Irrigation Engineering Interview Questions and Answers for freshers on “Tube Well – 2”.
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
Answer: a
Clarification: 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.
2. 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
Answer: b
Clarification: 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.
3. 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
Answer: d
Clarification: 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.
4. Rewhiding the well involves ____________________
a) heavy pumping of well
b) starting and stopping of pumping intermittently
c) forcing of the well water back into the aquifer
d) jetting with water at high velocity
Answer: b
Clarification: Rewhiding involves starting and stopping of pumping intermittently. It provides a relatively rapid change in the head of the well and can be done with any type of pump. However, the turbine pump installed with a foot valve is the most effective.
5. 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
Answer: d
Clarification: 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.
6. 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
Answer: d
Clarification: A normal tubewell lasts for about 15 to 20 years in Northern India. It may fail due to incrustation and corrosion.
7. 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
Answer: a
Clarification: 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.
8. 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
Answer: b
Clarification: 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.
9. 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
Answer: a
Clarification: 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.
10. The amount of water required from wells to mature a similar crop is more than that required in canal irrigation.
a) True
b) False
Answer: b
Clarification: 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.
11. 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
Answer: b
Clarification: 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.
12. Reversing the direction of flow by surging the well does help in removing the bridging.
a) True
b) False
Answer: a
Clarification: 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.
13. 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
Answer: d
Clarification: 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.
14. 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
Answer: a
Clarification: 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.
Irrigation Engineering for Interviews,