Paper No. 4
Presentation Time: 9:00 AM-6:00 PM
COUPLED SIMULATION OF SURFACE-SUBSURFACE HYDROLOGIC PROCESSES WITH THE OPEN-SOURCE FLOW AND REACTIVE TRANSPORT CODE PFLOTRAN
MILLS, Richard Tran1, BISHT, Gautam2, HAMMOND, Glenn E.3, LICHTNER, Peter4, KUMAR, Jitendra1, WATSON, David B.5 and BROOKS, Scott C.6, (1)Oak Ridge National Laboratory, 1 Bethel Valley Rd, MS 6301, P.O. Box 2008, Oak Ridge, TN 37831-6301, (2)Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., MS 50A4037, Berkeley, CA 94720, (3)Pacific Northwest National Laboratory, P.O. Box 999, MSIN K9-36, Richland, WA 99352, (4)Los Alamos National Laboratory, Los Alamos, NM 87545, (5)Oak Ridge National Laboratory, PO Box 2008, MS6038, Oak Ridge, TN 37831-6038, (6)Oak Ridge National Laboratory, P.O. Box 2008, MS 6038, Oak Ridge, TN 37831, rmills@ornl.gov
Advances in subsurface biogeochemical research and advanced computing capabilities have enabled the development of sophisticated, three-dimensional groundwater models employing multiple fluid phases and chemical components, coupled through a suite of biological and geochemical reactions at multiple scales. Such tools have enabled incredibly detailed simulations of contaminant fate and transport, but significant challenges remain in applying them to locations such as the Department of Energy Oak Ridge Reservation (ORR) in East Tennessee where strong interactions between surface and groundwater exist. For example, in Bear Creek Valley in Oak Ridge, losing reaches of Bear Creek may deliver nutrients (e.g., labile organic carbon) that are the limiting reactant for microbial consumption of nitrate contamination in the groundwater, and gaining reaches deliver contaminants to surface water. Besides studies of environmental contaminants, the ability to capture coupled surface/subsurface hydrologic interactions is important in eco-hydro-climatological studies, where accurately modeling soil moisture is critical for capturing vegetation dynamics and soil moisture-rainfall feedbacks.
To address such challenges, we have added a surface water component to PFLOTRAN. PFLOTRAN is an open-source (LGPL-licensed) code developed for simulation of multiscale, multiphase, multicomponent subsurface flow and reactive tranport problems on machines ranging from laptops to leadership-class supercomputers. We have coupled the Richards equation treatment of the subsurface domain with shallow overland flow equations by enforcing continuity of pressure and flux at the ground surface. The underlying solver framework allows significant flexibility in how the governing equations are solved, and we will compare different surface flow formulations and strategies for coupling the surface and subsurface flow domains. We will also present some preliminary coupled surface-subsurface simulations at the ORR, where explicit treatment of overland flow could further improve understanding of the influence of heavy precipitation events on contaminant transport.
