Just as it does when running MODFLOW, WEAP creates temporary MODPATH files for each scenario it calculates. The temporary filenames all start with "!MP!" to distinguish them from other files. Each of these is described below. For files that appear in the Name file, the file type is given in all caps in parentheses, e.g., "(MAIN)". Unless otherwise noted, a different file is created for each scenario. The input files are created by WEAP or MODFLOW; the output files are created by MODPATH.
The only file from the original Name file that will be listed in the new Name file is the Main file. All others are discarded or replaced. WEAP adds each of the following files: DIS, LOCATIONS, TIME, LIST, HEAD(BINARY), BUDGET, ENDPOINT, CBF, and TIME-SERIES.
WEAP links the Options Set to the Name file--it has the same filename as the Name file, but with a file extension of .mpo Therefore, each Name file can have a different group of Options Sets.
A new Main file is created from the original Main file, but the only change made is for a transient analysis, in which values for BeginPeriod BeginStep EndPeriod EndStep are changed, according to the Options Set for when the particles are released. This file does not vary by scenario, so there is only one temporary Main file for all scenarios. Note: if the user edits Porosity Data, the changes are made to the original Main file.
WEAP creates a new Discretization file by combining all the individual MODFLOW Discretization files from the scenario run into one Discretization file that includes all WEAP time steps (each WEAP time step is a MODFLOW stress period).
WEAP creates this file of starting particles locations and release times from the currently loaded Options Set. This file does not vary by scenario, so there is only one temporary Main file for all scenarios.
This file specifies the values of tracking time at which output is required for the time series results. So that results are available for each WEAP time step, WEAP creates this file by listing every time step in the simulation. This file does not vary by scenario, so there is only one temporary Time file for all scenarios.
The summary output file, with detailed information about the MODPATH run. It is shown to the user only if there is a problem and the TIME-SERIES file is not created.
Head file created by MODFLOW, for all stress periods.
Cell-to-cell flow file (.ccf) created by MODFLOW, for all stress periods.
The Endpoint file is created by MODPATH as a result. It is not used by WEAP, but is required to be in the Name file.
MODPATH creates this file from flow data in the MODFLOW BUDGET file, for use in backward tracking analysis.
This is the main MODPATH results file, which lists the location for each particle (in the LOCATIONS file) at each time (in the TIME file) in the simulation. WEAP display the 3-D vector pathlines from the results in this text file.
The Response file tells MODPATH which Name file and which options to use in the run. WEAP creates it based on the currently loaded Options Set.
There are some response file options on which WEAP does not give the user a choice. They are listed, along with the choice made by WEAP:
* STOP COMPUTING PATHS AT A SPECIFIED VALUE OF TRACKING
TIME?
No
* SELECT THE OUTPUT MODE:
* 1
= ENDPOINTS
* 2
= PATHLINE
* 3
= TIME SERIES
3
* DO YOU WANT TO COMPUTE VOLUMETRIC BUDGETS FOR ALL CELLS
?
No
* DO YOU WANT TO CHECK DATA CELL BY CELL ?
No
* SUMMARIZE FINAL STATUS OF PARTICLES IN SUMMARY.PTH FILE
? (This
is the LIST file.)
Yes
MODPATH uses advective transport to plot the particle paths. It does not model diffusion or dispersion of particles.
If the contrast in hydraulic conductivity between adjacent cells changes too abruptly, MODPATH may not be able to compute particle paths and will crash. In such cases, you may wish to adjust the hydraulic conductivity specification to reduce the contrast between adjacent cells. Such problems may occur if the contrast exceeds three orders of magnitude. The Horizontal Flow Barrier package has the potential to cause similar problems.
MODPATH does not continue to track particles once they have entered surface water bodies such as streams or lakes. If you are using MODPATH to delineate the well-head protection area and a stream or lake is part of the recharge area, you may need to consider the sources of water for the stream or lake when delineating the well-head protection area.
MODPATH expects the MODFLOW CCF file to have results for all MODFLOW time steps in each stress period. If there are several MODFLOW time steps, this file could become quite large. Reducing the number of timesteps per stress period will reduce the file size. If the original MODFLOW stress period length is much longer than the WEAP timestep (e.g., annual vs. monthly), you probably want to reduce the number of MODFLOW timesteps per stress period--it will calculate faster and create smaller files. For example, if the MODFLOW stress period is 365 days and the number of timesteps per stress period is 12 (one per month), because WEAP will change the stress period length to monthly, you probably want to reduce the number of timesteps per stress period to 1 so that it is still monthly.
MODPATH reserves file unit numbers between 80-99 for internal use. Therefore, do not use these numbers in your MODFLOW Name file.
MODPATH file comment lines start with @.
The particle tracking algorithm used by MODPATH can be implemented for either steady state or transient flow fields. However, when used with a steady state MODFLOW model, MODPATH will not consider any changes in pumping or recharge that occur after the first timestep. Therefore, a steady state model is a poor choice for one to link to WEAP.