Channel Water Storage Anomaly: A New Remotely Sensed Quantity for Global River Analysis

River channels store large volumes of water globally, critically impacting ecological and biogeochemical processes. Despite the importance of river channel storage, there is not yet an observational constraint on this quantity. We introduce a 26-year record of entirely remotely sensed volumetric channel water storage (CWS) change on 26 major world rivers. We find mainstem volumetric CWS climatology amplitude (CA) represents an appreciable amount of basin-wide terrestrial water storage variability (median 2.78%, range 0.04%-12.54% across world rivers), despite mainstem rivers themselves represent an average of just 0.2% of basin area. We find that two global river routing schemes coupled with land surface models reasonably approximate CA (within +/- 50%) in only 11.5% (CaMa-Flood) and 30.7% (HyMap) of rivers considered. These findings demonstrate volumetric CWS is a useful quantity for assessing global hydrological model performance, and for advancing understanding of spatial patterns in global hydrology.

Automated summary

River channels play a crucial role in storing large volumes of water globally, affecting ecological and biogeochemical processes. However, there is currently no observational constraint on the quantity of water stored in river channels. This study introduces a 26-year record of remotely sensed volumetric channel water storage (CWS) change on 26 major rivers worldwide, revealing the significant contribution of mainstem CWS climatology amplitude to terrestrial water storage variability in basins.