1) Intermingle 2) To flow into each other 
In hydrology, interflow is the lateral movement of water in the unsaturated zone, or vadose zone, that first returns to the surface or enters a stream prior to becoming groundwater. Interflow is sometimes used interchangeably with throughflow; however, throughflow is specifically the subcomponent of interflow that returns to the surface, as overla...
• (v. i.) To flow in.
(from the article `runoff`) in hydrology, quantity of water discharged in surface streams. Runoff includes not only the waters that travel over the land surface and through ...
See overflow.
Shallow infiltration to the soil, from where it may infiltrate vertically to an aquifer, move horizontally to a watercourse or be stored and subsequently evaporated.
In`ter·flow' intransitive verb To flow in. [ R.] Holland. 
to flow into each other; intermingle.