JNTU
JNTU B.Tech III WATER RESOURCES ENGINEERING Previous Question Paper (July/August - 2023 - R16)
Part A is compulsory. Answer all questions. In Part B, Answer any one question from each unit.
Part A
Sketch hydrologic cycle and indicate the components.
Answer
The hydrologic cycle is the continuous movement of water on, above, and below the surface of the Earth. It is driven by solar energy and gravity. The primary components are:
- Evaporation/Transpiration: Water changes from liquid to vapor from water bodies and vegetation.
- Condensation: Water vapor cools to form clouds.
- Precipitation: Water returns to the Earth as rain, snow, or hail.
- Infiltration: Water penetrates the soil to become groundwater.
- Runoff: Water flows over the land surface into streams and oceans.
A sketch would show a circular flow starting from the ocean, rising via evaporation, condensing into clouds, precipitating over land, and returning to the ocean through surface runoff and groundwater flow.
List methods used for control of evaporation losses.
Answer
Evaporation losses from water bodies can be controlled using the following methods:
- Storage reduction: Minimizing the surface area of the reservoir, such as by storing water in deeper, narrower reservoirs rather than shallow, expansive ones, reduces the area exposed to evaporation.
- Chemical films: Applying a thin, monomolecular layer of chemicals like cetyl alcohol (hexadecanol) on the water surface. This film acts as a barrier to water molecules escaping into the atmosphere without significantly affecting water quality or aquatic life.
- Mechanical covers: Using floating covers, such as plastic balls, rafts, or shade cloths, to physically cover the water surface, thereby reducing both solar radiation absorption and wind-induced evaporation.
- Wind breakers: Planting trees or constructing windbreaks around the perimeter of the reservoir to reduce wind velocity over the water surface, which decreases the rate of vapor transport away from the surface.
What do you mean by direct runoff hydrograph? Explain.
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What is base flow? How do you estimate it?
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What is specific yield? What factors influence it?
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State Darcy’s law and give its limitations.
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Differentiate between sprinkler and drip irrigation.
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Give methods used to control waterlogging.
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Give factors influencing time of concentration.
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With help of sketches, indicate different regimes of flow in alluvial channels.
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Part B
With help of sketch, explain the working of tipping bucket type rain gauge.
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The data pertaining to annual rainfall recorded at 6 rain gauge stations in a catchment is given below. For 10% error in the estimation of mean rainfall, find the optimum number of rain gauge locations required for the catchment.
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In a particular season, the catchment was found to have a phi-index of 0.4 cm/h. If a rainfall of 2.4 cm occurs in that season at a uniform rate in a 8 hour storm, find the resulting direct runoff depth on the catchment.
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What is infiltration and infiltration rate? Explain methods used to measure infiltration.
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The direct runoff hydrograph resulting from a 4 cm of effective rainfall of 6 hr duration are given below. Determine the area of the catchment and the ordinates of the 6 hr unit hydrograph.
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Explain the terms i) Effective rainfall ii) Baseflow and iii) Flood Hydrograph.
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What is synthetic hydrograph? Explain the purpose of synthetic hydrograph.
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With help of sketches explain the confined, semi-confined, unconfined and perched aquifers.
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A fully penetrating artesian well is pumping @ 1500 m3/day from an aquifer whose storage coefficient and transmissivity are 4×10-4 and 0.145 m2/min respectively. Find the drawdowns at a distance 3m from the production well after 1 hour of pumping and a distance of 350m after 1 day of pumping.
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Explain the terms i) Storage Coefficient ii) Permeability and iii) Transmissivity.
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A constant head permeability test was carried out on a soil sample of diameter 10 cm and length 15cm. If 100cc of water was collected in 100 seconds under a constant head of 50 cm, determine the coefficient of permeability of the soil sample.
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Explain advantages and disadvantages of irrigation.
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During a particular stage of the growth of a crop, consumptive use of water is 302mm/day. Calculate the frequency of irrigation and depth of water application if the amount of water available in the soil is i) 50% and ii) 80% of the max. Depth of available water in the root zone which is 80mm. Assume irrigation efficiency as 60%.
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Write a detailed note on methods of improving soil fertility.
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A reservoir is required to provide a single filling the water needs for the following crops. Calculate its capacity allowing for tank evaporation losses of 20% and canal seepage losses of 12%.
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Bring out a detailed comparison between Kennedys and Lacey’s theory and state their limitations.
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Design an irrigation channel using the following data: Longitudinal slope = 1 in 6000; Lacey’s silt factor = 1; Channel section = trapezoidal; Channel side slopes = 0.5 : 1. Also find the channel discharge.
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Explain the terms in Rational Method, used for computing the peak discharge from a catchment. Explain the limitations of the method.
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What are the advantages and disadvantages of channel lining? Explain the requirements of good lining material.
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