Shallow groundwater affects terrestrial ecosystems by sustaining river base-flow and root-zone
soil water in the absence of rain, but little is known about the global patterns of water table depth
and where it provides vital support for land ecosystems. We present global observations of water
table depth compiled from government archives and literature, and fill in data gaps and infer
patterns and processes using a groundwater model forced by modern climate, terrain, and sea
level. Patterns in water table depth explain patterns in wetlands at the global scale and vegetation
gradients at regional and local scales. Overall, shallow groundwater influences 22 to 32% of
global land area, including ~15% as groundwater-fed surface water features and 7 to 17% with
the water table or its capillary fringe within plant rooting depths.