<P> The role of soil water retention is profound; its effects are far reaching and relationships are invariably complex . This section focuses on a few key roles and recognizes that it is beyond the scope of this discussion to encompass all roles that can be found in the literature . </P> <P> The process by which soil absorbs water and water drains downwards is called percolation . </P> <P> Soil water retention is essential to life . It provides an ongoing supply of water to plants between periods of replenishment (infiltration), so as to allow their continued growth and survival . For example, over much of temperate Victoria, Australia, this effect is seasonal and even inter-annual; the retained soil water that has accumulated in preceding wet winters permits survival of most perennial plants over typically dry summers when monthly evaporation exceeds rainfall . Soils generally contain more nutrients, moisture, and humus . </P> <P> Soil moisture has an effect on the thermal properties of a soil profile, including conductance and heat capacity . The association of soil moisture and soil thermal properties has a significant effect on temperature - related biological triggers, including seed germination, flowering, and faunal activity . (more water causes soil to more slowly gain or lose temperature given equal heating; water has roughly double the Heat capacity of soil) </P>

Briefly mention the reason for using a large quantity of water