Groundwater resources of the world
About 35 % of the continental area (excluding Antarctica) is underlain by relatively homogeneous aquifers, and 18 % has groundwater, some of it extensive, in geologically complex regions. Almost half of the continental areas have generally small groundwater resources, confined to unconsolidated rocks close to the surface, where groundwater resources are usually sufficient for small to medium-sized population centres
Source: BGR & UNESCO