Question

Let us take the gross commanded area of a watercourse is 2000 hectares, 80% of which is culturable irrigable. Intensities of sugarcane and paddy are 30% and 50%. The duties of the crops at the head of the watercourse are 850 hectares/cumec and 1900 hectares/cumec. Find the discharge required at the head of the watercourse?

(a) 0.98 cumec

(b) 0.97 cumec

(c) 0.9 cumec

(d) 0.986 cumec

This question was posed to me in an interview.

Asked question is from Design Capacity for an Irrigation Canal topic in division Sediment Transport and Irrigation Channels Design of Irrigation Engineering

Answer 1

The correct answer is (d) 0.986 cumec

To explain: Given G.C.A = 2000 hectares

Now the C.C.A = 2000 x 80 / 100 = 1600 hectares

Intensity of irrigation for sugarcane = 30%

Area to be irrigated under sugarcane = 1600 x 30/100 = 480 hectares

Intensity of irrigation of paddy = 50%

Area to be irrigated under paddy = 1600 x 50/100 = 800 hectares

Duty of sugarcane = 850 hectares/cumec

Duty of paddy = 1900 hectares/cumec

Discharge for sugarcane = 480 / 850 = 0.565 cumec

Discharge for paddy = 800 / 1900 = 0.421 cumec

Now the total canal capacity at the head of watercourse is = 0.565 + 0.421 = 0.986 cumec.