Monthly Archives: February 2023

Some new map options in the Global Watersheds web app

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On the Global Watersheds app, I noticed that the OpenTopo map layers were not loading for me at all. I think I may have gone over some kind of limit.

As a workaround, I’ve added a whole bunch of new basemap options. A couple of them only work in certain regions. For example, GeoPortail France only works at higher zoom levels in France, and the USGS topographic maps can only zoom in to the US.

Some of the new basemap options have limits on the number of map tiles they will provide for free. So if one doesn’t work, try a different one. And if you have any feedback, let me know! 🙂

Demo: Use the Global Watersheds API and Python to automatically delineate watersheds

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It seems that a few people are discovering the mghydro watershed delineation API. Last Monday, the API handled requests for 9,679 watersheds over the course of a few hours. (Someone is very interested in the watersheds of France!)

One way to use the API is with GIS software, to fetch watershed boundaries and river centerlines from the web app and display them in your desktop GIS. Another use is to automate your requests, rather than using the online map interface. This could be useful if you want to delineate hundreds (or thousands!) of watersheds. However, remember that the results of automated delineation are very often wrong, so you should visually check each one.

Here is a demo in Python of how you could use the API to download watersheds for multiple outlet points. Click on the filename at the bottom to go to Github, where you can download the Jupyter notebook.