Aquifer modeling requires understanding and expertise on the different boundary conditions available to represent the physical process related to the groundwater flow regime on determined spatial and temporal discretizations. MODFLOW has a set of boundary conditions of specified head, specified flux and mixed. There is a particular boundary condition created for the representation of the interaction between a river and the surrounding aquifer: the River Package (RIV). This tutorial show the implementation procedure of a River Package (RIV) on a regional model with a discussion on the model output and water balance.
Input data as river path on shapefile format and base model files for the tutorial recreation can be found in the Input data part of this tutorial. Further information on the River Package (RIV) can be found on the Online Guide to MODFLOW-2005.
You can download the input data from this link.