The scientific study of subsurface water; hydrogeology: Geohydrology especially pertains to the study of the geologic settings of underground water.

Geohydrology is the branch of geology that studies the movement of subsurface water through rocks and the effect of moving water on rocks, including their erosion.

The term geohydrology is often used interchangeably with "hydrogeology". Some make the minor distinction between hydrologists or engineers who are applying themselves to geology (geohydrology), and geologists applying themselves to "hydrology" (hydrogeology).