Impact of groundwater extraction on hydrological process over the Beijing-Tianjin-Hebei region, China

Groundwater extraction influences water redistribution and hydrothermal processes, which significantly affect the water cycle and the sustainable development of the economy and environment. In this study, a high resolution (~1 km) land surface model that considered groundwater lateral flow and groundwater extraction was used to investigate the impacts of groundwater extraction on hydrological process. Simulations with and without groundwater extraction were conducted for the Beijing-Tianjin-Hebei (BTH) region for the period 2000-2012. The comparison of the simulated results and measurements from water wells, automatic weather stations, and satellite observations demonstrated the good performance of the model. Our results showed that groundwater extraction deepened the groundwater table depth by approximately 0.5-2 m across the plains and rapidly reduced terrestrial water storage (TWS; exceeding 24 cm per unit area) from 2000 to 2012. Both surface (2 cm) and deep (100 cm) soil moisture showed an increase of 0.01-0.02 m3 m(-3) due to groundwater extraction used for irrigation. Groundwater extraction changed the water and energy budgets, leading to a significant cooling effect in the irrigated areas of BTH. The latent heat flux showed an increase of 30 W m(-2) across the plains caused by the long-term exploitation. The surface soil moisture and latent heat flux increased mainly within the growing season due to farmland irrigation. The reduction in TWS was mainly due to the combined effects of over-exploitation and climate, while the contribution of extraction could not be ignored across the BTH region.