This set of Engineering Geology Multiple Choice Questions & Answers (MCQs) focuses on “Types of Aquifer and Aquifer Functions”.
1. Aquifers are distinguished into how many types on the basis of physical conditions under which water can exist in them?
Explanation: Two basic types of aquifers are distinguished on the basis of physical conditions under which water can exist in them: the unconfined aquifer and the confined aquifer.
2. Which aquifer is called water table aquifer?
a) Unconfined aquifer
b) Confined aquifer
c) Ground aquifer
d) Connate aquifer
Explanation: Unconfined aquifer is also called a water-table aquifer, and is the most common type encountered in the fields.
3. What is the pressure of upper surface of unconfined aquifer?
a) Very high pressure
b) Lower than atmospheric pressure
c) Equal to atmospheric pressure
d) Greater than atmospheric pressure
Explanation: In unconfined aquifer, the upper surface of water or the water-table is under atmospheric pressure which may be acting through the interstices in the overlying rocks.
4. What is the isolated water table held by a small extension of impervious rock called?
a) Underlying water
b) Secret water
c) Perched water
Explanation: Perched water table is the term used for isolated water table in an aquifer held by a small extension of impervious rock within a large pervious tract.
5. Supplies from perched water-table are reliable as source of water.
Explanation: Supplies from perched water-table which are isolated reservoirs are often not reliable as source of water.
6. What is the upper surface of water in a confined aquifer called?
a) Primary layer
b) Secondary layer
c) First layer
d) Peizometric layer
Explanation: Naturally water held in confined type of aquifer is not under atmospheric pressure but under a greater pressure due to the confining medium. The upper surface of water in a confined aquifer is called piezometric surface.
7. At many places where is the piezometric surface with respect to the ground level?
b) Same level
d) Inclined to ground level
Explanation: Artesian aquifer is, in fact, confined aquifer of such a geometry developed in suitable geological situations so that the mezometric surface is always above the ground level at many places when projected in elevation.
8. What is the speciality of the Artesian Water?
a) Has a characteristic colour
b) Has a characteristic odour
c) Requires no pumping
d) Requires special type of pumping
Explanation: When water is tapped from Artesian aquifers, it rushes up to and to great heights. Such wells are called Artesian wells, or flowing wells and the type of groundwater obtained from them, which often needs no pumping, as Artesian Water.
9. Storage capacity of a reservoir depends on __________
a) Porosity of rocks
c) Quality of solidity of rocks
d) Porosity and inter-connections
Explanation: The storage capacity of a reservoir depends on the porosity of the rock on the one hand and the nature and inter-connections of the pores.
10. What is the volume of voids in a rock mass expressed in percentage of total volume of rock called?
b) Voids ratio
d) Specific yield
Explanation: Porosity is defined as volume of voids in a rock mass expressed in percentage terms of the total volume of the rock.
11. Which types of rocks are highly porous?
d) Igneous and metamorphic
Explanation: Sedimentary rocks are relatively porous because there is a great variation in degree of packing on the one hand and in size, shape and arrangement of the grains on the other hand.
12. High porosity is alone sufficient to ensure water yield.
Explanation: Porosity is a property of primary importance in determining the water bearing qualities of a rock. Only porous rocks can be aquifers but high porosity itself is not sufficient to ensure water yielding capacity of a rock.
13. What is the quantity of water that a unit volume of aquifer drains by gravity called?
a) Porous volume
b) Water yield
c) Specific yield
d) Unit yield
Explanation: The water is released by aquifer under the force of gravity and depends both on the quantity and quality of the pores and other openings present in the rock. It is called specific yield and may be defined as “the quantity of water that a unit volume of aquifer drains by gravity.”
14. The term which is collectively responsible, along with specific yield, for total porosity of an aquifer is __________
a) Unit yield
b) Specific retention
c) Unit retention
d) Specific allowance
Explanation: Specific retention is the term used to express the amount of water retained by a unit volume of aquifer after allowing gravity drainage through it. Thus, specific yield and specific retention together sum up to the total porosity of an aquifer.
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