JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech IV Year GROUND WATER HYDROLOGY Previous Question Paper (July/August - 2022 - R18)
Answer any five questions. All questions carry equal marks.
Main
Distinguish between the following:
Aquifer and aquifuge
Answer
An aquifer is a saturated geological formation that contains sufficient permeable material to yield significant quantities of water to wells or springs. It possesses both high porosity and high permeability, allowing water to move through it easily. Examples include sand, gravel, and fractured limestone.
An aquifuge is a geological formation that is essentially impermeable and does not contain or transmit water. It lacks both porosity and permeability, acting as a complete barrier to groundwater flow. A solid, unfractured igneous rock formation is a typical example of an aquifuge.
Confined aquifer and water table aquifer
Answer
A water table aquifer, also known as an unconfined aquifer, is one where the upper surface of the zone of saturation is at atmospheric pressure. The water level in a well penetrating this aquifer stands at the same elevation as the water table. It is directly recharged by infiltration from the surface.
A confined aquifer is bounded above and below by impermeable or semi-permeable layers (aquitards or aquicludes). The water in this aquifer is under pressure greater than atmospheric pressure. When a well is drilled into a confined aquifer, the water level rises above the top of the aquifer to a level known as the piezometric surface. If the pressure is sufficient, the water may rise above the ground surface, resulting in an artesian well.
An undisturbed rock sample has an oven dry weight of 0.655 kg. After saturation with kerosene its weight is 0.732 kg. It is then immersed in kerosene and found to dispose 0.301 kg. What is the porosity of the sample?
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Compare Artesian well and flowing well and Influent and effluent streams.
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Adopting the usual notation, derive an expression for the steady state discharge of a well in an unconfined aquifer.
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List out the assumptions made in the analysis of steady radial flow into well.
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An unconfined aquifer has a thickness of 30 m. A fully penetrating 20 cm diameter well in this aquifer is pumped at a rate of 35 liters. The drawdown measured in two observation wells located at distances of 10 m and 100 m from the well are 7.5 m and 0.5 m respectively. Determine the average hydraulic conductivity of the aquifer. At what distance from the well the drawdown is insignificant?
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Write down the Thesis equation for the unsteady radial flow into a well in a confined aquifer. Explain each term in the equation.
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What do you understand by data curve, type curve and matching?
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Explain the following surface and sub-surface investigation methods along with its suitability, advantages and disadvantages.
Electrical resistivity method
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Geophysical logging
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How to reduce sea water intrusion into the aquifers.
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Explain five methods of control of sea-water intrusion into the aquifers.
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