SIGH-Map: Space-time InSAR-based groundwater head mapping: An integrated InSAR-MODFLOW framework for head calculation

Study region The study focuses on the Neyshabour Plain, an approximately 4900 km² sedimentary aquifer system in northeastern Iran bounded by the Binaloud and Kuhsorkh mountain ranges. Characterized by an arid to semi-arid climate, the region relies on groundwater for over 90% of its irrigation water demand. Excessive extraction has led to significant land subsidence of up to 16 cm/year, particularly in northern areas where compressible fine-grained sediment layers like clay and silt are concentrated. Study focus This research introduces a novel framework for calculating spatio-temporal groundwater head changes by integrating InSAR with MODFLOW. The study addresses limited monitoring networks by utilizing InSAR's capability to measure land subsidence caused by over-pumping. We calibrated a MODFLOW model, during the 2000–20 period, with a subsidence package using InSAR and in-situ measurements from the Neyshabour aquifer, Iran. InSAR analysis revealed significant subsidence up to 16 cm/year (2014–22). We simulated no-delay and delay interbeds cases, finding that storage coefficients from the delay interbeds case are more accurate for local inelastic conditions. Calibrated coefficients and InSAR data were integrated to calculate groundwater heads, for the 2014–22 period in which the 2020–22 period was used as an independent validation period, achieving high correlation (>0.8) with observed heads in subsidence zones. This framework allows near real-time, cost-effective groundwater head calculation using only InSAR deformation and calibrated storage coefficients. It addresses traditional groundwater head monitoring limitations by providing high spatial and temporal resolution in vast aquifer systems. New hydrological insight The SIGH-Map framework offers a transformative hydrological insight by establishing a robust hydromechanical link between satellite-observed surface deformation and subsurface groundwater head changes, particularly in data-scarce sedimentary aquifers. By integrating InSAR data with MODFLOW’s Subsidence (SUB) package, the work overcomes the traditional bottleneck of characterizing aquifer storage properties through the spatial calibration of elastic and inelastic skeletal storage coefficients. A critical finding is that extensive pumping in regions like the Neyshabour aquifer has driven head levels below preconsolidation thresholds, triggering inelastic consolidation and the permanent loss of aquifer storage capacity. Furthermore, this research provides a new site-specific finding for the Neyshabour aquifer by demonstrating that the delay interbeds case is significantly more accurate for simulating the hydrological responses than no-delay case, as it accounts for the previously unquantified time-lagged dissipation of pore pressure and the slow release of water from the region’s fine-grained interbeds. Ultimately, this framework enables high-resolution, near real-time mapping of hydraulic heads across vast aquifer systems, providing a cost-effective alternative to sparse monitoring well networks for evaluating groundwater depletion and managing subsurface resources.