Irrigation Engineering Questions and Answers for Entrance exams on “Factor Controlling Occurrence of Ground Water”.
1. An irrigation project is classified as a major project when the CCA involved in the project is more than ___________
a) 2000 hectares
b) 5000 hectares
c) 10000 hectares
d) 2500 hectares
Answer: c
Clarification: Culturable Command Area is the basis for the design of watercourse and the basis for the design of an irrigation project. The irrigation schemes in India are classified into three parts viz. Minor, Medium and Major Irrigation schemes depending upon the areas involved. Major irrigation scheme is the one where CCA involved in the project is greater than 10,000 hectares.
2. A minor irrigation scheme serves up to ________________
a) 100 hectares
b) 500 hectares
c) 1000 hectares
d) 2000 hectares
Answer: d
Clarification: The irrigation schemes in India are classified into three parts depending upon the areas involving culturable command area.
| Type of scheme | Areas involving CCA |
|---|---|
| 1. Minor irrigation scheme | < 2000 hectares |
| 2. Medium irrigation scheme | 2000 to 10000 hectares |
| 3. Major irrigation scheme | > 10000 hectares |
3. Energy is required in the utilisation of _____________
a) groundwater
b) surface water
c) both groundwater and surface water
d) capillary water
Answer: a
Clarification: For irrigation purposes, groundwater is largely tapped in India through wells and tube wells. Manual, wind, diesel or electric power can be used for lifting water from open wells. The subsequent development in the technique of tapping groundwater is the use of tube wells which requires diesel or electric power.
4. Which of the following property of geological formation represents its water storage capacity?
a) Permeability
b) Porosity
c) Both permeability and porosity
d) Transmissibility
Answer: b
Clarification: Porosity is the quantitative measurement of the interstices of voids present in the rock. In other words, it is the maximum amount of water that can be stored in the rock.
5. The zone of aeration in a groundwater profile does not include ___________
a) capillary zone
b) soil water zone
c) intermediate zone
d) saturation zone
Answer: d
Clarification: Depending upon the number of interstices present, the aeration zone is divided into three classes. The capillary fringe is a continuation of the zone of saturation and does contain some interstitial water. Soil zone is the depth from the surface penetrated by the roots of vegetation and the remaining intermediate part is intermediate zone.
6. In which of the following zone the stresses are beyond the elastic limits?
a) Zone of rock fracture
b) Zone of rock flowage
c) Zone of saturation
d) Zone of aeration
Answer: b
Clarification: In the zone of rock flowage, interstices are absent because the stresses are beyond the elastic limits. The rocks remain in a state of plastic flow and water present in this zone is known as internal water.
7. The rate of flow of water through ground strata can be estimated by _____________
a) Manning’s formula
b) Strickler’s formula
c) Dupuit’s equation
d) Darcy’s formula
Answer: d
Clarification: A French Scientist Mr. H Darcy on the basis of experimental evidence gave a law governing the discharge through soils. According to the law, the discharge is directly proportional to the head loss and the area of cross-section of the soil and inversely proportional to the length of the soil sample.
8. The relation between Transmissibility (T) and Permeability (K) for an aquifer of depth d is _______
a) K = T.d
b) T = K.d
c) T = K.log d
d) T = ln (Kd)
Answer: b
Clarification: Transmissibility is measured by the coefficient of transmissibility (T) and was introduced by Theiss. It can be defined as the rate of flow of water through an aquifer of unit width and full-depth under a hydraulic gradient and at a temperature of 20°C. The relation between K and T is given as T=K.d.
9. Darcy’s law is valid when the flow is ___________
a) laminar and steady
b) non-uniform
c) turbulent
d) both laminar and turbulent
Answer: a
Clarification: The Darcy’s law has been demonstrated to be valid only for laminar flow conditions because the flow in sands, silts, and clays is invariably laminar.
Mathematically, v = K.i where v = discharge velocity, K = coefficient of permeability and I = hydraulic gradient.
10. The coefficient of permeability indicates the ease with which water can flow through a soil mass. The soil type which has less permeability is __________
a) gravelly soil
b) clayey soil
c) sandy soil
d) both sandy and gravel soil
Answer: b
Clarification: The approximate average value of the coefficient of permeability in clayey soil is 0.04 x 10-5 cm/sec. The permeability coefficient of gravel soil is of the order of 4cm/sec and for sandy soil is 0.04 cm/sec.
11. Which of the following is the most important zone for a groundwater hydraulic engineer?
a) Zone of rock fracture
b) Zone of rock flowage
c) Zone of saturation
d) Zone of aeration
Answer: c
Clarification: This is the most important zone for a hydraulic engineer as this water has to be tapped out and the water in this zone is under hydrostatic pressure. In this zone, water exists within the interstice which is nothing but groundwater.
12. Which zone contains water that is under molecular attraction?
a) Zone of rock fracture
b) Zone of rock flowage
c) Zone of saturation
d) Zone of aeration
Answer: d
Clarification: Zone of aeration is the space above the water table and below the surface and the water exists in this zone by molecular attraction. The water in this zone is not at hydrostatic pressure and the gravity water moves through this zone.
Irrigation Engineering for Entrance exams,