Correct Answer - Option 4 : 96 cm
Concept:
Duty:
It is the area of land that can be irrigated with a unit volume of water supplied across the base period. It is generally expressed in hectare/cumec.
Delta:
It is the depth of water required to raise a crop over a unit area across the base period. It is generally expressed in cm or m.
Base period:
The time between the first watering of a crop at the time of its sowing to its last watering before harvesting is called the base period of the crop. It is expressed in days.
The relationship between duty, delta and base period is given by:
D = \(\frac{{8.64\; \times \;B}}{\Delta }\)
Where,
D = Duty in hectare/cumecs, \(\Delta \) = Delta in meter, and B = Base period of the crop in days.
Calculation:
Given:
D = 900 ha/cumec
B = 100 days
Than, \(\Delta = \frac{{8.64\; \times\; B}}{D}\)
\(\Delta = \frac{{8.64\; \times \;100}}{{900}}\)
Delta (\(\Delta \)) = 0.96 m = 96 cm
