Groundwater Modeling: Semi-Analytical Approaches for Heterogeneity and Reaction Networks

Reactive transport modeling for heterogeneous aquifers is challenging and computationally intensive. While numerical packages allow simulation of multiple species transport with aquifer heterogeneity, run times on high speed PCs and workstations make many jobs impractical. Stream tube approaches are computationally efficient numerical methods, and offer significant advantages in run time over more numerical methods. In this study, a new stream tube model was developed for multiple species reactive transport in a heterogeneous aquifer. The model is based on a primary hypothesis that reactive transport in heterogeneous aquifers can be approximated with a linear transforms where reactivity and flow distributions are not coupled. For many cases, the method allows good accuracy and significant computational advantages, especially for complex reaction networks and more heterogeneous aquifers. The numerical experiments in this study have proved the hypothesis is correct. Comparisons are made between the new modeling approach, other analytical models and numerical models. Numerical agreements are reasonable for all of the tested cases, and significant computational time is saved with the new modeling approach. For a 2D aquifer simulation discussion in this study, the new approach is 1500 times faster than RT3D, one of the most popular numerical applications.