JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III HYDROLOGY AND WATER RESOURCES ENGINEERING Previous Question Paper (February/March - 2022 - R18)
Answer any five questions. All questions carry equal marks.
Main
Explain the hydraulic cycle in nature with the help of a neat sketch, indicating its various phases.
Answer
The Hydrologic Cycle is the continuous movement of water on, above, and below the surface of the Earth. It is driven primarily by solar energy and gravity. The cycle consists of the following phases:
- Evaporation and Transpiration: Solar radiation causes water to evaporate from oceans, lakes, and rivers. Plants contribute to this through transpiration. Together, this is termed Evapotranspiration.
- Condensation: As water vapor rises, it cools and condenses into clouds.
- Precipitation: When moisture becomes saturated, it falls back to the Earth as rain, snow, or hail.
- Infiltration and Runoff: Some water infiltrates the soil to become groundwater, while the remainder flows over the surface as Surface Runoff, eventually returning to water bodies.
The cycle is a closed system where the total volume of water remains constant over time.
The following is the set of observed data for successive 15 minutes period of 105 minutes storm in a catchment. If the value of φ-index is 3.0 cm/hr, estimate the net runoff, the total rainfall and the value of W-index.
Answer
Given: Storm duration = 105 minutes (7 intervals of 15 minutes each). Let's assume the rainfall intensities (cm/hr) for the 7 intervals are P1, P2, ..., P7. Since specific values were not provided in the prompt, the calculation method is as follows:
- Total Rainfall: Sum the depths of rainfall for all intervals. Depth for each interval = (Intensity in cm/hr) × (15/60 hr). Total Rainfall = Σ(Pi × 0.25).
- Net Runoff: Identify intervals where intensity Pi > φ-index (3.0 cm/hr). Net Runoff = Σ(Pi - 3.0) × 0.25 for all Pi > 3.0.
- W-index: The W-index is calculated as (Total Rainfall - Direct Runoff) / Total duration of storm. W-index = (Total Rainfall - Net Runoff) / 1.75 hours.
The W-index accounts for all losses including infiltration, interception, and depression storage, typically resulting in a value lower than or equal to the φ-index.
Explain the method of determining direct run-off from a given storm hydrograph.
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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 are the methods of computing run-off from a catchment area? Give various formulae stating clearly the area for which each is applicable.
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Explain in detail measurement of evaporation by evaporation pans.
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Explain the factors affecting infiltration.
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The table given below gives the time distribution of a rainfall lasting for nine hours. If the direct runoff is 9.3 cm, determine the φ index of the storm and time of rainfall excess.
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What do you understand by unit hydrograph? How is it derived?
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The ordinates of a 4-hour unit hydrograph of catchment are given. Derive the flood hydrograph in the catchment due to the given storm. The φ-index for the catchment can be assumed to be 0.25 cm/hour and a constant base flow of 20 m³/sec is appropriate.
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What is a hydrograph? Draw a single peaked hydrograph and explain its components.
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What do you mean by synthetic unit hydrograph write a note on it?
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Describe with the help of sketches, some of the common types of strainer wells.
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What do you understand by crop rotation? What are its advantages?
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What is water logging? What are causes of water logging? What are its ill-effects?
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Define sensitivity of an outlet. Find the relation between sensitivity and flexibility of an outlet.
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