I’ve just published a bunch of updates to the free Global Watersheds web app. Please check them out, and, as always, let me know if you have any questions or comments. I always love hearing from folks who use the app.

New Thematic Map Layers

Did you know you can change the basemap shown on the map, by clicking the layer selector at the top right? I’ve added three new thematic map layers — population density, land cover, and irrigated lands. These layers help illustrate human activities that can have big impacts on watersheds.

I chose to use a datalayer of population called GlobPop, by researchers in Beijing. This seemed to be the best among the alternatives I looked at (GPW4, GRUMP, LandScan, and WorldPop). This was actually quite surprising, as some of these other datasets are well-known and backed by large institutions.

The thematic map layers were developed by different teams of researchers using satellite imagery and machine learning. While they’re not perfect, they show how these tools can help us better understand our planet. I’m particularly excited to show you the “slider” feature on that lets you compare land cover in 2000 and 2020.

Another new layer displays dams from the Global Dam Watch database. It contains a total of 41,145 dams.

For more information about where these data come from, you can visit the About / Help page, or create a Watershed Data Report.

Watershed Data Report

After you’ve created a new watershed, you’ll see a new blue button on the left-side menu. Click this button to create a Watershed Data Report. The report summarizes a variety of information about the watershed:

I included some text in each section containing a brief introduction on how human and environmental factors affect watersheds.

1. Political Boundaries
2. Population
3. Land Cover
4. Hydrology
5. GRACE Total Water Storage
6. Irrigation
7. Dams

Some of the information in the report comes from the thematic layers that you can display on the map (for example, population, irrigated area, and land cover). The app calculates sums or averages over the pixels that overlap the watershed. In geographic information science, or GIS, this is referred to as “zonal statistics.” For a discussion of how I do these calculations, see Section 3.4 in my PhD thesis, Calculating Basin Means of [Gridded] Earth Observation Variables.

Finally, if you found the app useful for your classroom, business, or research, why not show your appreciation by buying me a cup of coffee?

Let me know if you found something interesting in your watershed report. How do you think this information could be useful for education, advocacy, or management? Are there any other environmental datasets you’d like to see included?

The water quality of the Seine has been making headlines, thanks to the 2024 summer Olympics in Paris. A few days ago, I discussed these issues with Kelly Yu from Radio Hong Kong.

I did my Master’s thesis on bacteria contamination of urban rivers, so it’s something I know a bit about… Paris has invested massively in improvements to the wastewater system, but much more needs to be done before the Seine will be consistently able to meet water quality standards for swimming.

This map shows the watershed, or drainage basin, upstream of Pont Alexandre III in Paris, where the Olympic open-water swimming events will be held:

The watershed covers 44,000 square kilometers, and includes cities, suburbs, farms, and forests. The watershed is an important determinant of the water quality in a river. In this case, every time it rains, pollutants are washed off of land surfaces and into lakes, rivers, and streams. Here is what I wrote about nonpoint source pollution in my MS thesis in 2003:

Runoff from land areas in the watershed is also a significant pathway by which bacteria enter surface waters. Urban runoff typically contains a variety of pollutants, including organic matter, oil and grease, nutrients, pesticides and herbicides, as well as bacteria and viruses. Bacteria in runoff can come from waste from pets and wildlife or may be attached to soil particles. In an urban setting, where storm drains are designed to get water away from roads and buildings as quickly as possible, nonpoint source pollutants are quickly delivered to surface waters, with little time for settling or decay to occur.

Paris also has a major illicit discharge problem, where boats and homes discharge sewage water directly to rivers or streams. I learned about this in an excellent article from the NY Times; this topic has received scant coverage in French-language media.

I defended my PhD thesis* in January, and decided it would be nice to put it online in HTML format. I have posted it here. The PDF is available via France’s open science portal HAL.

Heberger, Matthew. 2024. Improved observation of the global water cycle with satellite remote sensing and neural network modeling. PhD thesis. Sorbonne University, Paris, France. https://theses.hal.science/tel-04517802v1

My research had to do with using remote sensing data to describe the water cycle at the global scale, and explored methods to improve these data. There have been quite a few studies on this subject in the last several years, but we did a few things differently, namely using a much larger database of observations than previous studies, and using neural network models with some unique features. A few members of my committee said found my writing “pedagogic” and plan to share certain parts with their students. I hope that it is of some use to students or others interested in hydrology and remote sensing.

The PDF is formatted nicely and better for print. But the web version is nicer to read on a wider range of devices. It can also be resized or reformatted for easier reading. (When I’m reading long online documents, I like to use Firefox’s reader view.)

I used Latex and Overleaf to prepare the manuscript. I was hoping that it would be straightforward to convert to HTML. Unfortunately, it was not! I used the software pandoc to convert the document, but it required a lot of manual cleanup. Please let me know if you see any weird formatting or typos!

* In the US, it is customary to talk about a Master’s thesis, and a PhD dissertation. Under the British educational system, it’s the opposite. And in France, to obtain a doctoral degree, one writes une thèse.

I put together this list of journals with some info on their fees during my PhD research, and I’m sharing it here in case others may find it helpful. This information is likely to change fast, so make sure to verify.

Link to the Google Sheet.

During my PhD research, I became a convert to Latex for scientific writing, specifically using the website Overleaf.com. However, one feature that is missing is a good spelling and grammar checker. I like to use Microsoft Word for copyediting, as it has good built-in tools, and there are also plenty of addins available, like grammarly and ProWritingAid.

But first you need to get a clean export from Latex to Word, which is not straightforward.

Here is a method that works using Google Drive. It does not do a good job converting figures, tables, and equations, so I suppress those before continuing. It also helps to turn off hyphenation.

1. Add the following block to the preamble of the Latex document.

\usepackage[document]{ragged2e}
\usepackage[none]{hyphenat} % Turn off hyphenation
\usepackage{environ}
\RenewEnviron{figure}{} % Removes figures
\RenewEnviron{table}{} % Removes tables
\usepackage[nolists,nomarkers]{endfloat}
\renewcommand{\processdelayedfloats}{}
\pagestyle{empty} % Removes page numbers

2. Create a PDF document.

3. Upload the PDF to Google Drive.

4. In Drive, click the file to view it. At the top, click “Open with Google Docs.”

5. Choose File > Download > Microsoft Word (.docx)

Now you can download the Word file and copy edit at your leisure.

If you are interested in the Earth Sciences, you should consider attending the annual American Geophysical Union annual meeting. It is massive, with over 50,000 attendees, and thousands of scientific presentations, posters, lectures, and films. This can also make it feel overwhelming. Here are some highlights of the December 2023 conference in San Francisco from my point of view.

A former professor of mine, Rich Vogel from Tufts University, gave the Langbein Lecture. Being invited to give a named lectures is a big deal, equivalent to a lifetime achievement award. Even though he retired several years ago, he still publishes tons of papers and hasn’t lost any of his pep. It was a lot of fun.

I have really mixed feelings about poster sessions. On the one hand, it can be fun to get a quick view of a huge amount of research, and to meet researchers in person and talk to them about their work. On the other hand, it can be hard to learn much given the format. The Better Poster movement seems to have made very little impact. A good 95% of the posers are inscrutable walls of text.

I was honored to present my PhD research at the Annual Meeting of the American Geophysical Union in San Francisco, California, on December 15, 2023. My research is in the field of remote sensing and large scale hydrology. Here’s a copy of my slides if you’re interested:

Heberger_AGU_2023-12-15.pdf (2.5 MB)

For those interested in a deep dive, here is a link to the draft of my thesis (to be finalized after my defense in January). Here is a link to the final version of my PhD thesis:

• pdf
• html

Suppose you are interested in recreating my calculations or doing something related. The input datasets I used can be freely obtained via the sources listed in thesis Section 2, Datasets. The Appendix contains a much longer list of all the datasets I reviewed or considered using. I think it’s a good snapshot of remote sensing datasets describing the hydrologic cycle that were available circa 2023. The compiled data and Matlab scripts needed to perform the analysis can be downloaded from: https://doi.org/10.5281/zenodo.8101659.

I was delighted by the look of this watershed. Can you figure out where it is?

Just a few kilometers west of Bolivia’s capital, Sucre, lies the Maragua Crater, the site of a long-ago asteroid impact.

All of the top search results are about hiking out to visit it. There are 2,000 year old cave paintings, fossil dinosaur footprints, and incredible multicolor rock formations. Wow, new place to add to the bucket list!

Photo by Cody Hinchliff, flickr.