Using Ensemble Data Assimilation to Estimate Transient Hydrologic Exchange Flow Under Highly Dynamic Flow Conditions Academic Article uri icon

abstract

  • AbstractQuantifying dynamic hydrologic exchange flows (HEFs) within river corridors that experience highfrequency flow variations caused by dam regulations is important for understanding the biogeochemical processes at the river water and groundwater interfaces. Heat has been widely used as a tracer to infer steadystate flow velocities through analytical solutions of heat transport defined by the diurnal temperature signals. Under subdaily dynamic flow conditions, however, such analytical solutions are not applicable due to the violation of their fundamental assumptions. In this study, we developed a data assimilationbased approach to estimate the subdaily flux under highly dynamic flow conditions using multidepth temperature observations at a 5min resolution. If the hydraulic gradient is measured, Darcy's law was used to calculate the flux with permeability estimated from temperature responses below the riverbed. Otherwise, flux was estimated directly by assimilating multidepth temperature data at 1 or 2hr time intervals assuming onedimensional flow and heat transport governing equation. By comparing estimated fluxes with modelgenerated synthetic truth, we demonstrated that both schemes have robust performance in estimating fluxes under highly dynamic flow conditions. This data assimilationbased flux estimation method was able to capture the vertical subdaily fluxes using multidepth highresolution temperature data alone, even in the presence of multidimensional flow. This approach has been successfully applied to real field temperature data collected at the Hanford site, which experiences highly dynamic HEFs. Our study shows the promise of adopting distributed 1D temperature monitoring to capture spatial and temporal exchange dynamics in river corridors at a watershed scale or beyond.

published proceedings

  • WATER RESOURCES RESEARCH

author list (cited authors)

  • Chen, K., Chen, X., Song, X., Briggs, M. A., Jiang, P., Shuai, P., ... Zachara, J. M.

citation count

  • 5

complete list of authors

  • Chen, Kewei||Chen, Xingyuan||Song, Xuehang||Briggs, Martin A||Jiang, Peishi||Shuai, Pin||Hammond, Glenn||Zhan, Hongbin||Zachara, John M

publication date

  • May 2022