modpath

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General Module Function

The modpath module uses the cell by cell flow values generated from a MODFLOW project along with head values and other MODFLOW parameters to trace the path of a particle of water as it moves through the ground. The paths are calculated using the same algorithms used by U.S. Geological Survey MODPATH and the results should be similar.

The modpath module at this point does not handle transient simulations the same way that the U.S.G.S. MODPATH does. It treats each time step as a steady state model, and uses the parameters from the .dwr/.dwz file based on the starting time.

A valid modpath field file (.eff/.efz) should contain the following as cell data components: Head; CCF; ELEV_TOP; ELEV_BOT; and POROSITY. The Head component should contain the head value for each cell, the ELEV_TOP and ELEV_BOT should components should contain the elevation of the top of the cell, and the elevation of the bottom of the cell respectively, and the POROSITY should contain the flow due to porosity for that each cell. All other MODFLOW parameters (drains, wells, recharge, etc..) should be written into a .dwr/.dwz file.

Module Input Ports

The modpath module has five input ports. The first (leftmost) accepts field data usually from Load_EVS_Field or Read_TCF. The second port accepts data specifying the starting location of the particle paths, this data is typically generated by a slice, create_grid, isolines or place_glyph module. The third and fourth ports accept time values, this data can be generated with time_loop and is used to control the starting and ending values for transient models. The last port is the z exaggeration factor. This input causes the path generation to be calculated in an unscaled system ensuring that velocities are not scaled and are accurate, then scales the position of the paths.

Module Output Ports

modpath has five output ports. The first and second output ports (leftmost) pass the staring and ending times through. The third output port passes the z exaggeration factor. The fourth output port creates a new unstructured polyline mesh representing the particle paths. The output also contains a nodal data component referencing the velocity component. The rightmost and last output port can send modpath polylines to the viewer.

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Module Control Panel

The control panel for modpath is shown in the figure above.

TheDWR File:shows which .dwr/.dwz file has been selected, this file contains MODFLOW package data such as drains, wells, recharge, etc...For details on the DWR file format, see here.

TheDirectionradio buttons allow the user to specify forward or backward path projection. Both paths start from the specified starting points and travel until the selected option in either the "Time Options" category or the "Sink Options" category are satisfied.

TheZ Scaletype-in reflects the value of the z exaggeration port.

TheMap Componentradio buttons allow you to choose which computed data component to use for coloring the lines. Choices are Velocity, Time, Distance and Uncolored.

TheColoring Optionsradio buttons allow the user to specifyMagnitude(normal) orLog10(Magnitude)representation of the velocity data for coloring purposes. When velocities span several orders of magnitude working in log space is useful.

TheMin MagnitudeandMax Magnitudetype-ins display the min/max velocities represented in the input field. Changing these values allows the user to reset the min-max values for coloring purposes. NOTE: once you change these values they will not automatically update.

TheTime Options:radio buttons indicate a time based stopping condition for the particles. Run to end indicates that the particle will run until it cannot escape a cell due to lack of flow.

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Run for date allows a particle to travel from a start date to an end date.

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The duration option allows the particles to run for a duration of time in days.

TheSink Optionsradio buttons indicate stopping conditions for the particles based on the amount of flow through a cell. The Pass through cells with weak sinks option allows all particles to pass through a cell, unless that cell has a strong sink. The Stop in cells with weak sinks button does not allow a particle to pass unless the flow out of a cell is greater than or equal the flow into it. The last option, Stop if discharge to sink is > specified fraction of inflow to cell, allows the user to specify what fraction of inflow will stop particles in that cell. This fraction value is set using the Fraction slider which is visible when the last option is selected. Only values between zero and one are useful.