MODFLOW is a software for groundwater modeling developed by the USGS. The software is capable of representing conditions related to groundwater flow such as evapotranspiration, recharge, drainage, river interaction among others. Its finite different approach gives the capability to calculate the flow regime with exceptional control on water budget discrepancy. With MODFLOW one can rely on that the flow going in the model is the same as the flow going out of it, from the regional scale and on cross sections.