💧 IGW-NET · Quick Tutorial 10 of 31

Tutorial 10: Multiple Aquifer Layers

Model multi-layer aquifer systems with different conductivities, storage, and vertical leakance. Compare fully 3D vs quasi-3D approaches.

IGW-NET Tutorial 10 Prereq: MAGNET4WATER account 2 sections

This tutorial covers

  1. Building the 3D Synthetic Model
  2. What's Next

1Building the 3D Synthetic Model

Step 1 — Load the Tutorial 9 Model

Click Load Save/Load to load the single-layer synthetic model from Tutorial 9. Submit for simulation to establish the baseline. This becomes Layer 1 — the shallow aquifer with K = 35 ft/d, river boundary on the west, prescribed head on the east, and a pumping well.

Step 2 — Add Layer 2: Leaky Confining Layer

Click Add Layer Settings the 'Add Layer' option to add a 2nd layer underneath Layer 1. In the Default Attributes menu, configure the confining layer:

Hydraulic conductivity: 3 ft/d (10× lower than the aquifers — restricts vertical flow)
Top elevation: unchecked (automatically matches the bottom of Layer 1)
Layer thickness: 25 ft

Click Assign to apply. This thin, low-K layer acts as a semi-permeable barrier — water can leak through it slowly, but the two aquifers behave semi-independently.

Step 3 — Add Layer 3: Deep Aquifer

Click Add Layer to add a 3rd layer underneath Layer 2. Configure Settings the deep aquifer:

Hydraulic conductivity: 35 ft/d (same as Layer 1 — productive aquifer)
Top elevation: unchecked (matches bottom of Layer 2)
Layer thickness: 120 ft

You now have a complete three-layer system: shallow aquifer (180 ft) → confining layer (25 ft) → deep aquifer (120 ft). Total system thickness: 325 ft.

Step 4 — Simulate and Analyze in 3D

Click View Analysis Submit to submit the 3D model for simulation. Then use 'Display Charts' under Analysis to view:

Cross-section: Shows head distribution across all three layers — higher heads in the deep aquifer where it's confined, lower heads near the pumping well in Layer 1, and the confining layer separating the two flow systems
Mass balance: Shows flow between layers — how much water leaks through the confining layer
3D surface chart: Visualizes the aquifer geometry and flow in three dimensions

Step 5 — Save or Publish

Click Save Publish to save or publish the 3D model for future use.

Three-layer model configuration showing Layer 1 (shallow aquifer, K=35 ft/d, 180 ft), Layer 2 (confining layer, K=3 ft/d, 25 ft), and Layer 3 (deep aquifer, K=35 ft/d, 120 ft) with input parameter dialogs for each layer
Figure 2: Three-layer geological model — Layer 1 (shallow aquifer, K=35 ft/d), Layer 2 (confining layer, K=3 ft/d, 25 ft thick), Layer 3 (deep aquifer, K=35 ft/d, 120 ft thick). Each layer has its own properties set in the Default Attributes menu. Top elevations chain automatically — each layer's top matches the bottom of the layer above.
3D simulation results showing cross-section through all three layers with head contours, flow vectors, vertical leakage through the confining layer, and 3D surface visualization of the aquifer system
Figure 3: 3D simulation results — cross-section reveals head distribution across all three layers. The confining layer (thin, low-K middle zone) creates a head difference between the shallow and deep aquifers. Flow vectors show horizontal flow within the aquifers and slow vertical leakage through the confining layer. The 3D surface chart renders the complete geological structure.

Key Concepts

Leaky confining layers: A confining layer with K = 3 ft/d is not impermeable — it's "leaky." Water moves through it slowly, driven by the head difference between the aquifers above and below. The leakage rate depends on the confining layer's K, thickness, and the head difference across it. In real aquifer systems, leaky confinement is the norm — truly impermeable layers are rare.

Head differences between layers: In a single-layer model, there's one head value per location. With multiple layers, each layer has its own head at the same xy location. The head difference between layers drives vertical flow through the confining layer. If the deep aquifer has higher head than the shallow aquifer, water flows upward — this is the mechanism behind artesian wells and flowing springs.

Automatic layer stacking: When you add a new layer, IGW-NET automatically sets its top elevation to match the bottom of the layer above. You only need to specify the thickness. This ensures geological consistency — no gaps or overlaps between layers.

Each layer is independent: Each aquifer layer has its own set of zones, lines, boundaries, wells, and properties. A pumping well in Layer 1 doesn't directly affect Layer 3 — it affects it indirectly through leakage across the confining layer. You can add features to any layer independently, building complexity progressively.

2What's Next

With multi-layer modeling mastered, continue the learning path:

Tutorial 11: Model Hierarchy — manage multiple nested models across scales, each potentially multi-layered
Tutorial 15: Stochastic Flow Model — add random heterogeneity within layers to represent real geological complexity
Tutorial 23: 3D Flow Visualization — immersive 3D rendering of multi-layer flow fields