Using the Particle Tracking Module

The Particle Tracking Module places a water particle (point) at each septic tank location. It uses the Groundwater Flow Module outputs for velocity direction and velocity magnitude to simulate flow paths from a septic tank to a nearby water body.

Data Inputs

Once you are satisfied with the Groundwater Flow Module’s data outputs, it is time to move on to the Particle Tracking Module. Access the [ArcNLET.pyt] ArcGIS Python Toolbox and the ArcNLET-Py ArcGIS Pro toolsets within.

Figure 11-1: The ArcNLET-Py Python Toolset and Particle Tracking Module in the Catalog Pane.

1. Double-click the [2 Particle Tracking] module, and the particle tracking Python toolset opens in the [Geoprocessing Pane].

   1. Take a moment to review the data inputs, outputs, and parameters. Please remember that data inputs and outputs marked with a red asterisk [*] are required for the geoprocessing operation.

2. Click the drop-down arrow next to [Parameters] to expose the options.

3. Data inputs:

   1. Input Source Locations (point)

      1. Lakeshore Example input vector point: [PotentialSepticTankLocations.shp]

   2. Input Water Bodies (polygon)

      1. Lakeshore Example input water body polygons: [waterbodies.shp]

   3. Input Velocity Magnitude [m/d] (raster)

      1. Groundwater Flow Module output raster: [velmag50]

   4. Input Velocity Direction [°wrt N] (raster)

      1. Groundwater Flow Module output raster: [veldir50]

   5. Input Soil Porosity (raster)

      1. Lakeshore Example input raster: [porosity]

Figure 11-2: The Particle Tracking Module in the Geoprocessing Pane.

4. There are several options for selecting data for a geoprocessing tool in ArcGIS Pro. If you are unfamiliar with ArcGIS Pro geoprocessing tools, please use the following URL to learn how to use geoprocessing tools. URL: https://pro.arcgis.com/en/pro-app/latest/help/analysis/geoprocessing/basics/run-geoprocessing-tools.htm

5. Use the [Map], [Catalog View], [Catalog Pane], or [Folder Icon] to select the necessary data inputs.

   1. If you have the data from the Lakeshore example in a [Map] in your ArcGIS Pro Project file and the [Geoprocessing Pane] open, you can drag and drop the necessary inputs or select the files from the drop-down menu for each of the input fields.

Figure 11-3: Selecting Particle Tracking Module Data Inputs in the Map View.

2. If you have the data from the Lakeshore example open in a [Catalog Pane] or [Catalog View] and the [Geoprocessing Pane] open, then you can drag and drop the necessary inputs.

Figure 11-4: Selecting Particle Tracking Module inputs by dragging and dropping from the Catalog View.

3. You can also click the [Folder Icon] next to each field to select the data inputs using the Windows File Explorer. To use this method, you must use the Windows File Explorer to navigate to the […\2_lakeshore_example_phosphorus\2_Particle_tracking_module\Inputs] folder to select each data input and click [OK].

Figure 11-5: Selecting Particle Tracking Module inputs from the Windows File Explorer.

Data Outputs and Parameters

Storing your files in an organized and appropriately named manner is good practice when selecting locations for data outputs. Earlier in this exercise, we used the Windows File Explorer or ArcGIS Pro [Catalog Pane] to create a new folder titled [LakeshoreExampleOutputs_YYYY_MM_DD]. The folder stores the output shapefiles.

1. If you need to create a new file folder in ArcGIS Pro, use the [Catalog Pane], right-click on the folder [……\2_lakeshore_example_phosphorus\2_Particle_tracking_module\Outputs], hover over the option [New] in the submenu, and click [Folder].

Figure 11-6: The Lakeshore example output folders in the Windows File Explorer.

2. Select the necessary data output by clicking the [Folder Icon] next to the [Output Particle Paths (Polyline)] field in the [Geoprocessing Pane].

   1. The Windows File Explorer opens, and in the left pane under [Project], click the drop-down arrows to expand the [Folders] and ArcGIS Pro home folder.

   2. Please note that when typing the data output into the provided field in the [Geoprocessing Pane], the outputs are automatically stored in the folder with the [Input Velocity Magnitude [L/T] (raster)].

3. Select the […\2_lakeshore_example_phosphorus\2_Particle_tracking_module\Outputs] folders.

   1. Click the above output folder to store the output vector shapefile from the Particle Tracking Module. The file path and name for the [Output Particle Paths (Polyline)] is […\2_lakeshore_example_phosphorus\2_Particle_tracking_module\Outputs\paths50.shp]

4. Type the name of the shapefile output into the [Name] field with no file extension and click [OK].

   1. The ArcNLET-Py ArcGIS Pro Python toolset automatically assigns the correct file types, and if you enter a file type, a warning is triggered.

5. Data output:

   1. The output particle paths (polyline).

      1. Lakeshore Example output shapefile: [paths50]

6. The Parameters are related to model validation and verification. For the Lakeshore Example, the WB Raster Resolution and Step Size parameters are automatically set from the [lakeshore.img] DEM file.

   1. Flow Path Truncation

      1. Please check the box for this option: [Checked Box]

         1. The Flow Path Truncation option trims line features intersecting the water body polygons and extending particle paths that fall short of the water body polygons. Furthermore, enabling Flow Path Truncation requires more processing time.

   2. WB Raster Resolution [m]

      1. Default value: [5]

   3. Step Size [m]

      1. Default value: [10]

   4. Max Step

      1. Default value: [1000]

Figure 11-7: Selecting the data output location from the Windows File Explorer for the Particle Tracking Module.

7. Double-check to ensure all red astricts [*] are removed from the [Geoprocessing Pane], indicating that all necessary data inputs and outputs have the correct file type and are accessible.

Figure 11-8: The Particle Tracking Module data inputs and output in the Geoprocessing Pane.

The particle paths are shown in red and the OSTDS points are blue.

Execute the Module

1. Once satisfied with the data input and output selections, click [Run] in the [Geoprocessing Pane].

Figure 11-9: The Run button in the Geoprocessing Pane.

2. The ArcNLET-Py Particle Tracking Module begins to process data, and the progress bar appears. The runtime can vary depending on the data sets’ file sizes, spatial scale, and raster cell size.

Figure 11-10: The Progress Bar in the ArcGIS Pro Geoprocessing Pane for the Particle Tracking Module.

3. ArcGIS Pro indicates the tool is finished with a green notification box at the bottom of the [Geoprocessing Pane]. You may click [View Details] for more information about the process, including data inputs and output(s), start and end times and dates, and a success or failure message.

Figure 11-11: The green notification box in the ArcGIS Pro Geoprocessing Pane for the Particle Tracking Module.

View and Verify Results

If you have your data inputs in an open [Map] in ArcGIS Pro, the data output(s) are automatically added to the [Contents Pane] and the [Map View]. Alternatively, if you do not have your input data in a [Map], nor do you have a [Map View] open in your ArcGIS Pro Project, and you ran the ArcNLET-Py Particle Tracking Module from the [Geoprocessing Pane], then your results are accessible via the [Catalog Pane] or [Catalog View] in the output folder [LakeshoreExampleOutputs_YYYY_MM_DD].

Figure 11-12: The ArcNLET-Py Particle Tracking Module output in the Catalog Pane

1. Take a moment to review the shapefile output to ensure your data has been processed correctly. Your data processes must be done correctly because data outputs from the Particle Tracking Module are used as data inputs in the subsequent module.

   1. Please note that if your vector shapefile outputs are not line features originating from your potential contamination sources (septic tank locations) towards the proximal surface water body polygons, then this is an indicator that there might have been an error processing the data inputs.

      1. For example, you should have one segmented particle path for each septic tank location in the output particle path shapefile. You may notice several thousand individual line features for the potential septic tank locations.

2. If there seems to be an issue with the output particle paths shapefile, please ensure all your data inputs are correct, in an accessible file folder, and uncorrupted.

   1. If you continue having issues processing your data, please [View Details] as mentioned in Section 5.7.3 to see if empty datasets were created as outputs. Empty datasets indicate an issue with the input data, or ArcGIS Pro does not have read/write access to input or output file locations.

   1. If you cannot find a solution to the issue, then please submit a [New issue] in the ArcNLET-Py GitHub repository (Issues · ArcNLET-Py/ArcNLET-Py · GitHub) as described in the GitHub instructions at Creating an issue - GitHub Docs.

Figure 11-13: The ArcNLET-Py Particle Tracking Module outputs in the Contents Pane and Map