Saubhagya Rathore: Divining infrastructure impacts on watersheds

Growing up exploring the parklands of India where Rudyard Kipling drew inspiration for The Jungle Book left Saubhagya Rathore with a deep respect and curiosity about the natural world. He later turned that interest into a career in environmental science and engineering, and today he is working at the Department of Energy’s Oak Ridge National Laboratory to improve our understanding of watersheds for better climate prediction and resilience.

Water factored greatly in Rathore’s childhood, which he spent in remote areas of India where his father worked with the cavalry regiment of the nation’s army. Summer vacations were spent on his grandparents’ farm in the arid state of Rajasthan, where Rathore was fascinated by the pumping and irrigation systems that drew groundwater for crops and livestock.

His attraction to the ways of water continued as he completed an undergraduate thesis focused on seawater intrusion in coastal groundwater systems while earning a degree in civil engineering from the Indian Institute of Technology in Bombay.

Rathore then moved to the United States to attend the Georgia Institute of Technology, where he studied environmental fluid mechanics and water resources engineering with a focus on analytical and numerical modeling, earning master’s and doctoral degrees. His Georgia Tech research revolved around coastal groundwater dynamics, specifically how variations in soil and geology affect salinity intrusion, and how chemicals, nutrients and other components flow and interact in coastal ecosystems.

He joined ORNL as a postdoctoral researcher in 2020 after getting to know some of the hydrologists and modelers in the lab’s Watershed Systems Modeling group. “I was looking to expand my research area and was very interested in the type of work ORNL was doing in watersheds. The research took me out of my comfort zone and gave me an opportunity to expand my science horizons,” Rathore said. He was hired as staff about a year later.

WaDE-ing into a better understanding of watersheds

Rathore has been involved in several hydrology and solute transport modeling projects at the lab, most recently the newly launched, ORNL-led Watershed Dynamics and Evolution Science Focus Area, or WaDE.

WaDE scientists focus on the Tennessee River Basin, using a combination of experiments, observations and computer models to better understand how watersheds store, process, transport and discharge water and chemicals across diverse environmental conditions and land cover patterns. Rathore’s work focuses on interdisciplinary modeling — developing a configurable virtual watershed incorporating hydrology, water temperature and stream metabolism. That virtual laboratory will give scientists the ability to conduct numerical experiments.

“A watershed is a bit like a living organism that breathes, exchanges gases with the atmosphere, digests nutrients and relies on water. Climate change and human-induced stressors can make watersheds ‘sick’ and disrupt their normal functioning,” Rathore said. “Our focus is on stream metabolism as an indicator of watershed function, how it will respond under different hydrological regimes and land cover patterns. There’s a human element too, in terms of urbanized landscapes and the introduction of impervious surfaces.”

He devised a modeling strategy called stream-aligned meshing that improves the representation of stream channels and artificial drainage infrastructure in watershed simulations. This capability has its genesis in a hydrology and nutrient export project called COMPASS-Great Lakes Modeling that is focused on agricultural watersheds in the western Lake Erie Basin to better understand algal blooms driven by fertilizer runoff.

Infrastructure like ditches, tile drains, culverts and pumps can have a significant impact on how nitrates and phosphates move from croplands to the lake, Rathore said. Developing and incorporating a fine-tuned representation of engineered drainage features resulted in an improved simulation that reflected actual field hydrology and observations and alleviated extra model calibration.

He also developed workflows to evaluate and recommend designs for stream tracer tests as well as to interpret resulting observational data that informs simulations.

Rathore will build on these capabilities to better reflect drainage infrastructure for stormwater management in one of DOE’s Urban Integrated Field Laboratories (IFL) in Southeast Texas, where ORNL will model a large watershed encompassing Beaumont and Port Arthur. The area includes many communities at risk from coastal storms as well as the influence of historical oil and gas production, refining and distribution. The project will analyze and predict potential climate events and mitigation strategies for consideration by decision-makers in the region.

Modeling manmade, natural influences on vulnerable communities

“The IFL is a fascinating project with potential real-world applications,” Rathore said. “It’s the first time we will integrate a human system and a natural system. The hydrology will be challenging. It’s a coastal area that is heavily managed and part of it sits below sea level, so the water does not always drain by gravity. It’s influenced by big levees, drainage canals and pumping systems, but then you also have to account for what’s happening upstream in the basin.”

The area also has great potential for compound flooding, Rathore said. In that scenario, multiple events may happen simultaneously to worsen flooding, such as an overflowing river, a drainage system saturated by excess precipitation, and a storm surge from the Gulf of Mexico.

The field lab will be one of the largest modeling domains Rathore and his colleagues have taken on, representing about 12,000 square miles. Connecting inland and coastal ecosystems will likely occupy his research in the years ahead, Rathore said, as some 40% of the world’s population lives within some 60  miles of a coastline.

“When you have freshwater and seawater interacting, you get density-driven flow dynamics, salinity changes and mixing that drives some very cool biogeochemistry,” Rathore said. “What happens downstream along the coast is also heavily influenced by big cities and agricultural activities upstream. I’m interested in figuring out how to connect these inland watershed processes that control water quantity and quality and then upon reaching the coast interact with salinity variations and dynamics like tides. There’s a lot to learn.”

That learning is also due to  interactions with scientists from a variety of disciplines under one roof at ORNL, Rathore said. “We have specialists including hydrologists, ecologists and molecular biologists, and biogeochemists. At the meetings for some of our big, multidisciplinary projects like WaDE, I get to hear their updates and learn a lot, even though I’m not in their field. My colleagues are generous with their time in answering my questions. Their commitment and support is so essential to early career scientists, as is access to the high-performance computing and other capabilities available at the lab.”

Stepping out of the comfort zone

Away from the office, Rathore is taking a smaller-scale approach to the natural world via birding and photography — pastimes developed during the pandemic that have stuck with him. His favorite bird is the mockingbird, which Rathore says he admires for its assertive nature, wide-ranging vocalizations and melodious singing. He also appreciates the great outdoors of East Tennessee. “I really like the physical setting of the lab,” Rathore said, “the four seasons and the flora and fauna and getting out to hike, kayak and camp.” He has also recently expanded his interest in Indian classical music and has decided to try playing a traditional flute himself.

His advice for young scientists? “Don’t be afraid to branch out, to step out of your comfort zone into a new science area that may seem intimidating but where you think your skillset can apply. You’ll be supported and have the opportunity to talk to people from different science domains. Even a steep learning curve can be fun.”

Rathore’s research is supported by the DOE Office of Science Biological and Environmental Research Program.

UT-Battelle manages ORNL for DOE’s Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, visit https://energy.gov/science. — Stephanie Seay