Implementation of Groundwater Lateral Flow and Human Water Regulation in CAS-FGOALS-g3

Both groundwater lateral flow (GLF) and human water regulation (HWR) significantly impact hydrological processes, climate, and even socioeconomic sustainable development. Reasonably representing these processes in climate system models is vital for improving hydrological predication and climate modeling. In this study, schemes including GLF and HWR were implemented into the Flexible Global Ocean-Atmosphere-Land System model grid-point version 3 (CAS-FGOALS-g3) to investigate the hydroclimatic effects of GLF and HWR. Three groups of simulations using CAS-FGOALS-g3 were conducted for the period from 1976 to 2010. Comparisons between the simulations and the observations show their good performance in reproducing the hydrological processes. Results show that soil moisture and latent heat flux increased when GLF was included in the western United States, northern Australia, and northern South America, along with a shallower water table depth. The largest increases in latent flux are located in regions without water and energy limitations. Increased summer precipitation occurred in the western United States due to the wetting and cooling effects of GLF. Latent heat flux significantly increases in three key regions of the world (central United States, north China plain, and northern India), caused by wetting surface soil due to irrigation. The atmosphere also responded to HWR, with cooling at the 850 hPa level over northern India and Pakistan. Decreased precipitation occurred in India because the upward movement was weaker as a result of HWR. GLF can replenish the groundwater depression cone caused by overexploitation, especially in thick aquifers. Plain Language Summary Groundwater lateral flow and human water regulation significantly impact hydrological processes and climate. In this study, we implemented the schemes including groundwater lateral flow and human water regulation into the Flexible Global Ocean-Atmosphere-Land System model to investigate the hydroclimatic effects of groundwater lateral flow and human water regulation. Comparisons between the simulations and the observations show their good performance in reproducing the hydrological processes. Groundwater lateral flow can replenish the groundwater depression cone caused by overexploitation, especially in thick aquifers. Human water regulation weakens the upward movement in India and reduces the summer precipitation. Both groundwater lateral flow and human water regulation affect soil moisture and energy fluxes at the land surface. These results suggest that groundwater lateral flow and human water regulation, which are generally simplified or excluded in climate system models, may provide missing parts for modeling water and energy fluxes and improving water management.