Parameter Tree:
EARTH SCIENCE > TERRESTRIAL HYDROSPHERE > SURFACE WATER > SURFACE WATER PROCESSES/MEASUREMENTS > RUNOFF

Definition:
The measurement of the flow of water in a stream, usually expressed in cubic feet per second; the net effect of storms, accumulation, transpiration, melt, seepage, evaporation, and percolation.

Reference:
Dictionary of Earth Science, 5th ed. 1997. Sybil Parker, ed. in chief. McGraw-Hill.