Modeling Land Subsidence Under Future Water Stress: The Influence of Groundwater Exploitation, Climate Change, and Inter-Basin Water Diversion

Land subsidence driven by groundwater exploitation poses a critical threat under future water stress from population growth, urbanization, and economic expansion. While the relationship between groundwater level (GWL) fluctuations and land subsidence has been studied, limited research has explored their co-evolution under future development, climate change, and groundwater management aimed at stabilizing or reversing GWL decline. The long-term effects of large-scale water transfer projects, such as China's South-to-North Water Diversion (SNWD) project, on subsidence remain unclear despite their role in reducing extraction pressures and recovering groundwater level. This study develops a coupled groundwater flow and land subsidence model for a key city in the SNWD's middle route, incorporating water demand projections (from Shared Socioeconomic Pathways, SSPs), climate change scenarios (from CMIP6), and water diversion strategies. Results indicate that future (until 2050) GWL changes and subsidence are primarily driven by water demand (over 50%) and water diversion (up to 45.3%), with climate change having a minor effect (under 18.6%). Over the period extending from 2020 to 2050, subsidence recovery could reach 56.8 mm (averagely 1.9 mm/yr) with reduced demand and increased diversion. However, in a worst-case scenario characterized by rising demand and absence of diversion optimization, subsidence could worsen by up to 439.9 mm (averagely 14.7 mm/yr). Water diversion could be 15 times more effective in mitigating subsidence under higher water-stress conditions, while prohibiting deep groundwater extraction for agriculture could lead to a 4.4-fold improvement in GWL recovery and subsidence mitigation. This study highlights the role of technology, policy, and optimized water diversion in managing GWL and mitigating subsidence under future uncertainties.