S.S. Papadopulos and Associates. Inc., in collaboration with the University of Waterloo, has developed a powerful, state-of-the-art particle tracking software for groundwater models with unstructured grids. Armed with high-order Runge-Kutta ODE solvers and multi-threading support, mod-PATH3DU is the most powerful particle tracking program available for MODFLOW and MODFLOW-USG.

Main mod-PATH3DU Webpage:

Online Manual:

​Key Features

  • Semi-analytical particle tracking algorithm – The Waterloo Method
  • Supports all cell geometries available to MODFLOW-USG, including nested grids, quadpatch and quadtree, Voronoi, and triangular.
  • Implicit weak sink support – accurately track particles in the vicinity of a pumping well
  • Uses global coordinates
  • MODFLOW (structured, rectangular grid) support




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SSP&A's software is provided "AS IS", without warranty of any kind, including, without limitation, the warranties of merchantability, fitness for a particular purpose and non-infringement. We request only that application of the software and production of results using the code is accompanied by a suitable acknowledgment. The entire risk and responsibility as to the quality and performance of the Software is borne by the user. SSP&A disclaims all other warranties.