MODPATH-RW: A Random Walk Particle Tracking Code for Solute Transport in Heterogeneous Aquifers

Area of Science:

• Hydrogeology
• Computational methods
• Environmental science

Background:

• Simulating solute transport in heterogeneous geological systems is crucial for environmental and hydrogeological studies.
• Classical grid-based solvers often suffer from numerical dispersion, particularly in advection-dominated scenarios.
• Accurate concentration predictions are vital for reactive transport modeling.

Purpose of the Study:

• To present a new solute transport code implementing the Random Walk Particle Tracking (RWPT) method.
• To enable seamless integration of RWPT with industry-standard groundwater flow models like MODFLOW.
• To provide a tool for accurate solute transport simulation in complex geological settings.

Main Methods:

• The study extends the MODPATH particle tracking model to implement RWPT.
• A novel method determines exact particle cell-exit positions considering advection and dispersion.
• The code supports unstructured grids, concentration reconstruction, and parallel processing (OpenMP).

Main Results:

• The developed RWPT code accurately simulates solute transport, avoiding grid-induced numerical dispersion.
• The program facilitates sequential particle transfer between flow model cells.
• Parallel processing significantly speeds up simulations in heterogeneous systems.

Conclusions:

• The presented RWPT solute transport code offers a robust and efficient alternative to traditional methods.
• Its integration with MODFLOW and accurate simulation capabilities are beneficial for reactive transport studies.
• The code is validated through numerical test cases against established transport models.