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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 ...
Distribution uniformity or DU in irrigation is a measure of how uniformly water is applied to the area being watered, normally expressed as percentage, and not to be confused with efficiency. [1] The distribution uniformity is often calculated when performing an irrigation audit. The DU should not be confused with the coefficient of uniformity ...
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.
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.
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 ...
For free flow, the equation to determine the flow rate is simply Q = CH a n where: Q is flowing rate (ft 3 /s) C is the free-flow coefficient for the flume (see Table 1 below) H a is the head at the primary point of measurement (ft) (See Figure 1 above) n varies with flume size (see Table 1 below) Parshall flume discharge table for free flow ...
In locations where a municipal connection is not possible or practical, the required water may be drawn from an open body of water (e.g., lake, pond, river) or a water storage tank. Hydraulic calculations determine if the available water supply pressure is adequate to provide the sprinkler system design flowrate.
The sodium adsorption ratio (SAR) is an irrigation water quality parameter used in the management of sodium-affected soils.It is an indicator of the suitability of water for use in agricultural irrigation, as determined from the concentrations of the main alkaline and earth alkaline cations present in the water.