Question

Given that a particular crop requires about 20 cm depth of water at an interval of 40 days, and the base period is 400 days. Find the delta for the crop? Now using this delta find the duty of water for the crop?

(a) 150 cm, 1150 hectares/cumec

(b) 180 cm, 1825 hectares/cumec

(c) 200 cm, 1728 hectares/cumec

(d) 195 cm, 1920 hectares/cumec

The question was posed to me by my school principal while I was bunking the class.

Question is taken from Water Requirements topic in section Water Requirements of Crops of Irrigation Engineering

Answer 1

Correct choice is (c) 200 cm, 1728 hectares/cumec

Best explanation: Given that base period is 400 days at an interval of 40 days. This number of waterings as = 400/40 = 10

Now delta = 10 x 20 = 200 cm.

Now we have relation between delta and duty as –

Delta = (864B)/D

B = base period, D = duty

200 = (864 x 400)/D

D = 864 x 2 = 1728 hectares/cumec.