Advancing Stream Metabolism Modeling Through the IDEAS-Watersheds and Watershed Dynamics and Evolution Science Focus Area Partnership
Authors
Scott L. Painter1* ([email protected]), Ethan T. Coon1, Jesus D. Gomez-Velez1, Phong Le1, Saubhagya Rathore1, David Moulton2
Institutions
1Oak Ridge National Laboratory, Oak Ridge, TN; 2Los Alamos National Laboratory, Los Alamos, NM
URLs
Abstract
The modeling partnership between the Interoperable Design of Extreme-Scale Application Software (IDEAS)-Watersheds project and the Watershed Dynamics and Evolution (WaDE) Science Focus Area (SFA) is developing a virtual watershed capability focused on hydrology, water temperature, and stream metabolism. This capability is critical for WaDE’s efforts to gain a transferable understanding of hydro-biogeochemical function of watersheds with heterogeneous land covers. The IDEAS-WaDE partnership is using the Advanced Terrestrial Simulator (ATS) code for flow and transport coupled to PFLOTRAN for biogeochemical reactions. The work uses ATS’s unique multiscale configuration for stream corridor reactive transport.
Toward the goal of improving inferences about stream metabolism from time-resolved oxygen measurements, the team configured the multiscale reactive transport capability in ATS to represent key processes controlling stream oxygen dynamics, including gross primary production in the stream channel, ecosystem respiration in the hyporheic zone, and oxygen exchange with the atmosphere. Researchers are now using that capability to assess limitations of the widely used single-station method for estimating metabolism from time-resolved oxygen measurements.
The partnership is also developing high-resolution watershed models of East Fork Poplar Creek in Tennessee to support the three science themes in the WaDE SFA. To facilitate that effort, several enhancements have been made to ATS and the workflows that support it. An improved representation of sunlight incident on streams, which is an important control on stream metabolism and temperature, was implemented by extending Watershed Workflow to represent stream shading at high resolution, accounting for stream geometry (width and bank height) and vegetation height. New algorithms to produce high-quality stream-aligned computational meshes were also implemented in Watershed Workflow. Related to that, the team developed a new capability in ATS to perform transport simulations on the stream-associated subdomain of a larger watershed flow model, which will enable a range of numerical experiments to help understand the relationship between stream metabolism and the surrounding watershed.