MODFLOW-SURFACT™ is a powerful 3D finite-difference flow and transport modeling code that offers substantial advancements over public-domain versions of MODFLOW. For example, MODFLOW-SURFACT™ addresses rewetting of drained cell, handling of pumping wells, solute transport problems, numerical dispersion and oscillations, and impacts of transient flow storage effects on transport. What’s more, highly efficient, mass-conserving algorithms enable MODFLOW-SURFACT™ Version 4 to deliver accurate solutions faster than ever before.