Features Both its software features and the range of physical processes covered make FEFLOW unique among today's groundwater modeling software. No matter whether you need to quickly confirm rule-of-thumb assumptions for everyday engineering decisions or you apply large complex models as a basis for multi-million Euro or Dollar investments with possibly detrimental environmental impacts - FEFLOW provides the exactly right proportion between ease of use and necessary complexity of the approach. Simulation The simulation needs to be accurate and efficient for all relevant cases: Steady-state or transient simulation Different time-stepping methods: constant time steps varying pre-defined time steps fully automatic time-stepping procedure using predictor-corrector or aggressive target-based schemes Different approaches for free surface calculations: moving meshes linearized relationship for the saturation vs. relative conductivity curve with residual water depth fully unsaturated modeling Parameter estimation tool on base of PEST (by J. Doherty) Efficient control of the simulation process with customizable real-time diagrams for all important model results Solvers Newton and Picard iteration techniques for nonlinear problems Fast iterative and direct solvers like PCG and Restarted-OR-THOMIN with powerful preconditioners Alternatively algebraic multigrid solver (SAMG by K. Stueben) Analysis Analysis and postprocessing features are crucial for calibration and results evaluation. FEFLOW provides easy-to-use tools and visualization options: Diagram windows for observation wells Export of model parameters and results as values, vector plots and images Budgeting of water, solute, and heat flows for the model domain or parts of it Particle tracking with isochrone markers Steady-state or transient 2D or 3D view