MODPATH Version 7 Release Notes
                              MODPATH-7 Version 7.2.001
                                  December 15, 2017

     This file describes changes introduced into MODPATH version 7 with 
each official release; these changes may substantially affect users. 

NOTE: Any use of trade, product or firm names is for descriptive purposes 
      only and does not imply endorsement by the U.S. Government.
      
Limitations of the current version (MODPATH 7.2.001)
----------------------------------------------------

1. MODPATH supports rectangular, quad-refined unstructured grids for simulations based on
   MODFLOW-USG and MODFLOW-6. For simulations based on MODFLOW-USG, unstructured grids can 
   be refined both horizontally and vertically from layer to layer. For simulations based 
   on MODFLOW-6, only horizontal refinement is allowed. The maximum refinement level contrast 
   between horizontally adjacent grid cells must not be greater than 1. That means that any 
   grid cell can be connected to either 0, 1, or 2 grid cells across any adjacent horizontal 
   face.  For MODFLOW-USG unstructured grids that permit vertical refinement, vertically 
   adjacent grid cells can be connected to 0, 1, or 4 grid cells across the top or bottom face. 
   These types of unstructured grids commonly are referred to as smoothed quadtree or 
   quadpatch grids.
   
2. MODFLOW-USG simulations intended for use with MODPATH-7 should always use ghost 
   nodes to minimize the effects of flow oscillations from cell to cell. MODFLOW-6 simulations
   intended for use with MODPATH-7 should use either ghost nodes or the XT3D package, which
   implements an inter-cell velocity computation scheme that minimizes flow oscillations 
   with a similar degree of effectiveness as ghost nodes. Ghost nodes need to be computed 
   externally by the user for each specific grid in contrast to XT3D which handles all of the 
   necessary computations internally without any extra input from the user.
   
3. Although ghost nodes greatly reduce flow oscillations, significant flow oscillations often 
   are present in the vertical direction in the immediate vicinity of internal sources and sinks 
   even when ghost nodes are used. At the present time, we recommend that the same plan view 
   unstructured grid be used for all model layers to avoid the problem with vertical flow 
   oscillations.
   
4. This version of MODPATH currently is restricted to grids that have square grid cells in 
   plan view. Particle tracking simulations based on traditional structured grid MODFLOW simulations 
   are not restricted to square cells.


Version History
---------------

o Version 7.2.001  December 2017

   - MODPATH now supports MODFLOW-6.
   
   - Input for unstructured grid simulations with MODFLOW-USG was redesigned to take more advantage of
     existing MODFLOW-USG data files and to reduce redundant input data. The MODPATH unstructured grid
     file (MPUGRID) used in previous releases of MODPATH_7 is no longer supported.
     
   - Added x-y origin offset and grid rotation information to the endpoint, pathline, and timeseries file 
     headers so that particle coordinates can be converted to world coordinates by post-processing programs.
     
   - Fixed a problem reading the LAYCBD array in the MODFLOW-2005 discretization file.
   
   - Fixed a problem reading forward slash (/) path delimiters in file names in the simulation data file.
   
   - Fixed a problem that caused particles not to stop at cells with a zone number equal to the stop zone 
     when the automatic stop zone option was selected.
     
   - Other bug fixes and output format changes.


o Version 7.1.000  September 26, 2016

   This version is the initial public release.