MODFLOW is a three dimensional model of groundwater by the method of finite differences. It has a modular structure that allows quick and easy modifications in order to adapt the model to any real application.
MODFLOW allows simulation in both steady and unsteady state. The nature of the aquifer can be free, confined or semi-confined. The generated flows may come from pumping from external or internal points to the model, from recharge wells, surface recharge, evapotranspiration, etc.
Each of the parameters that form the model can be defined. The hydraulic transmissivities can be defined for each layer and spatially differentiated, being able to be anisotropic (restricted taking into account the principal directions aligned with the grid). The storage coefficient may be heterogeneous. In addition to simulate the flow of groundwater, MODFLOW may include capabilities related to, for example, solute transport and to groundwater management.
The equation of groundwater flow is solved using finite difference approximation. The flow region is divided into cells, where the average characteristics are assumed to be uniform. The cells are distributed grid. This way it allows to the layers of the model may have a different thickness. The flow equation is written for each block, allowing full compliance with the real case modeling.