💧 IGW-NET · Quick Tutorial 3 of 31

Tutorial 3: Particle Tracking

Track forward and backward particle paths through a computed groundwater flow field to delineate flow patterns, capture zones, and travel times.

IGW-NET Tutorial 3 Prereq: MAGNET4WATER account 2 sections

This tutorial covers

  1. Forward Particle Tracking
  2. What's Next

1Forward Particle Tracking

Step 1 — Load Parent Model and Create Submodel

Click 'Other Tools' > 'LoadModel' > 'Local Model File' to load the parent model domain using a previously saved model file from Tutorial 1 (Steady 2D Flow Modeling). Submit the parent model for simulation ('Simulation tools' > 'SIMULATE') to generate the regional flow solution that will provide boundary conditions for the child model. Then add a submodel (as in Tutorial 2) and apply 'Boundary Conditions from Parent Model'.

Step 2 — Access Particle Tracking Tools

Click ParticleTK button the 'ParticleTK' button to access the particle tracking toolkit. Choose Particle Line option showing dropdown menu 'Particle Line' from the dropdown to release particles along a polyline.

Step 3 — Place Particles

Use the cursor to place polyline vertices with single clicks on the map. The particle polyline appears as a series of bright yellow line segments with circles at the vertex locations. Each vertex becomes a particle release point. Place the polyline perpendicular to the expected flow direction for best visualization of flow patterns.

Step 4 — Submit for Simulation

Click Submit button to submit the submodel for simulation. A prompt appears asking to confirm forward tracking — choose 'OK' to apply forward particle tracking. The solver computes flow and traces all particle paths simultaneously.

Step 5 — View Particle Path Lines

Each particle traces a path from its release point to its discharge location, revealing the flow structure of the aquifer — where water travels, how fast, and where it exits the system. Particles and particle path-lines are automatically displayed in the map display when particles are involved in the simulation. Particle tracking options can be specified in the 'Simulation Settings' tab of the 'Domain Attributes' menu.

Step 6 — Save or Publish

Click Save button Save options to save or publish the model with particle tracking results for future use.

Model domain with yellow polyline placed across the flow field for particle release, showing vertices as circles along the line
Figure 2: Polyline added to the model domain for placing particles — the yellow line segment with circles at vertices defines where particles are released into the flow field.
Forward particle tracking results showing pathlines flowing from the polyline release points through the aquifer to discharge locations, with head contours and flow vectors visible
Figure 3: Forward particle tracking results — pathlines trace from the release polyline through the aquifer, revealing flow patterns, convergence zones, and discharge points. Each line represents the journey of one water "droplet" through the subsurface.

Key Concepts

Multiple release methods: This tutorial demonstrates polyline release. IGW-NET also supports releasing particles as individual points (click to place), within a polygon (area-based), and around a pumping well (capture zone analysis). Each method serves a different analysis purpose.

Forward vs backward tracking: Forward tracking answers "where does this water go?" Backward tracking answers "where does this water come from?" Both use the same computed flow field — only the direction of tracing differs.

Nested model advantage: By performing particle tracking in a nested submodel, you get fine-resolution pathlines with regional-scale boundary conditions. The particles respect the true flow field, not artificial boundaries.

2What's Next

With particle tracking mastered, continue the learning path:

Tutorial 4: Water Balance — analyze where water comes from and where it goes, quantitatively
Tutorial 5: Contaminant Transport — go beyond pathlines to simulate actual plume migration with dispersion and decay
Tutorial 8: Calibration — match your model to observed data before relying on particle tracking for decisions