Duty and Delta

Duty (D): It is defined as the area of the land irrigated by a unit discharge of water flowing continuously for the duration of the base period of the crop, it is denoted by D. It is measured in hectares/m3/s. Duty is essential while designing the physical structure of water storage and conveyed system.

Factors' Affecting Duty of Water:

• Type of Crop
• Type of Soil
• Climatic Condition
• Method of Irrigation

Delta (Δ): Each crop requires a certain amount of water after a certain fixed interval of time, Delta is the total depth of water in centimetre required by a crop to come to maturity.

Relation Between Duty and Delta:

Let consider a crop of base period B days, to this crop 1 cumec of water is applied for B days

then,

V= 1 x (B x 24 x 60 x 60)

 = 86400 B cubic meter

Let V cubic meters of water mature D hectare of land

D hectare of land = D x 10000 Sq meter

Where,

D = Duty of water on the field

Δ = Delta, depth of water supplied to filed

B = Base period of crop in days