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Environmental
Sciences
Water Resources and Management
Hydropower Generation-I
Paper No: 5 Water Resources and Management
Module: 21 Hydropower Generation-I
Development Team
Principal Investigator
&
Co- Principal Investigator
Prof. R.K. Kohli
Prof. V. K. Garg & Prof. Ashok Dhawan
Central University of Punjab, Bathinda
Paper Coordinator Dr Hardeep Rai Sharma, IES
Kurukshetra University, Kurukshetra
Content Writer Prof. Rajesh Kumar Lohchab, Guru Jambheshwar
University of Science and Technology, Hisar
Content Reviewer
Prof. ( Retd.) V. Subramanian, SES , Jawaharlal
Nehru University, New Delhi
Anchor Institute
Central University of Punjab
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Hydropower Generation-I
Description of Module
Subject Name Environmental Sciences
Paper Name Water Resources and Management
Module
Name/Title Hydropower Generation -I
Module Id EVS/WRM-V/21
Pre-requisites
Objectives To understand the concept and components of Hydropower generation
Keywords Hydropower, Rivers, Dams, Turbines, Power house,
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Learning Objectives
1. To understand the history and basics of hydropower
2. To understand the role of solar power through water cycle in generation of hydropower
3. To explain the components of Hydroelectric Power Plant
4. To explain the advantages and disadvantages of Hydroelectric Power Plant
Introduction
Based on resources, power generation can be classified as coal and gas based thermal power plants
(TPP), hydro power plants (HPP), nuclear power plants (NPP) and renewable energy based power
generation plants. Power generation in India is unevenly distributed because hydro resources are
available in Himalayan region, while fossil fuel resources are available in the central and western
parts. For optimization of these resources, the power systems in our country were categorized into five
power regions in the 1960s (Ramanathan and Abeygunawardena, 2007). That’s why regional power
grids were developed. Later on in the 1980s a national grid was formed which strengthened the
intraregional and inter-regional transmission systems. The Indian power system is also connected with
the Bhutan and Nepal power systems.
Hydro Energy
Hydro power stations use the potential energy of water when it falls due to gravity. The fall and
movement of water is part of water cycle. The force of moving water can be extremely powerful.
Hydropower is a renewable source of energy. It is one of the cheapest sources of energy. Electricity
production by hydropower is cheap because once a dam is built water is available free of cost.
History of Hydropower
From centuries hydropower has been used as source of energy. Greeks were using hydropower to
produce flour from wheat 2,000 years ago. The force of falling water has been used to generate
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electricity since late 19th century and first hydroelectric power plant was built on the Fox River in
1882.
Hydropower Resource Potential of India
India is ranks fifth in terms of hydropower potential in the world. It is mainly spread on six major river
systems. The Ganga, Indus and Brahmaputra account for about 80% of the total potential of Indian
hydropower (Ramanathan and Abeygunawardena, 2007).
Rationale for hydropower
Hydropower is an established technology with cost effective renewable source of energy. Other
benefits of hydropower plants are:
Water supply
Flood and drought control, and irrigation
Navigation and recreational activities
Electricity production without interruptions
Safe operation with minimum risks
Environmental and socially sustainable
Large energy storage and operation flexibility for balancing the seasonal load
How Hydropower Works?
Hydroelectric power is a form of solar energy. The hydrological cycle is a sun driven process of water
transport from the oceans to the atmosphere and from the atmosphere back to the earth surface and
oceans. The hydrological cycle discoverer, Bernard Palissy (1580 CE), declare that rainfall itself is
adequate for the maintenance of rivers. It explains the nonstop movement of water on, above and
below the earth surface. The water travels from one source to another i.e. from river to ocean, or from
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the ocean to the atmosphere and back by evaporation, condensation, precipitation, infiltration, surface
runoff and subsurface flow. During this it undergoes through liquid, solid (ice) and vapor (gas) phase.
This cycle extend from an average depth of about one km in the lithosphere (the crust of the earth), to
a height of about 15 km in the atmosphere. The water cycle maintain of life and ecosystems on the
earth and used for households, industries, agriculture and production of power.
Water Reservoirs
A reservoir is an artificial lake constructing by making a dams across rivers to store water. It can also
be formed on natural lake by constructing a dam at Lake outlet. They are used for power generation,
downstream water supply, irrigation, flood control, canals and recreation. Reservoirs are highly
managed structure used to balance the flow by taking in water during high flows and releasing it
during low flows in controlled manner. Recreational uses of reservoir are fishing, boating bird
watching, landscape painting, walking and hiking. Large reservoirs retain water for months or even
years of average inflows basis and also provide flood protection and irrigation services. The design
and provision of these services in a hydropower plant dependents on environment and social needs.
Catchment Area and Watershed
Catchment area is the area of land from which water is drain into river. It is also known as river basin,
catchment basin, drainage basin, drainage area and watershed. It acts like a funnel and all water from
this is channeled to a single point into a river. Catchment areas are topographically separated from
each other by a ridge, hill or mountain and line which divide watershed or surface runoff between two
adjacent river basins is called the topographic water divide, or the watershed divide or simply the
divide. A network of rain gauges is placed to assess of water resources of a catchment. For each rain
gauge catchment area should be small for accuracy and better results. Rain gauge density is expressed
as area covered per gauge. According to IS: 4987-1968 the density of rain gauge network is one
station per 520 km2 in plains, one in 260 to 390km2 in moderately elevated area i.e. up to 1000m and
one in 130 km2 hilly area.
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Hydrograph
It is a graphical representation of discharge variation with time thus it is the representation of rainfall
input of a catchment. The discharge recorded in hydrograph is the combined result of surface runoff,
interflow and base flow. Direct and indirect methods of flow measurements are used to calculate the
discharge of a stream. Direct measurement of discharge in a stream is carried out velocity method,
dilution techniques, moving boat method etc. whereas indirect measurement of discharge is done by
using hydraulic structures like weirs and gated structures and slope area method.
Unit Hydrograph
When one cm of rainfall is applied at a uniform rate at a specified time period over the catchment area
uniformly is referred as unit hydrograph. Unit hydrograph are used to predict the flood in a catchment
by a storm.
Effective Rainfall Hydrograph
Effective rainfall hydrograph (ERH) is the subtraction of initial losses and infiltration losses from the
rainfall hydrograph. It causes direct runoff which includes both surface runoff and interflow. Effective
rainfall is slightly higher than the excess rainfall.
Hydropower Theory
The dam holds the water to create the height difference necessary to maintain potential energy. Water
flow continues to the river downstream of the dam. The two vital factors necessary for hydropower
generations are the flow and the head of the stream or river. The flow is the volume of water which
can be captured and re-directed to turn the turbine generator, and the head is the distance of water
fall on its way to the generator. The larger the flow more will be the water, and higher the head higher
will be the distance the water falls, thus the more energy is available for conversion to electricity.
Double the flow and double will be the power, and double the head, double will be the power again.
A low head site i.e. head of ≤10 meters, you need to have a good volume of water flow to generate
electricity. A high head site i.e. head of ≥20 meters gravity will give you an energy boost.
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Kinetic energy of falling water is harnessed to provide electrical power. It depends on flow and height
of the falling water. Hydroelectric Power is a Function of Height and Volume.
Power = Head x Flow x Gravity
The theoretical power from a site is calculated by equation given below (Gaiusobaseki, 2010):
P = ηρQgh
Where:-
P = Power (W)
η = Dimensionless efficiency of the turbine (Approx 0.9)
ρ = Density of Water (1000 kg/m3)
Q = Volumetric flow rate (m2/s)
G = Acceleration due to gravity (9.8m/s2)
h = Height difference between inlet and outlet (m)
Energy from Hydro-power
The potential theoretical energy in a volume of elevated water can be calculated by:
W = ρ V g h
Where:
W = energy (J)
V = volume of water (m3)
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The Physics of Hydropower:
Based on the conservation of energy, hydropower energy transfer is as below:
Potential Energy → Kinetic Energy → Mechanical Energy → Electric Energy
Potential Energy:
Head level is the difference between the maximum heights of water to the minimum height of the
water. It is directly proportional to the potential energy. A high head level would mean that the
potential energy of the hydropower system is very high. The effective head is the difference between
the energy head at the entrance to the turbine and the energy head at the exit of the draft tube. When
the volume of waters moves from the maximum level to the minimum level for a height of h, work
will be produced and defined by the equation;
𝑊𝑜𝑟𝑘 = 𝐹𝑜𝑟𝑐𝑒 x 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒
𝑊 = 𝜌𝑔𝑉ℎ
Using the equation for work, it is possible to calculate the theoretical power output of the hydropower
system. This is done by differentiating the work equation with respect to time.
𝑃𝑜𝑤𝑒𝑟 = 𝑊𝑜𝑟𝑘/ 𝑇𝑖𝑚𝑒
𝑑𝑃 = 𝑑𝑊 /𝑑𝑇
𝑃 = 𝜌𝑔𝑄ℎ
Where Q is the volumetric flow rate through the turbine, Power is measured in units of Watts.
Kinetic Energy:
As the water hits the impulse vanes, a dynamic force will exist in order for the vanes or buckets to start
rotating. The rotation of the vanes converts the potential energy to kinetic energy. The force on the
moving vane or bucket by a jet of water is derived as the equation of force:
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W = Weight of the water striking the vane
v = relative velocity of water with respect to moving vanes
m = coefficient for loss of velocity moving across vane
𝜃 = angle of deflection of the jet from its original direction
The relative velocity can be found using the equation:
𝑣 = 𝑉 − 𝑢
V = absolute velocity of the water
u = absolute linear velocity of the bucket
Dams
A dam increases the head or height of the water and controls its flow. Dams release water to generate
electricity and excess water is released through special gates called spillway gates during heavy rain
falls. Oldest known dam is Jawa Dam in Jordan constructed in 3000 BC. It was 9 meters high and 1 m
wide stone wall supported by a 50 m wide earth rampart. Kallanai Dam is the fourth oldest dam in the
world and it still serves the people of Tamil Nadu, India. The dam was constructed by King Karikala
Chola of the Chola Dynasty in the 2nd century AD. A dam holds large amount of water in a lake or
reservoir. The higher the level of water in a reservoir, the more will be available potential energy for
electricity generation. Basin wise power generation capacity in India is shown in Table 1.
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Table1: Basin-wise (CWC) power capacity
CWC Basin Counts of Dams Total Unit Total Capacity (MW)
Brahmani 11 5 250
Brahmaputra 13 37 1014
Cauvery 23 36 611
East 2 9 9 76
Ganga 84 87 3188
Godavari 59 61 2794
Indus 15 70 4841
Krishna 22 65 4591
Mahanadi 14 14 365
Mahi 3 8 380
Minor NE 1 3 105
Narmada 6 2 90
Pennar 2 2 20
Supernarekha 3 2 130
Tapi 6 4 300
West1 8 15 2240
West 2 36 80 3847
Hydropower Plants
The flowing water contains a huge amount of kinetic energy which can rotate the wheels for
generating motion energy for generating electricity. Hydroelectric power plants use turbine generators
to produce electricity, just as thermal (coal, natural gas, nuclear) power plants do, except they do not
produce heat to spin the turbines.
Hydroelectric Power Plant
Hydropower plant consists of three parts (Figure 1).
1. A power plant
2. A dam
3. A reservoir
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To generate electricity, dam gates open and water from the reservoir allowed to flow through large
tubes called penstocks. The fast-moving water spins the blades of turbines at the bottom of the
penstocks. The turbines are connected to generators to produce electricity which is transported via
huge transmission lines.
Figure 1: Components of Hydropower Generation (Source: modified https://water.usgs.gov/edu/wuhy.html)
Head and Flow
The amount of electricity generation in a hydro power plant depends upon head and flow of water.
Head is distance of water drops from highest level of the reservoir/dam to the point where turbine
installed. A high head plant needs less water flow than a low-head plant to produce the same amount
of electricity.
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Storing Energy
Hydropower plant has ability to store energy as water can be stored in a reservoir and released when
needed for electricity production. Storage also makes it possible to save water for high energy demand
period and low rainfall such as summer.
Power station
In the power station, turbines and generators convert the kinetic energy of the water into electricity. A
hydro power plant may have more than one power station.
Spillway
A spillway releases water from the power station back into a river, stream or lake. It is a channel
designed to slow the water back to its normal speed.
Size of Hydropower Plant
Large Hydropower
According to U.S. Department of Energy (US DOE, 2004) large hydropower are those which have a
capacity of more than 30 MW. Major dams of world and India are shown in Table 2 and 3,
respectively.
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Table 2: Major Dams in the World
Name of Dam
River Height (m) Type Country
Jinping-1 Dam Yalong 305 Concrete arch China
Nurek Dam Vakhsh 300 Embankment earth fill Tjakistan
Xiaowan Dam Lancang 292 Concrete arch China
Xiluodu Dam Jinsha River 285.5 Concrete arch China
Grade Dixence Dixence 285 Concrete gravity Switzerland
Enguri Dam Enguri 271.5 Concrete arch Georgia
Vajont Dam Vajont 261.6 Concrete arch Italy
Nuozhadu Dam Lancang 261.5 Embankment China
Manuel Moreno
Torres Dam
Grijalva 261 Embankment Earth-
fill
Mexico
Tehri Dam Bhagirathi 260.5 Embankment Earth-
fill
India
Mauvoisin Dam Bagnes 250 Concrete Arch Switzerland
Laxiwa Dam Yellow River 250 Concrete Arch China
Deriner Dam Coruh River 249 Concrete Double-arch Turkey
Gilgel Gibe iii Dam Omo River 246 Roller-compacted
concrete gravity
Ethopia
Alberto Lieras Guavio River 243 Embankment Earth-
fill
Colombia
Mca Dam Columbia River 243 Embankment Earth-
fill
Canada
Sayano
Shushenskaya Dam
Yenisei River 242 Concrete Arch-gravity Russia
El Cajon Dam Humuya River 234 Concrete Double-arch Honduras
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Table 3: Major Dams of India
Dam River Height
(m)
Type Storage
Capacity
(MCM)
Hydro
electricity
generation
Bhakra
Nangal Dam
Satluj
River
226 Concrete
gravity Dam
9867.84 1325 MW
Tehri Dam Bhagirathi
River
260 Earth and rock-
Fill Dam
3540 2400 MW
Hirakud-Dam Mahanadi
River
60.96 Composite
Dam
4,823 307.5 MW
Nagarjuna
Sagar Dam
Krishna
River
124 Masonry Dam 11553 960 MW
Sardar
Sarovar Dam
Narmada
River
163 Gravity Dam 9500 1,450 MW
Indira Sagar
Dam
Narmada
River
92 Concrete
Gravity Dam
12220 1,000 MW
Koyna Dam Koyna
River
103.02 Rubble-
Concrete dam
2980.69 1,920 MW
Nathpa Jhakri
Dam
Satluj
River
concrete
gravity dam
1500 MW
Idukki Dam Periyar
River
106.9 Gravity-
Masonry Dam
1998.57 780 MW
Small Hydropower
According to U.S. Department of Energy (US DOE, 2004) small hydropower are those which have a
capacity of 100 kilowatts to 30 MW. Some of some dams of India are Given in Table 4.
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Table 4: Small Hydro Power Projects
Sr.
No.
Station Operator Location Unit/Capacity
(MW)
1 Donkaryl APGenco Andhra Pradesh 1x25
2 Jayakwadi Dam - Maharastra 1x12
3 Ujjani Dam MahaGenco Maharastra 1x12
4 Bhatgar MSPG Co Ltd. Maharastra 1X16
5 Kambang Project NHPC Arunchal Pradesh 3x2
6 Sippi Project NHPC Arunchal Pradesh 2x2
7 Nimmo-Bazgo NHPC Leh, Jammu & Kashmir 3x15
8 Chutak NHPC Karrgil, Jammu & Kashmir 4x11
9 Chenani-1 JKPDC Jammu & Kashmir 5x4.66
10 Nagarjuna Sagar fall
pond power house
APGenco Andhera Pradesh 2x25
11 Potteru Hydro Electric
Project
OHPC Koraput, Odisha 2x3
12 Bhavanl Kattalal
Barrage
TNEB Tamil Nadu 4x15
13 Rangit NHPC Sikkim 3x20
14 Babail UP Jal Vidyut
Nigam Ltd.
Uttar Pradesh 2x1.5
15 Belka UP Jal Vidyut
Nigam Ltd.
Uttar Pradesh 2x1.5
16 Bhandardara-1 Dondson
Lindblom HP
Pvt. Ltd.
Maharastra 1x14.4
17 Little Ranjit WBSED Co
Ltd.
West Bengal 2x1
Micro Hydropower
Micro hydropower plants are those which have capacity of up to 100 kW. A micro hydropower plant
can produce enough electricity for a home, farm, ranch, or village.
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Classification of Small Hydro in India: Dams can be classified as:
Type of Project
Range
Pico 5 KW & Below
Micro 100 KW & Below
Mini 2000 KW & Below
Small 2500 KW & Below
Diversity of Hydropower
Hydropower plants are primarily classifies in three functional categories: run-of-river (RoR), reservoir
(or storage) HPP, and pumped storage plants (PSP). The RoR hydropower plant harnesses energy for
electricity production mainly from flow of the river.
Advantages of Hydro Energy
1. It is a renewable form of electricity generation.
2. It is a very effective method of converting mechanical energy into electricity.
3. No greenhouse gas emissions.
4. It does not pollute the air like thermal power plants that burn fossil fuels.
5. It can produce electricity on demand by control flow of water.
6. It provides clean electricity.
7. It creates reservoirs for recreational opportunities like fishing, swimming and boating.
8. Other benefits may include water supply and flood control.
Floods
Flood is a condition of river overflowing from its banks because of the abnormal meteorological
conditions like heavy rainfall, melting of snow from the catchment, shifting of the river course, bank
erosion, or blocking of river, or breaching of the river flood banks. Floods are very common in India,
particularly in the rivers basins of Kosi, Brahmaputra, Godavari, Narmada and Tapti. Floods are
responsible for loss of life and property, damage to crops, famine, epidemic diseases and other indirect
losses.
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Flood Control
The damages of floods can be minimized by adopting the following control measures.
1. Construct reservoirs and detention basins to provide a temporary storage of the peak floods.
2. Adopting soil conservation measures in the catchment area.
3. Construct flood banks, dykes, or flood walls.
4. Construct and improve channel by deepening river training works.
5. Construct bypasses or flood ways to divert a part of the flood through these.
6. Set up short term and long term warning systems of flood forecasting like rhythm signals and
radar centers at vulnerable areas.
Disadvantages of Hydro Energy
Hydropower plant needs dams to create reservoirs at lakes or rivers, which flooded a large piece of
land. Therefore there is a loss of farmland and residential areas which need shifting of people in new
homes in new areas. Due to submergence of area there is loss of flora and fauna and disruption to
animal, plant and aquatic ecosystems. Migration of fish is stopped by construction of dam, thereby
their breeding and survival is adversely affected. Hydropower plant can impact water quality and flow
by lowering the dissolved oxygen levels in the water. A minimum flow of water in downstream of a
hydropower plant is required for the survival of riparian habitats. New hydropower plant affects the
local environment and may compete with other uses for the land. Humans, flora, and fauna may lose
their natural habitat. Local cultures and historical sites may be impinged upon.
Scientists have traced the cause of over 100 earthquakes worldwide to dams. Filling of
reservoirs of large dams has triggered seismic activity because it create extra water pressure in
the micro-cracks and fissures in the ground under and near a reservoir. The water in the rocks
acts as lubricant in faults which are already under tectonic strain.
Sediments are the soil particles produced during erosion of soil and rocks by water and wind in
the catchment and these are transported with flowing water in the river. By constructing a dam
we retard the velocity of flow water which results in settling of sediments having density more
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than water at the bottom of reservoir under the force of gravity. It results in reduction of
storage capacity and overall life of the reservoir. Sedimentation in a reservoir is a nonstop and
complex process which affects the useful life of a reservoir. The monitoring of sediment and
sedimentation process at bottom of reservoir is essential for efficient management of reservoir
and river basin.
Decreases in silt and nutrients in downstream of a river decrease soil fertility in riparian land,
which harms the plants and animals that live and grow there. It causes animal habitat to drops
and loss of biodiversity.
Summary
In this module we learnt about:
What is hydropower and how it works?
What is hydrological cycle? What its role in hydropower generation?
How the hydroelectric power plants works?
What are components hydroelectric power plants?
What are advantages and disadvantages of hydroelectric power plants?
References
U.S. DOE (2004). Hydropower: setting a course for our energy future. United State Department of
Energy, Washington D.C.
Ramanathan K. and Abeygunawardena P. (2007). Hydropower development in India: a sector
assessment. Asian Development Bank
Gaiusobaseki T. (2010). Hydropower opportunities in the water industry. International Journal of
Environmental Sciences 1(3):392-402.
