Geodetic Deformation Inversion of Groundwater Variations in the Golmud River Basin, Northwestern China

The Golmud River Basin is a typical inland arid river basin in the Qaidam Basin, and the dynamics of its groundwater storage are of great importance for regional ecological security and water resources management. To address the limited spatial representativeness of traditional hydrological station networks and the relatively low spatial resolution of satellite gravimetry such as the Gravity Recovery and Climate Experiment (GRACE), this study develops a multi-source geodetic inversion framework for groundwater estimation by using Interferometric Synthetic Aperture Radar (InSAR), Global Navigation Satellite System (GNSS), and GRACE satellite gravimetry. Surface deformation with high spatial resolution over the Golmud River Basin is derived from Sentinel-1 SAR images from 2017 to 2021. After correcting for modeled non-hydrological loading effects and screening observations to reduce the influence of potential non-hydrological signals, groundwater spatiotemporal variations are inverted based on elastic loading theory. The results show that from 2017 to 2021, surface deformation in the Golmud River Basin is jointly controlled by river dynamics, mineral extraction, and urbanization, forming a spatial pattern of river corridor zones and mining-related patches. Groundwater storage shows an overall increasing trend during the study period, with a particularly significant increase in the southwestern region, reaching more than 20 mm/a. A synthetic experiment demonstrates that the proposed method can recover prescribed groundwater signals at a spatial resolution of approximately 40 km under the tested conditions. Compared with the InSAR-derived estimates, GRACE-derived groundwater variations exhibit a smaller seasonal amplitude, potentially reflecting the effects of limited spatial resolution and spatial signal smoothing. The WaterGAP Global Hydrology Model (WGHM) estimates are substantially smaller in magnitude than those derived from InSAR and GRACE, highlighting the uncertainties associated with model-based groundwater estimates in this high-altitude basin. Groundwater in the Golmud River Basin experienced a rapid increase during 2017 to 2019, which is likely driven by increased precipitation and lower temperatures associated with a La Niña event, indicating a teleconnection between global climate variability and regional water resource changes. This study provides a technical reference for refined groundwater monitoring at a tens-of-kilometers scale in small and medium-scale arid basin systems.