Canals, Headworks and Cross-Drainage
JKSSB Junior Engineer (Civil) · Irrigation Engineering · 18 practice questions with answers and explanations: 11 Easy, 5 Medium, 2 Hard.
Sample questions
Sample Easy question 1
The purpose of lining an irrigation canal is to:
- Increase the seepage
- Increase the roughness
- Reduce seepage losses and control erosion
- Make the canal wider
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Answer: C. A lined canal also has a higher velocity and needs a smaller section.
Sample Easy question 2
A distributary head regulator is built to:
- Measure the silt
- Control the discharge entering a distributary from the parent canal
- Store the canal water
- Drain the field
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Answer: B. The canal escape is a different structure that releases surplus water.
Sample Easy question 3
A canal fall is provided when:
- The canal is lined
- The ground slope is steeper than the permissible bed slope of the canal
- The ground is flat
- The canal carries silt
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Answer: B. The fall drops the canal bed to keep the velocity within safe limits.
Sample Medium question 4
The silt factor of 0.25 mm silt is:
- 1.76
- 0.88
- 0.50
- 0.44
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Answer: B. f = 1.76 × √0.25 = 1.76 × 0.5 = 0.88.
Sample Medium question 5
A canal with a cross-section of 10 m² and a mean velocity of 0.8 m/s carries a discharge of:
- 0.08 cumec
- 12.5 cumec
- 8 cumec
- 80 cumec
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Answer: C. Q = A × V = 10 × 0.8 = 8 m³/s.
Sample Medium question 6
By Lacey's formula the wetted perimeter of a regime channel is P = 4.75 √Q. For Q = 25 cumec, P is:
- 25 m
- 118.75 m
- 47.5 m
- 23.75 m
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Answer: D. P = 4.75 × √25 = 4.75 × 5 = 23.75 m.
Sample Hard question 7
By Lacey's formula V = (Q f² ÷ 140)^(1/6), for Q = 140 cumec and a silt factor f = 1.0, the regime velocity is:
- 1.4 m/s
- 0.5 m/s
- 2.0 m/s
- 1 m/s
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Answer: D. V = (140 × 1 ÷ 140)^(1/6) = 1^(1/6) = 1 m/s.
Sample Hard question 8
By Kennedy's formula V₀ = 0.55 m D^0.64, with m = 1 and a depth of 2 m, the critical velocity is about:
- 2.0 m/s
- 1.10 m/s
- 0.55 m/s
- 0.86 m/s
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Answer: D. V₀ = 0.55 × 2^0.64 = 0.857 m/s.