Runoff is the measurement of the flow of water into a lake, stream or other waterbody, usually expressed in cubic feet per second. The flow is produced by rainfall from storms, precipitation accumulation or transpiration, melting ice or snow, seepage, evaporation, and percolation. 

Determining the runoff potential of an area is important data for water resources and agricultural management, especially after storm events and wildfires. Runoff can alter water quality as chemicals from fertilizers, debris, and waste products enter water bodies. 

Space-based platforms such as satellites cannot directly measure runoff; however, they can remotely measure things useful for predicting runoff. These data are then input, along with ground-based data, into land surface models to estimate runoff.