Water balance

Water balance

In hydrology, a water balance equation can be used to describe the flow of water in and out of a system. A system can be one of several hydrological domains, such as a column of soil or a drainage basin.[citation needed] Water balance can also refer to the ways in which an organism maintains water in dry or hot conditions. It is often discussed in reference to plants or arthropods, which have a variety of water retention mechanisms, including a lipid waxy coating that has limited permeability.



A general water balance equation is:

P = Q + E + ΔS


P is precipitation
Q is runoff
E is evapotranspiration
ΔS is the change in storage (in soil or the bedrock)

Extensive water balances are discussed in agricultural hydrology.
A water balance can be used to help manage water supply and predict where there may be water shortages. It is also used in irrigation, runoff assessment (e.g. through the RainOff model [1]), flood control and pollution control. Further it is used in the design of subsurface drainage systems which may be horizontal (i.e. using pipes, tile drains or ditches) or vertical (drainage by wells).[2] To estimate the drainage requirement, the use of an hydrogeological water balance and a groundwater model (e.g. SahysMod [3]) may be instrumental.

The water balance can be illustrated using a water balance graph which plots levels of precipitation and evapotranspiration often on a monthly scale.

Several monthly water balance models had been developed for several conditions and purposes. Monthly water balance models had been studied since the 1940s.[4]


Several diagnostic measures in hydrology can be used to select and evaluate the performance of water balance models



See also


  1. ^ "Rainoff, surface runoff model". http://www.waterlog.info/rainoff.htm. Retrieved 2010-07-28. 
  2. ^ "Free articles and software on drainage of waterlogged land under irrigation". http://www.waterlog.info. Retrieved 2010-07-28. 
  3. ^ "Sahysmod groundwater model". http://www.waterlog.info/sahysmod.htm. Retrieved 2010-07-28. 
  4. ^ Xu, C.-Y.; V.P. Singh (1998). "A Review on Monthly Water Balance Models for Water Resources Investigations". Water Resources Management 12 (1): 31–50. doi:10.1023/A:1007916816469. 

External links

  • Article on water and salt balances: [1]

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • water balance — n the ratio between the water assimilated into the body and that lost from the body also the condition of the body when this ratio approximates unity * * * fluid b …   Medical dictionary

  • water balance — vandens pusiausvyra statusas T sritis Kūno kultūra ir sportas apibrėžtis Santykis tarp suvartoto ir visais būdais iš organizmo pašalinto vandens. Kai vandens praradimas viršija 2 % kūno masės, sumažėja ištvermė. atitikmenys: angl. fluid balance;… …   Sporto terminų žodynas

  • water balance — vandens balansas statusas T sritis ekologija ir aplinkotyra apibrėžtis Vandens pritekėjimo ir sunaudojimo elementų tam tikrame plote (vandeningoje sistemoje) kiekybinė išraiška (elementų algebrinė suma). Vandens pritekėjimo elementai yra šie:… …   Ekologijos terminų aiškinamasis žodynas

  • water balance — vandens apykaita statusas T sritis Kūno kultūra ir sportas apibrėžtis Gyvybiškai svarbus organizmo rodiklis – suvartoto ir pašalinto vandens santykis. Vanduo sudaro vidutiniškai 55–60% suaugusio žmogaus kūno masės. Normali vandens apykaita per… …   Sporto terminų žodynas

  • water balance —   in any natural system, inputs of water must equal outputs plus or minus changes in storage since water cannot be created or destroyed …   Geography glossary

  • water balance — noun Date: 1911 the ratio between the water assimilated into the body and that lost from the body; also the condition of the body when this ratio approximates equilibrium …   New Collegiate Dictionary

  • water balance — noun : the ratio representing the difference between water assimilated into the body and that lost from the body (as in urine, feces, and sweat) and being under average conditions approximately equal to unity …   Useful english dictionary

  • Water balance — Водокрасочный баланс; Баланс вода краска …   Краткий толковый словарь по полиграфии

  • water-balance —    An instrument designed to measure evaporation by gravimetry [16] …   Lexicon of Cave and Karst Terminology

  • water-balance — …   Useful english dictionary