Water resourcs engineering

GUIDED BY: NILESH RATHOD
UTTEJANA CHAUDHARI
Elements of
Civil Engineering
Prepared by : Kajol Panchal
WATER RESOURCS ENGINEERING
1

Topics
 Introduction
 Hydrologic Cycle
 Sources of Water
 Water use and its Conservation
 Introduction to dams
 weirs, barrages and check dams
2

Introduction
 Hydrology is the science which deals with the
occurrence,distribution and movement of water on the
earth,including that in the atmosphere and below the
surface of the earth.
 Water occurs in the atmosphere in the form of
vapour,on the surface as water,snow or ice and below
the surface as the ground water occupying all the voids
within a geologic stratum.
3

Hydrologic Cycle
The movement or circulatory system of water
on the earth's surface and through the atmosphere
is known as the hydrologic cycle.
Hydrologic Cycle is the process of transfer
of moisture from the atmosphere to the earth in the
form of precipitation, conveyance of the precipited
water by streams and rivers to ocean and lakes etc ,
and evaporation of water back to the atmosphere.
4

Process Of The Hydrologic Cycle :
 The water from the surface sources likes lakes, rivers,
ocean, etc. converts to vapour by evaporation due to
solar heat.
 The vapor goes on accumulating continuously in the
atmosphere.
 This vapor is again condensed due to the sudden fall
of temperature and pressure.
 Thus clouds are formed,these clouds again causes the
precipitation (i.e. rainfall).
5

 Some of the vapour is converted to ice at the peak
of the mountains.
 The ice again melts in summer and flows as rivers
meet the sea or ocean.
 These processes of evaporation , precipitation and
melting of ice go on continuously like an endless
chain and thus the balance is maintained in the
atmosphere.
 This process is known as “Hydrologic Cycle”.
Thus, the Hydrologic Cycle may be expressed
by the following simplified equation.
Precipitation = Run off + Evaporation
6

Application of hydrology
Determination of the capacity of a reservoir from
the rainfall records and yearly discharge
observation of a river.
Determination of peak flow of a river. (peak flood)
Determination of suitable site for hydroelectric
power generation.
Sources of water supply in a town or city.
Methods to be adopted for the flood forecasting
and flood control.
Availability of water for navigation
8

Sources of water
 The primary sources of water include: rainwater, surface water
(stored in lakes, streams, and ponds), and groundwater. The
distribution of water, however, is quite varied; many locations have
plenty of it while others have very little.
 Water exists on earth in three forms
1. solid (ice)
2.liquidor
3.gas (water vapour).
 Oceans, rivers, clouds, and rain, all of which contain water, are in a
frequent state of change (surface water evaporates, cloud water
precipitates, rainfall infiltrates the ground, etc.).
However, the total amount of the earth's water does not
change. Owing to glaciers, rivers and Groundwater flow.9

 Water is essential to life. Without it, the biosphere that
exists on the surface of the earth would not be possible.
The earth is called as the ‘water’ planet, water's molecular
arrangement of water is very simple, two hydrogenatomsto
each oxygen atom.
 One special characteristic of water is its ability to change
state very easily under earth conditions. It can be found
readily on the planet in all of its three forms, solid, liquid,
and gas.
 The average annual rainfall in the country is 1170 mm,
which corresponds to annual precipitation, including
snowfall of 4000 Billion Cubic Metres (BCM).
10

Water resources % total water
Ocean 97.6
Ice and snow 2.07
Ground water 0.28
Lakes and reservoirs 0.009
Saline lakes 0.007
Soil moisture 0.005
Biological moisture in plants
and animals
0.005
Atmosphere 0.001
Swamps and marshes 0.0001
Rivers and streams 0.0001
Total 100
11

Types of water
The available fresh water is continuously collected
, purified and distributed through the Hydrological
Cycle as we explained. Thus the water which is
available as fresh water is devided into 2 parts :
1) Surface water
2)Sub-surface water(ground water)
12

A)Surface water : Most surface water originates directly from
precipitation in the form of rainfall or snow. The various surface
water sources are described as under ;
(I) Seawater :
(II)Ponds And Lakes :
 As per earth resources distribution, the oceans contain
about 97% of the total water in world.
 As oceans water contain high concentration of salts in
solution it become uneconomical to make water potable.
A natural large sized depression formed on the surface
of the earth ,when gets filled up with water is know as
pond and lake.
If the size of the depression is comparatively small,it
may be termed as a “Pond” & when the size is large it
may be termed as a “Lake”.
The quality of water in a lake is generally good and
13

(III) Streams And Rivers:
(IV) Impounding Reservoirs :
Rainfall that does not evaporate or infiltrate , runs
off the surface to sea , in the form of streams and
rivers.
Larger streams may however , be used as sources
of water by providing storage reservoirs , barrages
etc.
Rivers are the most important sources of water for
public water supply schemes.
A barrier in the form of a dam is constructed across
the river , so as to form a pool of water on the
upstream side of the barrier .
This pool or artificial lake formed on the upstream
side in know as a Impounding reservoirs.
The quality of this reservoir water is not much
different from that of a natural lake.
14

(B)Ground water :
 The main source of ground water is precipitation(rain) .
 A portion of rainfall falling on the earth’s surface infiltraces
into ground , travels down and when checked by impervious
layer to travel further down, from ground water.
 Study of subsurface flow is equally important since about 30%
of the world’s fresh water resources exist in the form of ground
water.
 Water bearing formations of the earth’s crust act as cobduits for
transmission and as reservoirs of storage of Ground water.
15

Types of Aquifer:
(A)Unconfined Aquifer :
• An Unconfined Aquifer is one in which a free water surface i.e, a
water table exists. So it also known as water table Aquifer.
• In such an aquifer, the water table varies in undulating form and in
slope.
• Recharge of this aquifer takes place trough infiltration of
precipition from the ground surface.
• A well driven into an unconfined Aquifer will indicate a static
water level corresponding to the water table level at that location.
a well drilled in this type of aquifer is known as a “WATER
TABLE WELL”
16

(B) Confined Aquifer :
• A confined aquifer is an aquifer which is sandwiched
between two impervious strata.
• The water in a confined aquifer is under pressure. The
piezometric surface is much higher than the top level of the
aquifer at that point.
• If the water level in the well drilled in a confined aquifer
rises above the ground surface, water flows out freely
without any pump, such a well is called a “Flowing
Artesian well”.
• If the water level is below the ground surface, the well
water does not flow freely and well is called a “Non –
Flowing Artesian well ”.
18

Types of Water Wells :
A Water Well is a hole or shaft , usually vertical ,
excavated in the earth for bringing ground water to the
surface.
Water wells may be classified as:
(1) Open wells or Dug Wells
(2) Tube wells
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(1)Tube Wells :
 A tube well is a long pipe sunk into the
ground intercepting one or more water bearing
strata.
 Diameter : 80mm to 600mm
 two types of tube wells :
(i) Shallow tube Wells : Depth - 30 m,
Yield - 20
(ii)Deep tube Wells : Max Depth - 600m
Yield - 800
hourm /3
hourm /3
(2)Open wells or Dug Wells :
Open wells are the wells which
have comparatively large diameter
but low discharges and are not
very deep.
 Diameter : 1m to 10m & Yield
: 20 or lesshourm /3
20

water requirements for different Uses
1. Water supply:- municipal water supply, industrial
water supply.
2. Irrigation:- for different crops .
3. Hydropower :-power generation.
4. Navigation:-recreation .
21

Water requirements for municipal supply
Use Liters/day/person
Domestic 135
Industrial use 50
Commercial 20
Public utility 10
Water losses 55
total 270
The total yearly water required for public supplies in liters
can be obtained as follow :
= Design Population * Per capita demand * 365
22

Water requirements for irrigation
 For proper growth and maturity of the crops, vital
importance through the crop period.
 Every crop requires a certain quantity of water after
certain fixed interval , thought the period of growth.
23

Water requirements for hydropower
generation
Hydroelectric power is generated by running the turbine
blades by the energy of the following water and thus the
generation of electricity from the generator coupled to
the turbine.
24

Water requirements for navigation
Navigation is important use of water ,which provides
us transport without any consumption of water.
25

Water requirements for recreation
 The basic requirements for recreation is that boating ,
fishing , swimming , and other water sport.
26

Conservation of water
• The most essential among all the natural resources on earth is
water. Rainwater is a precious gift of nature. A step to conserve
water is the step to secure the future.
• Over the years rising populations , growing industrialization &
expanding agriculture have pushed up the demand for water
• The efforts have been made to collect water by building dams
and reservoirs and digging wells , Some counties have also tried
to recycle water.
So water conservation has become the need of the day.
• Water conservation is the most effective and environmentally
sound methods to fight global warming.
 Aim : To improve the efficiency of use of water & reduce
losses and waste.
27

 There are various methods used to conserve water
some of them as follows :
1) For sewage disposal some new techniques should be
developed to reduce water consumption.
2) By maintaining canals i.e., canal lining we can reduce
conveyance losses.
3) Certain measured should be adopted to reduce
evapotranspiration losses from crops.
4) Water harvesting should be made compulsory for every
one to conserve water.
5) We can also conserve the water by different conservation
measurements.i.e, Domestic ,Agricultural ,Industrial &
Rain Water Harvesting.
28

 Benefits to conserve the water :
1) If you save water it can save your money bills.
2) Reduction in interior water use cuts waste water
flows, especially overflowing of gutters which
contaminate the environment.
3) Environment benefits include eco – system and
habitat protection.
4) Water conservation helps in improving the quality of
your drinking water.
29

 A dam is a hydraulic structure of fairly impervious
material built across a river to create a reservoir on its
upstream side for impounding water for various
purposes.
 A dam and a reservoir are complements of each other.
 Dams are generally constructed in the mountainous
reach of the river where the valley is narrow and the
foundation is good.
 Generally, a hydropower station is also constructed at
or near the dam site to develop hydropower.
 Dams are probably the most important hydraulic
structure built on the rivers. These are very huge
structure and require huge money, manpower and time
to construct.
31

Gravity Dam
A gravity dam resists the water pressure and other forces due
to its weight (or gravitational forces).
Usually made of cement concrete and straight in plane are
approx triangular in cross-section, with apex at the top.
At present, it is second highest after Grand Dixence Dam in
Switzerland (284 m high).
Koyna Dam (MR), Rihand Dam (UP), Sardar Sarovar Dam,
etc are few examples of concrete gravity dams.
Nagarjuna Sagar Dam (125 m) is highest masonry dam of
the world. It is also the largest storage capacity dam of India
dams.
32

Advantages Gravity Dam
 maintenance cost of a gravity dam is very low.
 ƒdoes not fail suddenly. There is enough warning of the
imminent failure and the valuable property and human
life can be saved to some extent.
 ƒGravity dams are quite strong, stable and durable.
 ƒcan be constructed during all types of climatic
conditions.
Disadvantages Gravity Dam
Gravity dams of great height can be constructed
only on sound rock foundations.
initial cost of a gravity dam is usually more than
that of an earth dam.
require more skilled labour than that in earth
dams.
usually take a longer time in construction than34

EARTH DAMS
 An earth dam is made of earth (or soil) and resists the forces
exerted upon it mainly due to shear strength of the soil.
 Usually built in wide valleys having flat slopes at flanks.
 They are of zoned sections, with an impervious zone (called
core) in the middle and relatively pervious zones (called
shells or shoulders) enclosing the impervious zone on both
the sides. Nowadays majority of dams constructed are of this
type.
 Hirakund dam (Orissa) is the longest earthen dam of the
world (25.3 km).
35

 Advantages EARTH DAMS
 Disadvantages EARTH DAMS
can be constructed in a relatively short period.
are more earthquake-resistant than gravity dams.
skilled labour is not required in construction of an
earth dam.
are usually cheaper than gravity dams if suitable
earth for construction is available near the site.
cannot be designed as an overflow section.
maintenance cost of an earth dam is quite high. It
requires constant supervision.
 sluices cannot be provided in a high earth dam to
remove slit.
37

ROCKFILL DAMS
• A rockfill dam is built of rock fragments and boulders of
large size.
• Rockfill dams are quite economical when a large quantity of
rock is easily available near the site.
 A dry rubble cushion is placed between the rockfill and the
membrane for the distribution of water load and for
providing a support to the membrane
 The highest dam of India is Tehri dam (261 m), which is
earth and rockfill type.
38

Advantages Rockfill dams
 Are quite inexpensive if rock fragments are easily
available.
 Can be constructed quite rapidly.
 Can better withstand the shocks due to earthquake
than earth dams.
 Can be constructed even in adverse climates
Disadvantages Rockfill dams
Rockfill dams require more strong
foundations than earth dams.
Rockfill dams require heavy machines for
transporting, dumping and compacting rocks
40

ARCH DAMS
• An arch dam is curved in plan, with its convexity towards the
upstream side.
 Transfers the water pressure and other forces mainly to the
abutments by arch action.
 Section is triangular and is comparatively thinner.
 It may have a single curvature or double curvature in the
vertical plane.
 The arch d Only one - Iddukki dam (169 m high) in Kerala.
 ƒExamples - Juguri dam (272 m), Russia, Vaiont dam (262 m),
Italy, Manvoisin dam (237 m) Switzerland.
41

Manvoisin dam (237 m) Switzerland42

Advantages ARCH DAMS
 An arch dam requires less concrete as compared to a gravity dam
as the section is thinner.
 Arch dams are more suited to narrow, V-shaped valley, having
very steep slopes.
 An arch dam can be constructed on a relatively less strong
foundation because a small part of load is transferred to base
Disadvantages ARCH DAMS
The arch dam requires sophisticated formwork, more
skilled. labour and richer concrete .
The arch dam cannot be constructed in very cold climates
because spalling of concrete occurs due to alternate freezing
and thawing.
The speed of construction is relatively slow.
43

BUTTRESS DAMS
 Buttress dams are of three types:
(i) Deck type, (ii) Multiple arch-type, and (iii) Massive-head type.ƒ
 A deck type buttress dam consists of a sloping deck supported by buttresses. ƒ
 Buttresses are triangular concrete walls which transmit the water pressure from
the deck slab to the foundation. ƒ
 Buttresses are compression members. ƒ
 The deck is usually a reinforced concrete slab supported between the buttresses,
which are usually equally spaced. ƒ
 In a multiple-arch type buttress dam the deck slab is replaced by horizontal
arches supported by buttresses. The arches are usually of small span and made of
concrete.
 ƒIn a massive-head type buttress dam, there is no deck slab. Instead of the deck,
the upstream edges of the buttresses are flared to form massive heads which span
the distance between the buttresses.
44

Buttress dams require less concrete than gravity dams.
Uplift/ice pressure is generally not a major factor Can be constructed on
relatively weaker foundations. Power house and water treatment plants,
etc.
can be housed between buttresses vertical component of the water
pressure on deck prevents the dam against overturning and sliding failures.
can be designed to accommodate moderate movements of foundations
without serious damages.
Heat dissipation is better in buttress dams.
Advantages Buttress Dam
Disadvantages Buttress DAMS
Buttress dams are more susceptible to damage and sabotage.
Buttress dams cannot be constructed in very cold climates because
of spelling of concrete.
Because the upstream deck slab is thin, its deterioration may
have very serious effect on the stability.
46

Check dam
 Check dam is a small dam ,which can be either temporary or
permanent ,built across a minor channel, or drainage ditch.
 Similar to drop structure in purpose ,they reduce erosion and
gullying in the channel and allow sediments and pollutants to
settle.
 They also lower the speed of water flow during storm events.
 It can be built with logs , stone or sandhogs of these ,the former
two are usually permanent or semi-permanent and the sandbag
check dam is usually for temporary purpose.
 Also ,there are check dams that are constructed with rockfill or
wooden boards. It is possible to build them out of easily
available materials, check dams range in size ,shape and coast.
47

 Check dams are constructed in natural channels to impound
the runoff water up to certain depth in the channel.
 Small check dams are constructed over the stream bed
there by checking runoff and increasing the contact
period of the rain water with underlying formation.
 The water is harvested by digging wells very near to the
infiltration zone.
 The place in the upstream just above a check dam is a good
place to put in a percolation structure.
 Silt that builds up behind the dam creates good farmland ,
which can be planted after the rains while it reatains
moisture.
48

Barrage
• A barrage is the type of low-head , diversion dam which consists of a
number of large gates that can be opened or closed to control the amount
of water passing through the structure , and thus regulate and stabilize
river water in the upstream for use in irrigation and other systems
• According to world commission on Dams, a key difference between a
barrage and a dam is that a dam is built for water storage in reservoir,
which raises the level of water significantly.
• During the floods, the gates are raised to clear off the high flood
level,enabling the high flood to pass down stream with afflux.When the
flood reduces the gates are lowered and flow is obstructed thus raising the
water level to the upstream of the barrage.
• Due to this their is less silting and better control over the water level in the
river.
However, barrages are much more costlier than weirs.
50

Weir
• A weir is a barrier across a river designed to alter its flow
characteristics .The weir is a solid obstruction put across the
river to raise its water level and divert the water into the canal.
• If a weir also stores water for tiding over small periods of
short supplies ,it is called as “A Storage Weir”.
• The main difference between a storage weirs and dam is only
in height and duration for which the supply is stored.
• During the floods the shutters may be dropped down to allow
water to flow over crest of the weirs.
 Uses : To alter the flow of rivers to prevent flooding, measure
discharge & help render rivers navigiable.
52

Classification :
Weirs are classified into two heads,
- According to the criterion of the design of the floors;
(i) Gravity Weirs
(ii) Non Gravity Weirs
- According to the material of construction & certain
design features ;
(i) Masonry weirs with vertical drop or vertical drop
– weirs.
(ii) Rockfill weirs with slopping aprons.
(iii)Concrete weirs with a downstream glacis.
53

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