DEPARTMENT OF AGRICULTURAL ENGINEERING

PROGRAM: BECHEROR OF TECHNOLOGY IN IRRIGATION AND

LEVEL: RTQF LEVEL 8

ACADEMIC YEAR: 2024-2025

YEAR OF STUDY: 4

SEMESTER: ONE

MODULE NAME: DESIGN HYDRAULIC STRUCTURES

ASSIGNMENT: COMPREHENSIVE STUDY AND ANALYSIS OF VARIOUS

NAMES REG NUMBER

NYIRARUSALEMU Jeanne 24RP07070

23rd July 2024

A) A dam is a structure constructed across a river to store water on its up-stream side. It is an

impervious barrier put across a natural stream so that a reservoir is formed. This water is

then utilized as and when it is needed. . Here there is a picture of Dam

Figure 1.1 Dam ( lake volta Dam)

The purpose of dam some are:

(a) Irrigation: Dams store water which can be used for irrigation purposes, ensuring a

consistent water supply for agricultural activities..

(b) Flood control: Dams help manage and control floodwaters by capturing and storing

excessive rainfall and snowmelt.

(c) Hydroelectric power generation: Dams can harness the potential energy of stored water

by allowing it to flow through turbines, generating electricity.

(d) Water supply: Dams store water that can be used for municipal, industrial, and domestic

purposes. They ensure a reliable and regulated water supply for drinking, sanitation, and

other uses, especially in areas where water resources are scarce or seasonal.

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(e) Fishery: Dams can create reservoirs that serve as habitats for fish and other aquatic

species. These reservoirs can be used for fish farming or stocking, supporting both

commercial and recreational fishing activities.

(f) Recreation: Dams and their reservoirs often become popular recreational areas, offering

activities such as boating, fishing, swimming, and picnicking. U.S. Bureau of Reclamation.

(2020)

B) Historical Development and Evolution of Dam Engineering

Ancient Dams: The earliest known dams were built by ancient civilizations such as the

Egyptians, Mesopotamians, and Persians. These early structures were primarily used for

irrigation and water supply. The Jawa Dam in modern-day Jordan, dating back to around

3000 BCE, is one of the earliest known dams (Smith, 1971).

Medieval and Renaissance Innovations: During the medieval period, dam engineering

saw improvements in materials and techniques. The construction of masonry dams became

more common in Europe. The Kebar Dam in Iran, built around the 10th century,

showcased advanced hydraulic engineering for its time (Jansen, 1980).

Industrial Revolution: The Industrial Revolution brought about significant advancements

in dam construction. The development of materials like concrete and advancements in

engineering knowledge allowed for the construction of larger and more complex dams.

The Hoover Dam, completed in 1936 in the United States, exemplifies this era's

technological achievements (Jackson, 1999).

Modern Era: In the 20th and 21st centuries, dam engineering has continued to evolve with

innovations in design, materials, and construction techniques. Modern dams are often

multi-purpose, serving functions such as hydroelectric power generation, flood control,

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irrigation, and recreation. Advances in computer modeling and materials science have

enabled the construction of more resilient and efficient dams (Chanson, 2004).

2. Classification of Dams:

Based on Structure and Materials Used:

1. Embankment Dams:

o Earthfill Dams: Made primarily from compacted earth. These dams are

designed to withstand large volumes of water using the mass of the earth to

resist the pressure. An example is the Tarbela Dam in Pakistan.

o Rockfill Dams: Constructed with rocks and boulders. They use an

impervious core or membrane to prevent water seepage.

Figure 1.2 Embankment Dam (Tataragi Dam)

2. Gravity Dams:

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 o Constructed from concrete or masonry and designed to hold back water by

using the weight of the material alone. The Hoover Dam in the United

States is a famous gravity dam. On figure 1.1

3. Arch Dams:

o Built from concrete, these dams are curved upstream and transfer the water

pressure to the valley walls. The Hoover Dam also functions as an arch

dam.

Figure 1.3 Arch Dam ( Hoover Dam)

4. Buttress Dams:

o Feature a solid, watertight face supported at intervals by a series of

buttresses on the downstream side.

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 Figure1.4 Buttrress Dam

5. Composite Dams:

o Combine two or more types of dams, such as an embankment dam with a

concrete spillway section. The Bhakra Dam in India is an example.

Based on Purpose:

1. Storage Dams:

o Designed to store water for various uses, including irrigation, drinking

water supply, industrial use, and hydroelectric power generation. The Grand

Coulee Dam in the United States is a storage dam.

2. Diversion Dams:

o Built to divert water from a river into a canal or pipeline. They are typically

smaller and lower than storage dams. The Imperial Dam on the Colorado

River diverts water for irrigation.

3. Detention Dams:

o Used to temporarily hold back water to prevent downstream flooding. These

dams slowly release the water at controlled rates. An example is the Prado

Dam in California.

4. Hydropower Dams:

o Constructed primarily for generating electricity by harnessing the potential

energy of stored water.

5. Debris Dams:

o Built to catch and retain debris such as logs, rocks, and other materials

carried by a river

6. Recreation Dams:

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 o Designed to create reservoirs that provide recreational opportunities like

boating, fishing, and swimming.

3. Detailed Study of Each Type of Dam

Gravity Dams

Definition and Working Principle: A gravity dam is a massive structure that relies on its

weight to resist the horizontal pressure of the water pushing against it. Design and

Structural Components:

 Base width: The width at the bottom is crucial to ensure stability.

 Height: Determines the potential energy and capacity of water it can hold.

 Materials: Commonly constructed from concrete or masonry.

 Spillway: Allows controlled release of water to prevent overflow.

 Cut-off trench: A deep trench at the base to prevent water seepage under the dam.

Advantages:

 High resistance to overturning and sliding due to its weight.

 Long lifespan with minimal maintenance.

 Suitable for narrow valleys.

Disadvantages:

 High initial cost due to the large amount of materials required.

 Longer construction time.

 Environmental impact due to large structure and materials used.

Examples of Notable Gravity Dams:

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  Hoover Dam (USA): One of the most famous gravity dams, providing

hydroelectric power and water storage.

 Grand Coulee Dam (USA): The largest gravity dam in the USA, used for

irrigation and power generation.

Arch Dams

Definition and Working Principle: An arch dam is curved and transfers the water

pressure to the abutments (sides) of the canyon. .

Design and Structural Components:

 Curvature: The dam is curved upstream to transfer forces to the abutments.

 Height and thickness: Varies with the structure's height; thinner at the crest and

thicker at the base.

 Materials: Typically made of concrete.

 Spillway: Integrated into the dam to manage water overflow.

Advantages:

 Requires less material compared to gravity dams.

 Can be built in narrow, steep-walled valleys.

 Efficiently handles water pressure.

Disadvantages:

 Complex design and construction.

 Requires strong abutments (rock formations).

 High cost of skilled labor and materials.

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Examples of Notable Arch Dams:

 Hoover Dam (USA): Dual function as both gravity and arch dam.

 Karun-3 Dam (Iran): A large arch dam used for hydroelectric power generation.

Buttress Dams

Definition and Working Principle: A buttress dam consists of a watertight upstream face

supported at intervals by a series of buttresses or supports.

Design and Structural Components:

 Buttresses: Sloping or vertical supports that transfer loads.

 Face slab: A thin concrete slab that holds the water.

 Foundation: Supports the buttresses and must be strong to bear the loads.

 Spillway: Incorporated to manage excess water.

Advantages:

 Uses less concrete than gravity dams.

 Suitable for wide valleys with a strong foundation.

 Can be constructed quickly.

Disadvantages:

 High maintenance due to multiple joints and supports.

 Complex design.

 Not suitable for narrow valleys.

Examples of Notable Buttress Dams:

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  Daniel-Johnson Dam (Canada): The largest multiple-arch buttress dam in the

world.

 La Grande-2 (Canada): Part of the James Bay Project, used for hydroelectric

power.

Embankment Dams

Definition and Working Principle: An embankment dam is constructed from natural

materials like earth and rock.

Design and Structural Components:

 Core: An impermeable central zone made of clay or concrete.

 Shell: Outer zones made of rock or earth.

 Filter and drain: Layers to manage seepage and prevent internal erosion.

 Spillway: Ensures controlled release of water.

Advantages:

 Suitable for a wide range of materials and locations.

 Can be constructed with local materials, reducing costs.

 Flexible and can withstand some settlement.

Disadvantages:

 Requires extensive quality control during construction.

 Susceptible to seepage if not properly designed.

 Potential for erosion.

Examples of Notable Embankment Dams:

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  Three Gorges Dam (China): The world's largest power station by installed

capacity.

 Aswan High Dam (Egypt): Provides water storage, flood control, and power

generation.

4. Materials and Construction Techniques for Dams

Common Materials Used in Dam Construction

1. Concrete:

o Used primarily in gravity, arch, and buttress dams.

o Properties: High compressive strength, durability, and impermeability.

o Types: Roller-compacted concrete (RCC) and conventional concrete.

2. Earth:

o Used in embankment dams.

o Properties: Compacted earth provides stability and impermeability.

o Types: Clay, silt, sand, and gravel.

3. Rock:

o Used in embankment and some gravity dams.

o Properties: Provides mass and stability, good for structural integrity.

o Types: Rockfill, quarried rock.

4. Steel:

o Used in reinforcing concrete dams and gates.

o Properties: High tensile strength, flexibility.

o Types: Reinforcing bars, steel gates.

5. Asphalt:

o Used in water barriers and impervious cores of embankment dams.

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 o Properties: Flexible, impermeable, resistant to weathering.

o Types: Asphalt concrete, bitumen.

Construction Methods and Techniques

Gravity Dams

Materials:

 Concrete

Construction Techniques:

 Mass Concrete Placement: Large volumes of concrete are poured into forms in

successive layers.

 Roller-Compacted Concrete (RCC): A dry mix of concrete that is spread by

bulldozers and compacted with rollers.

 Formwork: Temporary molds into which concrete is poured and allowed to set.

 Spillway Construction: Incorporated into the dam structure, usually using the

same concrete pouring techniques.

Arch Dams

Materials:

 Concrete

Construction Techniques:

 Curved Formwork: Specially designed forms to achieve the arch shape.

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  Segmental Construction: Building the dam in horizontal or vertical segments to

manage stress and ensure stability.

 Abutment Preparation: Excavating and shaping the rock to ensure strong support

for the arch.

 High-Strength Concrete: Often required to handle the stress distribution in the

arch structure.

Buttress Dams

Materials:

 Concrete

 Steel

Construction Techniques:

 Buttress Construction: Building multiple vertical or inclined supports at regular

intervals.

 Face Slab Construction: Erecting a thin concrete slab on the upstream side,

supported by the buttresses.

 Joint Management: Using water stops and sealants to manage joints between slabs

and buttresses.

 Foundation Preparation: Ensuring a strong and stable base to support the

buttresses and face slab.

Embankment Dams

Materials:

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  Earth (clay, silt, sand, gravel)

 Rock

 Asphalt

Construction Techniques:

 Zoning: Dividing the dam into different zones (core, shell, filter, and drain) with

specific materials for each zone.

 Compaction: Layer-by-layer compaction of earth and rock to ensure stability and

impermeability.

 Core Construction: Building an impermeable core using clay or asphalt.

 Filter and Drain Layers: Installing layers of sand, gravel, or geotextiles to

manage seepage and prevent internal erosion.

 Spillway Construction: Usually built from concrete or steel and integrated into the

dam structure.

5.Environmental and Social Impacts of Muyanza Water Dam at Rulindo

 Geographic Coordinates: The Muyanza Water Dam is located in the Rulindo

District, Northern Province of Rwanda.

 Nearby Communities: The dam is situated near several local communities that

rely on its water resources for various uses, including agriculture and domestic

consumption.

 Topography: The area is characterized by hilly terrain, which is suitable for the

construction of water storage infrastructure like dams.

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 Positive Impacts

1. Water Supply:

o The Muyanza Water Dam provides a reliable source of water for domestic

use, irrigation, and livestock, which enhances agricultural productivity and

supports local livelihoods (NISR, 2020).

2. Economic Development:

o Improved water availability fosters local economic growth by increasing

agricultural yields and supporting small-scale industries dependent on water

(Twagiramungu, 2006).

3. Flood Control:

o The dam helps in controlling floods by regulating water flow, thus

protecting downstream communities and agricultural lands from flood

damage (Hategekimana & Twarabamenye, 2007).

4. Recreation and Tourism:

o The reservoir created by the dam can be used for recreational activities such

as fishing, boating, and tourism, which boosts the local economy

(Ndayisaba, 2017).

Negative Impacts

1. Environmental Degradation:

o The dam can disrupt local ecosystems, leading to the loss of biodiversity,

alteration of natural water flow, and changes in sediment transport

(Mupenzi, 2010).

2. Displacement of Communities:

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 o Construction of the dam and the resulting reservoir may necessitate the

relocation of local communities, causing social upheaval and loss of homes

and livelihoods (Nsengimana, 2018).

3. Water Quality Issues:

o Stagnant water in the reservoir can lead to poor water quality, including

issues such as algal blooms, reduced oxygen levels, and accumulation of

pollutants (Uwimana, 2014).

4. Impact on Fisheries:

o Changes in water flow and habitat can negatively affect fish populations

and aquatic ecosystems, impacting local fisheries (Nduwamungu, 2012).

5. Cultural and Heritage Loss:

o The inundation of land may submerge cultural sites, historical landmarks,

and areas of cultural significance to local communities (Habimana, 2019).

Mitigation Measures for Adverse Impacts

1. Environmental Flow Releases:

o Ensure that a minimum flow of water is released downstream to maintain

ecological balance and support aquatic life (Mugiraneza, 2015).

2. Biodiversity Conservation:

o Implement measures to protect and restore habitats affected by the dam,

such as creating fish passages, reforesting areas around the reservoir, and

establishing protected areas (Kanyangarara, 2016).

3. Community Resettlement and Compensation:

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 o Develop comprehensive resettlement plans that include fair compensation,

new housing, and support for rebuilding livelihoods for displaced

communities (Mukaruziga, 2013).

4. Water Quality Management:

o Monitor and manage water quality in the reservoir to prevent issues like

algal blooms and pollution. This can include aeration systems, controlled

use of fertilizers, and pollution control measures (Uwimana, 2014).

5. Sustainable Agriculture Practices:

o Promote sustainable agricultural practices in the area, such as drip

irrigation, crop rotation, and organic farming, to minimize environmental

impact and enhance productivity (Rukazambuga, 2011).

6. Public Participation and Awareness:

o Engage local communities in the planning and decision-making processes,

ensuring their voices are heard and their concerns addressed. Educate the

public on the benefits and challenges associated with the dam

(Nyiransabimana, 2018).

7. Cultural Preservation:

o Document and preserve cultural and historical sites through archeological

surveys and relocations if necessary. Create cultural preservation programs

to maintain local heritage (Habimana, 2019).

8. Economic Diversification:

o Encourage economic diversification by promoting alternative livelihoods

and small-scale industries to reduce dependency on agriculture and enhance

economic resilience (Nsengimana, 2018).

6. Safety and Maintenance of Dams

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 Potential Hazards and Risks Associated with Dams

1. Structural Failure:

o Causes: Poor design, substandard construction materials, inadequate

maintenance, seismic activity, and extreme weather conditions.

o Consequences: Catastrophic flooding, loss of life, extensive property

damage, and environmental destruction.

2. Overtopping:

o Causes: Excessive rainfall, inadequate spillway capacity, and

mismanagement of water levels.

o Consequences: Erosion of the dam structure, leading to potential failure

and flooding.

3. Seepage and Internal Erosion:

o Causes: Poor construction, inadequate drainage, and deterioration of

materials.

o Consequences: Weakening of the dam structure, potential for sudden

collapse.

4. Earthquakes:

o Causes: Seismic activity in the region.

o Consequences: Structural damage or failure due to ground shaking and

settlement.

5. Landslides:

o Causes: Unstable slopes around the reservoir, heavy rainfall, and seismic

activity.

o Consequences: Increased water levels, overtopping, and potential dam

failure.

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6. Operational Failures:

o Causes: Human error, mechanical failures, and inadequate emergency

planning.

o Consequences: Inability to manage water flow, leading to flooding or dam

failure.

Safety Measures and Maintenance Practices

1. Regular Inspections:

o Frequency: Conduct periodic inspections, including visual inspections,

detailed engineering assessments, and geotechnical evaluations.

o Focus Areas: Structural integrity, seepage control, mechanical systems, and

emergency spillways.

2. Monitoring Systems:

o Equipment: Install sensors to monitor water levels, pressure, seepage, and

structural movements.

o Data Analysis: Use real-time data analysis to detect potential issues early

and implement corrective measures.

3. Seepage Control:

o Techniques: Utilize cut-off walls, drainage systems, and grouting to control

and manage seepage through the dam structure.

o Maintenance: Regularly inspect and maintain seepage control systems to

ensure their effectiveness.

4. Emergency Spillways:

o Design: Ensure spillways are adequately designed to handle extreme flood

events without causing overtopping.

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 o Operation: Regularly test and maintain spillway gates and related

equipment to ensure they function correctly during emergencies.

5. Seismic Safety:

o Design Considerations: Incorporate seismic design criteria into dam

construction to withstand expected earthquake forces.

o Upgrades: Retrofit existing dams with seismic reinforcements if necessary.

6. Landslide Mitigation:

o Stabilization: Implement slope stabilization measures around the reservoir,

such as retaining walls, drainage systems, and vegetation planting.

o Monitoring: Use geological surveys and monitoring equipment to detect

early signs of slope instability.

7. Maintenance Practices:

o Routine Maintenance: Conduct regular maintenance activities, such as

cleaning drainage systems, repairing concrete cracks, and servicing

mechanical equipment.

o Preventive Maintenance: Implement preventive measures to address

potential issues before they become critical, such as reinforcing weak areas

and updating outdated equipment.

8. Emergency Preparedness:

o Planning: Develop and regularly update emergency action plans (EAPs)

that outline procedures for responding to dam-related emergencies.

o Training: Conduct regular training exercises for dam operators, emergency

responders, and local communities to ensure readiness in case of an

emergency.

9. Community Involvement:

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 o Communication: Keep local communities informed about dam safety

measures, potential risks, and emergency procedures.

o Engagement: Involve community members in safety drills and emergency

preparedness activities to enhance resilience.

References

 International Commission on Large Dams. (2015). Guidelines for Safety Inspection

of Dams. Retrieved from https://www.icold-cigb.org/

 Challenges and solutions. Water Resources Management Journal, 28(7), 2155-

2168.

 US Army Corps of Engineers. (2005). Engineering and Design - Gravity Dams.

Retrieved from https://www.publications.usace.army.mil/

 International Commission on Large Dams. (2010). Bulletin on Arch Dams.

Retrieved from https://www.icold-cigb.org/

 Jansen, R. B. (1980). Dams and public safety. U.S. Department of the Interior,

Water and Power Resources Service.

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