JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III Year WATER RESOURCES ENGINEERING Previous Question Paper (September - 2021 - R16)
Answer any five questions. All questions carry equal marks.
Main
What do you understand by precipitation? Explain various types of precipitation.
Answer
Precipitation is the collective term for all forms of water particles, whether liquid or solid, that originate in the atmosphere and fall to the ground. It occurs when atmospheric water vapor condenses into droplets or ice crystals that grow large enough to overcome air resistance and fall due to gravity.
The primary types of precipitation, classified based on the mechanism of lifting the air mass, are:
- Cyclonic Precipitation: Caused by the lifting of moist air due to pressure differences. It is further divided into Frontal precipitation (where two air masses of different temperatures meet) and Non-frontal precipitation (where air converges into a low-pressure area).
- Convective Precipitation: Occurs when a localized parcel of air is heated by the earth's surface, becomes less dense, and rises rapidly. As it cools at higher altitudes, it condenses to form intense, short-duration showers, often accompanied by thunderstorms.
- Orographic Precipitation: Occurs when moisture-laden air masses are forced to rise over mountain barriers. The air cools adiabatically, leading to condensation and rainfall on the windward side, while the leeward side remains in a rain shadow area.
- Turbulent Precipitation: Caused by the friction of the earth's surface, which creates turbulence in the air flow, forcing it to rise and condense.
A catchment has five rain gauge stations. In a year, the annual rainfall recorded by the gauges are 78.8 cm, 90.2 cm, 98.6 cm, 102.4 cm and 7.4 cm. for a 6% error in the estimation of the mean rainfall, determine the additional number of gauges needed.
Answer
To determine the number of additional rain gauges required, we first calculate the mean and standard deviation of the existing data.
Next, calculate the standard deviation (σ):
The coefficient of variation (Cv) is:
Given the allowable error (ε) = 6%, the optimum number of gauges (N) is calculated as:
Rounding to the next whole number, the total required gauges N = 74. Since 5 gauges already exist, the additional gauges needed are:
What is run-off? What are the factors that affect the run-off from a catchment area?
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In a river basin a station A was inoperative during a storm, while stations B, C, D and E, surrounding A were in operation, registering 74 mm, 88 mm, 71 mm and 80 mm of precipitation. The coordinates of B, C, D and E are (9, 6), (12, -9), (-11, -6) and (-7, 7) respectively, with co-ordinates of A as (0.0). Estimate the missing storm precipitation of station A by the inverse distance method.
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What is hydrograph? Draw a single peaked hydrograph and explain its components.
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Under what conditions a synthetic unit hydrograph is used? Explain how it is derived using Snyder’s relations?
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What do you understand by unit hydrograph? How is it derived?
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Define S-curve hydrograph. How it constructed and what are its uses?
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Derive an expression for discharge from a well in unconfined aquifer. The well fully penetrates it.
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Describe with the help of sketches, some of common types of strainers used in tube wells.
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Explain the percussion method of drilling a tube well.
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Distinguish clearly between a shallow well and a deep well. How does a deep well differ from a tube well in confined aquifer?
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What do you understand by crop rotation? What are its advantages?
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A water course has a cultivable commanded area of 1200 hectares. The intensity of irrigation for crop A is 40% and for B is 35%, both the crops being Rabi crops. Crop A has a kor period of 20 days and crop B has kor period of 15 days. Calculate the discharge of the water course if the kor depth for crop A is 10 cm and for B it is 16 cm.
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Explain various types of canals, according to various classification systems.
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Using lacey’s basic regime equations, derive an expression for lacey’s scour depth.
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