Hydrologic and climatic responses to global anthropogenic groundwater extraction

In this study, a groundwater (GW) extraction scheme was incorporated into the model CESM1.2.0 to create a new version called CESM1.2_GW, which was used to investigate hydrologic and climatic responses to anthropogenic GW extraction on a global scale. An ensemble of 41-yr simulations with and without GW extraction (estimated based on local water supply and demand) were conducted and analyzed. The results revealed that GW extraction and water consumption caused drying in deep soil layers but wetting in upper layers, along with a rapidly declining GW table in areas with the most severe GW extraction, including the central United States, the north China Plains and the north of India and Pakistan. The atmosphere also responded to GW extraction, with cooling at the 850 hPa level over the north of India and Pakistan and a large area in north of China and central Russia. Increased precipitation occurred in the north China Plains due to increased evapotranspiration from irrigation. Decreased precipitation occurred in north of India because the Indian monsoon and its transport of water vapor were weaker as a result of cooling induced by GW use. Additionally, the background climate change may complicate the precipitation responses to the GW use. Local terrestrial water storage was shown to be unsustainable at the current high GW extraction rate. Thus, a balance between reduced GW withdrawal and rapid economic development must be achieved in order to maintain a sustainable GW water resource, especially in regions where GW is being over-exploited.