Trace the path of mining contaminants

Artisanal mining is a method of extracting minerals using basic mining techniques, often with little or no concern for law, safety, or environmental impact. In parts of the Amazon, artisanal mining techniques are used to extract gold from sediments. The process involves clearing forest, making pools, washing sediment into them, and then amalgamating the small particles of gold from the sediment with mercury and burning the mercury off. The process results in deforestation, sedimentation of streams and rivers, and mercury and cyanide contamination. In this tutorial, as a researcher at an environmental nonprofit organization, you want to determine which downstream areas are impacted by contaminants that leach from mining sites into the network of streams and rivers in the Amazon basin.

To identify mining sites, you’ll use a map containing open-source data from the Amazon Mining Watch, which is generated by interpreting satellite images using machine learning. You’ll create a Sketch layer to add points at some mining sites near the rivers. Finally, you’ll use the Trace Downstream tool to create a feature layer that maps the downstream flowpaths. This output can be used in a presentation for your nonprofit on how mining impacts rivers in the Amazon.

This tutorial was last tested on November 6, 2023.

Requirements

• ArcGIS organizational account with a Publisher or Administrator role

Trace the path of mining contaminants

View the map

To identify areas that may be contaminated by mining runoff, first you'll open a map that shows possible mining sites.

1. Go to the Trace downstream from mines item page.

   

   This is the item description page for a map showing mining sites in the Amazon. You will use this map to identify a mining site and trace downstream from it.

2. On the ribbon, click Sign In. Sign in with your ArcGIS organizational account.

   

   Note:

   You must sign in because you will be creating data in your account.

3. At the top of the item page, click Open in Map Viewer.

   

   This tutorial uses Map Viewer.

   Note:

   Depending on your organizational and user settings, you may have opened Map Viewer Classic. ArcGIS Online offers two map viewers for viewing, using, and creating maps. For more information on the map viewers available and which to use, please see this FAQ.

   

   A map of the Amazon basin appears, with red patches showing sites identified by the Amazon Mining Watch machine learning algorithm as being probable mining sites. Note that not all of the sites are mine sites, and not all mining sites are detected. You can read more about interpreting the results.

Zoom to a mining site

Now you'll zoom in and view a mining site. This map has two bookmarks at places where mining has been detected. You will view one of them now.

1. On the Contents toolbar, click Bookmarks.

   

2. On the Bookmarks pane, click Mining site 1.

   

   The map zooms to the bookmarked location.

   

   Next, you'll change the basemap to view imagery of the site.

3. On the Contents toolbar, click Basemap.
   

   The Basemap pane appears. ArcGIS Online includes a number of basemaps to provide context for your data.

4. In the Basemap pane, click Imagery to switch to the Imagery basemap.

   

   The basemap changes to the Imagery basemap.

   The mining site is hidden by the mine_locations feature layer.

5. On the Contents toolbar, click Layers.

   

   The Layers pane appears.

6. In the Layers pane, point to the mine_locations layer, and when the Visibility indicator appears, click it to hide the layer.

   

   The mine_locations layer is hidden, and you can see the mining site on the Imagery basemap.

   

   This site shows a pattern of forest clearing, pool construction and flooding, and various colors of ponds caused by different water depths, sediment levels, and chemical treatments. Contaminated water and sediments from these sites can leak into waterways. In the next section, you will make a point at this site, which you will use to trace the flowpath downstream.

Add a point to mark a site

The Trace Downstream tool takes point features as input. You will add a point at this site to allow you to trace where contaminated water and sediments will flow.

1. On the Settings toolbar, click Add Sketch.

   

   The Sketch pane appears.

   

   You will use the default sketch tool, a point tool.

2. Move the pointer over one of the pools on the site, and click to add a sketch point.

   

   The point shows with a marker on the map.

   

   You've added a point to mark this site. Next you'll zoom to another site and add another point.

Mark another site

Now that you've marked one mining site, you'll use the bookmark to zoom to another site and add a point there.

1. On the Contents toolbar, click Bookmarks.
2. In the Bookmarks pane, click Mining site 2.

   

   The map zooms to the second site.

   Now you'll add another point.

3. Move the pointer over one of the pools on the site, and click to add a sketch point.

   

   You've added points to mark two mining sites.

Save the sketch layer

Now you'll save the layer that contains the two points so you can use it to identify contaminant flow paths.

1. On the Contents toolbar, click Layers.
2. In the Layers pane, for the Sketch layer, click the Options button.

   

3. In the list of options, click Rename
4. Type River contamination points and your initials, and click OK.

   

   You added your initials because feature layers need to have unique names within an ArcGIS Online organization.

Trace downstream from the points

You've identified two locations at mines and you are now ready to trace downstream from them to identify the flowpaths that mining contaminants will follow.

1. In the Layers pane, click the River contamination points_your initials layer to select it.

   

2. On the Settings toolbar, click Analysis.

   

3. In the Analysis pane, click Tools.

   

4. In the Tools pane, click in the Search box.

   

5. In the Search box, type trace downstream.
6. In the search results, click Trace Downstream.

   

7. On the Trace Downstream tool, in the Input layer section, click the Layer button.

   

8. Click the River contaminants locations (Points) layer.

   

9. Accept the default values for the Downstream path settings.

   

   Note that you can change the maximum length of the paths and the units and clip the output.

10. Scroll down to the Results layer section, and for Output line feature, type River Contamination and your initials.

    

    Some tools consume credits when they run, but the Trace Downstream tool does not, so you do not need to click Estimate credits.

11. Click Run.

    After a few seconds, a message will appear that the process succeeded.

    

    The new River Contamination layer with your initials is added to the Layers pane.

    

12. In the Layers pane, for the River Contamination layer, click the options button and click Zoom to.

    

    The map zooms to show the two features in this layer.

    

13. On the map, click one of the trace results.

    

    A pop-up shows the length of the trace downstream and the ID of the point.

    For more information about how the Trace Downstream tool works, visit the tool documentation.

In this tutorial, you learned how to create a hosted feature layer with lines from the Trace Downstream tool. These lines trace the downstream flowpaths from points at mining sites near rivers in the Amazon. These lines show the paths that contaminants from the mines take as they flow downstream. This information could be used in a presentation by your nonprofit.

You can find more tutorials in the tutorial gallery.

Acknowledgements

• The mine_locations hosted feature layer is based on a dataset produced by the Amazon Mining Watch project. It was imported from its original GEOJSON format.

  The data was generated using machine learning techniques on Sentinel-2 satellite imagery. For more information, see the Methodology section of the project repository.

  The data is available under CC BY 4.0. In publication, cite Earth Genome, with reference to the Gold Mine Detector and Map GitHub repository.

  You can access the data in its original format on the mining-detector GitHub repository.

• National Geographic Style Map sources: Esri, HERE, Garmin, FAO, NOAA, USGS, © OpenStreetMap contributors, and the GIS User Community
• World Hillshade layer sources: Esri, Airbus DS, USGS, NGA, NASA, CGIAR, N Robinson, NCEAS, NLS, OS, NMA, Geodatastyrelsen, Rijkswaterstaat, GSA, Geoland, FEMA, Intermap, and the GIS user community
• World Imagery layer sources: Esri, Maxar, Earthstar Geographics, and the GIS User Community