Rainfall that is not infiltrated runs down slope as overland flow. Rainfall carried as overland flow may infiltrate further down slope, or it may enter a stream channel. Infiltrated rainfall is initially stored in the soil profile as soil moisture. Ground water may enter streams, lakes, oceans, or it may be stored for long time periods in aquifers. Not all soil water will be lost to percolation or lateral subsurface flow.
Soils can hold a certain amount of water against gravity.
Soil water held against gravity is eventually lost as evapotranspiration. It is the ability of the soil to hold water against gravity which makes plant life possible. Rainfall which enters a stream channel becomes stream flow. Stream flow can be attributed to either storm flow or base flow. During, as well as shortly after a storm event, stream flow is dominated by storm flow resulting from overland flow and lateral subsurface flow.