Development of Inter-Grid Cell Lateral Unsaturated and Saturated Flow Model in the E3SM Land Model (v2.0)

Abstract

Abstract. The lateral transport of water in the subsurface is important in modulating the terrestrial water-energy distribution. Although few land surface models have recently included lateral saturated flow within and across grid cells, it is not a default configuration in the Climate Model Intercomparison Project version 6 experiments. In this work, we developed the lateral subsurface flow model with both unsaturated and saturated zones in the Energy Exascale Earth System Model (E3SM) Land Model version 2 (ELMv2.0). The new model, called ELMlat, was benchmarked against PFLOTRAN, a 3D subsurface flow and transport model, for three idealized hillslopes that included a convergent hillslope, divergent hillslope, and titled V-shape hillslope with variably saturated initial conditions. ELMlat showed comparable performance with PFLOTRAN in terms of capturing the dynamics of soil moisture and groundwater table for the three benchmark hillslope problems. Specifically, the mean absolute errors (MAE) of the soil moisture in the top five layers between ELMlat and PFLOTRAN were within 1 % ± 4 % and the MAE of water table depth were within ± 0.3 m. Next ELM_lat was applied to the Little Washita experimental watershed to assess its prediction of groundwater table, soil moisture, and soil temperature. The spatial pattern of simulated groundwater table depth agreed well with the global groundwater table benchmark dataset generated from a global model calibrated with long term observations. The effects of lateral groundwater flow on the energy flux partitioning were more prominent in low land areas with shallower groundwater tables, which the difference of simulated annual surface soil temperature could reach 0.4–0.5 °C at low land areas between ELMv2.0 and ELMlat. Incorporating lateral subsurface flow in ELM improves the representation of the subsurface hydrology which will provide a good basis for future large-scale applications.

Global 1km Land Surface Parameters for Kilometer-Scale Earth System Modeling

“…Krakauer et al (2014) have highlighted the significance of between-cell groundwater flow, which becomes comparable in magnitude to recharge at grid spacings smaller than 10 km. Advancements have been made in ESMs to address hillslope-scale processes, including the representation of intrahillslope lateral subsurface flow within grid cells in CLM5 (Swenson et al, 2019), the development of explicit lateral flow processes between grid cells (Qiu et al, 2023), and the incorporation of topographic radiation effects within and between grid cells (Hao et al, 2021). Another notable example is the integrated hydrology-land surface model ParFlow-CLM, which incorporates three-dimensional groundwater flow, two-dimensional overland flow, and land surface exchange processes (Maxwell, 2013).…”

“…The 1 km land surface parameters are publicly available at https://doi.org/10.25584/PNNLDH/1986308 (Li et al, 2023).…”

Impacts of Topography‐Driven Water Redistribution on Terrestrial Water Storage Change in California Through Ecosystem Responses

“…To reduce the computational burden, quasi-3D schemes were developed to represent intercell (2-D) lateral saturated subsurface flow and vertical soil water flow separately (Fan et al, 2007;Felfelani et al, 2021;Shen et al, 2013;Xie et al, 2012;Zeng, Xie, et al, 2018;Zeng et al, 2016). Recently, Qiu et al (2023) incorporated intercell lateral unsaturated and saturated flow in a land model. But the high computational cost, the data volume, and complexity required by these 3-D and quasi-3D approaches constrains their uses for global applications.…”

“…Recently, Qiu et al. (2023) incorporated intercell lateral unsaturated and saturated flow in a land model. But the high computational cost, the data volume, and complexity required by these 3‐D and quasi‐3D approaches constrains their uses for global applications.…”

Simulation of Compound Flooding Using River‐Ocean Two‐Way Coupled E3SM Ensemble on Variable‐Resolution Meshes

“…Our proposed framework in this study would facilitate seamless integration of other new E3SM capabilities, including the lateral flow transport in the land subsurface (Qiu et al, 2023), land-river two-way coupling (D. Xu, Bisht, Zhou, et al, 2022), and land-ocean coupling, all of which will contribute to a fully coupled ESM with a more realistic representation of the land-river-ocean interaction. These processes vary across a range of spatiotemporal scales and are critical to global water and carbon cycling (Najjar et al, 2018;N.…”