contamination is released at once, then the source is removed. The plume migrates downstream as a "slug" — spreading, diluting, and eventually dissipating. Peak concentration decreases over time. This represents one-time spills, accidental releases, or historical contamination events.
Injection well: Contaminated water is injected at a point source. The plume expands radially from the well before being carried downstream by the regional flow. This simulates deep-well disposal, tracer tests, or remediation injection scenarios.
Monitoring Wells and Breakthrough Curves
A breakthrough curve is a plot of concentration vs. time at a fixed observation point. It answers critical questions: When does the plume arrive? How high does concentration get? How long does it take to reach steady state (continuous source) or pass through (instantaneous source)? Breakthrough curves are essential for risk assessment — determining whether a drinking water well will be impacted and when.
2What's Next
With contaminant transport mastered, continue the learning path:
Tutorial 6: Vertical Details — extend to 3D with multiple aquifer layers, confining units, and vertical plume migration
Tutorial 7: Transient Modeling — add time-varying pumping and seasonal recharge to see how plumes respond to dynamic conditions
Tutorial 8: Calibration — match your model to observed data before making predictions about contaminant fate