Three quarters of the Earth's surface is covered by the waters of the oceans, lakes, rivers, streams and springs. When drilling in the subsurface, usually water can be found. This is just a different depths (groundwater or groundwater).

The process known as "water cycle" is that by which the ocean water evaporates and precipitates on earth, where it is distributed in rivers and lakes, mainly ensuring groundwater recharge. This water is used by plants, animals and man.

Water vapor is produced by evaporation on land and water bodies, and transpiration of living beings. This vapor circulates through the atmosphere and falls as rain or snow. Upon reaching the surface, the water follows two paths:

In amounts determined by the intensity of the rain as well as porosity, permeability, thickness and antecedent soil moisture, some of the water is discharged directly into streams and rivers, where it is absorbed into the oceans and inland water bodies the rest infiltrates into the ground.

Some water is infiltrated soil moisture, and can evaporate directly or penetrate plant roots for transpiration from leaves. The portion of water that exceeds the forces of cohesion and adhesion of soil, filtered down and accumulates in the call saturation zone to form an underground water reservoir, whose surface is called water table.

Under normal conditions, the water level increases as intermittently filling or recharging will, and then declines as a result of continuous drainage gutters are natural springs.