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The energy required per unit mass of water vaporized. (J g −1) L v = Volumetric latent heat of vaporization. The energy required per unit volume of water vaporized. (L v = 2453 MJ m −3) E = Mass water evapotranspiration rate (g s −1 m −2) ET = Water volume evapotranspired (mm s −1) Δ = Rate of change of saturation specific humidity ...
The Penman equation describes evaporation (E) from an open water surface, and was developed by Howard Penman in 1948. Penman's equation requires daily mean temperature, wind speed, air pressure, and solar radiation to predict E. Simpler Hydrometeorological equations continue to be used where obtaining such data is impractical, to give comparable results within specific contexts, e.g. humid vs ...
The Blaney–Criddle equation is a relatively simplistic method for calculating evapotranspiration.When sufficient meteorological data is available the Penman–Monteith equation is usually preferred.
In the irrigation industry, matched precipitation rate (MPR) is a term that is used to calculate the amount of precipitation in a given area is uniform. In order to be "matched" all sprinkler heads in a given zone must have the same rate of precipitation.
Irrigation scheduling is the process used by irrigation system managers to determine the correct frequency and duration of watering. The following factors may be taken into consideration: Precipitation rate of the irrigation equipment – how quickly the water is applied, often expressed in inches or mm per hour.
A leaching model is a hydrological model by which the leaching with irrigation water of dissolved substances, notably salt, in the soil is described depending on the hydrological regime and the soil's properties. The model may describe the process (1) in time and (2) as a function of amount of water applied.
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Crop consumptive water use is the amount of water transpired during plant growth plus what evaporates from the soil surface and foliage in the crop area. The portion of water consumed in crop production depends on many factors, especially the irrigation technology.