Run the Models and View Results

After WEAP does it calculations for each scenario, including running MODFLOW at each timestep, WEAP combines all the individual MODFLOW input files for a scenario (one set for each WEAP time step--each set represents one MODFLOW stress period) into one set of files that covers all WEAP time steps (the set has as many MODFLOW stress periods as there are WEAP time steps in the entire simulation).  WEAP runs this large MODFLOW model, and then runs MODPATH, using the currently loaded MODPATH Options Set.  Just as it does when running MODFLOW, WEAP creates temporary MODPATH files for each scenario it calculates.  (Because a complete set of new input files are created and kept for each scenario, you will be able to run them yourself in MODPATH outside of WEAP, if you want to examine the results in more detail, or to make slight changes to the inputs. Note that any changes you make directly to these temporary input files will be lost the next time WEAP does its calculations, so you are advised to save them in another directory if you want to preserve them. The temporary filenames all start with "!MP!" to distinguish them from other files.)  MODPATH can only calculate particles in active cells.  If a cell goes dry, any particles in that cell will not exist.  Check the MODFLOW report on dry cells to determine if this is happening.

In the Results View, choose Supply and Resources \ Groundwater \ MODFLOW \ Particle Pathline. On the Chart tab, WEAP displays particle pathlines as 3-dimensional vectors.  Each particle will display as a line showing its path over time in three dimensions. Using the mouse, click and drag on the chart to rotate it, or move the sliders below to manipulate it. Shift-click and drag to pan the chart, or use the mouse wheel to zoom in or out.  Click the "Rotate" button to start it spinning.  Position the mouse on or near a point on a 3-D pathline to see a description of it in the status bar at the bottom of the WEAP window.  Click the "Top," "Front" or "Left" buttons to switch to a 2-D view showing a cross-section as seen from the chosen face (top, front or left).

The lines are plotted in one of two coordinate spaces, depending on the setting of the "Show X,Y" checkbox at the top.  If "Show X,Y" is checked, the coordinates are X,Y,Z, all in length units (e.g., feet or meters) selected at the top.  X is the distance from the left face of column 1, Y is the distance from the front face of the last row, and Z is the elevation.  These are based on column and row widths, and cell elevations, from the MODFLOW Discretization file.  If "Show X,Y" is not checked, the coordinates are Column, Row, Elevation, where Column and Row are fractional positions within a cell (e.g., Row=5.5 is the middle of row 5), and Elevation is in length units selected at the top.  Go to the Table tab to see the 3-D coordinates for each particle and time step.  The coordinates are shown either as (Row, Column, Z) or (X, Y, Z).  You can turn off the "Y=0" button to the right of this chart to magnify the changes in elevation over time.

Each particle is listed in the legend (using the format chosen for the current MODPATH Options Set).  For example, it might include the Layer, Row, Column coordinates where it was released: "Particle 1: (1, 10, 22)".  Note: If there are multiple particles per cell or multiple releases times, there will be particles with the same starting coordinates in their names.

The 3-D pathlines are made up of connected 3-D line segments, each of which connects the position of a particle on two successive time steps.  Each point shown corresponds to the position of the particle at the end of that timestep.  You may select to see all months and years and all particles, or select subsets of them.  Tip: You can speed up the display by selecting just one month from each year to display.  For example, select December only and each line segment will show the jump in the position from the end of December in one year to the end of December in the next year.  (See chart below for an example of this.)  Click the Arrowhead icon on the right tool bar to show or hide arrowheads on each line segment.

You can change the MODPATH options or starting particles positions without leaving the Results View--click the "Particle Generation and MODPATH Options" dropdown button on the upper right to quickly switch from one options set to another.  When you change it, MODPATH will automatically recalculate using the new particles and MODPATH options.  You can also edit or add Options Sets--click the "Edit" button to the right of the dropdown box to go to the Edit Particle Generation and MODPATH Options screen.  When you exit that screen, MODPATH will automatically recalculate if you had made any changes.  Because the normal WEAP or MODFLOW calculations do not need to be re-run when the MODPATH options have changed, this process is very quick.

The color of each line segment represents one of several different types of information, selected by the "Color by" dropdown box just above the legend (in the example below, it is set to "Color by Particle").  In two cases, the entire pathline for a particle will have a single color (Color by Pathline, Color by Release Time); in the other cases, each line segment of each particle pathline can have a different color, representing information about the particle either during the time it moved from the beginning of the line segment to the end of the line segment (Color by Velocity) or at the moment when it was at the end of the line segment (Color by Travel Time, Color by Absolute Time, Color by Travel Distance, Color by Elevation, Color by Layer, Color by Layer (fractional)).

For "Color by Particle," you can change the color scheme and whether or not to use patterns for the lines; the other choices all use the rainbow palette, without patterns.  For choices other than "Color by Particle," you can set how many different colors to use--click the rainbow button on the toolbar on the right (see above).

Here is an example showing the plume that results from releasing particles at the same location over successive time steps, using a forward tracking analysis.  In this scenario, pumping rates increase over time, which causes the particles released later (shown in blue and purple) to move more quickly towards the well (at row 7, column 25).

On the Map tab, WEAP overlays 2-dimensional particle pathlines on top of the Schematic.  Here is an example showing the capture zone for a well, using a backward tracking analysis of particles arranged on faces 1, 2, 3 and 4 of the well cell (at row 7, column 25), all released at the end of the simulation (December 2027) and traced backwards in time.  By choosing Color by Travel Time, the colors show how long it takes each particle to reach the well.

From the Map tab, the pathlines can be saved as a GIS Shapefile.  Click the button on the toolbar to the right and choose save as "GIS Shapefile (SHP)".  You can choose to create a separate line in the shapefile for each particle pathline line segment (there is a line segment for each timestep for each particle), or group together all the line segments for each particle into one line. When saving lines segments separately, WEAP will include information in the shapefile's attribute table for each particle timestep, such as distance traveled and velocity.  This information will be useful if you later want to display the shapefile in a GIS program, such as ArcGIS, and color code the line segments by these attributes.

The Scenario Explorer View can display multiple pathline results (saved as Favorites) for different Particle Generation and MODPATH Options, or for different scenarios.  In this example, favorites have been saved for the same variable but for different scenarios, showing how the particle plume is strongly affected by pumping (one scenario has pumping; the other scenario does not).  Choose "From Favorite" to see both scenarios.  Click the "Axis Scale" button on the right to use the same scales for the axes so that the different charts can be easily compared.