Groundwater over‐extraction and associated land subsidence in Lucknow, Ganga Basin, India: Insights from space geodetic observations

The Gravity Recovery and Climate Experiment (GRACE & FO) satellite and in situ data from the Ganga River Basin (GRB) in India, one of the largest groundwater reservoirs, indicate a significant decline in water storage resulting from human activities and excessive groundwater use. This extraction is also causing widespread land subsidence. We present the patterns of land deformation, likely linked to groundwater dynamics in and around Lucknow, one of the largest cities in the GRB, based on data from Sentinel‐1, global navigation satellite system (GNSS) and in situ measurements collected between 2014 and 2024. The maximum subsidence rate exceeds ∼36 mm/year in Charbagh, Indira Nagar and surrounding areas, where a significant drop in groundwater levels is recorded, indicating that groundwater over‐extraction is the principal cause of land subsidence. The independent estimates of skeletal storativity from subsidence and groundwater variations compare well with mean skeletal storativity values of 4.73 × 10−3 over the study area. Analyses also indicate irreversible significant subsidence near the Charbagh area. Space geodetic observations of deformations caused by hydrological changes align well with in situ observations. This suggests that a synergistic combination of methods can enhance understanding of groundwater storage changes and the associated vertical ground motion at higher spatial and temporal resolutions.