Q40. Which crop is least efficient in water use among these choices?
[UPSC Civil Services Prelims GS-I (10 October 2021)]
(A) Sugarcane
(B) Sunflower
(C) Pearl millet
(D) Red gram
Answer: (A) Sugarcane
Explanation: Sugarcane has a long growing period and demands substantial water over its crop cycle. Pearl millet and red gram are more adapted to relatively dry conditions. Water productivity varies by region, variety and irrigation management.
Q39. In drip irrigation, water is mainly supplied according to which crop requirement?
[RSMSSB Agriculture Supervisor (2021)]
(A) Seed rate
(B) Soil slope
(C) Consumptive use
(D) Harvesting method
Answer: (C) Consumptive use
Explanation: Consumptive use refers principally to evaporation from soil and transpiration from plants. Drip irrigation schedules are designed to replace water required in the active root zone with relatively small, controlled applications.
Q38. What is a main benefit of drip irrigation?
[JKSSB Junior Engineer Civil (2021)]
(A) Increased runoff
(B) Greater waterlogging
(C) Reduced yield
(D) Higher crop yield with efficient water use
Answer: (D) Higher crop yield with efficient water use
Explanation: When designed well, drip systems keep root-zone moisture closer to crop demand while minimizing excessive wetting outside planted rows. This can improve water-use efficiency and, under suitable conditions, produce higher yields.
Q37. For expensive irrigation supplies, which outcome should be maximized?
[MPSC Engineering Services Civil (2021)]
(A) Water applied per hectare
(B) Conveyance losses
(C) Crop output per unit of water
(D) Soil saturation time
Answer: (C) Crop output per unit of water
Explanation: Where water is costly, efficient scheduling aims to obtain more valuable crop output from each unit used. Measuring crop yield or economic return per unit of irrigation water helps guide investment and water allocation.
Q36. What is the cultivable command-area threshold for a major irrigation project in India?
[JKSSB Junior Engineer Civil (2021)]
(A) More than 2,000 ha
(B) More than 5,000 ha
(C) More than 10,000 ha
(D) More than 20,000 ha
Answer: (C) More than 10,000 ha
Explanation: A major irrigation project has a cultivable command area exceeding 10,000 hectares. The category is based on potential agricultural area served, not simply the volume stored or the dam’s physical height.
Q35. How frequently a crop should be irrigated chiefly depends on which factors?
[GPSC Assistant Engineer Civil (2021)]
(A) Only field shape
(B) Only irrigation canal length
(C) Soil, crop and climate
(D) Only fertilizer type
Answer: (C) Soil, crop and climate
Explanation: Different soils store different quantities of plant-available water, crops have varying rooting depths and climate drives evapotranspiration. Scheduling irrigation therefore considers soil properties, crop stage, atmospheric demand and available rainfall.
2020 Previous-Year Questions
Q34. The Baithali irrigation project is associated with which Rajasthan district?
[RSMSSB JE Electrical/Mechanical (26 December 2020)]
(A) Jhalawar
(B) Kota
(C) Baran
(D) Bundi
Answer: (C) Baran
Explanation: Baithali is an irrigation project associated with Baran district in southeastern Rajasthan. Local projects like this are often examined through project–district identification because they form an important part of state water-resource geography.
Q33. An irrigation channel designed by Lacey’s theory has mean velocity 1.5 m/s and silt factor 1. What is its hydraulic mean radius?
[UPPSC Assistant Engineer Civil (13 December 2020)]
(A) 2.5 m
(B) 1.5 m
(C) 5.625 m
(D) 6.525 m
Answer: (C) 5.625 m
Explanation: Lacey’s empirical relation gives hydraulic radius R = 2.5 V²/f. Substituting V = 1.5 metres per second and f = 1 yields R = 2.5 × 2.25 = 5.625 metres.
Q32. What is the crossing called when an irrigation canal passes above a drainage channel?
[UPPSC Assistant Engineer Civil (13 December 2020)]
(A) Aqueduct
(B) Super passage
(C) Level crossing
(D) None
Answer: (A) Aqueduct
Explanation: An aqueduct conveys canal flow across the top of a natural drain when sufficient vertical clearance exists. A super passage is the reverse arrangement, with the drain above the canal. Such structures preserve independent flow paths.
Q31. Approximately what percentage of Uttar Pradesh’s irrigated area was under canals in the examination data?
[UPPSC RO/ARO GS-I (20 September 2020)]
(A) 25%
(B) 29%
(C) 28%
(D) 27%
Answer: (A) 25%
Explanation: The paper used an older breakdown placing about one-quarter of irrigated area under canals. Tube wells contributed a much larger portion. Such percentages are date-sensitive and should not be interpreted as current statistics.
