Test: Duty and Delta of a Crop - Civil Engineering (CE) MCQ

Every type of crop requires different amount of water for its complete growth in certain fixed intervals of time. The time interval between two consecutive intervals is called a rotation period.

Duty: It is the number of hectares of land irrigated for full growth of a given crop by a supply of 1 cumec of water continuously during the entire base period of that crop.
Delta: The total water depth required by a crop to attain its full maturity in its base period.
Base Period: The time period that elapsed for the instant of the showing of crop to the instant of its harvesting is called base period or crop period.
The relation between Duty (D), Delta (Δ) and Base period (B) is given as:

Calculation:
Given data,
B = 110 days
D = 1400 hectares/cumec
Hence, the delta for a crop

Δ = 0.678 m = 68 cm

Duty: It is the number of hectares of land irrigated for full growth of a given crop by a supply of 1 cumec of water continuously during the entire base period of that crop.
Delta: The total water depth required by a crop to attain its full maturity in its base period.
Base Period: The time period that elapsed for the instant of the showing of crop to the instant of its harvesting is called base period or crop period.
The relation between Duty in hectares/cumec (D), Delta in meter (Δ) and Base period in days (B) is given as:

Calculation:
Given data,
B = 130 days
Δ = 0.864 m
Hence, the delta for a crop

D = 1300 hectares/cumec

The relation between Duty (D), Delta (Δ), and Base period (B) is given as:

Calculation:
Base period (B) = 240 days
Duty (D) = 1728 hec/cumec

Δ = 1.2 m = 120 cm

Duty: It is the number of hectares of land irrigated for full growth of a given crop by a supply of 1 cumec of water continuously during the entire base period of that crop.
Delta: The total water depth required by a crop to attain its full maturity in its base period.
Base Period: The time period that elapsed for the instant of the showing of crop to the instant of its harvesting is called base period or crop period.
The relation between Duty (D), Delta (Δ) and Base period (B) is given as:

Δ = 1.4 m = 140 cm

Relation between Delta (Δ), Duty (D), and Base period (B) is given by:

Where
Δ is in cm, D is in hectares per cumec, and B is in days
Calculation:
Given data,
D = 864 hectares/cumecs
B = 120 days
The delta for a crop 

The total quantity of water required by the crop for its complete growth can be expressed in terms of depth of water standing on the field. This total depth expressed in cm is called delta.

When direct irrigation is used, then the units of duty, always expressed in hectares/cumec. Then duty is called flow duty.

According to the number of hectares/cumec, if the irrigated area is large or small then it is called high or low duty respectively.

This type of area is not kept under cultivation because, to restore the fertility of the soil, to provide pasture land for animals, to prevent water logging in the land.