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Global Rivers Group
@Virginia Tech

We use satellites, models, and fieldwork to study Earth's freshwater

Home: Overview

We're an academic research group in the Department of Geosciences at Virginia Tech. We are recruiting students and postdocs who are interested in using emerging technology to solve problems involving freshwater resources. 

What we do

We study inland waters using satellite data, fieldwork, and computer models. We seek to understand how climate change and land use are altering the global water cycle, in particular river and lake hydrology. With rapid advancements in sensor technology, computing power, and model sophistication, it is an exciting time to be studying freshwater at the global scale. 


Why we do it

Water is widely considered to be the world’s most vital natural resource, yet freshwater systems are being rapidly degraded by human activities. Our work is motivated by a desire to promote the conservation, management, and understanding of Earth's surface water resources. 

Home: Services


Updated Oct 20, 2023

Oct 12, 2023—Three Virginia Tech undergraduate students join the Global Rivers Group as Undergraduate Research Assistants. Welcome, Tori Cooper, Jordan Lavey and Shaurya Prakash!

Sep 17, 2023—Katie and Ryan travel to Toulouse, France to attend the first SWOT Science Team Meeting since the launch of the SWOT satellite in December 2022: 

Sep 13, 2023—Baby boy Alden Allen joins the Global Rivers Group family. 

Aug 29, 2023—The GRG hosts Dr. Fangfang Yao as a visiting scholar for 2 days in Blacksburg. Fangfang is a postdoctoral researcher at University of Virginia and studies global remote sensing of hydrology, particularly lakes  

Aug 26, 2023—The GRG participates in the "Fall into the New" river cleanup event near Blacksburg. We spent the morning traversing the New River in 4 canoes, collecting items including cans, golf balls, and a tire! 

Aug 14, 2023—Luisana Rodriguez Sequeira joins the Global Rivers Group as an incoming Masters student in Geosciences. Luisana graduated cum laude from the University of California at Santa Cruz in 2022 as a double major in Earth Sciences and Mathematics. She will be working on a project investigating relationships between water quality and plastic pollution in freshwater bodies. Welcome aboard, Luisana! 

Aug 10, 2023—Dr. Katie McQuillan joins the Global Rivers Group as a Virginia Tech Presidential Postdoctoral Fellow. Katie received her PhD from NC State University in the Geospatial Analytics Center working with Dr. Katie Martin. She will be working on using the SWOT satellite's measurements to estimate evaporation rates in reservoirs. Welcome to the GRG, Katie! 


Aug 8, 2023—Paper published in Earth System Science Data entitled "Lake-TopoCat: a global lake drainage topology and catchment database", led by Md Safat Sikder and Jida Wang at Kansas State University. This paper harmonizes global lake and river hydrography data together to create novel and freely available lake topography dataset:

Aug 2, 2023—George, Ryan, Emily, Molly, Carter, Yohtaro and Katie all submit their abstracts to the 2023 AGU Fall Meeting in San Francisco, CA. See you there! 


July 31, 2023—Hana Thurman joins the lab as an incoming M.S. student in Geosciences. Hana graduated summa cum laude from the University of Virginia with a B.S. in Environmental Sciences and Engineering in 2019. She will be using new radar data from the recently launched NASA/CNES SWOT satellite to study inland waters. Welcome to Blacksburg, Hana! 

July 20, 2023—George, Molly, Emily and Yohtaro lead 46 11th and 12th graders to Kentland Farm, VA to conduct field activities along Toms Creek and the New River as part of the VT College of Science Physical Science Summer Camp Program. Campers also contributed to GRG research by generating training and validation data for machine learning algorithms, designed to classify streams from from high-resolution remote sensing imagery. 

July 13, 2023—Paper published in River Research and Applications entitled, "When does a stream become a river?", in which we propose that "streams" are flowing water bodies in channels narrower than 15 m and "rivers" are in channels 15 m or wider.

July 3, 2023—Carter and George travel to Nederland, Colorado to do fieldwork in beautiful Indian Peaks Wilderness. Carter will spend 4-6 weeks surveying headwater streams with GRG team members as part of our NSF funded project on constraining scaling principles of the river-atmosphere interface. 

June 20, 2023—George presents findings from Riggs et al (2023) and Riggs et al (2023) at the SWOT Discharge Algorithms Working Group meeting. 

June 14, 2023—George travels to Bristol, UK to attend the RIOS workshop, which had the goal of establishing a global river observation network with an emphasis on carbon dynamics.  

May 26, 2023—Paper published in Nature Communications entitled "Diminishing Storage Returns of Reservoir Construction" led by Yao Li at Texas A&M. This study shows that newly built reservoirs are not filling up with as much water as older reservoirs. 

May 26, 2023—Paper published in Environmental Research Letters entitled "Extending global river gauge records using satellite observations" led by Ryan Riggs. This study assembles the largest known compilation of public stream gauge data (N=45,837 gauges) and fills in the gaps in gauge records using satellite observations. Another impressive publication from Ryan!

May 25, 2023—Yohtaro Kobayashi joins the Global Rivers Group as a summer research intern. Yohtaro is a PhD student in the Department of Biological Systems Engineering at Virginia Tech focusing on characterizing riparian vegetation using lidar remote sensing. Welcome, Yohtaro! 

May 15, 2023—Paper published in Geophysical Research Letters entitled "Turning lakes into river gauges using the LakeFlow algorithm" led by Ryan Riggs. This study demonstrates that SWOT data can be used to estimate lake inflows and outflows, important information for water resource management. Great work, Ryan!

May 3, 2023—George gives a flash talk entitled, "Improving Ecological Forecasting with Context-aware Sensor Webs" at the Frontiers in Ecological Forecasting meeting, Blacksburg, VA.

May 1, 2023—GRG future postdoc Katie McQuillan selected for the VT Presidential Postdoctoral Fellowship to work on estimating reservoir evaporation loss using novel SWOT satellite radar observations for water resources management. Congratulations, Katie, we are looking forward to your arrival in August! 


April 25, 2023—Sister review papers published in Global Biogeochemical Cycles entitled "Inland Water Greenhouse Gas Budgets for RECCAP2: 1. State-of-the-Art of Global Scale Assessments" and "Inland water greenhouse gas budgets for RECCAP2: 2. Regionalization and homogenization of estimates". This long-running project was led by Dr. Ronny Lauerwald at the University Paris-Saclay. We produced a large-group consensus evaluation of the sources and sinks of greenhouse gasses emissions from non-vegetated inland water bodies (rivers, streams, lakes, reservoirs, and ponds). 
Part 1:; Part 2: 

April 14, 2023—Dr. Jessica Fayne from Michigan Earth and Environmental Sciences visits Virginia Tech to meet with the GRG and give a Geosciences Departmental Seminar entitled, "Advances in Active Remote Sensing for Hydrologic and Climate Change Monitoring". 


April 7, 2023—GRG MS student Carter Boyd is awarded a Virginia Space Grant Consortium Fellowship to conduct research this summer. Congratulations, Carter! 

April 7, 2023—Paper published in Water Resources Research entitled, "A Framework for Estimating Global River Discharge From the Surface Water and Ocean Topography Satellite Mission" led by Michael Durand at The Ohio State University. This paper introduces the world to how the SWOT satellite's observations will be used to estimate river discharge globally: 


Mar 22, 2023—Paper published in Nature Communications entitled, "Satellites reveal hotspots of global river extent change" led by Qianhan Wu, Linghong Ke and Chunqiao Song at the Chinese Academy of Sciences, the University of Hong Kong, and Hohai University. This paper quantifies global changes in river extent and attributes observed changes to dam construction, shifting channel geomorphology, and  hydrology:

Feb 23, 2023—Molly Stroud presents her research at the VT Geosciences Student Research Symposium (GSRS). Her talk is entitled, "Assessing optical remote sensing and gauge products to study global sediment transport dynamics in rivers".  

Feb 20, 2023—UNC Professor and NASA SWOT Hydrology Lead, Dr. Tamlin Pavelsky meets with the GRG on Monday as part of a day-long visit to Virginia Tech. Great to see you, Tamlin! 

Feb 8, 2023—GRG PhD student, Emily Ellis, wins the Virginia Tech Nutshell Games (1 of 5 winners). Emily's flash talk on measuring river water temperature from space wowed the audience and earned her a sizable monetary award! Congratulations, Emily! 

Jan 30, 2023—George presents the research of the GRG at the Virginia Tech Interdisciplinary Graduate Education Program (IGEP) in Remote Sensing Seminar Series. George has joined the IGEP this spring as a faculty member:

Dec 16, 2022—The GRG team got up early at AGU to watch the NASA/CNES Surface Water Ocean Topography (SWOT) satellite launch from Vandenberg Air Force Base in the Central Coast of California. The SWOT satellite is the first satellite with a primary focus on inland waters. George has been working on SWOT for over 10 years and several other GRG members will be working with SWOT data in the coming years. 

Dec 14, 2022—George publishes a commentary in Nature News & Views entitled, "Cause of the 2020 surge in atmospheric methane clarified", which is a critique and summary of Peng et al.'s Nature article, "Wetland emission and atmospheric sink changes explain methane growth in 2020". [news article in Wired]. 

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