JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III GROUND WATER DEVELOPMENT AND MANAGEMENT Previous Question Paper (March - 2024 - R16)
Answer all questions. Part A is compulsory. Answer any one question from each unit in Part B.
Part A
What is effective porosity?
Answer
Effective porosity is the volume of interconnected voids in an aquifer that can store and transmit water. It is a crucial parameter in groundwater hydrology as it represents the actual storage capacity and the potential for water movement within an aquifer. Unlike total porosity, which includes all voids (even isolated ones), effective porosity considers only those pores that are connected and thus contribute to groundwater flow. It is typically expressed as a fraction or percentage of the bulk volume of the aquifer material.
Define the following: i) Aquiclude ii) Aquifuge iii) Aquitard
Answer
Definitions:
Aquiclude: An aquiclude is a geologic formation that is impermeable or has extremely low permeability, effectively preventing the significant movement of groundwater through it. While it may contain water, it cannot yield water in significant quantities to wells or springs. Examples include unfractured clay layers or dense unfractured rock.
Aquifuge: An aquifuge is a geologic formation that is both impermeable and incapable of storing water. It neither transmits nor stores water. These formations are essentially barriers to groundwater flow and storage. Examples are very dense, unfractured igneous or metamorphic rocks.
Aquitard: An aquitard is a geologic formation of intermediate permeability that significantly restricts the rate of groundwater flow but does not prevent it entirely. Aquitards can transmit some water, but at a much slower rate than aquifers. They often act as confining layers between aquifers, slowing down or impeding the vertical movement of groundwater. Clay layers with some sand lenses are typical examples.
Define Hydraulic conductivity.
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Explain transmissivity and write the units used for it.
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Write the 3D equation for steady ground water flow.
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Write the equation for steady radial flow for confined aquifer.
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Name any two surface and sub-surface investigation methods of ground water.
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What is the necessity of sub surface investigation of ground water?
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What is Conjunctive Use of Ground Water?
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Why does sea water intrusion occur?
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Part B - Unit I
An undisturbed sample of a medium sand weighs 486.64g. The core of the undisturbed sample is 300 cm3. The sample is oven dried for 24 hours at 110oC to remove the water content. The core sample weighed 449.98 g. Determine the bulk density, void ratio, water content, and saturation percentage of the sample. Assuming quartz to be predominant mineral with ρm = 2.65 g/cm3.
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Explain the divisions of sub surface water with a neat diagram.
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Water table of an aquifer drops by 100 cm over an area of 1000 km2. The porosity and specific retention of the aquifer material are 25% and 5% respectively. Find the amount of water drained out (expressed in km3) from the area?
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Define the terms Specific Yield and Specific Retention.
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Part B - Unit II
A 20cm long field sample of silty, fine sand with a diameter of 10 cm is tested using falling head permeameter. The falling head tube has a diameter of 3 cm and the initial head is 8 cm. Over a period of 8 hour the head in the tube falls to 1 cm. Estimate the hydraulic conductivity of the sample.
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What is the Theis Equation for Unsteady flow into a well fully penetrating a confined aquifer?
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Elaborate on the Cooper-Jacob approximation for solving to estimate transmissivity (T), storativity (S).
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If the horizontal cylinder of soil shown below figure 1 has a coefficient of permeability of 0.01 cm/sec. Calculate the amount of flow through the soil.
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Part B - Unit III
What are the assumptions in Dupuit’s and Theim’s equations?
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Referring to the figure 2 given below, if the distance and the observed piezometric surface drop between two adjacent wells are 1000 m and 3 m, respectively, find an estimate of the time it takes for a molecule of water to move from one well to the other. Assume steady unidirectional flow in a homogeneous silty sand confined aquifer with a hydraulic conductivity K=3.5 m/day and an effective porosity of 0.35.
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The drawdown is 3 m in an observation well which is 10 m away from the pumping well (drilled in an artesian aquifer) after 10 min of pumping. What is the time since pumping started, for the same drawdown in another observation well 20 m away from the pumping well?
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Explain Recuperation test.
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Part B - Unit IV
Explain Electrical resistivity and Seismic refraction methods of exploration.
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Explain the applications of GIS and Remote Sensing in Artificial Recharge of Ground water.
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Define artificial recharge and explain the favorable conditions for artificial recharge.
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Explain the basin type of ground water recharge with neat diagram.
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Part B - Unit V
Explain the performance of drilling methods in different types of geologic formations.
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What is Percussion Drilling, explain with neat diagram?
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What is sea water intrusion, explain with neat diagram?
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Explain Upconing of saline water.
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