That portion of precipitation or irrigation on an area which does not infiltrate or evaporate, but instead is discharged from the area. / Dissolved chemicals, etc, included in such water.

plural of runoff

Overland flow of excess water (with or without accumulated contaminants) that cannot be absorbed by the ground as infiltration.

Water leaving farm fields, polluted by animal waste and fertilizers.

plural of surface runoff

A form of alternative or preferential voting system in which voters rank candidates, and votes for the worst performing candidate are re-allocated to the voters' next-highest choices until one candidate has reached the threshold for election.