MODFLOW is the code developed by the USGS for the simulation of groundwater flow in steady and transient flow conditions. MODFLOW can represent a wide variety of physical process related to the groundwater flow regime as recharge, evapotranspiration, wells, among others. Latest development in MODFLOW allow the simulation of flow and transport in the unsaturated flow zone with the UZF and MT3D packages. From the beginning of the MODFLOW development the water balance on the groundwater models was a strong part of the modeling process with high accuracy in between the balance of water going in and out of the system. On any groundwater flow model build on MODFLOW there absolutely control over the water coming from the specified boundary conditions and the discrepancies are minimal.

A right understanding of a groundwater flow regime implies the comprehension of the flow direction, distribution of hydraulic heads and water balance. Most of the professional in groundwater modeling are very capable in setting up a model and representing model output as flowpaths, water tables and hydrogeological cross sections but when it comes to understand and evaluate groundwater management related questions, much deficiencies are found in the reports and profesional capabilities.

Having a complete understanding of the groundwater flow regime requires the evaluation of the inflows and outflows on certain parts of the model, or the interaction among layers. This tutorial shows the whole procedure of setting up the Zone Budget Package on a regional groundwater flow model in MODFLOW with Model Muse. The tutorial covers the parameter input process as well as the zone budget simulation with a description of the output data with an analysis of the interaction between zones.