Module 7 - Design of Irrigation Structures PDF

**AGRITECH 213-IRRIGATION AND DRAINAGE** **MODULE 7- DESIGN OF IRRIGATION** **STRUCTURES** **INTRODUCTION** **LEARNING OUTCOME** The student must be able to: 2\. Identify the different diversion structures **LEARNING CONTENT** **TOPIC 1. Conveyance Structures: The Backbone of Irrigation Syst...

**AGRITECH 213-IRRIGATION AND DRAINAGE** **MODULE 7- DESIGN OF IRRIGATION** **STRUCTURES** **INTRODUCTION** **LEARNING OUTCOME** The student must be able to: 2\. Identify the different diversion structures **LEARNING CONTENT** **TOPIC 1. Conveyance Structures: The Backbone of Irrigation System** Conveyance structures are essential components of irrigation systems, responsible for transporting water from sources like rivers, reservoirs, or canals to agricultural fields. These structures ensure efficient and reliable water delivery, optimizing crop productivity. Among water/passageway structures are culvert, canals, pipelines, siphons, drop structure, chutes and aqueducts. 1. **Culverts:** Culverts are small channels that allow water to flow under roads, railroads, trails, or similar obstructions. They are typically embedded in the ground and made of materials like concrete, metal, or plastic. Culverts are essential for maintaining drainage and preventing waterlogging in infrastructure projects. 2. **Canals:** Canals are open channels that carry water over long distances. They are commonly used in traditional irrigation systems to transport water from a source to fields. Canals require careful design and maintenance to prevent water loss through seepage and evaporation. 3. **Pipelines:** Pipelines are enclosed conduits that transport water under pressure. They are suitable for long distances and areas with steep slopes. Pipelines can be made of various materials like concrete, steel, or plastic. They are commonly used in modern irrigation systems to ensure efficient and reliable water delivery. 4. **Siphons:** Siphons are structures that use atmospheric pressure to convey water across depressions or obstacles. They are commonly used in canal systems to avoid constructing bridges or tunnels. Siphons require careful design to maintain sufficient pressure head and prevent air ingress. 5. **Flumes:** Flumes are open-channel flow measuring devices. They are used to measure the flow rate of water in canals and pipelines. Flumes are essential for monitoring water usage and optimizing water distribution in irrigation systems. 6. **Drop Structures:** Drop structures are used to dissipate excess energy in a channel, preventing erosion and damage to the channel bed. They can be simple structures like a sudden drop or more complex structures like a hydraulic jump. 7. **Chutes:** Chutes are inclined channels used to convey water over a steep slope. They are often used to transport water from a higher elevation to a lower elevation, such as from a reservoir to a canal. 8. **Aqueducts:** Aqueducts are structures that carry water over valleys, hills, or other obstacles. They can be elevated channels, tunnels, or a combination of both. The Roman aqueducts are famous examples of ancient aqueduct systems that supplied water to cities and towns. **Design Considerations for Conveyance Structures** The design of conveyance structures is a complex process that involves several factors, including hydraulics, hydrology, structural engineering, and environmental considerations. The goal of effective design is to ensure the efficient and reliable delivery of water, minimize water losses, and protect the environment. A. **Hydraulic Design** 1. Flow Rate- The flow rate determines the volume of water that needs to flow through the structure per unit of time. It\'s crucial to ensure that the structure can handle both normal and peak flow conditions. 2. Velocity- The water\'s velocity affects its ability to transport sediment and erode the channel. A balanced velocity is essential to prevent both sedimentation and erosion. 3. Cross-sectional Area- The cross-sectional area of the channel or pipe determines its capacity to carry water. The shape and size of the cross-section are important factors in hydraulic design. 4. Energy Loss- Energy is lost due to friction, bends, curves, and structures. Minimizing energy loss is crucial for efficient water delivery. B. **Structural Design** Structural design ensures the physical integrity of conveyance structures, ensuring they can withstand various loads and environmental conditions. Key considerations include: 1. **Material Selection**: Choosing appropriate materials that are durable, resistant to corrosion, and cost-effective. Factors like the type of structure, soil conditions, and water quality influence material selection. For instance, concrete is commonly used for canals and pipelines, while steel or plastic pipes are suitable for high-pressure applications. 2. **Structural Strength:** Ensuring the structure can withstand loads from water pressure, soil pressure, and other external forces. This involves analyzing stresses and strains to determine the required thickness and reinforcement. 3. **Stability:** Designing the structure to be stable and resistant to erosion and sedimentation. This includes considering factors like slope stability, foundation conditions, and scour protection measures. C. **Environmental Considerations** Environmental considerations are crucial in the design and operation of conveyance structures. By minimizing water pollution, protecting ecosystems, and conserving water resources, engineers can ensure that these structures have a minimal negative impact on the environment. 1. **Water Quality:** To minimize water pollution, it is essential to avoid using harmful construction materials and to implement measures to prevent contamination of water bodies during construction and operation. 2. **Ecological Impact:** To protect ecosystems, engineers should design structures that minimize disturbance to natural habitats and avoid fragmentation of ecosystems. Additionally, measures should be taken to protect aquatic life, such as fish and other aquatic organisms. 3. **Water Conservation:** To conserve water, structures should be designed to minimize water losses due to seepage, evaporation, and leakage. Efficient water management practices, such as timely maintenance and repair, can also help reduce water loss. **TOPIC 2: DIVERSION STRUCTURE** What is diversion structure? Diversion structures consist of ridges or channels that are used to temporarily divert water around or from an area that is under construction or being stabilized. Specific applications includes perimeter control, diversion away from disturbed slopes, and diversion of sediment-laden water to treatment facilities. Diversion structures route runoff in excess of base flow to storage facilities during wet period, for later use during dry period. Flood diversion structures such as dikes, are also useful methods for mitigating the adverse effect of torrential rain and at the same time capturing the excess water for later use. The following types of structures have been used to divert flood water for water supply augmentation purposes. **Types of Diversion Structures** 1. **Weirs:** Weirs are barriers constructed across a river or stream to raise the water level upstream and divert water into a canal. They can be classified based on their shape, such as sharp-crested weirs, broad-crested weirs, and ogee weirs. 2. **Barrages:** Barrages are more complex structures than weirs, often consisting of a series of gates that can be raised or lowered to control the flow of water. They are commonly used to divert water for irrigation, hydropower generation, and flood control.  3. **Dams:** Dams are large structures built across rivers or valleys to store water. They can be used to divert water for irrigation, generate hydroelectric power, and provide water for domestic and industrial use. 4. **Transverse Dike:** A transverse dike is a structure built perpendicular to the flow of a river or stream to divert water into a canal. It is often used in conjunction with a weir or barrage to increase the head of water and improve the efficiency of the diversion. 5. **Water Traps:** Water traps are structures designed to capture and store water from runoff or rainfall. They can be used to supplement irrigation water supplies during dry periods. 6. **Toroba:** A Toroba is a traditional irrigation system used in the Philippines, particularly in the Cordillera region. It is a simple diversion structure made of rocks and logs, used to divert water from streams into rice paddies. **Common Diversion Structures and Their Use** **Factors Affecting the Choice of Diversion Structure:** **TEACHING AND LEARNING ACTIVITIES** **Build a Model Irrigation System** **Materials:** - Cardboard box - Plastic tubing - Plastic bottles - Soil/Clay - Water **Procedure:** 1. **Design:** Sketch a simple irrigation system with a water source, a diversion structure, a conveyance channel, and a field. 2. **Construct:** Use the cardboard box to create a model landscape. Cut channels in the cardboard to represent canals. 3. **Diversion:** Use a plastic bottle with holes punched in the bottom to simulate a diversion structure. 4. **Flow:** Fill the plastic bottles with water and observe the flow of water through the channels. 5. **Experiment:** Try adjusting the height of the water source or the size of the holes in the bottle to observe how it affects the flow rate and distribution of water. Discuss your conclusion. **RECOMMENDED LEARNING MATERIALS RESOURCES FOR SUPPLEMENTARY READING** https://image.app.goo.l/hvSFdexMY7Rf(VW68 hhtps://images.app.goo.l/FRFFnMG4A1myng3U6 **FLEXIBLE TEACHING LEARNING MODALITY (FTLM) ADOPTED** Blended Learning Modality (Online and Modular Teaching **ASSESSMENT TASK** 1. What is Conveyance structure and Diversion Structure? \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 2. Give at least five examples in each structure. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ **REFERENCES** Iwata,Shingo. (2020) "Soil-Water Interaction: Mechanisms Application, Second Edition, Revised Expanded"., CRC Press Viliam Novak, Hana Hlavacikova. (2019). Applied Soil Hydrology. Springer International Publishing. Inocencio, A. (2018). "*Current challenges in agricultural water resource development and management in the Philippines".* Goyal, Megh Raj. Tripathi, Vinod K. (2018). Wastewater Management for Irrigation: Principle and Practices. Apple Academic Press. Goyal, Megh R. Panigrahi P. (2019). Sustainable Micro Irrigation Design System for Agricultural Crops:Methods and Practices