INTERGEO Agenda - english

River water storage variations produce elastic loading deformation that can, in principle, be detected by Global Navigation Satellite System (GNSS) observations. However, transient river-stage-induced loading signals are usually small, localized, and difficult to separate from broader hydrological loading and common-mode errors. Here, we present the first GNSS observation of transient river water storage variations along the Rhine River in northwestern Europe, using a dense regional GNSS network and daily river-stage observations. After removing large-scale hydrological loading and regional common-mode signals, we identify coherent vertical land motion signals associated with transient river-stage changes. The detected signals have amplitudes of approximately 1 mm and persist over time scales of 14–60 days. Spatially, the response is concentrated along the Rhine corridor, with sensitivity extending up to approximately 300 km from the river. Two representative events, in October 2011 and July 2021, show clear transient deformation patterns related to river-stage variations. In particular, the October 2011 event exhibits a downstream migration of GNSS-observed uplift following river-level recession, with an apparent propagation speed slower than that of the river-stage wave. The GNSS-derived deformation is approximately five times larger than predicted by PREM-based purely elastic loading models driven by river-stage observations, and its propagation speed is about half that of the river-stage wave. This discrepancy suggests that the observed signals reflect not only direct river-water loading but also delayed bank storage and groundwater responses in the river corridor, as supported by groundwater model simulations and well observations. This study highlights the potential of GNSS as a complementary observation system for monitoring transient terrestrial water storage changes at regional scales.