Water balance

As water balance, even field water balance refers to the balance of precipitation, evaporation, runoff, and storage change based on an area and a period. The water balance plays a major role when you want to determine how much water is in a region for use. The available quantity is less than in air humidem usually in arid.

It is based on doing the water balance or water balance equation:

Changed:

Where N is the precipitation, the A runoff, evaporation and V? S is the storage change in the underground. It can be the potential or actual evaporation V. For sufficiently long periods? S = 0

From a negative climatic water balance is when the annual potential evaporation is greater than precipitation a year. A positive water balance is when the real evaporation is less than precipitation and thus to that surface runoff and infiltration of water into the ground is possible.