💧 IGW-NET · Quick Tutorial 9 of 31

Tutorial 9: Synthetic Model

Build a simple synthetic groundwater model from scratch — ideal first tutorial for new users. Covers grid setup, boundaries, and running a simulation.

IGW-NET Tutorial 9 Prereq: MAGNET4WATER account 2 sections

This tutorial covers

  1. 2D Synthetic Model
  2. What's Next

12D Synthetic Model

Step 1 — Enter Synthetic Mode

Click Utilities menu and select 'Go to Synthetic Case Area' under Utilities. This switches IGW-NET from map-based mode to synthetic mode — creating an empty rectangular domain with no geographic context. Synthetic model empty canvas showing rectangular domain You now have a blank canvas to build any conceptual model you can imagine.

Step 2 — Set Uniform Aquifer Properties

Click Settings to open the Default Model Input Parameters window. Set the following to constant, uniform values:

Hydraulic conductivity: 35 ft/day
Recharge: 0 in/year (no recharge — isolating boundary-driven flow)
Top elevation: 0 m
Bottom elevation: -180 ft

With uniform properties and no recharge, the flow pattern depends entirely on the boundary conditions — the simplest possible system for understanding fundamental behavior.

Step 3 — Add a River (Head-Dependent Boundary)

Click ZonePoly and SaveShape buttons the 'ZonePoly' and 'SaveShape' buttons to add a river zone along the left (west) boundary. Set the properties:

Title: "River"
Stage: -1 m (constant)
Bottom elevation: -2.5 m (constant)
Leakance: 5 day⁻¹ (constant)

This creates a head-dependent flux boundary — the river exchanges water with the aquifer based on the difference between river stage and aquifer head. Water flows into or out of the aquifer depending on which has higher head.

Step 4 — Add a Prescribed Head Boundary

Click DrawLine and SaveShape to create a prescribed head polyline along the right (east) boundary with a constant value of -3 m. This fixes the head at -3 m along the entire eastern edge — representing a large water body or a known water level from field data. Combined with the river on the west, this drives flow from west to east (higher head to lower head).

Step 5 — Add a Pumping Well

Click Well button the 'Well' icon to insert a pumping well near the eastern edge. Assign a pumping rate of -200 GPM (negative = extraction). The well creates a cone of depression that distorts the regional flow pattern — water is pulled toward the well from all directions, competing with the regional west-to-east gradient.

Step 6 — Submit and View Results

Click Submit to submit the model for simulation. View the results — head contours, flow vectors, and the interaction between the regional gradient and the well's capture zone. Because everything is uniform and controlled, you can clearly see how each boundary condition contributes to the flow field.

Step 7 — Save or Publish

Click Save Publish to save or publish the synthetic model for future experimentation.

Synthetic model setup showing the rectangular domain with river zone along the west boundary (head-dependent), prescribed head polyline along the east boundary (-3m), pumping well near the east edge (-200 GPM), and input parameter values for conductivity (35 ft/d), recharge (0), and aquifer geometry
Figure 2: Complete synthetic model setup — river on the west (head-dependent), prescribed head on the east (-3m), pumping well (-200 GPM), uniform K = 35 ft/d, no recharge. North and south boundaries are no-flow by default. Every element is user-defined — no Data Center involved.
Synthetic model simulation results showing head contour lines flowing from west (higher head near river) to east (lower head at prescribed boundary), with a cone of depression around the pumping well distorting the regional flow pattern. Flow vectors show water converging on the well from all directions.
Figure 3: Simulation results — head contours show the regional gradient from river (west) to prescribed head (east), distorted by the pumping well's cone of depression. Flow vectors converge on the well. Because the model is synthetic and uniform, the physics are transparent — every feature of the flow pattern can be traced to a specific boundary condition or stress.

The Power of Synthetic Modeling

Isolation: In a real-world model, many factors interact simultaneously — heterogeneous conductivity, complex recharge patterns, multiple wells, irregular boundaries. It's hard to understand what causes what. In a synthetic model, you control everything. Set recharge to zero and you isolate boundary-driven flow. Use uniform K and you isolate the effect of geometry. Change one thing at a time and watch what happens.

Experimentation: Try doubling the pumping rate. Move the well. Change the river stage. Add heterogeneity. Each experiment builds intuition about how aquifer systems behave — intuition that makes you a better modeler when you tackle real sites.

Verification: For simple configurations (uniform K, simple boundaries), analytical solutions exist (Theis, Dupuit, Toth). Building the equivalent synthetic model and comparing numerical results against the analytical solution verifies that the solver is working correctly. This is how you build trust in your tools.

Teaching: Students start in synthetic mode to learn the fundamentals — then graduate to map-based mode with real data. The same tools, the same interface, but progressively more complexity. This is the IGW-NET educational philosophy: learn by doing, starting simple.

2What's Next

With synthetic modeling mastered, continue the learning path:

Tutorial 10: Aquifer Layers — add multiple geological layers with distinct properties (works in both synthetic and map-based modes)
Tutorial 15: Stochastic Flow Model — add random heterogeneity to a synthetic domain and explore its effects on flow
Tutorial 20: Theis Solution — compare your synthetic model against the analytical solution for verification