In hydrology, interflow is the lateral movement of water in the unsaturated zone, or vadose zone, that returns to the surface or enters a stream.
[1] Interflow is sometimes used interchangeably with throughflow;[1] however, throughflow is specifically the subcomponent of interflow that returns to the surface, as overland flow, prior to entering a stream or becoming groundwater.
[2] Interflow occurs when water infiltrates (see infiltration (hydrology)) into the subsurface, hydraulic conductivity decreases with depth, and lateral flow proceeds downslope.
[1] As water accumulates in the subsurface, saturation may occur, and interflow may exfiltrate as return flows, becoming overland flow.
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