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Given the coarse accuracy of the Blaney–Criddle equation, it is recommended that it be used to calculate evapotranspiration for periods of one month or greater. [ 1 ] The equation calculates evapotranspiration for a 'reference crop', which is taken as actively growing green grass of 8–15 cm height.
RSC should not be higher than 1 and preferably less than +0.5 for considering the water use for irrigation. [5] The formula for calculating RSC index is: RSC index = [HCO 3 + CO 3] − [Ca + Mg] RSC index = HCO 3 /61 + CO 3 /30 – Ca/20 – Mg/12 (in case the ionic concentrations are measured in mg/L or ppm as salts)
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.
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 ...
To avoid the inherent complexity of determining stomatal and atmospheric conductance, the Food and Agriculture Organization proposed in 1998 [1] a simplified equation for the reference evapotranspiration ET 0.
A system can be one of several hydrological or water domains, such as a column of soil, a drainage basin, an irrigation area or a city. The water balance is also referred to as a water budget. Developing water budgets is a fundamental activity in the science of hydrology. According to the US Geological Survey: [4]
The blue figure shows an example of results of a computer aided calculation with the amplified drainage equation using the EnDrain program. [11] It shows that incorporation of the incoming energy associated with the recharge leads to a somewhat deeper water table .
This can be used to calculate mean values (expectations) of the flow rates, head losses or any other variables of interest in the pipe network. This analysis has been extended using a reduced-parameter entropic formulation, which ensures consistency of the analysis regardless of the graphical representation of the network. [ 3 ]