IRRIGATION Flashcards
1
Q
What is soil moisture?
A
Water added to a soil mass during irrigation is
held in the pores of the soil and is termed was
soil moisture.
2
Q
Define crop yield and productivity.
A
The crop yield from irrigation is expressed as
qulntal/ha or tonnes/ha. The productivity of the
crop is expressed as crop yield per mm depth
of water applied
3
Q
Explain different types of soil water.
A
Soil water may be classified in the following three
categories. (i) Gravitational water (ii) Capillary
water (iii) Hygroscopic water
4
Q
What do you mean by capillary water?
A
It is that the water which is retained in the soil
after the gravitational water has drained off from
the soil. Capillary water is held in the soil by
surface tension as a continuous film around the
soil particles and in the capillary pores between
the soils particles.
5
Q
What do you mean by gravitational water?
A
It is that water which is not held by soil but
drains out freely under the influence of gravity.
6
Q
What Is meant by soli moisture tension?
A
Soil moisture tension Is defined as the force per
unit area that must be exerted in order to extract water from the soil. In other words, it is a
measure of the tenacity with which water is
retained in the soil.
7
Q
What do hygroscopic water?
A
It is that water which Is absorbed by the
particles of dry soil from the atmosphere and It
held as a very thin film on the surface of the soil
particles due to adhesion or attraction between
surface of particles and water molecules.
Note: Below the permanent wilting point, the
soil contains only hygroscopic water.
8
Q
What do you mean by soil moisture stress?
A
Soil moisture stress is defined as the sum of
the soil moisture tension and osmotic pressure
of soil solution.
9
Q
What is kor watering, kor depth and kor
period?
A
The first watering after the plants have grown a
few centimeters high is known as kor watering.
10
Q
What is paleo irrigation?
A
It is defined as the watering done prior to the
sowing of a crop. This is done to prepare the
land for sowing and to add sufficient moisture
to the soil which would be required for the initial
growth of the crop.
11
Q
What is lift irrigation and drip irrigation?
A
Lift Irrigation: Lift Irrigation is a method of
irrigation In which water is not transported by
natural flow (as in gravity-fed canal systems)
but is lifted with pumps or other means.
Drip Irrigation: Drip irrigation is an irrigation
method that saves water and fertilizer by
allowing water to drip slowly to the roots of
plants, either onto the soil surface or directly
onto the root zone. through a network
of valves, pipes and emitters. It is done through
narrow tubes that deliver water directly to the
base of the plant.
12
Q
What is irrigation?
A
Irrigation is the artificial application of water to
the land or soil. It is used to assist in the growing
of agricultural crops, maintenance of
landscapes. and revegetation of disturbed soils
in dry areas and during periods of inadequate
rainfall.
13
Q
READ page 164
A
Read page 164
14
Q
What is crop
A
A crop is a plant or animal product that can be
grown and harvested extensively for profrt or
subsistence.
15
Q
Which soil is best for crop production
A
loamy soil
16
Q
What is rainwater harvesting
A
Rainwater harvesting is a technique of collection
and storage of rainwater into natural reservoirs
or tanks or the infiltration of surface water into
subsurf~ce aquifers (before it is lost as surface
runoff)
17
Q
What is alkalinity of soil? How do you reduce
it?
A
Alkalinity of soil refers to the presence of alkali
salts (like NaCI, Na2C03, Na2S04, etc.) in the
soil. These salts are soluble in water. If the water
table rises up, the soluble alkali salts move up
with water and get deposited in the soil.
Alkalinity of soil can be reduced by leaching
18
Q
1.27 What do you mean by Intensity of Irrigation?
(ESE 2017
A
Intensity of irrigation is defined as the
percentage of the Irrigation proposed to be
irrigated annually. Usually the areas Irrigated
during each crop season (Rabi, Kharif, etc) ~re
expr~ssed as a percentage of the CCA WhiCh
rep~el)ents_ t~e int~nsity of jrrlgation t9r the crop
. :season . .
19
Q
What is check flooding?
A
The crop area is divided into some plots which
are relatively leveled by checks or bunds. Water
from field channels is allowed to enter to each
plot or check basin and the plot are flooded to
the required depth.
20
Q
What is a furrow?
A
A long, narrow trench made in the ground by a
plough, especially for planting seeds or
irrigation
21
Q
What is the work of NWDA?
A
National Waterway Development Agency
(NWDA) is an autonomous body set up in July
1982 to carry out water balance and other
studies based on scientific approach and
optimum utilization of water resources of the
Indian river system and thus to help in
development of Indian river system.
22
Q
What is gross irrigation requirement (GIR)?
A
It is defined as the amount of water required to
meet the field irrigation requirements plus the
amount of irrigation water lost in conveyance
through the canal system by evaporation and
by seepage.
23
Q
What is delta and duty? How duty varies
along length of canal?
A
Duty represents the area irrigated by the unit
amount of water (generally taken as 1 cumec).
It relates the area of a crop irrigated and the
quantity of irrigation water required during crop
growth. Duty increases as water moves from
canal outlet top field.
Delta is the total depth of water required for a
crop during the entire period the crop is in the
field and is denoted by 6.
24
Q
command area ?
A
the total area that Is to be served by an irr project
. It includes cultivable and non
25
Name some of the barrages
Farakka barrage
Prakasham barrage
Jobra barrage
Asan barrage
26
2.12 Differentiate between CCA and GCA.
read from pdf
27
Name some Rabi, Kharif and Zald crops.
| . . (ESE 2017
Khanf: R1ce. maize, mungbean g d • roun nut
cotton, soyabean, sugarcane, etc '
Rabi: wheat, barley,mustard, gram, tomato,
potato. etc
Zaid: Watermelon, muskmelon, bittergourd,
cucumber, pumpkin, etc
28
WhatisPWP?
Permanent wilting point (PWP) or wilting point
0NP) is defined as the minimal point of soil
moisture the plant requires not to wilt. If moisture
decreases to this or any lower point a plant wilts
and can no longer recover its turgidity when
placed in a saturated atmosphere for 12 hours.
29
What is field capacity?
| ESE 2017
Reid Capacity is the amount of soil moisture or
water content held in the soil after excess water
has drained away and the rate of downward
movement has decreased.
30
What is carrier canal?
A carrier canal is a canal which is used for both
direct irrigation and tor feeding water to another
canal. Thus it acts as an irrigation canal as well
as feeder canal. E.g., Upper Chenab Canal in
West Punjab (Pakistan).
31
What is feeder canal?
A feeder canal is a canal which is constructed
only to feed another canal. No direct irrigation
is carried out from a feeder canal e.g, Indira
Gandhi Feeder canal.
32
What Is leaching?
In this process, land is flooded with adequate depth of water. The alkali salts present in the
soil gets dissolved in this water which percolate'
down to join the watertable. The process is
repeated till the salts in the top layer of the land
are reduced to such an extent that some salt
resistant crop can be grown. This process is
known as leaching
33
What do you mean by suspended load?
Sediment load is maintained in suspension due
| to the turbulence of the flowing water.
34
What do you mean by bed load?
Sediment load moves along the bed with
occasional jumps into the channel is called bed
load.
35
What are the function of cross regulators?
• They facilitate communication, since a road
can be taken over them with a little extra
cost.
• The help to absorb fluctt1ations in the various
sections of the canal system, and hence
to prevent possibilities of branches in the
tail reaches.
• They help to control discharge at an outfall
of canal into another canal or lake.
• They help to control water surface slope
tor bringing the canals to regime slope and
section.
36
What are the drawbacks of Lacey's theory?
The various drawbacks of Lacey's theory are as
follows:
The true regime conditions defined by
Lacey's are only theoretical and may not
be achieved in actual practice.
The derivation of various equations by
considering a single factor called silt factor
f is not satisfactory as there can be different
value of f for the bed and the sides.
Silt charge and silt grade have not been
defined properly by Lacey.
Lacey indicated that a true regime channel
has a semi-elliptical section but the same
is not supported by any of his equations.
By lining the canal, we mean that the earthen
surface of the channel is lined with a stable
lining surface, such as concrete, titles.
asphalt etc
37
3.8 What are the functlona of dlatrlbutry head regulators?
read page 168
38
What Is rigid boundary of canal?
Algid boundary canal: When the velocity of
flow through a canal is very small, the channel
bed does not move at all and the channel
behaves us a rigid boundary channel. As the
flow increases, a stage Is reached when the
shear force exerted by the flowing water on the
bod particles will just exceed the force opposing
their movement. At this stage, few particles of
tile bed must start moving. This condition Is
called as Incipient motion condirion
39
What is a Canal?
Canals, or navigations, are human-made
channels, or artificial waterways, for water
conveyance, or to service water transport
vehicles.
40
What is true regime?
True regime: A channel is said to be in true
regime if there is no silting and no scouring.
This condition is attained when silt load entering
the channel must be carried through the channel
section.
41
What are different forces on gravity dam?
| ESE 2016, 2017
```
Water pressure
• Uplift pressure
• Pressure due to earthquake forces
• Silt pressure
• Wave pressure
• Ice pressure
```
42
What are the requirements of a good
| module?
• Module should be simple, so that it can be
easily constructed or fabricated by local
masons or technicians.
• Module should work efficiently with a small
working head.
• The outlet should be cheaper, since they
are required in large number.
• The outlet should be such as to avoid
interference by cultivators, thus preventing
under tapping of water by cultivators.
• It should draw its fair share of silt
43
What are the disadvantages of Siphon
| Spillway?
The following are the limitation of a siphon
spillway.
• It is unable to pass ice and debris.
• There is a possibility of clogging of the
siphon duct and siphon breaker vents with Ans.
debris or leaves
44
What are the advantages of Siphon Spillway?
The following are the advantages of a siphon
spillway over the other types of spillways.
• It is able to pass full capacity discharges
with narrow limits of head water rise.
• It is automatic in action without involving
any mechanical devices or moving parts.
• Its discharge per unit length is more
because it has a higher operating head.
• There is practically no maintenance cost
and it is leak proof.
• The cost of acquisition of areas which will
get submerged between maximum water
level and full reservoir level is minimum in
this case.
• The height of the dam above the crest of
the spillway is also reduced significantly.
• It is useful in sucking up sediment from
the bed of the reservoir when It is In full
action during floods.
45
What are the effects of silting In reservoir
operation?
(ESE 2015)
Effects of silting In reservoir operation:
• The deposition of sediment In the reservoir
i.e. silting reduces the effective storage of
reservoir.
• Also with the passage of time, the reservoir
capacity goes on reducing and the stage
may reach when whole reservoir may gat
silted LJp.
• With reduced capacity of reservoir. the
effective head of water decreases which
have an adverse effect on the power
generation by turbines
46
Define causeway, aqueduct, culvert.
| ESE 2016
Causeway: Whenever a road embankment is
constructed across a flat terrain, in order to drain
off the runoff collected on the road side, the
road on the embankment is lowered to the
natural ground level at frequent intervals thus
aiJowing water to flow across the road. This is
called as causeway.
Aqueduct: An aqueduct is an arrangement
wherein the canal water is carried above the
drain/river.
-Culvert: A culvert is usually any bridge with
· .. span less than 8 m.
47
Why are weep holes provided and where are
they used?
(ESE 2016, 2017)
Weep holes are used to dispose off the drainage
water that has managed to seep into the dam.
Weep holes acts as safety provider to the dam.
48
What is stable type river?
River which does not change its alignment.
slope and its regime significantly is called a
stable river
49
What Is aggrading type river?
An aggrading river is a silting river. Such a river
increases its bed slope. which Is called building
up of slope.
50
What is virgin rivers?
In arid zones, a river water may completely dry
before it joins another river or the ocean. Such a
river is called a virgin river
51
What is bandalling?
Bandalling is a method of river training which is
generally used to confine the low water flow In a
single channel for maintaining required depth
for navigation.
52
What Is river water training?
In easy words river training means to guide and
confine the flow to the river channel, and to
control and regulate the river bed configuration,
thus ensuring safe and effective disposal of
floods and sediment loads.
53
What are the different river training works?
| ESE 2017
Different river training works are:
* Embankments
* Guide banks
* Spurs or groynes
* Cutoffs
* Bed pitching and bank reactment
54
What Is trap efficiency?
| (ESE 2016
It is defined as the percentage of the sediment
deposited in the reservoir even inspite of taking
precautions and measures to control its
deposition
55
What Is pitching In river? How Is It done?
| ESE 2015
Pitching In river: Pitching is a river training Work
wherein the river banks are protected by stone
pitching or by concrete blocks or brick lining.
• For pitching, the banks of the river are first
made stable with slope varying from 1 : 1
to 2: 1.
• The banks are then pitched so as to make
them rough enough to resist the erosion
action of river
56
What is the purpose of pitching of banks
Pitching In general refers to protection of banks ns. of rivers by laying stones or concrete blocks
Mostly stone pitching Is adopted If stones ar~
locally available. Pitching makes the river banks
more resistant against erosion
57
Why rivers changes their courses in 50 to
100 years?
(ESE 2016)
Rivers change their course because when the
silt charge is in excess quantity then that
required for stability, the rivers start building up
their own slope by depositing the silt on the
river bed. Thus the river reach becomes an
aggrading type. This aggrading is the main
process which leads to change in the river
course
58
Why fish ladders are provided?
| ESE 2017
A fish ladder, also known as a fishway, fish pass
or fish steps, is a structure on or around artificial
and natural barriers (such as dams, locks and
waterfalls) to facilitate diadromous fishes' natural
migration.
59
Why is rip-rap provided?
| ESE 2016
Rip-rap: Rip-rap is the range of rocks place
along the coast line in order to protect the
structures located along the coast line. The size
of the rocks used range from 100 mm to over
600mm.
60
How do you take off a canal from a dam?
| ESE 2017
Canal should be taken off tangentially from a
| dam.
61
What are the types of flow over a Spillway?
In general, flow over the spillway is critical flow
62
What are the methods to calculate capacities
| of reservoirs?
Relation between Inflow, outflow, and
storage data for a reservoir
• Fixing the reseNoir capacity from the annual
inflow and outflow data
• Fixation of reservoir capacity with the help
of mass curves of inflow and outflow
• Fixation of reseNoir capacity analytically
using sequent peak algorithm.
63
What are the different methods used for the
dissipation of hydraulic energy of the water
stored in dam?
The various methods used for dissipation of
hydraulic energy of water stored in dam are:
```
• Stilling basin type energy dissipaters:
These are of two types viz.:
Hydraulic jump type stilling basin
o Hydraulic jump with horizontal apron
o Hydraulic jump with sloping apron
- Jet diffusion type stilling basin
o Jet diffusion stilling basin
o Interacting jet dissipaters
o Free jet stilling basin
o Hump stilling basin
o Impact stilling basin
• Bucket type energy dissipaters: These are
of following types:
Solid roller bucket
Slotted roller bucket
Ski jump bucket
```
64
What are the major factors to be considered for construction of dam in hilly region
Dam construction In hilly regions: The
tollm'\ling factors need to be considered for
construction of a dam in hilly region:
(a) Purpose of dam i.e. dam is to be
constructed for storage purpose or for hydro
power generation or for irrigation etc.
(b) Number of beneficiaries to be served by
the dam.
(c) Availability of hard rocks for abutments.
(d) The valley should be deep and narrow for
large storage volume.
(e) The area upstream of the dam should open
in a large expense so that sufficient volume
for storage is available.
(f) Head available if the dam is to be used for
hydro power generation.
(g) Seismic characteristic of the area where
dam is to be located.
(h) Availability of approaches for the dam.
(i) Minimum dry weather flow of the river.
G) HFL in the river reached in the past and
expected in future.
(k) Amount of precipitation in the catchment.
(I) Number of people which will get affected
by the construction of dam.
(m) Impact of dam on environment i.e., EIA
(Environment Impact Assessment) studies.
(n) Design life of the dam
65
What do you mean by drainage condition In
| retaining wall?
Drainage of water as a result of rainfall or other
wet conditions is very Important to the stability
of a retaining wall. Without proper drainage, the
backfill can become saturated, which has the
dual impact of increasing the pressure on the
wall and lessening the resistance of the backfill
material to sliding. Granular backfill material offers good drainage, easy compaction, increased sliding resistance
66
Why impervious core and pervious on U/S and D/S ?
nice answer
67
What precaution you will take while you are
| constructing a dam?
These precautions must be taken in the
construction of dam
(a) Selection of dam site.
(b) Identification of earthquake prone area and
structure and identification of earthquakerelated safety concerns.
(c) Development of a site-specific geotechnical, exploration program.
(d) Design of the foundation, dam, and
appurtenant structures.
(e) Design of a system of instrumentation to
monitor the performance of the dam. foundation, and appurtenant structures.
(f) Development of an initial reservoir-filling and
surveillance plan and of reservoir drawdown criteria.
(g) Preparation of designer's operating criteria
and identification of special considerations
to be observed during construction and operation.
(h) Provisions for the automatic, independent
review by competent individuals of all
68
What Is economic height of dam?
The economic height of a dam Is that height of
the dam, corresponding to which, the cost of
the dam per unit of storage Is mlnlrnurn.
69
What Is a Spillway?
| ESE 2012, 2016, 2017
A spillway is a structure used to provide the
controlled release of flows from a dam or levee
Into a downstream area, typically the riverbed
of the dammed river Itself, they may be known
as overflow channels. Spillways ensure that the
·water does not overflow and damage or destroy
the dam.
70
What Is the difference between big and small
| dam?
Small dams:
(a) They serve the purpose of drinking water.
(b) Maintenance of small dam is cheaper.
(c) Small dams are part of water management
for big dams.
Big dams:
{a) Big dams run industries from Its power
generation.
(b) Super floods can only be controlled by big
dams.
71
What are Cofferdams and Check dome?
A check dam Is a small, sometimes temporary,
| ·. dam constructed across a swale, drainage ditch, or waterway to counteract erosion by reducing water flow velocity
72
What are the different types of Dam?
| ESE 2013, 2016, 2017
```
Buttress Dam .
Coffer Dam.
Diversion Dam .
Embankment Dam .
Gravity Dam .
Hydropower Dam .
Industrial Waste Dam .
```
73
What do you mean by weep hole?
| ESE 2013
These are the sort of escape holes usually
| provided In the retaining walls in order to dissipate the buildup of excess pore water
74
What Is fish ladder and purpose of it?
| (ESE 2013, 2017
Migratory fishes (such as Hilsa in India) move
from upstream to downstream in winter season
in search of warm water and return to their origin
upstream slightly before the monsoons. If no
arrangement is made in the weir or dam for the
fish to pass upstream then such migratory
fishes are found to strike against the water
current repeatedly In their effort to move up till
death. This leads to large scale destruction of
migratory aquatic species.
But most types of fishes can travel upstream
at 3 to 3.5 m/s. In general there Is a head
difference of about 5 to 6 m between the
upstream of weir or dam and downstream water
level In the river. If a simple opening is provided
in such a weir or dam then velocity of flow will
be too high.
Thus a fish ladder Is provided which dissipates
the flow energy In such a manner so as to provide
a smooth flow at sufficiently low velocity not
exceeding 3 to 3.5 m/s. Fish ladder Is
accomplished by providing a narrow opening
adjacent to the divide wall and provide suitable
waffles or staggering devices In it
75
8.19 What are the various hydraulic consideration
| In the design of bridges?
read from pdf
76
8.21 Explain Middle 3rd rule in context of dam/
| retaining wall.
Resultant of all the forces in a retaining wall/
dam should pass through middle third portion
of the base of structure to avoid tension
77
Define spillways and its types.
| ESE 2014
```
Spillway is a structure used to provide the
controlled release of flows from a dam or levee
into a downstream area. It's types are:
1. Ogee spillway
2. Chute spillway
3. Stepped spillway
4. Bellmonth spillway
5. Siphon spillway
```
78
What Is a design flood?
The Design Flood for a hydraulic structure may
be defined as:
• The maximum flood that any structure can
safely pass.
• The flood considered for the design of a
structure corresponding to a maximum
tolerable risk.
79
8.22 What is Caisson?
| ESE 2016
It is a large watertight chamber, open at the
bottom, from which the water is kept out by air
pressure and in which construction work may
be carried out under water.
80
8.25 What is river inter-linking?
Rivers interlinking: The river interlinking project
is a very mega project that aims to connect all
the Indian rivers through a network of canals
and reservoirs. This project is undertaken to
mitigate the problem of floods in certain PartS
of the country alongside the problem of draught
in the other parts of the country.
81
What is dead storage?
| ESE 2016
Dead storage: It is the water stored in a
reservoir below the minimum pool level. The
dead storage is not of much use for the
operation of the reservoir.
82
What is the basis for the electricity generation through dam?
In a hydel power project, the potential ener . dt gy of water ts use o generate the electric . h power. The water tn t e dam is at high head which is
made to pass through the shafts to reach the
turbine. By the time water reaches the turbine
it has huge kinetic energy which runs th~
turbine. This turbine in turn runs the generator
thereby giving electric power.
83
Various purposes of dams like electricity,
irrigation etc.
(ESE 2016)
```
Various purposes of dam:
• Electricity generation
• Irrigation
• Water supply
• Navigation
• Recreational facilities
• Rsheries
• Flood control
```
84
As a civil engineer which dam you will prefer
| earthen concrete rock or filled? . ' . (ESE 2016)
Concrete gravity dam is more preferable than
| other types of dC¥n.
85
Positives and Negatives of dam?
| ESE 2016
Positives of a dam:
* Hydropower generation
* Flood control
* Water supply and irrigation
* Tourism
* Navigation
Negatives of a dam:
•Inundation of surrounding area thereby leading to loss of land resource
•High construction cost
•Large gestation period i.e. large time required for construction
•Environmental degradation
•Rehabilitation of the affected population
•Increase in reservoir induced seismicity
•Development of humid environment which
is conducive for water borne diseases
86
What is difference between bed load and
suspension load?
(ESE 2016)
Bed load: Bed load consists of sediments that
move at the river bottom of just above it. These
are heavier particles generally sand and gravels.
Suspended load: These are the particles in
water above the river bottom. It generally
consists of finer particles like silt, clay etc.
87
What Is a stilling basin?
The stilling basin is a hydraulic structure located
between the outlet works of a dam and the tail water to where, should return excess flows safely. the stilling basin is a structure in which a hydraulic jump is generated and has been designed economically in terms of length, tail water level and scour.
88
Give ways of preventing floods.
| (ESE 2016, 2017
```
Reservoirs
• Levees
• Improvement of river channels
• Diversion of flood water to flood ways
• Watershed management for flood control
```
89
What are the types of gates in dam?
(i) Stop-logs/flash boards
(ii) Vertical lift gates
(iii) Radial gates
(iv) Ring gates
(v) Stoney gate
(
90
Where do we build Arch Dam?
An arch dam is most suitable for narrow gorges
or canyons with steep walls of stable rock to
support the structure and stresses
91
What is a Gravity Dam? How to design It?
| (ESE 2017}
A gravity dam is a dam constructed from
concrete or stone masonry and designed to hold
back water by primarily utilizing the weight of
the material alone to resist the horizontal
pressure of water pushing against it. Gravity
92
How to protect a dam?
The various points must be considered and kept
In mind:
• The overturning moment should be less
than the resisting Moment (considering
factor of safety).
• Impervious clay lining can also be provided
to prevent seepage of water through lt.
• Drainage galleries also help in providing
safety to the dam by decreasing the total
uplift force beneath the dam.
93
What are the Geological studies conducted
before dam construction?
(ESE 2017)
```
Geological studies conducted before dam
construction are:
• Narrow River Valley
• Occurrence of bedrocks at a shallow
depths
• Competent rocks to offer stable foundations
• Effect of Associated Geological Structures
• Leakages below Dams
```
94
What are Head Regulators?
| ESE 2017
A head regulator provided at the head of the
off-taking channel, controls the flow of water
entering this new channeL It also control silt entry
into the off-take channel.
95
Tell me the difference between dam and
| barrage?
```
Dam:
[ESE 2018}
• A dam is a storage headwork.
• Water gets elevated to a large height.
• The surplus water is allowed to flow through
the spillways only.
Barrage:
•
•
A barrage Is a diversion headwork .
Water gets elevated to a small height .
```
The surplus water Is allowed to flow through
the gates provided in the barrage thereby
adjusting the height of water In the barr age
96
Why do you think people resist for building
dams, particularly In the Himalayan region?
(ESE 2019)
Building of dam creates a huge reservoir behind
it which inundates a vast area thereby leading
to displacement and resettlement of nearby
population. Moreover, construction of dam
resulting reservoir poses serious environmental
threats
97
What Is balance reservoir?
Balancing reservoir balances the supply and the
demand of water. It is in fact a reservoir located
on the downstream of the main reservoir for
holding water let down from the main reservoir
in excess of that required for irrigation, power
generation and other purposes
