syn. prompt subsurface flow
(1) That portion of the precipitation which has not passed down to the water table, but is discharged from the area as subsurface flow into stream channels.
(2) Flow of water from ephemeral zones of saturation. It moves through the upper strata of a formation at a rate much in excess of normal base-flow seepage.
UNESCO/WMO International Glossary of Hydrology (2nd revised ed., 1992)