Understanding and quantifying the roles of river corridors in watershed function and dynamics
- Principal investigators: Tim Scheibe, Xingyuan Chen, Emily Graham, and James Stegen
- Annual reports: 2021 | 2019 | 2018 | 2016 | 2015 (Note: Reports are not issued during review years.)
Exchange of water between rivers and the surrounding subsurface environment is a vital aspect of watershed function. These hydrologic exchange flows (HEFs) stimulate biogeochemical activity in the subsurface adjacent to the river channel through provision of nutrients, mixing of dissolved reactants, and exposure to microbes. They also modulate water temperatures and thus play a key role in water quality, nutrient dynamics, and energy and material fluxes.
There is strong evidence that river corridor hydrobiogeochemical processes are highly variable among different stream orders and climatic, ecological, and geographical settings; these processes are also hypothesized to be highly sensitive to various environmental and anthropogenic disturbances including floods, drought, wildfire, land-use changes, and water use and management. A science focus area (SFA) program led by Pacific Northwest National Laboratory (PNNL) aims to predict river corridor and watershed system responses to disturbances at scales relevant to national water challenges. The SFA is supported by the Department of Energy’s (DOE) Office of Biological and Environmental Research (BER) as part of BER’s Subsurface Biogeochemical Research (SBR) program.
The SFA is performing studies over various settings and scales within the Columbia River Basin (CRB) in the Pacific Northwest and in other major river basins around the contiguous United States, the latter through collaborations with other SBR SFAs. Research activities within the SFA focus on understanding processes in the river corridor—which includes the surface water channel and other functionally connected features such as the hyporheic zone, near-shore groundwater aquifer, and riparian zone—and quantifying their cumulative effects at watershed and basin scales.
Key Scientific Questions
PNNL SBR SFA researchers are developing mechanistic understanding of coupled hydrologic and biogeochemical processes across a wide range of river corridor and watershed settings and translating that understanding into multiscale numerical models. Key questions include:
- How do HEFs, organic matter chemistry, microbial activity, and watershed disturbances interactively influence river corridor hydrobiogeochemical function and dynamics from reaction to basin scales?
- How can mechanisms that govern river corridor hydrobiogeochemistry be efficiently and sufficiently represented in integrated land surface models at scales relevant to regional and national water challenges?
Translating Process Understanding Across Scales
SFA research includes fundamental process identification and quantification, integration of modeling and experimentation at multiple spatial scales, and implementation of a novel and computationally efficient multiscale modeling framework. This framework incorporates new process understanding into detailed mechanistic models. These models, combined with spatially distributed observational data, are used to formulate simplified or surrogate models applicable at system scales. Accordingly, research activities are organized and coordinated through an iterative learning cycle of integrated models and experiments.
Watershed function can be disturbed by various changes in conditions, including long-term transitions such as land-use changes or climatic variations as well as episodic events such as wildfires, floods, droughts, or pest infestations. In the CRB, wildfires are becoming increasingly prevalent and intense. For example, the 2014 Carlton Complex fire burned over 250,000 acres causing nearly $100 million in damages and became the largest single wildfire in Washington state history. In general, widespread increases in fire activity in the western United States over the past 50 years have been well documented. Wildfires significantly alter the character of organic matter and amounts of nutrients delivered to river corridors; they also affect hydrologic responses to precipitation events leading to increased runoff and greater flood risk. The SFA is evaluating the impacts of these disturbances on river corridor hydrobiogeochemistry and their cumulative effects on watershed function and dynamics at basin scales.
Open Watershed Science by Design
Fully understanding the functioning and dynamics of large and complex watersheds like the Columbia River Basin is intractable for individual researchers or even a single research team. Through intentional application of open science principles [e.g., findable, accessible, interoperable, and reusable (FAIR) data and integrated, coordinated, open, and networked (ICON) science], the SFA is enabling and partnering with a community of researchers that can more effectively solve large scientific challenges. For example, the Worldwide Hydrobiogeochemical Observation Network for Dynamic River Systems (WHONDRS) is stewarded and coordinated by SFA scientists. WHONDRS is a global consortium of researchers that aims to understand how high-frequency river stage variations influence river corridor function across a wide range of geographical settings. The consortium is developing new instrumentation and protocols for sample collection that will extend new process understanding to river corridor and watershed systems worldwide. WHONDRS and similar collaborations are enabling the scientific community to do together what would be impossible to accomplish alone.
Map of WHONDRS Sample Collection Sites in Dynamic River Systems Worldwide
Mapping Underwater Chemical Activities
Researchers at PNNL re-engineered a technique known as electrical resistivity tomography to study waterway interactions. (2020)
Crowdsource Science for Disturbance Ecology. (2020)
WHONDRS Research Consortium
Overview of the aims and goals of the WHONDRS research consortium. (2019)
WHONDRS Surface Water Sampling Protocol
Demonstrates protocol for a global-scale community-enabled study of surface water metabolomics led by WHONDRS (2019)
WHONDRS Diel Cycling Study Protocol
Demonstrates protocol for 48-hour Diel Cycling Study for WHONDRS (2018)
New Hydrobiogeochemistry Sensor in River Corridors
New sensor technology for estimating the mass flux of water through subsurface sediments in dynamic systems. (2018)
Multidisciplinary Instrumentation and Modeling
Details of a Columbia River experiment to help predict hydrobiogeochemical function under future environmental conditions. (2017)
Real-time 4D Subsurface Imaging
2016 R&D 100 Award-winning imaging technology that enables researchers—for the first time—to take four-dimensional views of the subsurface. (2016)