When water deforms the planet: geodesy, a tool for hydrology?

Freshwater scarcity, a pressing consequence of climate change, threatens human populations and ecosystems. With icesheets and glaciers melting at alarming rates, rainfall becoming erratic and water evaporating faster, the stress on water resources reaches critical levels. As water demand intensifies, it becomes crucial to harness multiple observations of the rapidly changing water resources and enable evidence-based decision making to ensure sustainable water management. Modern geodesy, the study of the evolving shape of our planet, emerges as a newl tool to monitor dynamic hydrological processes from space, at unprecedented spatio-temporal scales, guiding the development of theories and models to predict their course.


This presentation will highlight recent developments in hydrogeodesy, which now reveal variations in the gravity field and surface deformation of the Earth caused by the redistribution of water masses, whether resulting from ice melt or agricultural exploitation, over timescales ranging from seasons to several decades. We will also explore the implications of these observations for our understanding of the complex interactions between hydrology and the solid Earth, particularly by studying the temporal evolution of the mechanical properties of the solid Earth, such as those of aquifers. Finally, although earthquakes are generally caused by tectonic or volcanic activity, we will examine how hydrological variations could, under certain conditions, influence seismic activity and provide interesting insights into physical processes associated with the seismic cycle.