Human water regulation, groundwater lateral flow and the movement of soil frost and thaw fronts affect water and thermal processes, as well as energy and water exchanges between the land surface and atmosphere. Reasonable representation of these processes in land surface models is very important to improving the understanding of terrestrial eco-hydrological processes and land-atmosphere interactions.

Recently XIE Zhenghui, ZENG Yujin, Liu Shuang and their co-authors in LASG/Institute of Atmospheric Physics, Chinese Academy of Sciences synchronously incorporated the schemes of anthropogenic water regulation, groundwater lateral flow and the movement of soil frost and thaw fronts into a land surface model, which is then named the Land Surface Model for Chinese Academy of Sciences (CAS-LSM). Meanwhile, they devised and implemented the schemes describing model resolution conversion between groundwater flow module and the land surface model to parallelly simulate the large-scale and high-resolution groundwater flow and its impacts. The framework of CAS-LSM and the model resolution conversion between groundwater flow module and the land surface model are respectively shown in Fig. 1 and Fig. 2.

Fig. 1 Schematic diagram of the land model CAS-LSM with groundwater lateral flow (GLF), human water use (HWR) and soil freeze-thaw fronts (FTFs). The main calculation process in CAS-LSM and its coupling with GLF, HWR and FTFs: the content in the black dashed box displays the main calculation process in CAS-LSM; the details in the blue dashed box show how the scheme of FTFs is coupled with the soil temperature module; the details in the orange dashed box show how the schemes of GLF and HWR are coupled with the soil hydrology module.

Fig. 2 Frameworks for linking the land surface model and the lateral groundwater flow module developed in this study and the resolution conversion in the determination of lateral groundwater flow.

Simulations using CAS-LSM were conducted for both Heihe River Basin in China and the globe, respectively, to investigate the impacts of anthropogenic water regulation and groundwater lateral flow on land processes and the response of frozen soil to climate change. Compared with observations, CAS-LSM reproduced the distributions of groundwater, evapotranspiration and permafrost reasonably, and well matched the temporal changes in ground temperature, heat fluxes and soil frost and thaw fronts, as Fig. 3 shows. The results show that water use raised the latent heat flux and reduced the sensible heat flux, net ecosystem exchange and streamflow recharging to an eco-fragile region, and the active layer thickness increased 8.63 mm/year for permafrost in Heihe River Basin, as Fig. 4 shows. Global groundwater lateral flow significantly modified the equilibrium water table patterns in North Africa, the Arabian Peninsula, central Asia and southern Australia, deepening the water tables by more than 6 m, as Fig. 5 shows. Results suggested that CAS-LSM is a potential tool for studying land surface processes.

Fig. 3 Validations for evapotranspiration, heat flux, groundwater, frozen soil and total water storage.

Fig. 4 Impacts of human water use on heat flux and water cycle, and the response of active layer thickness to climate change in Heihe River Basin.

This research finding has been published in Journal of Advances in Modeling Earth Systems and Journal of Geophysical Research – Atmospheres.

Fig. 5 Global equilibrium groundwater table depth patterns at ~1° resolution from (a) the CONTROL simulation, (b) the LATERAL simulation and (c) the LATERAL-CONTROL simulation, and the (d) annual and (e) seasonal time series of the global-averaged groundwater table depth from the CONTROL and LATERAL simulations. The stippled areas indicate the regions where the difference passed the 95% confidence level in the Student’s t-test.

This research finding has been published in Journal of Advances in Modeling Earth Systems and Journal of Geophysical Research – Atmospheres.

Citation:

Zhenghui Xie, Shuang Liu, Yujin Zeng, Junqiang Gao, Peihua Qin, Binghao Jia, Jinbo Xie, Bin Liu, Ruichao Li, Yan Wang, Longhuan Wang. A high-resolution land model with groundwater lateral flow, water use and soil freeze-thaw front dynamics and its applications in an endorheic basin, 2018. Journal of Geophysical Research- Atmospheres, 123. doi: 10.1029/2018JD028369.

(https://doi.org/10.1029/2018JD028369  )

Yujin Zeng, Zhenghui Xie, Shuang Liu, Jinbo Xie, Binghao Jia, Peihua Qin, Junqiang Gao. Global Land Surface Modeling Including Lateral Groundwater Flow, 2018. Journal of Advances in Modeling Earth Systems. In press. doi: 10.1029/2018MS001304.

(https://doi.org/10.1029/2018MS001304 )