JNTU
JNTU B.Tech III HYDROLOGY AND WATER RESOURCES ENGINEERING Previous Question Paper (August - 2022 - R18)
Answer any five questions. All questions carry equal marks.
Main
Describe various methods of computing average rainfall over a basin.
Answer
The average rainfall over a basin is typically computed using the following three primary methods:
- Arithmetical Mean Method: This is the simplest method, calculated by taking the arithmetic average of rainfall values recorded at all stations within the basin. It is suitable for flat terrain where rainfall is uniformly distributed.
- Thiessen Polygon Method: This method assigns weights to each station based on the area of the polygon surrounding it. The basin is divided into polygons by drawing perpendicular bisectors of lines connecting adjacent stations, and the average rainfall is the weighted mean of the station values based on these areas.
- Isohyetal Method: This is the most accurate method. Isohyets (lines of equal rainfall) are drawn based on point measurements. The average rainfall is calculated by determining the volume of water between successive isohyets, summing these volumes, and dividing by the total area of the basin.
Explain in detail about Global Water Budget.
Answer
The global water budget represents the balance of water movement across the Earth's surface, atmosphere, and oceans. It is governed by the principle of conservation of mass, where the total water volume remains constant over long periods.
Key components include:
- Oceanic Budget: Oceans cover about 71% of the Earth's surface and act as the primary reservoir. Evaporation from the ocean surface exceeds precipitation falling directly onto it, resulting in a net moisture transport toward land masses.
- Land Budget: Precipitation over land exceeds evapotranspiration. The surplus water returns to the oceans via surface runoff (rivers) and subsurface flow (groundwater).
- Atmospheric Budget: The atmosphere acts as a transport mechanism, moving moisture from oceanic sources to land areas. The residence time of water in the atmosphere is very short, typically about 9 to 10 days.
The global balance is expressed as: Precipitation = Evaporation + Change in Storage, where over a long-term global average, the change in storage is negligible.
With a neat sketch, explain the concept of hydrological cycle.
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Explain in detail about any one recording and one non-recording type rain gauges.
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A watershed of 695 km2 with six rainfall gauges can be divided into Theissen polygon with the data listed in the accompanying table. Using the total storm rainfall depth listed, find the average rainfall over the watershed.
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Calculate the Potential Evapotranspiration for an area in the month of August by Hargreaves and Blaney – Criddle method with the following available data: Latitude: 100N, Max. Temperature: 45.40C, minimum temperature: 22.60C, mean humidity: RHmean: 72.8%, actual sunshine hours: 8.25 hr., wind speed @ 4 m high – 4.57 m/s. Assume any other relevant data.
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Explain the methods adopted to estimate the evaporation from surface water bodies.
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The following observations were taken from a double ring infiltrometer with inside ring diameter of 40 cm. Plot the infiltration capacity curve and find the constant rate of infiltration that the experimental field have towards the end. Also compute the average infiltration rate for the first 30 minutes.
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Given below are the ordinates of a 6-h unit hydrograph for a catchment. Calculate the ordinates of the DRH due to a rainfall excess of 4.25cm occurring in the 6h.
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Exemplify the assumptions and applications of Unit Hydrograph in Water Resources Engineering problems.
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By means of neat sketch, explain about various components of single peaked hydrograph.
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The ordinates of a 4-hour unit hydrograph of catchment are given below. Derive the flood hydrograph in the catchment due to storm provided.
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An Unconfined aquifer has an area of 450 km2, thickness of 25.5m and a porosity of 75%. What is its specific retention if it can yield 1950 million m3 of free-draining water?
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Determine the mean depth of irrigation in a furrow 85 m long and spaced 50 cm apart with an initial flow of 2.75 l/s for a period of 45 minutes. The stream was then reduced to 1.0 l/s after it reached the tail end of the furrow and continued for another 60 minutes.
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Exemplify the causes, effects and remedial measures of Water logging.
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Design an irrigation channel on Kennedy’s theory, to carry a discharge of 55 cumec. Take N = 0.0225 and m = 1.05. The channel has a bed slope of 1 in 6500.
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