A first attempt to model global hydrology at hyper-resolution

Abstract

Global hydrological models are one of the key tools that can help meet the needs of stakeholders and policy makers when water management strategies and policies are developed. The primary objective of this paper is therefore to establish a first-of-its-kind, truly global hyper-resolution hydrological model that spans a multiple-decade period (1985-2019). To achieve this, two key limitations are addressed, namely the lack of high-resolution meteorological data and insufficient representation of lateral movement of snow and ice. Thus, a novel meteorological downscaling procedure that better incorporates fine-scale topographic climate drivers is incorporated, and a snow module capable of lateral movement of frozen water resembling glaciers, avalanches, and wind movement is included. We compare this global 30 arcsec version of PCR-GLOBWB (PCR - Global Water Balance) to previously published 5 and 30 arcmin versions by evaluating simulated river discharge, snow cover, soil moisture, land surface evaporation, and total water storage against observations. We show that hyper-resolution provides a more accurate simulation of river discharge, in particular for smaller catchments. We highlight that global hyper-resolution modeling is possible with current computational resources and that hyper-resolution modeling results in more realistic representations of the hydrological cycle. However, our results also suggest that global hydrological modeling still needs to incorporate land cover heterogeneity and relevant hydrological processes at the sub-kilometer scale to provide more accurate estimates of soil moisture and evaporation fluxes.