Tuesday, November 20, 2007

Physical actions in water cycle

The Physical actions in water cycle is of fives main types. They are evaporation, precipitation, infiltration, runoff, and subsurface flow.

The Evaporation is the transfer of water from the bodies of surface water into the atmosphere. This transfer requires a change in the physical nature of water from liquid to gaseous phases. Along with the evaporation, it can be counted transpiration from plants. Therefore, this transfer is sometimes referred to as evapotranspiration. 90% of atmospheric water comes from evaporation, while the left over 10% is from transpiration.

Precipitation is the atmospheric moisture that has formerly condensed to form clouds (changed from the gas phases to a liquid or solid phase), falling to the surface of the earth. This generally occurs as rainfall, but snow, hail, fog drip, and other forms participate too.

Infiltration into the ground is the transition from the surface water to the groundwater. The infiltration rate will depend upon soil or rock permeability with the other factors. Infiltrated water possibly will reach another compartment called as groundwater (i.e., an aquifer). The Ground waters tend to move slowly, so the water may perhaps return as surface water after storage within an aquifer for a period of time that can amount to thousands of years in few cases. The Water returns to the land surface at lower rise than where it infiltrated, under force of the gravity or the gravity induced pressures.

Runoff includes the variety of ways by which land surface water moves downward slope to the oceans. The Water flowing in streams and rivers can be delayed for a time in lakes. Not all precipitated water goes back to the sea as runoff; much of it evaporates before reaching the ocean or reaching an aquifer.

The Subsurface flow includes movement of water within the earth, either within the vadose zone or aquifers. After infiltrating, subsurface water can return to the surface or finally seep into the ocean.

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