UNIT-1

Define hydropower
Hydropower is a form of renewable energy that harnesses the kinetic energy of falling water to generate electricity. It is
typically generated by building a dam on a river to create a reservoir, which is then used to drive a turbine that generates
electricity. The amount of electricity generated by a hydropower plant depends on the volume of water flowing through
the turbine, the height of the drop (or head) of the water, and the efficiency of the turbine.

Define power
Power is the rate at which energy is transferred or work is done. It is typically measured in watts (W) or kilowatts (kW).
The formula for power is power = work/time. In electricity, power is the rate at which electric energy is being transferred,
and it is measured in watts (W) or kilowatts (kW). For example, a 100-watt light bulb uses 100 joules of energy per
second.
Explain the power situation in Nepal & world
Nepal currently relies heavily on hydropower as a source of energy, providing more than 90% of the country's electricity.
However, Nepal has faced power shortages and blackouts due to a lack of investment in new power projects, as well as
inadequate transmission and distribution infrastructure. The country also suffers from significant seasonal variation in
energy demand, which can make it difficult to meet the needs of its population.
Globally, hydropower is one of the most widely used forms of renewable energy and provides about 10% of the world's
electricity. However, the potential for hydropower varies greatly from country to country. Developing countries are
especially dependent on hydropower, as it is often a cost-effective and reliable source of energy. In addition, many
countries are increasing their use of renewable energy sources, such as wind, solar and hydropower as a way to reduce
their dependence on fossil fuels and to meet their commitments to reduce greenhouse gas emissions.

Classification of hydropower
1. Run-of-river: This type of hydropower uses the natural flow of a river to generate electricity, without the need for a
large reservoir.
2. Impoundment: This type of hydropower uses a dam to create a reservoir, which is then used to generate electricity.
3. Pumped-storage: This type of hydropower uses excess electricity to pump water into a reservoir at a higher elevation,
and then releases the water back through a turbine to generate electricity when demand is high.
4. Micro-hydropower: This type of hydropower generates a small amount of electricity, typically for local use, using
small-scale turbine and generator systems.
5. Tidal power: This type of hydropower harnesses the energy of tidal movements to generate electricity, typically using a
tidal barrage or a tidal turbine.
6. Wave power: This type of hydropower harnesses the energy of ocean waves to generate electricity, typically using
wave energy converters.

Types of power
1. Mechanical power: The power generated by machines and mechanical devices, such as engines and turbines.
2. Electrical power: The power generated by the movement of electric charges, such as in batteries and generators.
3. Thermal power: The power generated by heat, such as in boilers and nuclear reactors.
4. Chemical power: The power generated by chemical reactions, such as in fuel cells and batteries.
5. Nuclear power: The power generated by nuclear reactions, such as in nuclear power plants.
6. Solar power: The power generated by the sun's energy, typically using photovoltaic cells or solar thermal collectors.

Explain the potential of hydropower development in Nepal

Nepal has significant potential for hydropower development due to its many rivers and high elevations. The country has
an estimated hydropower potential of around 83,000 MW, of which only a small fraction has been developed so far. The
majority of this potential is located in the hilly and mountainous regions of the country, where rivers flow from high
elevations to low elevations. However, there are also some challenges to hydropower development in Nepal. One of the
main challenges is the lack of infrastructure and access to funding for large-scale projects. Additionally, the country's
rugged terrain and remote locations make it difficult to construct and maintain hydroelectric facilities. Moreover, lack of
proper Environmental and Social Impact Assessment, and proper resettlement program for the affected people also a
major concern. Despite these challenges, the potential for hydropower development in Nepal remains significant. The
development of hydropower in Nepal could play a key role in meeting the country's energy needs, reducing its
dependence on fossil fuels and helping to spur economic development.
What are the different stages of hydropower development?
The stages of hydropower development typically include:
1. Feasibility study: This stage involves conducting a detailed assessment of the potential site to determine the
hydropower potential and the technical, financial, and environmental feasibility of the project.
2. Design and engineering: In this stage, the project is designed and detailed engineering plans are developed. This
includes site layout, turbine and generator selection, and electrical and mechanical systems.
3. Permitting and environmental review: This stage includes obtaining necessary permits and approvals from local and
national government agencies, as well as conducting environmental impact assessments.
4. Construction: This stage includes the building of the dam, power station, and other infrastructure required for the
project.
5. Commissioning and operation: This stage includes testing and commissioning the project, and then operating and
maintaining it for the life of the project.
6. Decommissioning: This is the final stage of the hydropower development, where the hydropower plant is closed and the
site is returned to its natural state as much as possible.

Historical background & development of hydropower in Nepal

The history of hydropower development in Nepal dates back to the early 20th century, with the first hydroelectric project
being commissioned in 1911. This project was a small-scale scheme, with a capacity of only 180 kilowatts, located in the
western part of the country. In the decades that followed, the Nepalese government established several small hydroelectric
projects, primarily to meet the needs of local communities and small industries. However, the development of hydropower
in Nepal remained limited until the late 20th century. In the 1990s, the government of Nepal began to actively promote the
development of hydropower as a means of increasing the country's electricity generation and reducing its dependence on
fossil fuels. The government implemented a number of policies and programs to encourage private sector investment in
hydropower development and also worked to improve the legal and regulatory framework for the sector.
Since then, Nepal has seen an increase in hydropower development, with a number of large-scale projects being proposed
and constructed. As of 2021, the installed capacity of hydropower in Nepal is around 1,200MW, and the government aims
to increase it to 10,000MW by 2030. However, despite the government's efforts, the development of hydropower in Nepal
has been slow and still faces a number of challenges, including lack of infrastructure and access to funding, difficult
terrain and remote locations, and issues related to environmental and social impacts.

Major problems in hydropower development in Nepal

1. Lack of investment and funding
2. Difficulty in acquiring land and obtaining necessary permits and approvals
3. Limited technical expertise and capacity within the country
4. Environmental and social impacts, including displacement of local communities and damage to ecosystems
5. Dependence on neighboring countries for transmission and distribution of electricity
6. Political instability and lack of government support
7. Limited resources, including water and land, for large-scale hydropower projects
8. Limited access to electricity in remote and rural areas
9. High construction and maintenance costs
10. Vulnerability to natural disasters such as floods and landslides.

Different type of hydropower project that have been developed in Nepal

There are several different types of hydropower projects that have been developed in Nepal, including:
1-Run-of-river: This type of project utilizes the natural flow of a river to generate electricity, without the need for a large
dam or reservoir.
2-Storage: This type of project involves the construction of a dam or reservoir to store water, which is then released to
generate electricity during periods of high demand.
3-Pumped storage: This type of project uses excess energy from the electrical grid to pump water to a higher elevation,
which is then released through turbines to generate electricity during periods of high demand.
4-Micro hydropower: These are small-scale hydroelectric power plants, usually with a capacity of less than 100 KW,
typically used for rural electrification.
5-Mini-hydropower: These are small-scale hydroelectric power plants, usually with a capacity of between 100 KW and 10
MW. They are typically used for local power generation and grid supply.
Classification of hydropower plant
1. Low Hydro: Installed capacity less than 10MW. These plants typically have a low environmental impact and can be
used to serve small communities or to provide electricity for local industries.
2. Medium Hydro: Installed capacity between 10MW and 50MW. These plants are capable of serving larger communities
or supporting regional power grids.
3. High Hydro: Installed capacity greater than 50MW. These plants are usually used to generate large amounts of
electricity to support national power grids, and they have a high environmental impact.

Advantages & disadvantages of hydropower

Advantages of Hydropower:
1. It is a renewable energy source that does not produce greenhouse gas emissions.
2. It is a reliable source of electricity, especially when compared to other forms of renewable energy such as wind or solar
power.
3. Hydropower plants can provide a constant and predictable source of electricity, making them well suited to meet base
load electricity demand.
4. It can be used for irrigation, flood control and recreation.
5. It creates jobs and economic opportunities in the local area.
Disadvantages of Hydropower:
1. Building large hydroelectric facilities can have significant environmental impacts, including the displacement of local
communities and destruction of habitats.
2. The construction of dams and reservoirs can also disrupt the natural flow of rivers, leading to changes in water
temperature, sediment transport and fish migration.
3. The maintenance and operating cost of the hydroelectric facilities are high.
4. Droughts and low water levels can decrease the power generation of the hydroelectric facilities.
5. Hydropower plants can be affected by natural disasters such as floods, landslides and earthquakes.

Challenges of Hydropower Development in Nepal:

1. Lack of infrastructure: Nepal has a limited infrastructure and transportation network, making it difficult to construct and
maintain hydroelectric facilities in remote areas.
2. Access to funding: The high cost of building and maintaining hydroelectric facilities can be a barrier to investment, and
Nepal has limited access to international funding for these types of projects.
3. Environmental and social impacts: Hydropower development in Nepal can have significant environmental and social
impacts, including the displacement of local communities and destruction of habitats.
4. Complex legal and regulatory framework: Nepal's legal and regulatory framework for hydropower development is
complex and can be a barrier to investment.
5. Technical & financial capacity: Nepal lacks the technical and financial capacity to develop and operate large
hydroelectric projects, which requires international expertise and investment.

Define run off river

Run-off river systems refer to the flow of water from precipitation that runs off the land surface, rather than being
absorbed into the ground, and flows into rivers and streams. This water may come from rain, snowmelt, or other forms of
precipitation, and can be an important source of fresh water for human and natural communities. The flow of water in a
run-off river system can be influenced by factors such as the amount of precipitation, the slope of the land, and the type of
soil and vegetation present.

Main characteristics of ROR in hydropower project

1. Water is collected from precipitation, rather than being taken from a reservoir or other source
2. Water flow is highly dependent on weather and climate conditions
3. Can provide a consistent and reliable source of energy
4. Often has a relatively low environmental impact compared to other types of hydroelectric projects
5. Can be used in small scale and large scale projects
6. The cost of construction is usually lower than other hydroelectric

Typical layout of ROR hydropower

A typical layout of Run-of-River (ROR) hydroelectric power plant includes:
1. Intake: where water is collected from the river and directed into the power plant through a dam or weir.
2. Penstock: a large pipe or channel that carries water from the intake to the turbine.
3. Turbine: converts the energy of the flowing water into mechanical energy.
4. Generator: converts the mechanical energy from the turbine into electrical energy.
5. Power house: building or facility that houses the generator, turbine and other equipment used to produce electricity.
6. Tail race: channel or conduit that carries water away from the turbine after it has been used to generate electricity and
returns it back to the original source.

Define pumped storage plant

A pumped storage hydroelectric power plant is a type of hydroelectric power generation that uses excess energy from the
electrical grid to pump water to a higher elevation. This water is then stored in a reservoir or lake, and is later released
through turbines to generate electricity during periods of high demand. The pump turbines are reversible and can be used
to pump water back to the upper reservoir when there is an excess of electricity on the grid, making it a flexible source of
power. This allows for the storage of excess energy for later use. Pumped storage plants are generally used to provide a
consistent and reliable source of energy, especially during peak demand periods.

Main characteristics of Pumped storage in hydropower project

1- Uses excess energy from the electrical grid to pump water to a higher elevation
2- Water is then released through turbines to generate electricity during periods of high demand
3-Allows for the storage of excess energy for later use
4-Can provide a consistent and reliable source of energy
5-Can be used in combination with other forms of renewable energy
6-Can be used in small scale and large scale projects
7-The cost of construction is usually higher than other hydroelectric projects
8 -The environmental impact of the project can vary depending on the location and design of the project.

UNIT-2
Define Flow duration curve, plant capacity, power duration curve, firm power, secondary power, flow mass curve
& reservoir
1. Flow duration curve: It is a graphical representation of the frequency of various flow rates of a river or stream. It is
typically used to determine the average flow rate of a river or stream, as well as its variability over time.
2. Plant capacity: It is the maximum output of a hydroelectric power plant, measured in megawatts (MW) or kilowatts
(KW).
3. Power duration curve: It is a graphical representation of the relationship between the amount of electricity generated
by a hydroelectric power plant and the duration of time over which it is generated.
4. Firm power: It is the amount of electricity that a power plant can generate consistently and reliably, regardless of
fluctuations in water flow or other factors.

5. Secondary power: It is the amount of electricity that a power plant can generate in addition to its firm power, but
which may be less consistent and reliable due to fluctuations in water flow or other factors.
6. Flow mass curve: It is a graphical representation of the relationship between the amount of water flowing in a river or
stream and the rate at which it is flowing.
7. Reservoir: It is a large artificial lake or tank used to store water for later use, such as in a hydroelectric power plant. It
can also be used to regulate the flow of water in a river or stream, and can be used for irrigation and other purposes.

Uses of flow duration curve:

1. It helps to evaluate the flow expected certain percentage of time.
2. It is useful in planning and designing of water resource projects.
3. Flow duration curve also helps in the design of drainage systems and in the flood control studies.
4. Flow duration curve plotted in log graph provides the qualitative description of the runoff variability in the
Stream

Power demand variation: daily, weekly, monthly and annual variation of power.
1. Daily variation of power:
Electricity demand is usually lower during the night hours, with little domestic or commercial consumption.
Demand then begins to fall and drops off as people begin to retire to bed. Power demand at residence reduces during
office hours.
2. Weekly variation of power
Daily routine changes at weekend. If people stay at home during the weekend, power demand is more and if people spend
time on travels, the power demand at home reduces.
3. Monthly variation of power
We have different sorts of festivals throughout the years in different months. Festivals are the time when people gather
and celebrate. So power demand increases on gathering. Some festivals are celebrated by more people for longer duration
while some may be celebrated by some groups for different duration. Hence, power demand varies accordingly.
4. Annual variation of power
We go through different seasons in a year. During winter we require more power for heating and lighting purposes.
When the days are longer, lights are used for shorter duration while for the short days; lights are used for longer period.
During summer, we use electricity for cooling purposes. So, there are many variations in power consumptions annually.

Power grid: introduction and components of power grid system.

1. Power grid: The system of transmission of high voltage. The power system may be either isolated or the interconnected
system.
Isolated system is not connected to the national grid.

Components of power grid system:

The components of power grid system are:
1. Generation stations (Powerhouse, generators, transformers, switchgear)
Electricity is produced in the powerhouse. Thus produced electricity is stepped up using transformers. It is because
transmission of electricity at high voltage increases transmission efficiency. Switch gear is device or a combination of
device, intended for purpose of making, carrying and breaking electric currents in circuits under normal condition as well
as under abnormal conditions.
2. Transmission lines: Transmission lines are designed to carry electricity or an electrical signal over large distances with
minimum losses and distortion.
3. Load dispatch center: Load dispatch center is a coordinating agency for state electricity boards for ensuring a
mechanism for safe and secure grid operation. Load dispatch center is an important link between generation and
transmission, which co- ordinates the power requirements of consumers of electricity.
4. Substations: Sub-station is a component of a Power System which includes various equipment and is responsible for
stepping up voltage levels for transmission or stepping down voltage levels for distribution purpose. A transformer is the
heart of a sub-station which is responsible for changing the voltage levels without changing the frequency.
5. Distribution transformers: Before the power is supplied to the consumers, it should be stepped down to the suitable
voltage so that it can be safely used for the desired purposes.
6. Household/ consumers: Consumers are the ultimate components of the power system. They use electricity for various
purposes. In Nepal, the electrical equipment of 220-240 volt is used at a frequency of 50 Hz.

UNIT-3
Site selection of hydropower project
1. Water resource availability: The site should have a reliable and consistent water resource, such as a river or stream that
can be used to generate electricity.
2. Topography: The site should have a suitable topography, such as a steep slope, that can be used to generate electricity
through the use of a dam or other type of hydroelectric power plant.
3. Accessibility: The site should be easily accessible for construction and maintenance, with good road and transportation
infrastructure.
4. Environmental impact: The site should have minimal impact on the environment and local communities, such as on
habitats, downstream water resources, and cultural sites.
5. Geology: The site should have a stable geology, without any risk of landslides or earthquakes.
6. Legal and administrative aspects: The site should be available for development and should comply with all relevant
laws, regulations and permits.
7. Economic feasibility: The site should be economically feasible, taking into account the cost of construction, operation
and maintenance, as well as potential revenue from electricity sales.
8. Social aspects: The site should not have a negative impact on local communities and their livelihoods, and should
comply with the local people's needs and expectations.

Hydropower project planning stages: reconnaissance, pre-feasibility & feasibility studies

1. Reconnaissance: This is the initial stage of the hydropower project planning process, where a general assessment of the
potential of the site is conducted. This includes gathering basic information about the site, such as its location, water
resource availability, topography, accessibility and any potential environmental or social impacts.
The major objectives of reconnaissance studies are:
a. To identify the suitable project for the stated purpose.
b. To investigate and study various projects and their alternatives.
c. To provide preliminary cost figures in the performance of reconnaissance study.
2. Pre-feasibility Study: This stage involves a more detailed assessment of the site's potential, including an evaluation of
the water resource, the selection of the most appropriate type of hydroelectric power plant, and the estimation of the
project's costs and benefits. The pre-feasibility study is used to identify and evaluate alternative sites and technologies,
and to select the most promising option for further development.
The major objectives of pre-feasibility study are:
a. Establish the need and justification for the project.
b. Formulate the plan for developing the project.
c. Determine the technical, economic and environmental practicability of the project.
d. Define the limitations of the project.
e. Make recommendations for further action.
3. Feasibility Study: This stage is the most detailed and comprehensive stage of the planning process. It includes the
design of the hydroelectric power plant, the assessment of the environmental and social impacts, the estimation of the
project's costs and benefits, and the identification of any potential risks and mitigation measures. This study is used to
determine the technical and economic feasibility of the project, and to provide the basis for the project's detailed design
and construction.
The major objectives of the feasibility study are:
a. To ascertain the identified project for the implementation.
b. To sought the measures for financing the project.
c. To carry out detail design of the project.
d. To direct project towards construction.
Hydrological data processing: mass curve and flow duration curve (Weibull method)
1. Mass curve: Mass curve also called ripple curve is a plot of accumulated inflow volume against time. The mass curve
is used to determine reservoir capacity from uniform demand of flow and safe yield from reservoir from reservoir
capacity. It is prepared from the inflow hydrograph of a river.
For much water resource investigation, it is important to know the total volumes of water that have to be dealt with over
long periods. For such purpose, the most convenient method of representing the runoff data in the form of mass curve.
Characteristics of the mass curve:
1. It is continuously raising curve.
2. The slope at any point on the curve represents the inflow rate.
3. If the curve is horizontal, it represents no inflow at that time. Mass curve never fall down.
4. If the curve rises sharply, it indicates the high rate of inflow within that period.
5. Relatively convex rise indicate flood while concave depression indicate drought.

2. Mass demand curve: A demand curve is a plot between the demand and the time. If the demand is uniform, the
demand curve is horizontal and the mass demand curve is a straight line. Reservoir capacity by graphical method, using
mass curve of inflow and demand

Reservoir planning and regulations: classification, site selection, need of reservoir regulation, life of reservoirs
1. Reservoir: When a barrier is constructed across the river, the pool of water formed on the upstream side of the barrier
is called reservoir. Generally, the barrier may be weir or dam. We will be discussing about dam in chapter 4. However
dam and reservoir are complementary to each other.
Classification of reservoir:
Reservoir is mainly categorized into two types depending upon the purpose:
a) Flood control reservoir
As we know that the reservoir can regulate the inflow hydrograph. During the time of the flood, the inflow hydrograph
has high peak which can cause a serious effect on the downstream. Thus, if a reservoir is constructed then, the hydrograph
is regulated i.e. peak is reduced and the time base is enlarged so that the possible effects on downstream is reduced.
This type of reservoir may be further classified into two types:
1. Retarding type: It simply retards the flow without the control of gates or spillways
2. Detention type: Gates and spillways are used for the flood control.
b) Storage reservoir
The basic purpose of the storage reservoir is to store water when it is available in excess so that it can be used in the time
deficit.
The storage of water may be for different purpose as: Hydropower, Irrigation, Water supply to public or industries,
Navigation, Fishery and wild life, Recreation

Site selection for reservoir:

1. It should be located in the area of maximum inflow and minimum percolation.
2. The site should be located at the narrow opening of the basin so that the length of the dam and its appurtenance works is
reduced.
3. Site should be easily accessible by road and if required to construct them, cost of construction should be minimum.
4. Topography of the location should be such that there will be less submergence of the land and properties.
5. Site should be free from objectionable minerals and salts.
6. Located area should provide sufficient water depth with smaller water area so that the possibility of weed growth is
reduced and evaporation loss is less.
7. Construction materials for the dam should be available locally.
8. Suitable area should be available for the construction of staff quarters, labor colonies and godowns.
9. Heavy silt laden tributaries should not lead their discharge into the reservoir.

Life of reservoir:
It is impossible to completely stop the flow of sediment of water into the reservoir. A part of storage called dead storage is
made available to accommodate the volume of the sediment. However, with the passage of time the sediment starts to
encroach the useful storage of the reservoir. The useful life of the reservoir is said to exist till the storage is reduced to
20% of the designed capacity.
The encroachment of sediment depends upon:
 Capacity-inflow ratio
 Sediment size and content in the flow
 Reservoir operation
 Characteristics of the valley
The capacity inflow ratio is generally high at the beginning and gradually decreases and becomes minimum when the
catchment becomes stable.
Some terms related to life of reservoir:
a) Trap efficiency: It is the ratio of total sediment deposited in the reservoir to the total sediment flowing in the river.
Trap efficiency = total sediment deposited in the reservoir/total sediment flowing in the river
b) Capacity inflow ratio: It is the ratio of total capacity of the reservoir to the total inflow into the reservoir.
Capacity inflow ratio =capacity of reservoir/total inflow into the reservoir

Estimation of life of reservoir:

The useful life of reservoir can be estimated by:
1. Working out capacity-inflow ratio and finding the annual loss of reservoir capacity
2. Finding the correction factor for the settlement and consolidation of deposited sediment which is about 15% of total
over a period of 200 years.
3. Working out trap efficiency for different reservoir capacity, which may be obtained from graphs or tables.
4. Capacity curves are determined at intervals of 25, 50, 75, 100 years etc.
5. A plot may be developed to show available capacity in different zones and total capacity against time period.
6. The time when the reservoir fails to meet minimum basic demand as originally fixed is the useful life of the reservoir.

The layout of a hydropower project:

1. Intake structures: These are structures, such as dams or diversion canals, that are used to collect and channel water into
the hydroelectric power plant.
2. Powerhouse: This is the facility where the hydroelectric power is generated. It contains the turbines, generators, and
other equipment used to convert the energy of falling water into electricity.
3. Penstock: These are the pipes or tunnels that carry water from the intake structures to the turbines in the powerhouse.
4. Tailrace: This is the channel or pipe that carries water away from the turbines and back to the river or stream after it has
been used to generate electricity.
5. Transmission lines: These are the lines used to carry electricity from the power plant to the electrical grid or to the point
of use.
6. Substation: These are facilities used to step up or step down the voltage of electricity before it is transmitted over long
distances or distributed to consumers.
7. Control and monitoring systems: These are the systems used to control and monitor the operation of the hydroelectric
power plant and to ensure the safe and efficient generation of electricity.

UNIT-4
Define Dam
A dam is a barrier that is built across a river, stream, or other watercourse to hold back and control the flow of water
purpose:
1. Flood control: Dams can be used to hold back and control the flow of water during periods of heavy rain or snowmelt,
reducing the risk of flooding downstream.
2. Irrigation: Dams can be used to store water for later use in irrigation and other agricultural activities.
3. Hydropower: Dams can be used to generate electricity through hydroelectric power plants.
4. Water supply: Dams can be used to store water for later use in municipal and industrial water supply systems.
5. Recreational: Dams can be used to create lakes and reservoirs that can be used for recreational activities such as
swimming, boating, and fishing.

Types of dams
1. Gravity dam: This type of dam is made of concrete or masonry and relies on its own weight to hold back the water.
2. Arch dam: This type of dam is curved and is made of concrete or masonry. It relies on the force of the water pressing
against it and the weight of the dam to hold back the water.
3. Earth fill dam: This type of dam is made of earth and rock and relies on the weight of the material to hold back the
water.
4. Embankment dam: This type of dam is made of materials such as rock, gravel, sand or clay and is used to hold back the
water using the weight of the materials
5. Buttress dam: This type of dam is made of concrete or masonry and is supported by a series of vertical supports or
buttresses that transfer the weight of the water to the foundation.
6. Arch-gravity dam: This type of dam is a combination of arch and gravity dam and it uses both gravity and the arch
effect to hold back water
7. Rock fill dam: This type of dam is made of rock, gravel and other materials that are compacted and held in place by a
facing of concrete or masonry

Function of Dam
1 -Holding and controlling the flow of water: Dams are designed to hold back and control the flow of water in a river,
stream, or other watercourse.
2 -Flood control: Dams can be used to prevent or reduce flooding downstream by holding back water during periods of
heavy rain or snowmelt.
3 -Irrigation: Dams can be used to store water for later use in irrigation and other agricultural activities.
4 -Hydropower: Dams can be used to generate electricity through hydroelectric power plants.
5 -Water supply: Dams can be used to store water for later use in municipal and industrial water supply systems.
6 -Recreation: Dams can be used to create lakes and reservoirs that can be used for recreational activities such as
swimming, boating, and fishing.
7 -Navigation: Dams can be built to improve navigation, allowing boats and ships to pass through locks
8 -Erosion control: Dams can be built to protect the river banks and river bed from erosion.
9 -Fish passage: Some dams have fish ladder or fish lift to allow fish to pass through the dam to reach their spawning
ground.
10 -Sediment control: Dams can also be used to control sediment and debris that can accumulate behind the dam, which
can be harmful to the environment.

Criteria for selection of dam

1. Water resource availability: The site should have a reliable and consistent water resource, such as a river or stream, that
can be used to generate electricity, irrigation or other uses.
2. Topography: The site should have a suitable topography, such as a steep slope, that can be used to generate electricity
through the use of a dam or other type of hydroelectric power plant.
3. Accessibility: The site should be easily accessible for construction and maintenance, with good road and transportation
infrastructure.
4. Environmental impact: The site should have minimal impact on the environment and local communities, such as on
habitats, downstream water resources, and cultural sites.
5. Geological stability: The site should have a stable geology, without any risk of landslides or earthquakes.
6. Flood control: The site should be suitable for controlling floods downstream, or at least not worsen the flood situation
7. Economic feasibility: The site should be economically feasible, taking into account the cost of construction, operation
and maintenance, as well as potential revenue from electricity sales, irrigation or other uses.

General consideration for design of dam

1. Purpose of the dam: The design of the dam should be tailored to the specific purpose of the dam, such as flood control,
hydropower generation, irrigation, water supply, or recreation.
2. Water resource availability: The design of the dam should take into account the volume of water that will be impounded
and the maximum flood flow.
3. Topography and geology: The design of the dam should take into account the topography and geology of the site,
including the foundation conditions and the potential for landslides or earthquakes.
4. Materials and construction methods: The design of the dam should take into account the materials and construction
methods that will be used, including the type of dam (concrete, earthen, rockfill, etc.), the type of foundation, and the type
of spillway and outlet works.
5. Safety and stability: The design of the dam should ensure the safety and stability of the dam, taking into account the
potential for overtopping, seepage, and erosion.
6. Maintenance: The design of the dam should take into account the maintenance requirements and accessibility for future
maintenance.
7. Cost: The design of the dam should be cost-effective and affordable.

Straight gravity dam

A straight gravity dam is a type of dam that uses its own weight to hold back the water in a reservoir. The design principle
for a straight gravity dam is that the weight of the dam must be greater than the water pressure at the base of the dam. The
dam is typically made of concrete or masonry and is built across a valley or canyon, creating a reservoir behind it. Straight
gravity dams are typically used for water storage, irrigation, and hydroelectric power generation
Design principle of straight gravity dam
1. The weight of the dam must be greater than the water pressure at the base of the dam.
2. The dam is thick at the bottom and tapers towards the top, creating a triangular shape (trapezoidal cross section).
3. The dam must be anchored securely into the rock or soil foundation to prevent movement or instability.
4. The foundation of the dam must be strong and stable to support the weight of the dam and the water pressure.
5. The dam should be designed to withstand the forces of water, earthquakes and other natural forces.
6. The design should also consider the temperature variations and any settlement that may occur over time.

Define concrete gravity dam

A concrete gravity dam is a type of dam that uses its own weight and the strength of its concrete structure to hold back
water. It is similar to a straight gravity dam, but is made entirely of concrete, and like a straight gravity dam, it has a
straight face and a trapezoidal cross-section. The base of the dam is wider than the top, and the dam's height can range
from a few meters to several hundred meters.
General Consideration of concrete gravity dam
1. The weight of the dam must be greater than the water pressure at the base of the dam.
2. The dam is made entirely of concrete, and has a straight face and a trapezoidal cross-section.
3. The base of the dam is wider than the top, and the dam's height can range from a few meters to several hundred meters.
4. The dam is built across a valley or canyon, creating a reservoir behind it.
5. The dam should be designed to withstand the forces of water, earthquakes, and other natural forces.
6. The foundation of the dam must be strong and stable to support the weight of the dam and the water pressure.

Define Earthen dam

An earthen dam is a type of dam that is made of natural materials such as soil, clay, rock, or gravel. They are also
sometimes called embankment dams, as they are built by creating an embankment or a raised barrier of these materials
across a valley or canyon. The design principle of an earthen dam is that the weight of the embankment must be greater
than the water pressure at the base of the dam. The embankment is typically constructed using a combination of materials
such as soil, clay, rock, or gravel, and is reinforced with a layer of asphalt or concrete.
General consideration for design of earthen dam
1. The design should also consider the temperature variations and any settlement that may occur over time.
2. The dam should have an emergency spillway to discharge water in case of overtopping
3. The design and construction should consider the environmental aspects and impacts.
4. The dam should have an efficient and well-maintained system for monitoring and controlling the water level and
quality.
5. The dam should have a proper drainage system to prevent water from seeping through the embankment.
6. The dam should be designed to prevent erosion of the embankment by water and wind.

Causes of failure of earthen dam & their control measures

Causes of failure of earthen dam:
1. Overtopping: When the water level in the reservoir exceeds the top of the dam, it can cause erosion and instability.
2. Seepage: Water can seep through the embankment and weaken the structure.
3. Foundation failure: If the foundation of the dam is not stable or is composed of unstable materials, it can lead to failure
of the dam.
4. Earthquake: An earthquake can cause damage to the dam and result in failure.
5. Erosion: The erosion of the embankment by water and wind can cause instability and failure.
Control Measures:
1. Proper design and construction: A well-designed and constructed earthen dam will be less likely to fail.
2. Regular maintenance and inspections: Regular inspections and maintenance can identify and address potential issues
before they become critical.
3. Proper drainage: A proper drainage system can prevent water from seeping through the embankment and causing
damage.
4. Emergency spillway: An emergency spillway should be provided to discharge water in case of overtopping.
5. Monitoring and control system: An efficient and well-maintained system for monitoring and controlling the water level
and quality should be provided.

UNIT-5
Intake
Intake is a hydraulic structure, provided at the mouth (entrance) of a water conveyance system to withdraw water from a
reservoir or river to the power house.
Function of the Intake Structure
The following functions of an intake structure are:
i) To prevent entry of trash, debris, ice, boulders, logs of wood, etc. into the
ii) Conveyance system. This is achieved by providing a trash rack at entrance. To control the flow of water into
conveyance system by providing a gate or a valve.
iii) To enable smooth, easy and turbulence free entry of water into the water conductor system. This is achieved by
providing a bell mouth entry at the inlet mouth.
iv) To minimize sediment entry from the river into the water conveyance system. For this purpose, special device like silt
traps and silt excluders are provided.

Location of the Intake

The location of the intake depends on number of factors, such as dam type, reservoir geometry, quantum of water to be
diverted, topology, submergence, geotechnical conditions, and environmental considerations, especially those related to
fish life- sediment exclusion and ice formation, where necessary. Hence, this has to be decided on case to case basis
keeping in mind the following primary considerations.
-Adequate inflow.
-Least silt intake
-Least head loss
-Least environmental impact

Objectives of intake
1. Intake approach should be symmetrical to avoid velocity and to minimize entry head loss.
2. Submergence depth should be more than 70% of the intake pipe diameter to avoid entry of air pockets and vorticity.
3. Intake from straight reach, to be avoided and better coerce (force) water to follow curved path to avoid large entry of
silts.
4. Intake should preferably be located on concave side near the end of the curved stretch to avoid larger entry of silts.

Types of Intake
1. Surface intake: Water is taken from the surface of the reservoir or river into the dam's intake structure.
2. Submerged intake: Water is taken from the bottom of the reservoir or river into the dam's intake structure.
3. Shaft intake: Water is taken through vertical shafts or tunnels that lead to the dam's intake structure.
4. Canal intake: Water is taken from a canal or channel that leads to the dam's intake structure.
5. Low level intake: Water is taken from a low level in the reservoir or river into the dam's intake structure.
6. High level intake: Water is taken from a high level in the reservoir or river into the dam's intake structure.
7. Combined intake: A combination of the above types of intake methods can be used in the dam.

Basic requirement of ideal intake

An ideal intake for a hydroelectric power plant should have the following basic characteristics:
1. Adequate water flow: The intake should be able to collect enough water to meet the needs of the power plant, even
during low flow periods.
2. Sufficient head: The intake should be able to provide enough head (pressure) to drive the turbine and generate
electricity.
3. Easy access for maintenance: The intake should be designed to allow easy access for maintenance, cleaning, and repair
work.
4. Debris removal: The intake should have a trash rack or other debris-removal system to prevent large objects from
entering the power plant.
5. Low erosion: The intake should be designed to minimize erosion of the riverbed or surrounding area.
6. Fish passage: In case of a fish habitat, the intake should be designed to allow fish passage or have a fish ladder to avoid
fish mortality.
7. Environmental impact: The intake should be designed to minimize negative impacts on the surrounding environment,
such as water quality or downstream flow.
8. Cost-effective: The intake should be designed to be cost-effective to construct and maintain over time.

Write down the design step of intake

The design of an intake for a hydroelectric power plant typically involves the following steps:
1. Site selection: The first step is to select a suitable location for the intake based on factors such as water flow, head,
access for maintenance, and environmental impact.
2. Feasibility study: A feasibility study is conducted to determine the technical and economic viability of the proposed
intake design. This includes analyzing water flow and head data, evaluating different design options, and determining the
potential environmental impacts.
3. Hydrological and hydraulic analysis: Detailed hydrological and hydraulic analysis is conducted to determine the water
flow and head at the intake location, as well as to evaluate the potential impacts on downstream flow.
4. Design of the intake structure: The intake structure is designed based on the results of the feasibility study and
hydrological and hydraulic analysis. This includes determining the size and shape of the structure, as well as the materials
to be used.
5. Environmental impact assessment: An environmental impact assessment is conducted to evaluate the potential impacts
of the intake on the surrounding environment and to determine the measures that need to be taken to mitigate any negative
impacts.
6. Permit and approvals: Permits and approvals are obtained from the relevant authorities to construct and operate the
intake.
7. Construction and commissioning: The intake is constructed and commissioned according to the approved design, with
safety measures in place and regular monitoring to ensure proper functioning.

Which type of intake is most suitable in case of Nepal? Why?

Himalayan intake:
Himalayan intake is a special type of intake that has proper system for management of both floating debris and bed load.
1. It was invented by H stole in 1996.
2. It is a geometric design of an intake structure to be used in run-off-river hydropower intake in steep Himalayan Rivers.
3. The purpose is to maintain a reservoir volume for daily peaking by providing means of flushing of sediments from
reservoir.
4. The intake is designed to function in a river which carries both floating debris and large amount of coarse sediments,
including sizes up to rocks and boulders.

Design of Side Intake

a) Fixing invert level
The invert level of the intake shall be fixed considering the sediment content in the river and previous design and
construction experience. Generally, the invert level shall be 0.5 m to 2 m above the under sluice level is considered.
b) Determine the capacity of intake
Design discharge QD should be taken as 10% to 20% of the turbine discharge ie QD=1.1 to 1.2 of turbine discharge.
c) Entrance Velocity
The entrance velocity should be less than 0.6 m/sec. to 0.8 m/sec. However, for small system, the velocity can be up to 1
m/sec.
d) Calculate intake head loss
The loss through intake can be calculated by using formula as;
Intake loss (head loss) = K*V n2/2g, i.e. Hfi = K*Vn2/2g,
Where, Hfi is the intake head loss in meter, K= intake loss coefficient, Vn= normal velocity through intake in m/sec, g
=acceleration due to gravity,
Intake loss coefficient (K) = Ki + Kt
Where, Ki= intake loss due to sudden contraction, Kt=gradual contraction losses in the flow through the transition part of
the intake.

HYDRAULIC TUNNEL
Tunnel is an underground passage made without removing the overburden. They are constructed for the conveyance of
flow or the transportation purpose or for storage. We are here concerned with the conveyance of flow. Thus, the tunnel
has been termed as “hydraulic tunnel”.
Types Hydraulic Tunnel
1. Access tunnel: These tunnels are used to provide access to the dam or hydroelectric power station.
2. Drainage tunnel: These tunnels are used to collect and remove seepage water from the dam.
3. Penstock tunnel: These tunnels are used to transport water from the intake to the hydroelectric power station.
4. Tailrace tunnel: These tunnels are used to transport water from the hydroelectric power station back to the river or
reservoir.
5. Bypass tunnel: These tunnels are used to bypass the dam, allowing fish and other aquatic species to pass through.
6. Ventilation tunnel: These tunnels are used to provide ventilation to the dam and hydroelectric power station.
7. Pressure tunnel: These tunnels are used to increase the pressure of water being sent to the hydroelectric power station.

Advantages & disadvantages of tunnel

Advantages of tunnels:
1. They allow for efficient and safe transportation of people and goods, often reducing travel times and congestion on
surface roads.
2. They can provide an alternative route for vehicles, pedestrians, and trains, allowing for bypasses of natural obstacles
such as mountains and bodies of water.
3. They can be used for hydroelectric power generation and irrigation.
4. They can help to protect the environment by reducing the need for surface construction and land development.
Disadvantages of tunnels:
1. They can be expensive to construct and maintain.
2. They can be dangerous to construct, with risks to workers including cave-ins, floods, and toxic fumes.
3. They can be vulnerable to fires and other disasters, making evacuation difficult.
4. They can be affected by geological conditions, such as shifting soil and rock, that can make construction and
maintenance difficult.

Difference between Pressure Tunnel and Non-pressure Tunnel

1. Pressure tunnel: The tunnel is designed to withstand the pressure of the surrounding soil or rock.
1. Non-pressure tunnel: The tunnel is not designed to withstand the pressure of the surrounding soil or rock.
2. Pressure tunnels are typically used in areas with high water table or in cases where the surrounding soil or rock is prone
to collapse.
2. Non-pressure tunnels are typically used in areas with low water table or in cases where the surrounding soil or rock is
stable.
3. Pressure tunnels require specialized construction methods and materials, and are generally more expensive to construct
than non-pressure tunnels.
3. Non-pressure tunnels are typically easier and less expensive to construct than pressure tunnels.
4. Pressure tunnels are often used for water supply and irrigation systems
4. Non-pressure tunnels are used for transportation, mining, and other purposes.

Hydraulic Design of Tunnel

Basically, there are two flow conditions in the hydraulic tunnel design:
1. Free Flow Tunnel
Hydraulic design of the free flow tunnel is executed as the hydraulic design of canal and Manning's frictional factors are
used to compute the head loss in length.
2. Pressure flow tunnel
Hydraulic design of the pressure flow is computed as the pipe flow and the head loss is computed using Darcy/Weisbach
frictional factor. Discharge through a pressurized hydraulic tunnel is calculated using a continuity equation with control
volume approach. Q=AxV where, Q is the discharge in m³/sec. V is the velocity in m/sec. A is the area in m².

Design of tunnel lining

1. Tunnel lining is the structural elements that support the excavation and provide stability to the tunnel.
2. It is designed to resist the loads imposed by the surrounding soil or rock and the internal loads such as water pressure.
3. Tunnel lining design includes the selection of the appropriate lining material and thickness, as well as the layout of the
lining elements.
4. The most common lining materials are concrete, steel, and a combination of the two.
5. The thickness of the lining is determined by the loads it must support and the level of deformation that is acceptable.
6. The layout of the lining elements is designed to provide stability and support to the excavation, while also allowing for
easy construction and maintenance.
7. The design must also take into account the potential for ground movement and settlement, as well as the effects of
vibration and subsidence.
8. The design must also consider the long-term durability and maintenance requirements of the tunnel lining.
9. The design should be done by an experienced engineer who has knowledge of the specific site conditions and the
relevant codes and standards.

Size and shape of the tunnel

1. Size of tunnel:
The minimum diameter of the tunnel is fixed with consideration of transportation, excavation and hauling during
tunneling and should be greater than 2 m for circular section and in case of other shapes it should be greater than 1.9 m
in width and 2.1 m in height. Other sizes are fixed based on the requirements.
Shape of the tunnel
Generally used tunnel geometry in hydraulic design of tunnel is as follows:
a) Circular section
This section is most suitable from structural considerations. But it is difficult for excavation.
A =πD2/4
P = πD
b) D shaped section
This section is suitable for tunnels located in good quality rocks. The main advantage of this section is the added width of
the invert which gives more working space in the tunnel during driving and flatter invert which helps to eliminate the
tendency of wet concrete to slump and draw away from the tunnel sides.
A =πD2/8+ D.D/2
P = D + 2.D/2+πD/2
c) Horse-shoe section
These sections are compromise between circular and D shaped sections. These sections are structurally strong to
withstand external rock and water pressure. They are most suitable where a moderately good rock is available, advantages
of a flatter invert are required for the construction purposes and tunnel has to resist internal pressure.
A = 0.8293D2
P = 3.267D
d) Egg shaped section
When the tunnel is stratified, soft and very closely laminated and where rock fall are caused due to high external pressure
and tensile stress, egg shaped section may be considered.
A = 0.864 D2
P = 3.313D

Tunneling methods:
There are various methods of construction of tunnels which are discussed below:
a) Cut and cover method
Cut and cover method of tunnel construction is generally used to build shallow tunnels. In this method, a trench is cut in
the soil and it is covered by some support which can be capable of bearing load on it.
b) Drill and blast method
It is the most common method of tunnel construction in Nepal. The tunnel construction is done by drilling, blasting,
mucking and hauling. In drilling there are different types of cut such as parallel cut, angle cut etc.
c) Tunnel boring method
Bored tunnel method is modern technology. In this case, tunnel boring machines are used which automatically work and
makes the entire tunneling process easier. It is also quicker process and good method to build tunnel in high traffic
areas. Tunnels boring machines (TBM’s) are available in different types suitable for different ground conditions.
d) Shaft method
In this method tunnel is constructed at greater depth from the ground surface. The shaft is built up to the depth where
tunnel is required. Shaft is a permanent structure which is like well with concrete walls. At required depth, tunnels are
excavated using TBM’s. Shafts are provided at both inlet and outlet of tunnels. Intermediate shafts are also provided if
tunnel is too long. After the construction process, these shafts can also be used for ventilation purpose as well as
emergency exits.
e) Heading and benching method
In this technique, workers dig a smaller tunnel known as a heading. Once the top heading has advanced some distance
into the rock, workers begin excavating immediately below the floor of the top heading; this is a bench.
f) Pipe jacketing method
Pipe jacking method is used to construct tunnels under existing structures like road ways, railways etc. In this method,
specially made pipes are driven into underground using hydraulic jacks. Maximum size of 3.2-meter diameter is allowed
for tunnels.

Why tunneling is required in HPP

Tunneling is required in hydropower development for several reasons:
1. To divert water to the power station: Tunnels are used to divert water from a river or stream to the power station, where
it can be used to generate electricity.
2. To bypass natural obstacles: Tunneling can be used to bypass natural obstacles such as mountains or cliffs, allowing the
water to flow to the power station without interruption.
3. To minimize the environmental impact: Tunnels can be used to minimize the environmental impact of a hydropower
project by reducing the amount of land that needs to be flooded or cleared.
4. To improve safety: Tunnels can be used to improve safety by protecting the power station and other infrastructure from
potential natural disasters such as floods and landslides.
5. To increase efficiency and reduce costs: Tunneling can be used to increase the efficiency of a hydropower project by
reducing the amount of energy lost in transmission, and can also help to reduce costs by minimizing the need for extensive
surface infrastructure.

Lining of tunnel:
After excavation of tunnel, lining is done to increase hydraulic capacity of the tunnel, to reduce resistance, to increase
strength and to reduce losses from tunnel.
Advantages of lining
1. Provides strength and stability and facilitates tunneling in weaker strata.
2. The hydraulic resistance of the lined tunnel is much less than that of unlined tunnel.
3. The permissible velocity in lined tunnel is higher than that in unlined tunnel.
4. Lining can be done simultaneously as the excavation proceeds. This minimizes the danger of accidental rock falls in the
tunnel cavity.
5. The seepage losses through the tunnel is reduced significantly.

Type of lining
a) Shotcrete lining
Shotcrete is the generic name for cement, sand and fine aggregate concrete which is applied pneumatically and compacted
dynamically under high velocity. Shotcrete is used for the support of underground excavation. Shotcrete may be dry
shotcrete or wet shotcrete.
b) Plain concrete lining
The tunnels are lined with plain concrete when tunnel walls are to support outside pressure due to rock, but low pressure
inside.
c) Reinforced concrete lining
When internal pressure is high, plain concrete lining is inadequate and tension cracks are developed in lining. In such case
the tunnel can be reinforced to take up the tensile stresses.
d) Steel lining
Steel lining is provided to provide more tensile strength to the tunnel.
Settling Basin
A settling basin, also known as a sedimentation basin or clarifier, is a structure used to separate suspended solids from
water. It is typically used in wastewater treatment, storm water management, and other applications where the removal of
suspended solids is necessary. The basin works by allowing water to flow into the basin, where the suspended solids settle
to the bottom and the clarified water flows out of the basin. The design of a settling basin includes the determination of
the basin's size, shape, and depth, inlet and outlet structures, bottom slope, walls, and mechanism for removing the settled
solids.

Settling basin design

Size selection depends upon the volume of effluent and space available for the basin, because the smaller the minimum
particle size and the greater the inflow, the larger the basin must be. For aquaculture effluents, it should suffice to select a
minimum particle size with the range of 0.006 to 0.020 mm.
The critical settling velocity (Vcs) is the minimum velocity at which a particle can settle and yet be removed (Fig. 1). This
velocity can be determined by dividing the mean depth of the settling basin (D) by HRT:
Because HRT = V/Q, the above expression becomes:

Moreover, if we assign a depth of 1 m to the basin, V in cubic meters must equal the basin area (A) in square meters, and
the expression for Vcs becomes:

Because we are designing the basin, instead of calculating VCS, we can substitute VS (Table 1) and estimate the area of a
1-m-deep basin for a particular particle size and inflow rate.

Design Objective of Settling Basins

1. To provide a structure that allows for the separation of suspended solids from water
2. To ensure that the basin is able to handle the flow rate and volume of water to be treated
3. To design the basin with the appropriate size, shape and depth to optimize the settling of suspended solids
4. To control the flow of water into and out of the basin using inlet and outlet structures such as weirs or flumes
5. To design the basin's bottom slope to ensure a proper flow pattern and to prevent scouring of the settled solids
6. To design the basin walls that can withstand the hydrostatic and hydrodynamic forces of the water and to prevent
erosion
7. To provide a mechanism for removing the settled solids, such as a sludge scraper or a bottom-draw system

Design Criteria and Principle of Settling Basin

1. Optimum removal of sediments
The settling basin shall be designed to remove as much of the sediment load in water as is economically and hydraulically
possible (i.e., Exclusion of 95 to 100% of sediment loads).
2. Efficient flushing
The settling basin shall be designed to ensure efficient flushing of settled sediments so that frequent flushing during
floods, when the sediment content of river is at its peak, is not required.
3. Settling capacity
The size (i.e., length and width) of basin must be large enough to allow a large percentage of the fine sediment to fall out
of suspension and be deposited on the bed.
4. Storage capacity
The basin should be able to store the settled particles for sometime unless it is designed for continuous flushing.

Components of Settling Basin

The basin consists of inlet, settling and outlet zones.
1. Inlet Zone
This is the kind of transition designed for slowing down the velocity of flow by gradually increasing the depth of basin.
This is the initial zone where the transition from the headrace to the settling basin occurs and there is a gradual expansion
in the basin width.
2. Settling zone
This is the main part of the basin where settling of the suspended sediment is supposed to take place. The settling zone
length is also called as effective length of the basin.
3. Outlet zone
This is a kind of transition designed after the settling zone of a settling basin to facilitate for getting back the flow into the
conveyance system with design velocity by gradually narrowing the width and depth of the basin.

Settling velocity, horizontal velocity, and lifting velocity are all important parameters in the design and operation
of a settling basin or sedimentation tank.
1. Settling velocity: The settling velocity is the speed at which particles in a liquid medium settle to the bottom of a
container due to gravity. It is directly proportional to the size and density of the particles, and inversely proportional to the
viscosity of the liquid. The settling velocity is used to calculate the detention time required to allow particles to settle out
of the water.
2. Horizontal velocity: Horizontal velocity refers to the flow rate of water through the basin. It is important to ensure that
the horizontal velocity is not too fast, as this can cause particles to remain suspended in the water rather than settling out.
3. Lifting velocity: Lifting velocity is the minimum flow velocity required to lift particles or debris off the bottom of the
basin or tank. It is important to ensure that the lifting velocity is not exceeded during operation, as this can cause the
particles to be resuspended and carried out of the basin.

FOREBAY (HEADPOND)
A fore bay is an enlarged body of water provided just in front of the pen is provided in the case of run-of-river plants and
in the case of storage when the power house is located at a certain distance away from the water is carried from the
reservoir to the power house through a channel.
Importance of Forebay
A forebay is an important component in hydroelectric power plants as it serves as a reservoir or holding area for water that
will be used to generate electricity. The forebay regulates the flow of water into the power-generating turbines, helping to
maintain a consistent and efficient level of power production. Additionally, the forebay can also be used for sediment and
debris control, as well as for fish passage and protection. Overall, the forebay plays a critical role in the overall operation
and efficiency of a hydroelectric power plant.

Application of forebay
1. Regulating water flow: The forebay serves as a reservoir that regulates the flow of water into the power-generating
turbines, helping to maintain a consistent and efficient level of power production.
2. Sediment and debris control: The forebay can be used to control the sediment and debris that enters the hydroelectric
power plant, which can protect the equipment and improve the overall efficiency of the plant.
3. Fish passage and protection: The forebay can be designed with fish ladders or other features to allow for safe passage of
fish through the hydroelectric power plant and to protect fish populations in the area.
4. Water level control: The forebay can be used to control the water level upstream of the power plant, which can reduce
the potential for flooding and other negative impacts on the surrounding area.

Function of fore bay

i) To fulfill the immediate requirement of supplying water during start-up.
ii) To accommodate rejected water during turbine closure and spill extra water.
iii) It releases surge pressure as the wave travels out of the penstock pipe.
iv) It can also serve as a secondary/final settling basin and t particles that enter the headrace downstream of the settling
basin

Parts/Component of Forebay
Following are the parts of the typical forebay:
1. Inlet structure: Controls flow rate & direction of water into the forebay
2. Flow control devices: Regulates the flow of water into the forebay
3. Silt fence: Traps sediment and debris before entering the forebay
4. Scour protection: Prevents erosion around the inlet and along the shoreline
5. Water level control structures: Controls the water level in the forebay
6. Outlet structure: Controls flow rate & direction of water out of the forebay
7. Turbines/pumps: Generates electricity or moves water
8. Monitoring & control systems: Monitors and controls parameters in the forebay
9. Debris collection devices: Removes debris from the water.

Design Consideration for Forebay

i) Forebay is usually designed to supply about 2 to 4 minutes of design discharge to turbine.
ii) The water volume required in the forebay is calculated using the following formula.
Volume (V) = Q*t*60 where, Q is the design discharge. T is the detention time in minute.
iii) The length of the forebay is calculated using the following formula; L=V/BXH where, V is the volume of forebay in
m/sec. B is the width of forebay in meter. H is the depth of forebay in meter.
iv) Calculate the width of forebay by using the following formula; B=Q/(HXV) where, Q is the design discharge m³/sec.
V is mean velocity in m/sec. H is the depth of water in forebay in meter.
v) Storage depth Storage depth below the pipe invert should be allowed for a depth 300 mm or equal to pipe diameter,
whichever is larger is recommended for this purpose.
vi) Minimum submergence (S) or submergence head
The position of submergence head (depth of water above the crown of the penstock pipe) can be calculated as follows:
a) Hs≥ 1.5* Vp2/2g b) Hs = a x Vp x √d
Where, Vp is the velocity in penstock pipe, d is the diameter of penstock, a is the coefficient (0.545 for symmetrical,
0.725 for asymmetrical flow). The minimum submergence (Hs) should be taken as greater of above two cases.
vii) Sudden draw down depth (y)
In order that the inlet of penstock or pressure shaft remains fully submerged during sudden start up. The sudden draw
down in the forebay at the time of startup is calculated by using the following formula;
y = Vp* √ ([Lp.Ap)/g.Af] where, Vp is the velocity in penstock in m/sec. Lp is the length of penstock in metre, Ap is the
area of penstock in m². A is the plan area of forebay m²(L x B).
viii) A gate valve
A gate valve entrance to the penstock should be provided to make maintenance work on the turbine easier.
ix) Air vent
An air vent should be placed to release air as well as gases from the penstock.

Surge Tank
A surge tank is a cylindrical open-topped storage tank which is connected to the penstock at a suitable point. Surge tanks
are provided in the case p hydroelectric developments having long penstocks. When power house i located within a short
distance of headwork surge tanks are not required. The general arrangement of surge tank
Application of surge tank
1. Reducing water hammer damage: By absorbing the energy from water hammer, a surge tank can reduce the damage
that can be caused to the equipment in the hydroelectric power plant.
2. Water storage: A surge tank can be used to store water, which can be used to generate electricity during times of high
demand.
3. Improving system efficiency: A surge tank can improve the overall efficiency of the hydroelectric power plant by
regulating the flow of water and stabilizing the pressure within the system.
4. Protecting downstream: A surge tank can protect the downstream of the system, by absorbing excess flow and prevent
flooding of the downstream.

Function of Surge Tank

1. Regulates pressure in a piping system by absorbing sudden increases in pressure
2. Protects the piping system from damage caused by events such as pump start-up or shut-down, valve closures, or water
hammer
3. Maintains a stable flow of water
4. Smooth’s out fluctuations in flow and pressure
5. Provides additional water storage capacity during periods of high demand
6. Helps in preventing water hammer effect.

Type of Surge Tank

1. Air-charged surge tank: uses compressed air to absorb sudden increases in pressure.
2. Water-charged surge tank: uses the weight of water stored in the tank to absorb sudden increases in pressure.
3. Hydro-pneumatic surge tank: combines the use of both compressed air and water to absorb sudden increases in
pressure.
4. Gravity surge tank: uses the weight of water stored in the tank to absorb sudden increases in pressure.
5. Compound surge tank: it uses combination of two or more of the above-mentioned types of surge tanks.

Design of surge tank

A surge tank, also known as a surge chamber or pressure storage tank, is a component in a fluid distribution system that
helps to regulate pressure fluctuations and protect against water hammer. The design of a surge tank typically includes a
cylindrical or rectangular tank with an inlet and outlet pipe, an air cushion or bladder, and a control valve. The tank is
usually located downstream of a pump or other pressurized source, and its purpose is to store a volume of fluid that can be
quickly released or absorbed as needed to stabilize system pressure. The size and configuration of the tank will depend on
factors such as the flow rate, system pressure, and the type of fluid being transported.

Different types of settling basin

A. Conventional type
The basin is dewatered when it is taken out of operation. Sediments may be removed manually or with mechanical
equipment after the basin is dewatered. Deposited sediments may also be removed by lowering water level inside the
basin and generating swift flow in free surface gravity flow throughout the basin. Generally, two settling chamber are
constructed so that one can still be operated while other is closed for flushing.
B. Hooper type
Water level and water flow is maintained in the basin throughout the flushing period in order to facilitate continuous
power generation. Removal of sediments while the basin is operational may be achieved with continuous or intermittent
flushing or by use of some kind of suction or dredging device.
C. Beiri type
In Beiri type, the shutter mechanism in the bottom of the basin is made of two plates with series of opening. One plate is
fixed while other can be moved horizontally. Flushing is done when opening in both plate fall together. Sensor can be
placed at the bottom of the plate so as to sense the volume of sediment deposited in the chamber. Once the sediment
collected increases the desired level of deposition, one plate is moved over the other to match the opening and sediment is
flushed.
D. S4 (Serpent sediment sluicing system)
This is a new type of desanding basin which was developed by Haakon stole at the Norwegian Institute of Science and
Technology. It consists of a flushing channel and a flexible pipe called Serpent. This pipe can float or sink in water
depending upon the fluid filled inside it. When the serpent is filled with heavy fluid, it settles and flushing canal is closed
and sediment is deposited over it. When the deposition reaches a limit, the fluid in pipe is removed and light gas is
installed which facilitates floating of serpent and hence sediments are flushed through flushing channel.
Flushing of settling basin: flushing frequency (periodical and continuous)
Based on flushing mechanism, settling basin can be classified into two groups.
a) Continuous flushing type
This type of basin is designed with hoppers. The settled particles pass through the bottom of the hoppers to the collecting
channel and are flushed continuously.
1. Continuous flushing desanding basin uses surplus water for flushing i.e. about 10% of plant discharge.
2. These type of settling basin does not interfere power production during flushing process.
3. The design and operation of continuous type settling basin is complex compared to discontinuous type.
4. The main problem is clogging of the sediment extracting system.
Example: Hopper type and Hydro cyclone
b) Discontinuous flushing type
In this type of settling basin, sediments are not flushed continuously.
1. Discontinuous flushing desanding basin is of much simpler in design and are much less susceptible to clogging.
2. The main operating convenience is that plant output should be cut back for multi basin or shut down for single basin.
3. In first phase, the suspended sediments are allowed to settle in the settling zone.
4. In second phase, the deposited sediments are removed by different systems.

They are further classified into two classes:

i) Periodic flushing type
In this type of settling basin, power plant is shut down during flushing. Flushing is generally done by Conventional
gravity flushing method. Mechanical removal (Dredging) is also another means of sediment removal. If other means turn
out to be inefficient, the settling basin should be cleaned by manually removing the sediments.
Example: Conventional type settling basin
ii) Intermittent flushing type
In this type of settling basin, flushing is not continuous. However, power plant is not shut down during flushing.
Flushing is done at regular intervals and the power generation is done continuously.
Example: Beiri type and S4 type

PENSTOCKS/PRESSURE SHAFTS
A penstock is a large pipe or conduit that is used to transport water from a reservoir or forebay to the power-generating
turbines in a hydroelectric power plant. The water flows through the penstock under high pressure, which is then used to
turn the turbines and generate electricity. Penstock is typically made of steel or concrete, and is designed to withstand the
high pressure and flow of water. The Penstock also helps to control the flow of water into the turbines, which can help to
improve the overall efficiency of the hydroelectric power plant. It also act as a barrier for any debris and sediment that
might otherwise damage the turbine.

Thickness of the Penstock/Pressure Shaft

The thickness of the conduit is determined considering the hoop stress, (PD/2t) and balancing it with the allowable stress
of the material. Considering the pipe of diameter, D which is subjected to pressure, P the thickness of the pipe can be
computed by;
26st.t = PD or, t= PD/26st and t= PD/26st.n where, n is assumed when joint efficiency of welding. According to ASME,
considering allowance for corrosion is 0.15 cm. i.e., t= (PR/6stn-0.6 P) +0.15
Where, t is the thickness in cm. p is the pressure in kg/cm². R is the internal radius in cm. 6st is the allowable stress in
kg/cm². n is the joint efficiency factor and, 0.15 cm is allowance for corrosion.

Hydraulic Transit (Water Hammer)

Water hammer, also known as hydraulic transit or fluid hammer, is a pressure surge that occurs in a piping system when
the flow of fluid is suddenly stopped or rapidly reduced. This can happen when a valve is closed quickly, a pump is shut
off, or a pipe breaks. The sudden change in the flow of fluid creates a pressure wave that travels through the piping
system, resulting in a loud banging or hammering sound. Water hammer can cause damage to the piping system, including
leaks, broken pipes, and damage to valves and other components. It can also result in increased stress on the system and
may cause pipes to vibrate or make noise. Water hammer can be prevented by using devices such as surge tanks or air
chambers, which absorb the pressure wave and reduce its impact. Another way to prevent water hammer is by installing
check valves, which prevent the flow of fluid from suddenly reversing direction.

Water hammer effect

Water hammer is a pressure surge that occurs when the flow of water in a pipeline is suddenly stopped or slowed. It is
caused by the inertia of the water, which continues to move forward even after the flow has been disrupted. This can result
in a significant increase in pressure in the pipeline, which can cause damage to the equipment and infrastructure. The
water hammer effect can cause damage to pumps, valves, pipes, and other components in a hydroelectric power plant. It
can also cause leaks and even flooding, which can lead to safety hazards and other problems.
The water hammer effect can occur due to a number of reasons,
Such as the closing of a valve or gate, the failure of a pump or turbine, or changes in the flow rate of water. To mitigate
the water hammer effect, hydroelectric power plants may use a variety of techniques such as surge tanks, air chambers,
and slow-closing valves. These methods can help to absorb the energy from the water hammer, which can reduce the
damage caused by the pressure surge and help to improve the overall efficiency of the power plan

UNIT-6
Define spillway
A spillway is a structure or channel that is designed to safely convey excess water from a dam, reservoir, or other water
storage facility to a downstream location. The main purpose of a spillway is to release water from the storage facility in a
controlled manner, preventing flooding or overtopping of the dam.
Spillways come in different designs and types, including:
1. Overflow spillway: this type of spillway is typically used for small dams and is simply an open channel that allows
water to overflow and flow downstream.
2. Controlled spillway: this type of spillway is used for larger dams and includes a gate or other control mechanism that
can be adjusted to control the flow of water.
3. Chute spillway: this type of spillway is a channel that directs water downstream at a steep angle to increase its velocity
and dissipate energy.
4. Tunnel spillway: this type of spillway is a conduit that conveys water through a tunnel or pipe to the downstream.
5. Ogee spillway: This type of spillway is designed to reduce the velocity of water and prevent erosion downstream of the
dam. It is called so as it has a shape of S or Ogee.
6. Morning Glory spillway: This type of spillway is an circular opening with a smooth curved inlet and outlet, this design
is effective in reducing the velocity of water and preventing erosion downstream.

Function of Spillway
1. A spillway is a structure that safely conveys excess water from a dam or reservoir to a downstream location
2. The main purpose of a spillway is to release water in a controlled manner, preventing flooding or overtopping of the
dam
3. Spillways come in different designs and types, including overflow spillway, controlled spillway, chute spillway, tunnel
spillway, ogee spillway and morning glory spillway
4. The design of spillway is critical for the safety of the dam and downstream areas, and must be able to handle extreme
events such as the Probable Maximum Flood (PMF)
5. Spillway also helps in reducing the water level in the reservoir during monsoon or heavy rainfall to prevent any damage
to the dam structure.

Cavitation
Cavitation is a phenomenon in which rapid changes of pressure in a liquid lead to the formation of small vapor-filled
cavities, in places where the pressure is relatively low. When subjected to higher pressure, these cavities, called ”bubbles”
or ”voids”, collapse and can generate shock wave that is strong very close to the bubble, but rapidly weakens as it
propagates away from the bubble. Spillways for medium and high head dams may be exposed to high velocity flows and
the associated destructive phenomenon of cavitation. Cavitation may occur at rough spots in the surface of the chute or
tunnel, at local discontinuities in the finished surface such as construction joints, and at locations along critical flow
profiles having significant deviations from design specifications.

Preventive measures of cavitation in spillway

1. The prevention of the cavitation phenomenon can be effected by eliminating op-opportunities for flow separation, by
limiting flow velocities to noncavitating levels, or by maintaining sufficiently high operating pressures.
2. Elimination of any opportunity for flow separation, including the construction of very smooth surfaces which have
negligible surface roughness and which are devoid of holes or grooves, will eliminate the occurrence of cavitation.
3. Flow surfaces must not exhibit significant deflection so that the high velocity jet will remain positively supported at all
times, and construction joints must be perfectly level so that no protrusion into nor away from the flow is experienced.

Gate & Their type

Gates are an important component of a dam and are used to control the flow of water through the dam. There are several
types of gates that can be used in a dam, including:
1. Radial gates: These are circular gates that rotate around a central axis. They are typically used in hydroelectric power
generation, and are located at the base of the dam near the power station.
2. Tainter gates: These are vertical lift gates that are hinged at the top and lift straight up to control water flow. They are
typically used in large dams, and are located at the base of the dam near the power station.
3. Spillway gates: These are large gates that are used to release water from the reservoir when the water level becomes
too high. They are typically located at the top of the dam, near the spillway.
4. Outlet works gates: These are smaller gates that are used to release water from the reservoir for irrigation or other
uses. They are located at the base of the dam, near the outlet works.
5. Sluice gates: These are gates that are used to control the flow of water through a channel or canal. They are typically
located at the base of the dam, near the outlet works.
6. Low-level outlet gates: These are gates that are used to release water from the reservoir for irrigation or other uses.
They are located at the base of the dam, near the outlet works.

Define Energy dissipation

Energy dissipation refers to the process of reducing the energy of a fluid or other system by converting it into another
form. This can occur through a variety of mechanisms, such as friction, turbulence, or heat transfer.
In the context of fluid dynamics, energy dissipation refers to the process of reducing the kinetic energy of a fluid, such as
water or air, by converting it into other forms of energy, such as heat or sound. This can be achieved through various
means, such as friction, turbulence, or heat transfer.
In hydraulic engineering, energy dissipation is an important aspect of the design of spillway, channels, and other water-
conveying structures. Energy dissipation is necessary to reduce the velocity of water and prevent erosion downstream of
the dam.
Types of energy dissipaters
1. Stilling basins: A stilling basin is a large, shallow concrete basin that is used to dissipate the energy of water as it flows
out of a spillway or other structure. The basin helps to slow the water down and reduce its velocity, preventing erosion
downstream.
2. Pipes and culverts: Pipes and culverts can be used to dissipate energy by creating turbulence and friction within the
fluid, converting kinetic energy into heat energy.
3. V-notch weirs: A V-notch weir is a type of spillway that uses a V-shaped opening to dissipate energy by creating a
turbulent flow. The V-shape causes the water to spread out and slow down, reducing its velocity and preventing erosion
downstream.
4. Energy dissipation channels: These channels have a specific design to reduce the energy of the fluid by creating a
turbulent flow, by creating a drop or slope on the channel bed, or by using roughness elements.
6. Drop structures: Drop structures, such as drop inlets, drop boxes and drop shafts, are used to dissipate the energy of
water as it drops from one elevation to another. The structures create turbulence and friction within the fluid, converting
kinetic energy into heat energy.

Role of tail water depth

The role of tail water depth refers to the depth of the water downstream of a dam, spillway, or other water-conveying
structure. Tail water depth plays an important role in the design and operation of these structures by providing information
on the hydraulic conditions downstream.
1. Tail water depth is used to calculate the head loss through the structure, which is necessary to determine the discharge
capacity of the spillway and the efficiency of the energy dissipation system.
2. Tail water depth is used to determine the magnitude of the downstream forces acting on the structure, which is
important for the design of the structure to withstand the forces without failure.
3. Tail water depth also plays an important role in the stability analysis of the dam and the design of the foundation.
4. Tail water depth is also used in the design of the downstream channels and structures such as embankments, training
walls and other protection structures.
5. Tail water depth also plays a crucial role in controlling the water level in the reservoir during monsoon or heavy rainfall
to prevent any damage to the dam structure.
Design of stilling basin
A stilling basin is a hydraulic structure used to dissipate the energy of incoming water flow. It is typically used in canals
or channels to slow down and spread out the flow of water, which can prevent erosion and improve safety.
1. A stilling basin is a hydraulic structure used to dissipate energy of incoming water flow.
2. It typically includes a pool or basin that is wider and shallower than the adjacent channel.
3. It has a series of steps or weirs to slow and spread out the flow of water.
4. It may also include energy dissipation devices such as boulders, gravel, or splash walls.
5. The design must consider factors such as flow rate, velocity, volume of water and potential for erosion or scouring.
6. Design should ensure safety for any human or aquatic life in or around the basin.

UNIT-7
Define turbine
A turbine is a mechanical device that converts the energy of a fluid (such as water, steam, or gas) into rotary motion to
generate electricity. Turbines have a rotor (a shaft with blades or vanes) that spins when the fluid flows over it. The rotor
is connected to a generator, which converts the mechanical energy of the rotor into electrical energy.

Characteristics or Performance of turbine

1. Head: Head affects the pressure and kinetic energy of water, which in turn affects the efficiency and output of the
turbine.
2. Flow rate: The flow rate of water affects the kinetic energy of water and the efficiency and output of the turbine.
3. Efficiency: Efficiency of the turbine is affected by various factors such as design, condition and maintenance of the
turbine.
4. Temperature: High temperature can cause thermal expansion and wear on the components, which can reduce the
efficiency and output of the turbine.
5. Vibration: Vibrations can cause damage to the components and affect the performance of the turbine.
6. Turbine design: The design of the turbine, including the shape and size of the blades, affects the performance of the
turbine.

Types of turbines
1. Pelton wheel turbine: It is a type of impulse turbine that is used in high head, low flow hydroelectric power plants. It
works by directing a high-pressure water jet at the turbine's blades to make the rotor spin.
2. Francis turbine: It is a type of reaction turbine that is used in medium head, medium flow hydroelectric power plants. It
works by allowing water to flow through the turbine, which causes the rotor to spin.
3. Kaplan turbine: It is a type of propeller turbine that is used in low head, high flow hydroelectric power plants. It works
by allowing water to flow through the turbine, which causes the rotor to spin.

Working principle of pelton turbine (Impulse Turbine)

The Pelton turbine is a type of impulse turbine that is used in high head, low flow hydroelectric power plants. It works on
the principle of converting the kinetic energy of a high-pressure water jet into mechanical energy that is used to spin the
rotor of the turbine.
Here’s how it works:
1. Water is collected in a reservoir or forebay and is directed through a penstock to the Pelton turbine.
2. The high-pressure water is then directed through a set of nozzles, which convert the water's pressure energy into kinetic
energy by accelerating the water to a high velocity.
3. The high-velocity water jet is directed at the turbine's runner, which is a wheel with cups or buckets attached to the
outer edge.
4. As the water jet impacts the cups or buckets, it pushes them around the runner, which causes the rotor to spin.
5. The spinning rotor is connected to a generator, which converts the mechanical energy of the rotor into electrical energy.
6. After passing through the turbine, the water is directed back into the river or other water source.

Components of pelton turbine

A Pelton turbine typically consists of the following main components:
1. Nozzles: The nozzles are used to convert the pressure energy of the water into kinetic energy by accelerating the water
to a high velocity before it reaches the turbine runner.
2. Turbine runner: The turbine runner is the wheel with cups or buckets attached to the outer edge that the high-velocity
3. Water jet impacts. The runner is connected to the rotor, which spins as the water jet pushes the cups or buckets around
the wheel.
4. Rotor: The rotor is connected to the turbine runner and spins as the water jet pushes the cups or buckets around the
5. Wheel. It converts the kinetic energy of the water jet into mechanical energy.
6. Generator: The generator is connected to the rotor and converts the mechanical energy of the rotor into electrical
energy.
7. Bearings: Bearings are used to support the rotor and allow it to spin smoothly.
8. Shaft: The shaft is used to transfer the mechanical energy from the turbine rotor to the generator.
9. Control valves: Control valves are used to regulate the flow of water to the turbine and to control the speed of the
turbine

Working principle of Francis turbine

The Francis turbine is a type of reaction turbine that is used in medium head, medium flow hydroelectric power plants. It
works on the principle of converting the potential and kinetic energy of the water into mechanical energy that is used to
spin the rotor of the turbine.
Here's how it works:
1. Water is collected in a reservoir or forebay and is directed through a penstock to the Francis turbine.
2. The water enters the turbine at the bottom, and it is guided by a set of guide vanes into the turbine runner.
3. The water is directed through the runner, which is a wheel with radial blades. The water flows over the blades and
makes the rotor spin.
4. As the water flows through the turbine, it loses both pressure and kinetic energy.
5. The spinning rotor is connected to a generator, which converts the mechanical energy of the rotor into electrical energy.
6. After passing through the turbine, the water is directed back into the river or other water source.

Some of the key applications and advantages of Pelton turbines include:

1. High Efficiency: Pelton turbines are highly efficient at converting the kinetic energy of the water jet into mechanical
energy.
2. High Head: Pelton turbines are designed to work with high head applications, typically over 300 meters, making them
ideal for mountainous regions.
3. Low Flow: Pelton turbines are designed to work with low flow rates, typically less than 50 cubic meters per second.
4. Low-Cost: Pelton turbines are relatively simple in design, easy to maintain and repair, and have low manufacturing
costs, making them a cost-effective option for hydroelectric power generation.

Components of Francis turbine

1. Guide vanes: The guide vanes are used to direct the water into the turbine runner, and to control the flow rate and
direction of the water.
2. Turbine runner: The turbine runner is the wheel with radial blades that the water flows over. The runner is connected
to the rotor, which spins as the water flows over the blades.
3. Spiral casing: The spiral casing around the runner of the turbine is known as the volute casing or scroll case.
Throughout its length, it has numerous openings at regular intervals to allow the working fluid to impinge on the blades of
the runner.
4. Runner blades: Runner blades are the heart of any turbine. These are the centers where the fluid strikes and the
tangential force of the impact causes the shaft of the turbine to rotate, producing torque.

Working principle of Kaplan turbine

The Kaplan turbine is a type of propeller turbine that is used in low head, high flow hydroelectric power plants. It works
on the principle of converting the kinetic and potential energy of the water into mechanical energy that is used to spin the
rotor of the turbine.
Here's how it works:
1. Water is collected in a reservoir or forebay and is directed through a penstock to the Kaplan turbine.
2. The water enters the turbine at the bottom, and it is guided by a set of guide vanes into the turbine runner.
3. The turbine runner is a propeller-shaped wheel with adjustable blades, that the water flows through. The water flows
over the blades and makes the rotor spin.
4. As the water flows through the turbine, it loses both pressure and kinetic energy.
5. The spinning rotor is connected to a generator, which converts the mechanical energy of the rotor into electrical energy.
6. After passing through the turbine, the water is directed back into the river or other water source .
Components of Kaplan turbine
1. Scroll Casing: It is a spiral type of casing that has decreasing cross section area. The water from the penstocks enters
the scroll casing and then moves to the guide vanes where the water turns through 90° and flows axially through the
runner.
2. Guide Vane Mechanism: It is the only controlling part of the whole turbine, which opens and closes depending upon
the demand of power requirement. In case of more power output requirements, it opens wider to allow more water to hit
the blades of the rotor and when low power output requires it closes itself to cease the flow of water.
3. Draft Tube: The pressure at the exit of the runner of Reaction Turbine is generally less than atmospheric pressure. The
water at exit cannot be directly discharged to the tail race.
4. Runner Blades: The heart of the component in Kaplan turbine are its runner blades, as it the rotating part which helps
in production of electricity. Its shaft is connected to the shaft of the generator

Application of Kaplan Turbine

1. Kaplan turbines are widely used throughout the world for electrical power production.
2. It can work more efficiently at low water head and high flow rates as compared with other types of turbines.
3. It is smaller in size and easy to construct.
4. The efficiency of Kaplan turbine is very high as compares with other hydraulic turbine.

Selection of turbine & their specific speed

The selection of a turbine for a hydroelectric power plant is based on various factors, including the head and flow rate of
the water, the desired output power, the cost, and the environmental impact. Different types of turbines are better suited
for different head and flow rate ranges, and each type of turbine has a specific speed range that it is designed to operate
within.
1. Pelton turbine: Pelton turbines are typically used in high head, low flow applications and are best suited for heads over
300 meters and flow rates less than 50 cubic meters per second. They typically operate at high speeds, around 600-1200
RPM.
2. Francis turbine: Francis turbines are typically used in medium head, medium flow applications and are best suited for
heads between 50 and 300 meters and flow rates between 20 and 200 cubic meters per second. They typically operate at
medium speeds, around 300-600 RPM.
3. Kaplan turbine: Kaplan turbines are typically used in low head, high flow applications and are best suited for heads
less than 50 meters and flow rates greater than 200 cubic meters per second. They typically operate at low speeds, around
120-300 RPM.

Introduction to bulb turbines

A bulb turbine is a type of hydroelectric turbine that is characterized by its unique "bulb" shape. The turbine is encased in
a bulb-shaped housing, which is typically made of reinforced concrete, and is located at or near the water's edge. The bulb
shape allows the turbine and generator to be integrated into one compact unit, which makes it ideal for use in a variety of
different applications.
Importance of bulb turbines
1. Compact design: Bulb turbines have a unique "bulb" shape which allows for a compact and easy installation.
2. Suitable for small hydroelectric power plants and independent power generation: Their compact design makes them
well-suited for use in small hydroelectric power plants and for independent power generation.
3. Remote locations: They are well-suited for use in remote locations where power transmission lines are not available.
4. Efficient and reliable: Bulb turbines are highly efficient and reliable, making them a cost-effective option for
hydroelectric power generation.
5. Easy maintenance and repair: They are easy to maintain and repair, which makes them more cost-effective.

A draft tube
A draft tube is a tube or conduit that is used to discharge water from a turbine or pump. It is connected to the outlet of the
turbine or pump and extends out into the surrounding body of water. The main function of a draft tube is to convert the
kinetic energy of the discharged water into potential energy. This increase in potential energy results in a higher head and
a greater discharge capacity, which can be used to generate electricity in hydroelectric power plants or to lift and transfer
fluids in other applications such as water treatment plants and irrigation systems
Importance of draft tube
1. Increases efficiency of turbine and pump by converting kinetic energy to potential energy
2. Helps to reduce velocity of discharged water and reduce erosion
3. Increases head and discharge capacity
4. Can be used to generate electricity in hydroelectric power plants
5. Can be used to lift and transfer fluids in other applications such as water treatment plants and irrigation systems.

Define tail race canal

A tail race canal is a channel or conduit that carries water away from a hydroelectric power plant's turbine or pump after it
has been used to generate electricity or lift and transfer fluids. The tail race canal is typically located downstream of the
turbine or pump and is designed to efficiently transport the water back to the original water source, such as a river or
reservoir. The design of the tail race canal must consider factors such as the flow rate, velocity, and volume of water to be
handled, as well as the surrounding topography and the potential for erosion or scouring
Importance of tail race canal
1. Carries water away from the turbine or pump after it has been used in hydroelectric power plant.
2. Helps to efficiently transport water back to the original water source, such as a river or reservoir.
3. Design must consider factors such as flow rate, velocity, volume of water, topography and potential for erosion or
scouring.
4. Ensures safety for any human or aquatic life in or around the canal.
5. Helps to maintain the water balance in the system

Define Pumps
A pump is a mechanical device that uses energy to move fluids or gases from one place to another. Pumps can be
classified into different types based on the type of fluid they are designed to handle (such as liquids, gases, or slurry) and
the way in which they move the fluid (such as positive displacement or centrifugal).
Positive displacement pumps use a mechanism, such as a piston, diaphragm, or rotor, to trap a fixed volume of fluid and
then move it through the pump. These pumps are typically used for low-flow, high-pressure applications.
Types of pump
1. Centrifugal pumps: These pumps use a rapidly rotating impeller to create a centrifugal force that propels the fluid
through the pump. They are commonly used for high-flow, low-pressure applications such as water supply, irrigation, and
cooling systems.
2. Reciprocating pumps: These pumps use the back-and-forth motion of a piston or diaphragm to move the fluid. They
are commonly used in oil and gas industry, and in applications that require high pressure such as fire fighting and pressure
washing.
Centrifugal pumps performance characteristics
1. Centrifugal pumps are high-flow, low-pressure pumps that use a rapidly rotating impeller to create a centrifugal force
that propels the fluid through the pump.
2. Characterized by a head-capacity curve, which shows the relationship between the head (pressure) and the flow rate of
the pump.
3. The head of the pump is directly proportional to the impeller diameter and the rotational speed.
4. The efficiency of the pump is affected by the design of the impeller and the size of the pump.
5. Centrifugal pumps are sensitive to changes in the viscosity of the fluid and can be affected by the presence of solids or
gases in the fluid.
Reciprocating pumps performance characteristics
1. Reciprocating pumps are pumps that use the back-and-forth motion of a piston or diaphragm to move the fluid.
2. They are commonly used in high-pressure applications such as oil and gas industry, and in applications that require
high pressure such as fire fighting and pressure washing.
3. The performance of reciprocating pumps is characterized by a curve of flow rate against the pressure, and it depends on
the type of the pump and the design of the piston.
4. Reciprocating pumps can handle liquids with high viscosity and can pump liquids with suspended solids.
5. They are relatively less efficient than centrifugal pumps, but can generate higher pressure.

Define power house

A power house is a building or facility that houses one or more generators used to produce electricity. The term is most
commonly associated with hydroelectric power plants, which use the energy of falling water to turn turbines that drive
generators to produce electricity. The power house may be located at the base of a dam, in the case of a hydroelectric
power plant, or may be a separate building connected to the dam by a penstock (a large pipe that carries water to the
turbines). Power houses can also house generators that are powered by other sources of energy, such as coal, natural gas,
or nuclear power.

Classification of powerhouse
Depending upon the location, the powerhouse can be classified as:
a) Surface powerhouse: Such powerhouse is constructed above the ground so that it has less space restrictions. But the
foundation analysis of such powerhouse should be very carefully examined. If solid bed rock is not available in surface
powerhouse option, special foundation treatment is essential.
b) Underground powerhouse: When enough space is not available is not available for surface powerhouse, underground
powerhouse is adopted. In some places where the cost of land is too expensive underground powerhouse can be more
feasible option. The water conveyance length and the penstock length can be shortened by providing underground
powerhouse. In same condition with good quality rock, the underground powerhouse may be economical.

Powerhouse structures
• Sub structure
The structure that is situated below the axis of the turbine is called sub structure. It is located below ground level and
includes draft tube, tailwater channel and galleries needed from structural considerations. It transmits the load to the
foundation strata.
• Intermediate structure
It extends from turbine axis to top of generator. It includes casing, governor, generator and its appurtenances. The turbine
floor is generally provided immediately above the turbine axis and it can be used to have access to the turbine runner.
• Super structure
It extends from generator floor to the roof of powerhouse. If consists of generator and governor control rooms, exciters
and auxiliary equipments needed for ventilation and cooling. It also consists of walls and roof with a main travelling
granty crane at the roof level.

Generator
A generator is a device that converts mechanical energy into electrical energy. It typically consists of a rotor (a rotating
part) and a stator (a stationary part), which are separated by an air gap. The rotor is connected to a prime mover, such as a
turbine or an engine, which provides the mechanical energy to turn the rotor. The stator contains a set of coils of wire,
which are surrounded by a magnetic field. As the rotor turns, it causes the magnetic field to cut through the coils of wire,
generating an electrical current in the process.
There are two types of generators:
a) Synchronous generator
These types of generators are equipped with DC excitation system associated with voltage regulator to provide voltage
and phase angle control before the generators are connected to the grid. Synchronous generators can run isolated from the
grid and produce power since excitation is not grid dependent. These are more expensive than asynchronous generator.
b) Asynchronous generator
These generators draw their excitation current from the grid, absorbing reactive energy by their own magnetism. They
cannot generate when disconnected from the grid because they are incapable of providing their own excitation current.

Working principle of governors in Pelton and Francis turbines.

The governing of a turbine is defined as the operation by which the speed of turbine is kept constant under all working
conditions. It is done automatically by means of governor, which regulates the flow through turbine, according to the
changing load condition. Governing of a turbine is necessary as turbine is directly coupled to an electric generator, which
is required to run at constant speed under load fluctuation. The frequency of power generation by a generator of a constant
number of pair of poles under varying load condition should be same. When the load on the generator decreases, the speed
of the generator increases beyond the normal speed. If the turbine or generator is to run at constant speed, the rate of flow
to the turbine should be decreased till the speed becomes normal. The governor of a Pelton turbine decreases or increases
the outlet area of the nozzle by moving the spear valve. In case of Francis turbine, the governor decreases or increases the
wicket gate.

Define reservoir characteristic curve & how will you prepare it

A reservoir characteristic curve is a graph that shows the relationship between the water level in a reservoir (also known
as the head) and the discharge from the reservoir. It is used to understand the behavior of the reservoir and its ability to
store and release water
To prepare a reservoir characteristic curve, the following steps are typically taken:
Measure the water level in the reservoir at different times throughout the year.
Measure the discharge from the reservoir at the same times as the water level measurements.
Plot the water level measurements on the y-axis and the discharge measurements on the x-axis to create a graph.
Connect the points on the graph to create the characteristic curve.
Analyze the curve to understand the behavior of the reservoir and its ability to store and release water.

Explain optimization of penstock pipe

Optimization of a penstock pipe in a hydroelectric power plant involves finding the most efficient and cost-effective
design for the pipe, in order to minimize losses and maximize the amount of energy that can be generated. The
optimization process typically includes the following steps:
1. Hydraulic analysis: A detailed hydraulic analysis is conducted to determine the flow and pressure conditions in the
pipe, taking into account factors such as water flow, head, and pipe size and material.
2. Losses calculation: The losses in the pipe are calculated, taking into account factors such as friction, turbulence, and
inlet and outlet losses.
3. Design optimization: Different design options are evaluated to determine the most efficient and cost-effective design
for the pipe, taking into accounts the results of the hydraulic analysis and losses calculation.
4. Cost-benefit analysis: A cost-benefit analysis is conducted to compare the costs and benefits of different design options
and to determine the most cost-effective option.

Reservoir sedimentation
Sedimentation in a reservoir refers to the process by which solid particles, such as soil and rock fragments, settle to the
bottom of the reservoir over time. This can occur as a result of erosion in the surrounding area, or from the inflow of
sediment-laden water. Sedimentation can have negative effects on a reservoir, such as reducing its storage capacity and
altering its water quality. To prevent or reduce sedimentation, measures such as erosion control, sedimentation basins, and
dredging may be employed. Reservoir sedimentation is the process by which solid particles, such as soil, rock fragments,
and other debris, settle to the bottom of a reservoir over time. This sedimentation can occur due to a variety of factors,
including:
1. Erosion in the surrounding area, which can wash sediment into the reservoir.
2. Inflow of sediment-laden water from tributaries or other sources.
3. Natural processes, such as river and stream sedimentation, which can cause the reservoir to fill with sediment over time.

Explain main features/characteristics of pondage run off river

A pondage run-off river system is a type of hydroelectric power generation in which water is stored in a reservoir or
"pondage" and then released as needed to generate electricity. The main features of this system include:
1. Water storage: A large reservoir is built to store water, which can be released as needed to generate electricity.
2. Run-off River: The system relies on the natural flow of a river to fill the reservoir, and the excess water is then released
to generate electricity.
3. Hydroelectric generation: The released water is used to power turbines, which generate electricity.
4. Controlled release: The release of water from the reservoir can be controlled, allowing for the generation of electricity
to be adjusted to meet demand.
5. Flexibility: The system can be used as a base-load power source, providing a steady supply of electricity, or as a
peaking power source, providing additional electricity during times of high demand.

Explain main features/characteristics of pump storage

Pump storage is a type of hydroelectric power generation in which water is pumped from a lower elevation reservoir to a
higher elevation reservoir during times of low electricity demand. The main features and characteristics of pump storage
include:
1. Water storage: Two reservoirs are required, one at a lower elevation and one at a higher elevation. The water is pumped
from the lower to the upper reservoir when electricity demand is low, and then released back down to generate electricity
when demand is high.
2. Pumping: The system uses pumps to move water from the lower to the upper reservoir, which requires a significant
amount of electricity.
3. Hydroelectric generation: The released water is used to power turbines, which generate electricity.
4. Flexibility: The system can be used as a peaking power source, providing additional electricity during times of high
demand, or as a load-leveling source, smoothing out fluctuations in electricity demand.
5. Energy storage: The system can be used to store excess energy generated from other sources, such as solar or wind
power, for later use.

Function of draft tube

1. Energy recovery: Draft tubes help to recover the kinetic energy of the water leaving the turbine and convert it into
potential energy. This increases the overall efficiency of the hydroelectric power generation system.
2. Pressure increase: Draft tubes can be used to increase the pressure of the water being discharged, which can be useful
for certain types of hydroelectric power generation systems, such as those that use a pondage run-off river system.
3. Reservoir replenishment: Draft tubes can also be used to raise the water level in a reservoir, which can be useful for
certain types of hydroelectric power generation systems, such as those that use a pump storage system.
4. Design: The design of draft tube is crucial to maximize the energy recovery and to prevent cavitation.
5. Maintenance: Regular maintenance is needed to ensure the draft tube is in good condition and that there are no
blockages or damage that would impede the flow of water.

Explain the detail about the method of calculation of penstock pipe diameter & thickness
1. Flow rate calculation: The first step in calculating the diameter and thickness of a penstock pipe is to determine the
flow rate of the water that will be passing through the pipe. This can be done by measuring the water flow rate at the inlet
and outlet of the pipe, or by using data from a hydraulic model of the system.
2. Head loss calculation: The head loss, or the pressure drop that occurs as water flows through the pipe, must be
calculated in order to determine the required pipe diameter and thickness. This can be done using the Darcy-Weisbach
equation, which takes into account factors such as the pipe's length, diameter, and roughness, as well as the flow rate of
the water.
3. Velocity calculation: The velocity of the water flowing through the pipe must also be calculated in order to determine
the required pipe diameter and thickness. A high velocity can cause erosion and vibration, and a low velocity can cause
sedimentation.
4. Pipe material: The choice of pipe material is important, as it affects the pipe's ability to withstand the pressure and flow
of the water. For example, steel pipes are more durable and can withstand higher pressures than plastic pipes, but they are
also more expensive.

Stilling basin
A stilling basin is a basin or tank that is used to dissipate the energy of fluid flow, typically in a river or stream. It is often
used in conjunction with a dam or other hydraulic structure to control the flow of water and reduce erosion. The stilling
basin slows down the water and allows sediment to settle out, helping to prevent downstream flooding and erosion. It can
also be used to improve water quality by allowing pollutants to settle out before the water is released.

Different type of stilling basin

1. Rectangular stilling basin: This type of basin is used to dissipate the energy of incoming flows and to settle out
suspended solids. It is often used in conjunction with a dam or spillway.
2. Trapezoidal stilling basin: This type of basin is similar to the rectangular stilling basin, but its sides are sloped to
provide a more gradual transition from the high-energy flow to the low-energy flow.
3. Circular stilling basin: This type of basin is used to dissipate the energy of incoming flows and to settle out suspended
solids. It is often used in conjunction with a dam or spillway.
4. Inlet/Outlet stilling basin: This type of basin is specifically designed to dissipate the energy of incoming flows and to
settle out suspended solids. it is generally used in the inlet or outlet of channels or other types of water conveyance
systems.

Function of stilling basin

1. Dissipates the energy of fluid flow, typically in a river or stream
2. Used in conjunction with a dam or other hydraulic structure to control the flow of water and reduce erosion
3. Slows down the water and allows sediment to settle out
4. Helps to prevent downstream flooding and erosion
5. Improves water quality by allowing pollutants to settle out before the water is released.

Cavitation problem
1. Cavitation is the formation and collapse of vapor bubbles in a liquid
2. Occurs when the pressure of the liquid drops below its vapor pressure
3. Can occur in pumps, valves, and other hydraulic equipment
4. Can cause damage to the equipment, such as erosion and pitting of metal surfaces
5. Can lead to reduced efficiency and increased noise levels in the system
6. Can also cause vibration in the system.
7. It can be resolved by increasing the inlet pressure or by using special materials which are cavitation-resistant.

Differentiate between flow duration curve and mass curve

1. A flow duration curve (FDC) shows the frequency of different flow rates in a stream or river over a period of time.
1. A mass curve, also known as a load duration curve, shows the frequency of different pollutant concentrations in a
stream or river over a period of time.
2. FDC is used to understand flow variability
2. MDC is used to understand pollutant variability.
3. FDC is plotted on the x-axis as percent of time and y-axis as flow rate.
3. MDC is plotted on the x-axis as percent of time and y-axis as pollutant concentration.

List out the progress hydrological studies in different level of study of hydropower project
The progress of hydrological studies in the development of a hydropower project typically follows several levels of study,
including:
1. Feasibility study: This is the initial stage of a hydropower project where the potential for hydropower development is
evaluated. Hydrological data such as streamflow, precipitation, and climatic conditions are collected and analyzed to
determine the availability and potential of hydropower resources.
2. Detailed Project Report (DPR): In this stage, more detailed hydrological studies are carried out to confirm the
feasibility of the project. Hydrological data is collected over a longer period of time, and more detailed analyses are
performed to estimate the annual energy potential, design flood and low flow scenarios, and other factors that will affect
the project's design and operation.
3. Environmental Impact Assessment (EIA): In this stage, the potential environmental impacts of the project are
evaluated. Hydrological data is used to assess the potential impacts of the project on water resources and the downstream
ecosystem.
4. Design and Construction: At this stage, the final design of the project is developed based on the results of the previous
stages. Hydrological data is used to design the project's structures, such as the dam, spillway, and power station, and to
ensure that the project will operate safely and efficiently.
5. Operation and Maintenance: Once the project is operational, hydrological data is used to monitor and manage the
project's water resources. This includes monitoring stream flow, precipitation, and other hydrological variables to ensure
that the project is operating within safe and sustainable limits.