Permeable and impermeable

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When we visualize rainfall occurring over a basin, we must necessarily consider two basic basin areas.
These areas are:

a permeable portion of the soil mantle

the impermeable portion of the soil mantle covered by streams, lake surfaces, marshes, and other impervious material directly linked to the streamflow network       The permeable area produces runoff when rainfall rates are sufficiently heavy, while the impermeable produces impervious and direct runoff from any rain.