Water balance
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- Note: The Water Balance method is also a winding mechanism used in mining
In hydrology, a water balance equation can be used to describes 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.
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[edit] Equation
A general water balance equation is:
- P = Q + E + ΔS
where
- P is precipitation
- Q is runoff
- E is evapotranspiration
- ΔS is the change in storage (in soil or the bedrock)
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, flood control and pollution control.
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.[1]
[edit] Diagnosis of water balance models
Several diagnostic measures in hydrology can be used to select and evaluate the performance of water balance models
[edit] Applications
- Evaluate the components of the hydrologic cycle
- Snowmelt simulation
- Climate change impact assessment
- Flow forecasting and project design
[edit] Types
- Models using precipitation (rainfall) as input
- Models using rainfall and temperature as input
- Models using rainfall and potential evaporation as input
- Models using daily input data
[edit] References
- ^ 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:.
[edit] External links
A paper on water and salt balances on the soil, in the rootzone, unsaturated zone, aquifer and their interactions can be found as reply nr. 4 to frequently asked questions on the FAQs page in [www.waterlog.info].
On the software page of the same site one can find a conceptual model (RainOff) of [rainfall-runoff] relations using a nonlinear reservoir applicable to (small) watersheds. Free download.
