Percolation
Percolation is the downward movement of water through soil pores and rock cracks toward deeper groundwater aquifers. Unlike infiltration (which is water entering soil from the surface), percolation is the continuing movement of that water through the soil profile and into the groundwater zone.
Real World
In the Chalk aquifers beneath the South Downs, rainwater takes decades to percolate through the rock before emerging as spring water — some water extracted today fell as rain in the 1980s.
Exam Focus
Distinguish percolation (vertical, through rock) from infiltration (surface entry) — confusing these loses marks on 'explain' questions.
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