How are numerical groundwater models developed and calibrated?

Groundwater modeling process: (1) Conceptualization - define aquifer boundaries, layers, flow system, (2) Grid design - finite difference (MODFLOW) or finite element, refined where detail needed, (3) Boundary conditions - specified head, flux, or mixed at model edges and internal features, (4) Parameter assignment - K, storage, recharge for each cell/element, (5) Calibration - adjust parameters to match observed heads and flows using inverse methods (PEST, UCODE), (6) Sensitivity analysis - identify influential parameters, (7) Validation - test on independent dataset, (8) Prediction scenarios. Uncertainty quantification essential for decision-making.