Water Movement Through Soil Or… Why did that bucket of water I spilled disappear into the ground.

Porosity The movement of water through the soil is controlled by certain characteristics. Porosity – The number of pores in a material compared to its volume. Usually expressed as a percentage. Well sorted Unsorted

Sorting Well sorted Well sorted soils contain rounded particles similar in size not closely packed. They are the most porous. Unsorted soils which contain different sized particles and are more closely packed are less porous. Unsorted

Soils with flattened or angular grains, such as clay soils, can pack closely together and have a low porosity.

Important – particle size alone may not affect the porosity of the soil. Soils with different particle size but with similar shape and packing can have the same porosity. 48% 48%

Permeability The ability of a soil to transmit water. The rate of permeability, or how fast the water moves through the soil, depends on the size of the pores and how the pores are connected. For example: sandy soils have large well connected pores buy clay soils do not. Therefore, sandy soils have a higher permeability than clay soils.

Permeability is Directly Related to Porosity

Runoff Occurs when rainfall exceeds permeability. Or when a soil is saturated and cannot retain more water. Or when the slope of a soil’s surface is too great to allow infiltration.

Capillary Action in Soil The movement of a liquid along the surface of a solid caused by the attraction of molecules of the liquid to the molecules of the solid.

The water table . . . The depth of the water table depends on three factors: Climate Season Location The water table is the top of the water-saturated ground.