Water Balance Equation

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Vast amounts of water on the earth’s surface are constantly recycled between the land and oceans - and the atmosphere​. For a confined area, which allows researchers to ignore water input from sources other than precipitation (rivers, lakes, etc.), a relatively simple equation can be written down to describe the balance of water:

Precipitation = Evapo​ration + Transpiration + Runoff + Recharge + Storage,

where

• Evaporation is the direct evaporative loss of water from the ground to the atmosphere;

• Transpiration is the passage of water through the plants and its release into the atmosphere;

• Runoff is the net surface-movement of water out of the system;

• Recharge is the percolation of water through soil to the water table; and

• Storage denotes the amount of water stored in the soil profile.​