Infiltration

Infiltration is the process by which water at the ground surface enters soil. Its rate depends on soil properties, surface conditions, and water supply.

Infiltration capacity: The maximum rate at which a soil can absorb water under specified conditions. It sets the upper limit on infiltration when water is available at the surface.
Soil texture: The relative proportions of sand, silt, and clay in a soil. Texture affects pore sizes and therefore the ease with which water enters.
Horton overland flow: Surface runoff produced when rainfall intensity exceeds the soil's infiltration capacity. It is a direct consequence of water arriving faster than soil can absorb it.
Surface runoff: Water flowing over the land surface toward streams, lakes, or other low areas. Runoff travels across the surface instead of entering soil at that point.
Hydraulic conductivity: A measure of how readily a porous material transmits water under a hydraulic gradient. It governs how readily infiltrated water moves through soil.
Soil structure: The arrangement of soil particles into aggregates and the pores between them. Connected pores and cracks can admit water faster than texture alone suggests.
Groundwater recharge: The replenishment of groundwater by water moving downward from the land surface. Infiltrated water can percolate through soil and replenish aquifers.
Percolation: The downward movement of water through soil and porous rock. Infiltration crosses the ground surface; percolation describes subsequent movement within the ground.
Soil water potential: The potential energy of water in soil relative to a reference state. Differences in water potential help draw surface water into initially dry soil.
Porosity: The fraction of a material's volume occupied by voids. Pore volume provides storage space for water entering the soil.

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