M. Hong, B. P. Mohanty
Although the role of soil moisture (SM) in controlling evapotranspiration (ET) has been studied over the past decades, the lack of a proper depiction of groundwater-induced drainage’s effects on the SM-ET cycle has been the primary constraint in Land Surface Models (LSMs). This shortcoming limited the ability of the LSMs to accurately capture the coupled terrestrial water-energy cycles based on hydraulic continuity among different surface and subsurface hydrologic domains. This study aims to present a novel LSM that describes soil drainage dynamics resulting from a two-way hydraulic continuum among the vadose zone, groundwater, and river. This study applied the BE3S scheme for the catchment-scale stream-hillslope continuum (Hong et al., 2020) to the National Water Model (NWM) hydrologic framework. We compared the NWM-BE3S against the original NWM across three major river basins in Texas (i.e., Trinity, Brazos, and Colorado). We showed the prominent role of soil properties in modulating the impact of groundwater-induced drainage on SM availability. This is because of distinct soil water retention curves, which clarify how SM sensitivity to soil bottom drainage (SBD) is shaped by soil texture. Also, the varying degrees of improvement in the estimates of SM and ET per the streamflow recession characteristics reveal that the recession parameters a and b , accounting for groundwater diffusivity, can predict the groundwater’s effects on the SM-ET coupled cycle. Overall, our results underscore the importance of soil properties in representing different dynamics of groundwater-induced SBD and its impact on terrestrial water and energy balance in LSMs.