Representing Bidirectional Hydraulic Continuum Between the Stream and Hillslope in the National Water Model for Improved Streamflow Prediction

Although hydraulic groundwater (GW) theory has been recognized as a promising tool for understanding the role of aquifer(s) in surface-subsurface hydrologic cycle, integrated modeling community still lacks proper structure to apply well-studied large-scale predictions. This study aims present novel that enables Boussinesq equation-based depiction bidirectional stream-hillslope processes applying GW model configurations. We BE3S's (Hong et al., 2020, https://doi.org/10.1029/2020wr027571) representation scheme catchment-scale continuum into National Water Model (NWM) and applied modified NWM (i.e., NWM-BE3S) three major basins Texas Trinity, Brazos, Colorado River basins). Since currently relies on single reservoir baseflow simulation, we used aquifer an alternative subsurface hydrology routine evaluated its predictive skill efficacy. identified implemented NWM-BE3S yielded noticeable improvements predicting streamflow aquifers exhibited higher nonlinearities observed recessions. The varying degree predictions per recession demonstrated not only (a) algorithmic enhancement (physics) but also (b) applicability theory-based two-way continuum. diagnosed each stream's state based exchanges dominant river infiltration or baseflow) were represented spatially NWM-BE3S.