Question 1
A household tube well is called Abyssinian tube well falls under _________
A. strainer type
B. cavity type
C. slotted type
D. both cavity and slotted type
View Answer
Answer: Option A
Explanation:
Abyssinian tube well is the most common type of tubewell used for household purposes. It is also a strainer type of the tube well and the length of the strainer used here is about 2 meters.
Question 2
A tube well is suitable when the subsoil formation is made up of _____________________
A. cracked and faulted rock
B. alluvium
C. alluvium and various layers of sandy soil, clayey soil, and gravel
D. clayey soil
View Answer
Answer: Option C
Explanation:
In India most of the land especially the Indo-Gangetic plains, Narmada valley consists of deep alluvial soils. The sub-soil water slowly penetrates and is stored in porous sand and gravel beds which are extensively found in India. Tube wells can be easily installed in such lands and are useful for irrigation.
Question 3
Bored tube wells in rocky consolidated formations as are encountered in the South Indian States of our country are usually drilled by _____________
A. rotary drilling rigs
B. percussion drilling rigs
C. down the hole hammer (DTH) rigs
D. cable method of drilling
View Answer
Answer: Option C
Explanation:
In rocky areas, down the hole hammer rigs (DTH rigs) are used to drill isolated holes of 10 to 15 cm in diameter. They are usually in the depth range of 100 m and mostly been constructed in southern states of India. This type of wells usually depends on joints and fissures in the rocks for their water supply.
Question 4
Corrosion of tubewell pipes may cause _______________
A. reduced discharge from the tubewell
B. excessive discharge of sand with water
C. discharge of highly alkaline water
D. increased pumping rate
View Answer
Answer: Option B
Explanation:
Due to the action of acidic water on the pipe, it is gradually destroyed by corrosion. The aquifer sand surrounding the well pipe comes out through the worn-out pipe walls bringing sand along with water. It results in the excessive withdrawal of sand along with the well water.
Question 5
Duty of wells expressed in hectares the well can irrigate to bring a crop to maturity because of ___________
A. well irrigation is a minor scheme
B. well water is lifted immediately and cannot be expressed in ha/m3/sec
C. well is situated in the middle of the commanded area
D. wells are owned by cultivators and so the source of supply is a private one
View Answer
Answer: Option B
Explanation:
In well irrigation water is lifted intermittently. The duty of a well is the area of land in hectares the well can irrigate annually and fully to bring a crop to maturity. It cannot be expressed in hectares/m3/sec for a base period of a crop.
Question 6
For good design, the uniformity coefficient (Cu) of the gravel material should preferably be ______
A. > 2.0
B. < 2.0
C. > 2.5
D. < 2.5
View Answer
Answer: Option D
Explanation:
The uniformity coefficient was proposed by Hazen. The value of the coefficient of the gravel material is preferably kept to be equal to or less than 2.5. A higher value may cause segregation of the gravel during pouring which will result in poor efficiency of the well.
Question 7
According to the Central Board of Irrigation and Power, the PA ratio for graded aquifer should be _______________
A. 9 – 12.5
B. 12 – 15.5
C. > 15.5
D. < 9
View Answer
Answer: Option B
Explanation:
The Central Board of Irrigation and Power suggested the following criteria for PA ratio.i. For uniform aquifers (having Cu < or = 2.0), the PA ratio should be in between 9 – 15.5ii. For graded aquifers (having Cu > 2.0), the PA ratio should be in between 12 – 15.5.
Question 8
In cavity tubewell, there is a possibility of water tapping through sides and the flow is radial.
A. True
B. False
View Answer
Answer: Option B
Explanation:
In cavity-type tubewell, water contribution to the bored hole takes place through the bottom layer only as is done by screen well. The flow in a cavity well is essentially spherical. In strainer type tubewell, water enters into the well from the sides and the flow is radial.
Question 9
Incrustation of the tubewell pipes may lead to _________________
A. reduced discharge from the tubewell
B. excessive discharge of sand with water
C. discharge of highly alkaline water
D. increased pumping rate
View Answer
Answer: Option A
Explanation:
The deposition of alkali salts on the inside walls of the pipe is called incrustation. It reduces the effective diameter of the well pipe and hence reduces the discharge of the tubewell. It cannot be completely eliminated.
Question 10
Reversing the direction of flow by surging the well does help in removing the bridging.
A. True
B. False
View Answer
Answer: Option A
Explanation:
The basic principle in well development is to cause reversals of flow that will rearrange the aquifer particles through the screen openings. This breaks down the bridging of the groups of particles. When the flow is in one direction small particles bridge between large particles across the screen openings.
Question 11
The amount of water required from wells to mature a similar crop is more than that required in canal irrigation.
A. True
B. False
View Answer
Answer: Option B
Explanation:
Delta in well irrigation is the total depth of water required to mature a crop in meters or centimetres. The delta of well water is about 66% of canal water because conveyance losses are minimum and well water is used at the right time in the right quantity.
Question 12
The appropriate life of a tubewell in India is of the order of ______
A. 1 year
B. 2 years
C. 5 years
D. 15 years
View Answer
Answer: Option D
Explanation:
A normal tubewell lasts for about 15 to 20 years in Northern India. It may fail due to incrustation and corrosion.
Question 13
The efficiency of the centrifugal pumps commonly used for lifting water from wells may be of the order of _____________
A. 30%
B. 65%
C. 90%
D. 95%
View Answer
Answer: Option B
Explanation:
Jet pumps have low efficiency of the order of 35% as compared to 65-85% for other centrifugal pumps. It is not used for irrigation tube-wells.
Question 14
The most widely used type of a deep state tube well in India is __________
A. cavity well
B. strainer tube well
C. slotted pipe gravel packed tube well
D. both cavity and strainer tube well
View Answer
Answer: Option B
Explanation:
Strainer type tubewell is a bored hole in which a metal pipe with suitable perforations is inserted. A strainer type tubewell is suitable when water-bearing stratum is available at less depth and there is a possibility of tapping water through sides. It is generally unsuitable for fine sandy strata.
Question 15
What is Pack Aquifer Ratio?
A. D50 of the gravel / D50 of the aquifer
B. D50 of the aquifer / D50 of the gravel
C. D60 of the aquifer material / D10 of the aquifer material
D. D60 of the gravel / D10 of the aquifer
View Answer
Answer: Option A
Explanation:
The gravel pack is usually designed on the basis of Pack Aquifer (PA) ratio. It is usually defined as the ratio of D50 size of the gravel pack material to the D50 size of the aquifer material. It should be designed before designing the size of the slots to be made in the well-screens.
Question 16
What is the measure of the fineness of an aquifer?
A. Average grain size
B. Effective diameter
C. Mean particle size
D. Uniformity coefficient
View Answer
Answer: Option B
Explanation:
Effective diameter is an index of the measure of the fineness of an aquifer. It is used for designing various intake components of a tubewell. For permeability D10 (i.e. 90% grains retained on the sieve) is taken as the effective size.
Question 17
The general average yield from standard tube wells is of order of____________
A. 5 L/sec
B. 50 L/sec
C. 500 L/sec
D. 5000 L/sec
View Answer
Answer: Option B
Explanation:
Tube well irrigation is very suitable where the subsoil formation is suitable for storing water. The general average yield from the standard deep tube-wells is of the order 40 to 50 liters/sec. Shallow tube-wells may yield as high as 15-20 liters/sec if located at proper places.
Question 18
Which drilling method is best suited for underground formations made of gravel, sand and clayey deposits?
A. Percussion drilling
B. Wash boring method
C. Rotary boring method
D. Reverse rotary method
View Answer
Answer: Option B
Explanation:
Percussion method is suitable for soft and fissured rock formations. The rotary boring method can be successfully used for rock as well as unconsolidated formations. The reverse rotary method is used for soft unconsolidated formations made of sand, silt or soft clay.
Question 19
Which is the fastest method of drilling and especially useful in unconsolidated formations?
A. Cable tool method
B. Water-jet boring method
C. Hydraulic Rotary method
D. Reverse Rotary method
View Answer
Answer: Option C
Explanation:
Hydraulic rotary method can handle hard and soft foundations with ease and the danger of accidents is lesser. The rate of drilling by this method for consolidated rock formation may vary from 10 to 15 m per day and in unconsolidated formations 100 to 150 m per day.
Question 20
Which log represents the type of strata existing at different depths and encountered during digging or boring of the wells?
A. Well logs
B. Resistivity logs
C. Radiometric logs
D. Sonic logs
View Answer
Answer: Option A
Explanation:
Resistivity logs indicate the values of the electrical resistivity of rocks at different depths. Sonic logs indicate the value of the velocity of compressional waves at different depths. Radiometric logs indicate the variations of radioactivity with depth.
Question 21
Which of the following drilling method is unsuitable in loose formations such as unconsolidated sand and gravel or quicksand?
A. Percussion drilling
B. Wash boring method
C. Rotary boring method
D. Reverse rotary method
View Answer
Answer: Option A
Explanation:
Percussion method of drilling the well hole is also known as the cable method of drilling. It is ineffective in loose material because of slumping and caving of the material around the drilling bit. This method is useful for cutting consolidated rocks from soft clay to hardest rocks.
Question 22
Which of the following gives an indication of the chemical quality of the groundwater?
A. Geological logs
B. Resistivity logs
C. Sonic logs
D. Thermal logs
View Answer
Answer: Option B
Explanation:
Resistivity surveys are based on the fact that water increases the conductivity of the rocks and thereby reducing their resistivity. Resistivity logs indicate the values of electrical resistivity of the rocks at different depths.
Question 23
Which of the following is an effective method for the development of well?
A. Surging
B. Pumping
C. Well development by compressed air
D. Jetting
View Answer
Answer: Option D
Explanation:
Development of well by high velocity jetting is one of the most effective methods. In this method, the fine particles are washed out of the aquifer due to the shooting of high-velocity water stream through the screen openings. These fines get back into the well due to the turbulence created by the jet. The entire surface of the screen can be covered by gradual raising, lowering and slowly rotating the jetting tool.
Question 24
Which of the following pump can effectively lift water under the maximum suction head of 6 to 8 meters?
A. A single-stage centrifugal pump
B. Submersible pumps
C. Turbine pumps
D. Jet pumps
View Answer
Answer: Option A
Explanation:
A centrifugal pump works effectively under the maximum suction head of 6 to 8 m. Such pumps can be used at places where the fluctuations in water table plus the depression head are limited to a maximum of 8 m. The borehole type pump is used for larger values.
Question 25
Which of the following pumps is also used for testing or development of wells?
A. Vertical turbine pump
B. Submersible motor pump
C. Jet pump
D. Airlift pump
View Answer
Answer: Option D
Explanation:
Airlift pumps are useful in removing objectionable gas, highly corrosive or abrasive water that damages parts of the pump submerged in the well. It is also used for testing or development of wells but is rarely used due to low efficiency.
Question 26
Which of the following strainer is used for shallow irrigation tube wells particularly in deltaic regions of developing countries?
A. Continuous slot type of strainer
B. Louver type of strainer
C. Pipe strainer with fine mesh jackets
D. Coir rope strainers
View Answer
Answer: Option D
Explanation:
Coir rope strainers are low-cost strainers and are generally used for shallow irrigation tube wells. The main disadvantage of such a strainer is its short life of 3 to 5 years. The rusting of the iron bars of the supporting frame and the loosening of the coir rope which expands on wetting are the causes of its failure.
Question 27
Which of the following tubewell is suitable when a deep bearing stratum lies below an impervious layer and water contribution can take place through bottom only?
A. Strainer type tubewell
B. Abyssinian tubewell
C. Cavity type tubewell
D. Slotted type tubewell
View Answer
Answer: Option C
Explanation:
A strainer type tubewell is suitable when water-bearing stratum is available at less depth and there is a possibility of tapping water through sides. The slotted type tubewell is intermediate to the strainer and cavity type tubewell and is used where both the above cannot be used.