George H. Allen

27 things we wish we’d known when we started our PhDs Nature - Nature’s survey of PhD candidates reveals hard-won wisdom on choosing supervisors, managing mental health and surviving academic culture.

27 things we wish we’d known when we started our PhDs

Nature’s survey of PhD candidates reveals hard-won wisdom on choosing supervisors, managing mental health and surviving academic culture.

We’re on Capitol Hill with 225 Earth & space scientists — including @aas.org and @planetarysociety.bsky.social — urging Congress to reopen the government and protect NASA science. 🚀🌍

Join us: buff.ly/a3YuGgY

#ScienceIsEssential #AGU

NASA-ISRO Satellite Sends First Radar Images of Earth’s Surface Preliminary images from the most powerful Earth radar satellite ever launched offer a tantalizing glimpse of the science the mission will be able to deliver.

First NISAR L-band images released! They look great! www.jpl.nasa.gov/news/nasa-is...

Looking for a postdoc, and interested in river-coastal linkages, #remote sensing, and time series analysis? Come work with us @natureatcal.bsky.social on an exciting project led by @rachelspatial.bsky.social! CC @sfs-src.bsky.social @aslo.org @cerfscience.bsky.social ‪‪@caseagrant.bsky.social‬

Volcanic island somewhere?

Ad for 2 graduate student positions and and 1 lab and field assistant position at UCSB. More info go to audreythellman.weebly.com

Hello freshwater friends! I’m starting a lab(!!) and recruiting 2 students to start Fall 2026 and a lab/field assistant to start this Fall 2025! Research topic is broad: rivers 🛶, ice/snow ❄️, nutrients 🍂, algae 🌱see below for more info

Please pass this along to any interested folks :)

Correct! SWOT has a 21-day repeat orbit but most places are observed more frequently because of swath overlap

SWOT Captures Hydrologic Waves Traveling Down Rivers Surface Water and Ocean Topography data show downstream changes in river height during a flow wave hydrologic event By removing the river's long profile, flow wave events are visualized as hydrog...

Absolutely - we are developing a method to automatically identify and track these flood waves with SWOT. Stay tuned! In the meantime, here's the first paper on the topic if you're interested: agupubs.onlinelibrary.wiley.com/doi/full/10....

"Seen" meaning retrieved water surface elevation data over rivers while a flood wave is propagating down a river. Here are three examples of flood waves/flow waves traveling down rivers, including one in the Colorado River, TX - near the Guadalupe River:

Flood waves like those that devastated Texas last week can be seen by the NASA #SWOT satellite. Another reason to support #NASA Earth Science

AGU H3S invites you to submit an abstract to our session at #AGU25 Thinking Outside the Box Plot:
Communicating Science Beyond the Paper! The session explores creative ways to communicate research. Conveners: @adischner.bsky.social
@acarneiromar.bsky.social
@gescilam.bsky.social
Cee Nell
Emily Ellis

AGU H3S invites you to contribute to our session at #AGU25 Hydrology Student, Postdoc, and
Early Career Flash Talks! This session highlights
research performed by fellow Early Career Researchers within the field of Hydrology. Conveners: Matthew Preisser and Kathryn Moore

Hang in there and give yourself a break!

Donut chart shows the relative contributions of each stream order to basin total river and stream surface area (RSSA)

This has implications for how we calculate river and stream surface area (RSSA) at the global scale

Stacked histograms of river widths colored by stream order in the Mississippi basin

Scaling these widths across the Mississippi basin, we find an emergent fractal distribution of river widths (black line)

River widths of each stream order exhibit predictable log-normal distributions.

🚨New paper🚨 shows a remarkably clean relationship between river width and stream order across the US

𝑇ℎ𝑒 𝑊𝑖𝑑𝑡ℎ𝑠 𝑜𝑓 𝑅𝑖𝑣𝑒𝑟𝑠 𝑎𝑛𝑑 𝑆𝑡𝑟𝑒𝑎𝑚𝑠 𝐴𝑐𝑟𝑜𝑠𝑠 𝑆𝑝𝑎𝑡𝑖𝑎𝑙 𝑆𝑐𝑎𝑙𝑒𝑠... 🔗 doi.org/10.1029/2025...

#hydrology #geomorphology #rivers #RemoteSensing

River widths of each stream order exhibit predictable log-normal distributions. Outer plots show distribution of river width measurements by stream order with fitted log-normal functions. Location parameter (μ) and scale parameter (σ) of log-normal fits are shown on each plot. Inner scatterplots show linear relationship between stream order (ω) and log-normal location parameter (upper scatterplot) and scale parameter (lower scatterplot).

Using multi-scale remote sensing and fieldwork, we found that river widths of each stream order exhibit a very predictable log-normal distribution:

Satellite measures river flow waves for the first time The researchers assessed waves on the Colorado River in Texas, the Ocmulgee River in Georgia and the Yellowstone River in Montana.

The Washington Post also covered our paper! Here's the article with a soft paywall: wapo.st/43UuquB

Hana (grad student in my group) will be doing a research internship at JPL this summer. Here she is on her first day on the job. Good luck, Hana!! 🚀🚀🚀

NASA-French Satellite Spots Large-Scale River Waves for First Time The SWOT mission captured the flood waves, which stretched from 47 to 166 miles long, as they traveled down rivers in Montana, Texas, and Georgia.

JPL and NASA news article covering the study

NASA-French Satellite Spots Large-Scale River Waves for First Time - NASA In a first, researchers from NASA and Virginia Tech used satellite data to measure the height and speed of potentially hazardous flood waves traveling down

NASA news article on our recent study on the #SWOT satellite's ability to capture hydrologic flow waves in rivers

Link to paper: doi.org/10.1029/2024GL113875

Map of the GRIT global river network. Source: Wortmann et al. (2025), Water Resources Research.

🌐 Introducing GRIT: the First Global Bifurcating River Network 🏞
developed by Michel Wortmann as part of the NERC Large Grant EvoFLOOD, in the Hydro-Climate Extremes group @oxfordgeography.bsky.social

Two of the observed flow waves were caused by large rainfall events. The third flow wave was likely caused by an ice jam failure. The morphology of the flood waves appears to be dependent on the cause

Three example flow waves shown with USGS gauge height data, reconstructed Surface Water and Ocean Topography (SWOT) water surface elevation (WSE) data, and spatial hydrographs (i.e., de-trended SWOT WSE measurements). (a) Colorado River, Texas, (b) Ocmulgee River, Georgia, and (c) Yellowstone River, Montana and North Dakota.

Three example flow waves on three rivers:

Example of how the Surface Water and Ocean Topography (SWOT) satellite's water surface elevation measurements can be used to record flow wave propagation over space and generate a “spatial hydrograph.”

Hydrologists! Ever heard of a Spatial Hydrograph? Our new paper in @agu.org GRL shows that the SWOT satellite can capture spatial flow waves propagating down rivers—something previously only only observable at river gauges: doi.org/10.1029/2024...

#SWOT #hydrology #RemoteSensing #EarthObservation

Delighted to see our @NERCscience @EvoFlood project research on changing flood hazard and risk profiled by @theAGU 💜 @lborouniversity

eos.org/research-spo...

Few support punitive funding cuts to colleges and universities - AP-NORC Most of the public believes that colleges and universities make significant contributions to scientific and technological advancement and think their federal research funding should be maintained.

The American public is broadly supportive of maintaining federal science and medical research funding, and against punishing universities by taking their funding away, according to a new poll:

Scientific figuring with three panels. Left panel shows a map of the Everglades in Florida overlaid with data from the SWOT mission. It shows very detailed water level data throughout the everglades. The second panel, in the upper right, is a scatterplot showing in situ gauge water level against SWOT water level. It shows a mean absolute error of 6.7 cm, a correlation coefficient of 0.996, and a mean bias of 6.8 cm. The third figure, a scatterplot in the lower right, shows that by averaging 30 or more SWOT pixels, high accuracy is possible.

Are water levels in wetlands important to you? @kica22.bsky.social's new paper in GRL shows that the SWOT satellite can measure water surface elevations in the Everglades with a mean absolute error of 6.7 cm. Check it out! agupubs.onlinelibrary.wiley.com/doi/10.1029/...

Congrats to Luisana Rodriguez Sequeira, who successfully defended her Master's Thesis on satellite #remotesensing of #microplastics in rivers! I had the pleasure of co-advising with Dr. Austin Gray @austindoug13.bsky.social. She presented to a standing-room-only crowd—well done, Luisana!

Map of global lake distribution, colored by the number of SWOT overpasses per 21 day cycle. There are many lakes with a high number of SWOT overpasses at high northern latitudes, but there are also tens of thousands to more than a million lakes on every continent. Lakes are graphed by latitude and longitude on the edges of the figure.

Do you work on lakes globally? Check out what is, to my mind, the most complete global database of lakes (~6M) and associated attributes, newly published in WRR. Also the basis for SWOT lake data. agupubs.onlinelibrary.wiley.com/doi/full/10....