 When the added capabilities are not used, MODFLOW-OWHM performs exactly like MODFLOW-2005, or MODFLOW-NWT, or MODFLOW-LGR (depending on the features used).There is an online input guide that explains the input for the packages that MODFLOW-OWHM supports and formal documentation is at the USGS Publications Warehouse.All version of MODFLOW listed above are constructed on what is called a structured grid.