⚠️Update March 27, 2023: I have temporarily disabled the “high precision flowpath tracing.” It turns out that this was still a little buggy, and not quite ready for prime time. The regular (low precision) flowpath routing should be working again.
Last month, many of you responded the poll I posted on the Global Watersheds page. I found out that most of you are just as interested in tracing downstream flowpaths as you are in delineating watersheds. To be honest, I added this feature to the app as a bit of an afterthought.
More detailed flowpaths
In higher precision mode (the default if you are zoomed in far enough or if you manually enter coordinates), the flowpath will now start from the nearest pixel to the point where you clicked. Previously, the flowpath only showed streams that are a part of the MERIT-Basins dataset. Now, the app will trace the flow from the origin, going downhill over land until it encounters a stream or river.
You can now share or embed your downstream flowpaths. After you’ve created a new flowpath, just click one of the sharing buttons at the left bottom. The link will point to a custom page with your flowpath. To embed a map widget, click the embed button </>, and copy and paste the code into a web page or blog post.
Here’s an example of both new features in action. On February 2, 2023, a train derailed in East Palestine, Ohio. According to the US Environmental Protection Agency, vinyl chloride and other toxic chemicals were “released to the air, surface soils, and surface waters.”
The spill occurred at: Latitude: 40.8361° N, Longitude: -80.5216° W. We can use the Global Watersheds app to find out what is downstream of this location. This can help us begin to understand where these chemicals can be transported by water, and what people and ecosystems could be at risk.
As always, if you encounter any bugs using these new features, send me a message!