Water Intake Structure’s Crucial Role in Water Management | From Access to Preservation

Water Intake Structure is a structure installed to collect the water from the water source having components such as gates and screens for regulation of water flow and preventing the debris from entering the flow. 

Thus, an intake structure is a transitional point from where water from a source flows into a conduit. 

Importance of Intake Structures in Water Resources Management

The significance of intake structures can be understood from the fact that they aid in the access, regulation, and protection of water resources during the water extraction for various purposes. 

Importance of Intake Structures:

1. Access to water resource
2. Water quality
3. Water supply reliability
4. Regulated water flow
5. Environmental preservation
6. Emergency preparedness

1. Access to Water Resource

Intake structures make it possible to extract water from different water resources like rivers, lakes, canals, or reservoirs. 

2. Water Quality

Water quality is ensured if uncontaminated location and proper design of intake structure is selected. The debris, aquatic life, sediments, and contaminants are removed by installations like screens, filters, and sedimentation chambers ensuring water quality. 

3. Water Supply Reliability 

Uninterrupted water supply to water treatment plants is ensured by intake structures. 

4. Regulated Water Flow

Intake structures stop the excess water during the floods and supply water even during the low level flow in the reservoir. Water flow can be controlled so that steady supply is ensured and thus help in water management too.

5. Environmental Preservation

Intake structures minimise their ecological footprint as they control the disruption to aquatic habitats and ecosystems. Thus, we can say that intake structures also help in the conservation of biodiversity.

6. Emergency Preparedness

Even during natural disasters or infrastructure disruptions, access to water is ensured by intake structures.

Function of Intake Structure

The main function of the intake structure is to help in safe withdrawal of water from the selected source of water such that the water flows into the intake conduit at the selected range of pool level of the source water.

Factors Governing the Location of an Intake Structure

• The location of the intake site should ideally be near the treatment plant so that cost of water conveyance is minimum.
• Intake structure should be built where the source has relatively purer water so that water treatment cost can be minimised. 
• Intake structure should not be located downstream of the site of disposal of waste water. Even nearby locations where wastewater is discharged should be avoided so that water contamination can be avoided.

There is a case study in India where not considering the above point resulted in the outbreak of JAUNDICE in 1956 in Delhi. As the contaminated water of Najafgarh drain mixed with the water of Yamuna river at the site of intake. 

Post this jaundice outbreak, Wazirabad barrage was constructed at the upstream of Najafgarh drain in 1958.

• The site should be so selected that it is easily accessible during floods. 
• Future additions and expansions should be kept in mind while selecting the site so that greater withdrawal of water at a future date can be possible. 
• The site for intake structure should not be located near the meandering river section. If it is essential to construct the intake structure near the meandering section, then diversion weir or barrage needs to be constructed. 

Also, intake structure should be constructed near concave curves rather than concave curves. Though scouring is more on the concave side of the curve, it can at least ensure continuous supply of water.

• The location for intake structure should be geologically stable.
• Good approach roads are necessary for easy access.

Components of Intake Structures

The major components of an intake structure are as follows:

1. Intake pipe (Channel)
2. Screens (Gates)
3. Trash racks
4. Fish screens
5. Velocity caps
6. Gates & valves
7. Sedimentation chambers
8. Pumps (Lift stations)
9. Access platforms & Walkways
10. Instrumentation  

Preventive Measures for Designing Intake Structures

• Hydrological Analysis: Most optimum location for the intake structure and its design capacity have to be determined by carrying out hydrological analysis.
• Water Quality Assessment: The water quality at the intake site has to be determined so as to implement relevant filtration techniques and treatment options.
• Environmental Impact Assessment: Environmental impact needs to be studied and suitable mitigation solutions should also be applied.
• Site Selection and Geotechnical Analysis: Geotechnical analysis of the site needs to be conducted to ensure accessibility, topography and other details of the site.
• Debris Management: To prevent the blockage in the path of intake, an appropriate debris management system needs to be applied. 
• Fish Protection: To minimise the loss to aquatic life, fish protection measures have to be carried out.
• Structural Design and Stability: Appropriate structural design has to be carried out for the intake structure so that it remains stable amidst hydraulic loads and environmental forces.
• Operational Flexibility: To adapt to change in flow conditions of the water source, adjustable gates, variable speed pumps, and redundant intake channels are provided. It provides flexibility in intake operation, optimises intake efficiency, and minimises downtime during maintenance.
• Monitoring and Maintenance: Different instrumentations are installed to monitor different aspects of intake structure like intake performance,  water quality parameters, and environmental conditions.

Maintenance of Intake Structure

Maintaining an intake structure is essential to ensure its longevity, functionality, and safety. Here are some key steps for maintaining an intake structure:

1. Regular Inspections:
   • Conduct routine inspections to identify any signs of wear, damage, or deterioration.
   • Check for cracks, corrosion, or structural weaknesses.
   • Inspect screens, strainers, and other components for clogs or blockages.
2. Cleaning and Debris Removal:
   • Regularly remove debris (such as leaves, branches, and sediment) from intake screens and grates.
   • Clean out accumulated silt or sand to maintain proper flow.
   • Ensure that trash racks are clear to prevent clogging.
3. Corrosion Protection:
   • Apply protective coatings to prevent corrosion of metal components.
   • Inspect and maintain cathodic protection systems if applicable.
4. Structural Repairs:
   • Address any cracks, leaks, or structural damage promptly.
   • Reinforce weak areas or repair concrete surfaces.
   • Replace damaged parts as needed.
5. Sealing and Waterproofing:
   • Seal joints, seams, and penetrations to prevent water leakage.
   • Apply waterproofing coatings to protect against water infiltration.
6. Monitoring and Instrumentation:
   • Install monitoring equipment to track water levels, flow rates, and structural stability.
   • Regularly calibrate instruments and ensure accurate readings.
7. Emergency Preparedness:
   • Develop emergency protocols for unexpected events (such as floods or earthquakes).
   • Train personnel on emergency shutdown procedures.
   • Maintain backup power sources for critical components.

Materials used for Intake Structures

Intake structures are vital components in water supply systems, allowing the withdrawal of water from natural sources. These structures are designed to withstand various forces and environmental conditions. Let’s explore the materials commonly used for constructing intake structures:

1. Stone or Brick Masonry:
   • Traditional and durable materials.
   • Used for smaller intake structures.
   • Provides stability and resistance to water pressure.
2. Reinforced Concrete (R.C.C.):
   • Widely used due to its strength and versatility.
   • Suitable for both small and large intake structures.
   • Resists water pressure, wave action, and environmental factors.
3. Concrete Blocks:
   • Precast concrete blocks are convenient for construction.
   • Assemble easily to form the structure.
   • Offers good resistance to water and weathering.
4. Thermoplastic Materials (Modern Trend):
   • In some modern engines, intake manifolds are made of thermoplastic materials.
   • Nylon 6/6 is commonly used for making intake manifolds in multi-cylinder engines¹.
   • Lightweight, corrosion-resistant, and cost-effective.
5. Waterproof Coatings and Sealants:
   • Applied to protect against water infiltration and leakage.
   • Enhances the durability of intake structures.
6. Metal Components (for Valves, Screens, and Strainers):
   • Stainless steel or corrosion-resistant alloys.
   • Ensures longevity and efficient operation.
7. Geotextiles and Geomembranes:
   • Used for erosion control and soil stabilization around intake structures.

Selection of Material for Intake Structure

Selecting the right material for an intake structure is crucial for its durability, functionality, and resistance to environmental factors. Let’s explore some considerations when choosing materials:

1. Site Conditions:
   • Consider the location of the intake structure (near the treatment plant, water quality, accessibility during floods, etc.).
   • Evaluate geological stability, erosion risks, and exposure to heavy currents.
2. Water Pressure and Wave Action:
   • The material should withstand water pressure and wave forces.
   • Reinforced Concrete (R.C.C.) and concrete blocks are commonly used due to their strength and resistance.
3. Corrosion Resistance:
   • If the intake is in a saline environment, use corrosion-resistant materials.
   • Stainless steel or alloys are suitable for metal components like valves and screens.
4. Waterproofing:
   • Ensure the material is waterproof to prevent leakage.
   • Apply protective coatings or use materials inherently resistant to water infiltration.
5. Structural Strength:
   • Consider load-bearing capacity and stability.
   • Stone or brick masonry provides stability for smaller structures.
6. Maintenance and Cost:
   • Evaluate long-term maintenance requirements.
   • Some modern engines use thermoplastic materials (e.g., Nylon 6/6) for intake manifolds due to cost-effectiveness and corrosion resistance.

Common Issues of Intake Structures

Common challenges faced that affect the functionality and longevity of intake structures are enlisted here:

1. Leakage:
   • When the  upstream water level is higher than downstream level, water may form an alternative underneath path. .
   • Even the cracks in the bottom or sides of the structure can lead to leakage, which will comprome the structure’s effectiveness.

Solution: Proper design, construction, maintenance

2. Erosion:
   • Water flow around the base of the structure leads to erosion.
   • There are other factors too leading to erosion like weak foundations, inadequate materials, or poor soil support.

Solution: Regular inspections and timely repairs

3. Siltation:
   • Siltation is the accumulation of sediment (silt) within the intake structure. Slitation can reduce water flow.

Solution: Regular cleaning and removal of silt 

4. Rot and Rust (Corrosion):
   • Wooden components can rot over time, which affects the structural integrity.
   • Metal parts are susceptible to rust and corrosion, especially when exposed to saline environments.

Solution: Protective coatings and proper material selection

Successful Intake Structure Projects in the US

Los Angeles Aqueduct Intake, California: 

The Los Angeles Aqueduct Intake structures are vital components of the city’s water supply system. These intake structures draw water from the Owens Valley and Eastern Sierra Nevada Mountains. 

These intake structures have served to provide a reliable water system to the people of the Los Angeles metropolitan area. This has been very crucial for the growth and development of the city.

C.W. Bill Young Regional Reservoir, Florida: 

The C.W. Bill Young Regional Reservoir is located in Tampa Bay, Florida. It features innovative intake structures designed to enhance water quality and reduce environmental impacts. 

The surface water runoff is collected and stored in these reservoirs for use during the periods of water scarcity.

Successful Intake Structure Projects in India

Narmada Dam Intake, Gujarat: 

The Narmada Dam, also known as the Sardar Sarovar Dam, has intake structures that harness water from the Narmada River for irrigation, drinking, and hydropower generation. The project has significantly contributed to water security and agricultural prosperity in Gujarat and neighboring states.

Future Trends in Intake Structure Development

Future trends in intake structure development are very likely to be made in the field of 

• advancements in technology, 
• evolving environmental regulations, 
• the need for sustainable water management practices. 

Here are some potential future trends with respect to Water Intake Structures:

1. Innovative Materials and Construction Techniques: 

The future of intake structure development could see a shift towards using innovative materials like FRP, composites, and nanomaterials accompanied by modern construction techniques. 

These advancements will lead to benefits like longer lifespan of the structure, resistance to corrosion, and a smaller environmental footprint as compared to traditional materials.

2. Smart Intake Structures:

The future of intake structures can be imagined as smart intake structures as they might be integrated with sensors. Implementation of automation technology in the construction of intake structures will provide real-time monitoring, adaptive control, and predictive maintenance. Water intake operations might be more optimized with the invention of smart intake structures with reduced energy needs. This will lead to increased efficiency with enhanced environmental sustainability.

3. Environmental-Friendly Design: 

Environment friendly designs of future intake structures may have fish-friendly intake screens, bypass channels for aquatic organisms, etc. This may lead to minimized ecological impacts and enhanced habitat conservation.

4. Modular and Prefabricated Intake Systems: 

Modular and prefabricated intake systems can lead to speedy construction and they might even be cheaper. Easier maintenance can be achieved if the structures are customized to suit the site conditions. 

5. Desalination Intake Innovations: 

With increasing water scarcity, intake structures for desalination plants will undergo innovation to optimize energy efficiency, minimize environmental impacts, and reduce costs. Advances in seawater intake technologies, such as submerged intake systems and intake dilution techniques, may be adopted to mitigate ecological disruption.

6. Climate-Resilient Design: 

Intake structures will need to be designed with climate change resilience in mind, considering factors such as changing precipitation patterns, sea level rise, and extreme weather events. This may involve raising intake structures to account for higher flood levels, incorporating adaptive management strategies, and enhancing infrastructure robustness to withstand climate-related impacts.

7. Hybrid Intake Systems: 

Hybrid intake systems that combine multiple intake methods, such as surface water intakes, groundwater wells, and rainwater harvesting systems, may become more common. These integrated systems offer greater resilience to water supply fluctuations and enhance overall water resource management.

8. Community Engagement and Stakeholder Collaboration: 

Future intake structure development will increasingly involve community engagement and stakeholder collaboration to ensure inclusive decision-making, address concerns, and promote social acceptance. Public participation and consultation processes will play a crucial role in shaping intake projects and fostering sustainable water governance.

Summary 

Intake structures play a crucial role in water supply systems, intercepting water from natural sources and facilitating its treatment. 

– Intake structures are important for collecting water from sources and regulating flow

– Importance of intake structures includes access to water, water quality, reliability, regulated flow, environmental preservation, and emergency preparedness

– Factors governing location of intake structures include proximity to treatment plant, water quality, and avoiding contamination sources

– Components of intake structures include intake pipe, screens, trash racks, fish screens, gates, sedimentation chambers, pumps, and instrumentation

– Preventive measures for designing intake structures include hydrological analysis, water quality assessment, environmental impact assessment, site selection, debris management, fish protection, structural design, and operational flexibility

– Maintenance of intake structures involves regular inspections, cleaning, corrosion protection, structural repairs, sealing, monitoring, and emergency preparedness

– Materials commonly used for intake structures include stone or brick masonry, reinforced concrete, concrete blocks, thermoplastic materials, waterproof coatings, metal components, and geotextiles

– Common issues of intake structures include leakage, erosion, siltation, and rot/rust

– Successful intake structure projects in the US include Los Angeles Aqueduct Intake and C.W. Bill Young Regional Reservoir

– Successful intake structure projects in India include Narmada Dam Intake in Gujarat

– Future trends in intake structure development may involve innovative materials, smart intake structures, and advancements in technology and environmental regulations.