Irrigation Engineering: Set 03

Irrigation Engineering Set 3 | Science Stoppers

1. For a gravity dam of height ‘H’, the total water pressure force acts at a height of: ऊंचाई ‘H’ वाले ग्रेविटी बांध के लिए, कुल जल दाब बल (water pressure force) किस ऊंचाई पर कार्य करता है?

A) H/2 from the base
B) H/3 from the base
C) H/4 from the base
D) 2H/3 from the base

Correct Answer: B
Explanation: The hydrostatic pressure distribution is triangular. The resultant force acts at the centroid of the triangle, which is H/3 from the base.

2. Match the Spillway types with their features:
1. Ogee Spillway | P. Used for high dams, follows lower nappe of a sharp-crested weir
2. Chute Spillway | Q. Suitable for earth dams, water flows through an open channel
3. Side Channel Spillway | R. Used when space for a straight crest is limited स्पिलवे प्रकारों का उनकी विशेषताओं के साथ मिलान करें:
1. ओगी स्पिलवे | P. ऊंचे बांधों के लिए, शार्प-क्रेस्टेड वियर के लोअर नैपे का अनुसरण करता है
2. च्यूट स्पिलवे | Q. मिट्टी के बांधों के लिए उपयुक्त, पानी एक खुले चैनल के माध्यम से बहता है
3. साइड चैनल स्पिलवे | R. उपयोग तब किया जाता है जब सीधे क्रेस्ट के लिए जगह सीमित हो

A) 1-P, 2-Q, 3-R
B) 1-Q, 2-P, 3-R
C) 1-R, 2-Q, 3-P
D) 1-P, 2-R, 3-Q

Correct Answer: A
Explanation: Ogee is the most common for concrete dams. Chute is standard for earth dams on flanks. Side channel spillways are used in narrow canyons.

3. Assertion (A): A divide wall is constructed to separate the under-sluices from the weir pocket.
Reason (R): It helps in creating a still pond in front of the canal head regulator to facilitate silt deposition. कथन (A): डिवाइड वॉल का निर्माण अंडर-स्लुइस को वियर पॉकेट से अलग करने के लिए किया जाता है।
कारण (R): यह सिल्ट जमाव की सुविधा के लिए नहर हेड रेगुलेटर के सामने एक स्थिर तालाब (still pond) बनाने में मदद करता है।

A) Both A and R are true and R is the correct explanation of A
B) Both A and R are true but R is NOT the correct explanation
C) A is true but R is false
D) A is false but R is true

Correct Answer: A
Explanation: The divide wall creates a “pocket” of relatively calm water, allowing heavier silt to settle before water enters the canal.

4. If the trap efficiency of a reservoir is 90% and the annual sediment inflow is 10,00,000 tonnes, find the amount of sediment deposited annually. यदि एक जलाशय की ट्रैप दक्षता 90% है और वार्षिक तलछट (sediment) प्रवाह 10,00,000 टन है, तो सालाना जमा होने वाली तलछट की मात्रा ज्ञात करें।

A) 1,00,000 tonnes
B) 9,00,000 tonnes
C) 10,00,000 tonnes
D) 5,00,000 tonnes

Correct Answer: B
Explanation: Deposited Sediment = Inflow × Trap Efficiency.
10,00,000 × 0.90 = 9,00,000 tonnes.

5. According to Bligh’s Creep Theory, the safety against piping is ensured if the creep length is: ब्लाई की क्रीप थ्योरी (Bligh’s Creep Theory) के अनुसार, पाइपिंग के खिलाफ सुरक्षा तब सुनिश्चित होती है जब क्रीप लंबाई हो:

A) L ≥ C.H
B) L ≤ C.H
C) L = H/C
D) L = C/H

Correct Answer: A
Explanation: L is the total creep length, C is Bligh’s coefficient, and H is the percolation head. Safety is achieved when the path of water is long enough to dissipate the head.

6. Statement I: A non-modular outlet is one whose discharge depends on the water level in both the distributary and the field channel.
Statement II: A Kennedy’s Gauge Outlet is a modular outlet. कथन I: एक नॉन-मॉड्यूलर आउटलेट वह है जिसका डिस्चार्ज डिस्ट्रीब्यूटरी और फील्ड चैनल दोनों के जल स्तर पर निर्भर करता है।
कथन II: कैनेडी का गेज आउटलेट एक मॉड्यूलर आउटलेट है।

A) Only I is correct
B) Only II is correct
C) Both I and II are correct
D) Neither is correct

Correct Answer: C
Explanation: Non-modular outlets (like submerged pipes) are affected by downstream levels. Rigid modules (like Gibbs) provide constant discharge regardless of levels.

7. In Khosla’s theory, the exit gradient ($G_e$) for a weir with floor length ‘b’, depth of downstream pile ‘d’, and head ‘H’ is given by: खोसला के सिद्धांत में, फ्लोर की लंबाई ‘b’, डाउनस्ट्रीम पाइल की गहराई ‘d’ और हेड ‘H’ वाले वियर के लिए एग्जिट ग्रेडिएंट ($G_e$) का सूत्र क्या है?

A) (H/d) × (1/π√λ)
B) (H/b) × (1/π√λ)
C) (H/d) × (λ/π)
D) (d/H) × (π√λ)

Correct Answer: A
Explanation: The formula is G_e = (H/d) \times (1/π\sqrt{λ}), where λ depends on the ratio α = b/d.

8. The most critical condition for the stability of the upstream slope of an earth dam is: मिट्टी के बांध की अपस्ट्रीम ढलान की स्थिरता के लिए सबसे गंभीर स्थिति कौन सी है?

A) Steady seepage
B) Sudden drawdown of the reservoir
C) During construction
D) Full reservoir level

Correct Answer: B
Explanation: In sudden drawdown, the water level in the reservoir drops quickly but pore water inside the soil cannot drain fast, creating high destabilizing pressure on the U/S slope.

9. A silt excluder is constructed at the: सिल्ट एक्सक्लूडर (Silt excluder) का निर्माण कहाँ किया जाता है?

A) Head of the canal inside the canal
B) Bed of the river in front of the head regulator
C) Tail of the canal
D) Cross regulator

Correct Answer: B
Explanation: Silt **Excluder** is in the river (upstream of canal). Silt **Ejector** is inside the canal after some distance from the head.

10. The base width ‘B’ of an elementary profile of a gravity dam for ‘no tension’ condition (ignoring uplift) is: बिना अपलिफ्ट के ‘नो टेंशन’ स्थिति के लिए ग्रेविटी बांध के एलीमेंट्री प्रोफाइल की आधार चौड़ाई ‘B’ क्या है?

A) H / √G
B) H / G
C) H √G
D) H / (G-1)

Correct Answer: A
Explanation: To ensure no tension at the base, the base width must satisfy B ≥ H / \sqrt{G}, where G is the specific gravity of dam material.

11. Calculate the wetted perimeter (P) for a Lacey’s regime channel carrying 100 cumecs of discharge. 100 क्यूमेक डिस्चार्ज ले जाने वाले लेसी रिजीम चैनल के लिए भीगे हुए परिमाप (P) की गणना करें।

A) 47.5 m
B) 38.0 m
C) 100.0 m
D) 4.75 m

Correct Answer: A
Explanation: P = 4.75 × √Q = 4.75 × √100 = 4.75 × 10 = 47.5 m.

12. A cross regulator is provided on: क्रॉस रेगुलेटर (Cross regulator) कहाँ प्रदान किया जाता है?

A) The off-taking canal
B) The main canal downstream of an off-take
C) The head of the main canal
D) The tail end only

Correct Answer: B
Explanation: A cross regulator is placed across the main canal to head up water so that it can flow into the off-taking (branch) canal even during low flow.

13. If the actual length of a river is 15 km and its axial length is 10 km, find the Tortuosity. यदि एक नदी की वास्तविक लंबाई 15 किमी और उसकी अक्षीय लंबाई (axial length) 10 किमी है, तो टोर्टुऑसिटी (Tortuosity) ज्ञात करें।

A) 0.67
B) 1.5
C) 150
D) 1.0

Correct Answer: B
Explanation: Tortuosity = Actual Length / Axial Length = 15 / 10 = 1.5.

14. The useful life of a reservoir is said to be terminated when: जलाशय का उपयोगी जीवन कब समाप्त माना जाता है?

A) 50% of its capacity is filled with sediment
B) 100% of its capacity is filled
C) It can no longer store water for the purpose it was intended
D) The dam starts leaking

Correct Answer: C
Explanation: Functional termination occurs when sediment reduces the storage so much that the reservoir’s primary goals (irrigation/power) cannot be met economically.

15. Assertion (A): Provision of a rock toe at the downstream end of an earth dam is essential.
Reason (R): It prevents the phreatic line from cutting the downstream face of the dam. कथन (A): मिट्टी के बांध के डाउनस्ट्रीम सिरे पर रॉक टो (rock toe) का प्रावधान आवश्यक है।
कारण (R): यह फिएटिक लाइन को बांध के डाउनस्ट्रीम चेहरे को काटने से रोकता है।

A) Both A and R are true and R is the correct explanation of A
B) Both A and R are true but R is NOT the correct explanation
C) A is true but R is false
D) A is false but R is true

Correct Answer: A
Explanation: Without a rock toe or drainage filter, the seepage line might exit on the downstream slope, causing sloughing and failure.

16. A fish ladder is provided in a diversion headwork for: डाइवर्जन हेडवर्क में फिश लैडर (Fish ladder) किसके लिए प्रदान की जाती है?

A) Sorting fish for the market
B) Safe migration of fish across the weir
C) Aeration of water
D) Preventing fish from entering the canal

Correct Answer: B
Explanation: It is an environmental feature that allows fish to swim upstream or downstream past the obstruction.

17. An infiltration gallery is a: इनफिल्ट्रेशन गैलरी (Infiltration gallery) क्या है?

A) Vertical well
B) Horizontal well under the river bed
C) Type of canal outlet
D) Spillway component

Correct Answer: B
Explanation: It is a horizontal tunnel with perforated walls placed in the sandy bed of a river to collect sub-surface water.

18. According to Kennedy’s theory, find the critical velocity ($V_o$) for a depth of flow $y = 1.0$ m and critical velocity ratio $m = 1.1$. (Formula: $V_o = 0.55 \cdot m \cdot y^{0.64}$) कैनेडी के सिद्धांत के अनुसार, 1.0 मीटर की प्रवाह गहराई और 1.1 के क्रांतिक वेग अनुपात (m) के लिए क्रांतिक वेग ($V_o$) ज्ञात करें।

A) 0.605 m/s
B) 0.55 m/s
C) 1.1 m/s
D) 0.64 m/s

Correct Answer: A
Explanation: V_o = 0.55 \times 1.1 \times (1.0)^{0.64} = 0.55 \times 1.1 \times 1 = 0.605 m/s.

19. The main purpose of providing a berm in a canal in partial cutting and partial filling is: आंशिक कटाई और आंशिक भराई वाली नहर में बर्म (berm) प्रदान करने का मुख्य उद्देश्य क्या है?

A) To increase the discharge
B) To protect the canal from silting
C) To provide a space for future widening and to reduce seepage
D) To act as a fish ladder

Correct Answer: C
Explanation: Berms provide stability to the banks, reduce the saturation gradient (seepage path), and allow for future expansion.

20. The difference between a weir and a barrage is that: वियर (weir) और बैराज (barrage) के बीच मुख्य अंतर यह है कि:

A) A weir has no gates, but a barrage has adjustable gates
B) A barrage has no gates, but a weir has
C) A weir is built across a river, but a barrage across a canal
D) They are both exactly the same

Correct Answer: A
Explanation: In a weir, the pond level is largely achieved by the raised crest. In a barrage, the pond level is controlled almost entirely by gates. [Image comparing a weir and a barrage structure]

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