Seminar: Jiaxin Xie

The proportion of streamflow that comes from groundwater remains highly uncertain. Previous estimates of this proportion were 86% (land surface model) or less than 28% (latest IPCC report). We compiled daily streamflow observations in 15,567 global watersheds to derive a bottom-up estimate of this proportion. Implications for groundwater simulation are as follows:

• Groundwater sustains 59% ± 7% of global streamflow, narrowing the wide range of Earth system model simulations (12% to 94%).

• At least 21% ± 3% of precipitation recharges groundwater, which is twice the recharge rate estimated in the IPCC AR6 report, suggesting a much more active role of groundwater in the water cycle than most models and global water cycle diagrams currently present.
• Soil emerges as the largest contributor to observational spatial variations in streamflow proportions from groundwater, while most Earth system models identify precipitation as the primary driver.