Gross irrigation requirement for each irrigation

Even in optimal projecting condition, there is no storage of all of the water in the root zone of plants. During the delivery and application of irrigation water, the water losses are experienced. It is considered that there is no delivery losses in water pipes transmitted with closed pipes. The total quantity of the required irrigation water for each irrigation is calculated by the following formula.

dg=dn/Ea (4)


dg: gross irrigation requirement, mm, dn: net irrigation requirement, mm,

Ea: irrigation application efficiency %.

Ea can be taken as 0.8 when the planning for sprinkler irrigation

2.3.2 Irrigation interval

It is an expression how many days elapsed between consecutive two irrigation. It can be determined with the help of the following formula.

Ti: dn/Etc (5)


Ti: irrigation interval, day

dn: Net irrigation requirement for each irrigation, mm ETc: evapotranspiration mm /day

Due to heavy textured soils have greater water-holding capacity, the irrigation interval increases depending on the net irrigation water, and it decreases in sandy soils. In suitable soil conditions, as reducing by half the irrigation period of a week or ten day period of irrigation, increasing irrigation efficiency can be achieved.

2.3.3 System capacity

The system capacity turned from water supply or irrigation duration is determined by the following formula.

Q=A*dt/3.6*T (6)


Q:System capacity, L/s A: Irrigated Area, da T: Irrigation duration, h