Relocation of River Storage From Global Hydrological Models to Georeferenced River Channels for Improved Load-Induced Surface Displacements

Abstract

Variations in terrestrial surface water storage cause elastic crustal displacements of several millimeters in the vertical direction on daily to seasonal time scales. Locally, strong signals with exceptionally high amplitudes can be observed along the major river channels. As the horizontal resolution of global hydrological models is typically limited to 0.5° × 0.5°, the generalized model drainage network leads to simulated river mass distributions that are not necessarily collocated with the real courses of the rivers. Moreover, the spreading of locally concentrated surface water on the coarse model grids leads to substantially underestimated amplitudes of simulated hydrologically induced surface displacements. We therefore develop a relocation procedure to improve such hydrological loading estimates, especially at locations near the river banks. We separate the water masses stored in the modeled river network from the total water storage and relocate them on a georeferenced river map with higher resolution. Applying the relocated river masses, simulated hydrological loading amplitudes increase by 0.2–5 mm for the vertical load-induced surface displacement along the major rivers, at the Amazon even up to additional 15 mm. The amplitudes for the horizontal load-induced surface displacements are slightly increased, up to maximum 3 mm. Besides changes in the distance to the mass loads, the horizontal displacement fields is also heavily affected by significant changes in the directions to the relocated river mass load. The comparison of modeled hydrologically induced surface displacement time series with Global Positioning System observations shows a significantly improved fit for stations in close proximity to larger rivers when applying the relocation procedure.