Who Builds Hydroelectric Dams?

Hydroelectric dams are large structures built across rivers to create reservoirs and harness the energy from flowing water to generate electricity. They operate by allowing water from the reservoir behind the dam to flow down through intake tunnels and spin large turbines connected to generators (see https://energyeducation.ca/encyclopedia/Hydroelectric_dam). The moving turbine blades cause magnets inside the generators to spin and produce an electric current.

The use of dams to harness hydropower dates back thousands of years, with simple water wheels capturing energy from rivers for milling grain. In the late 1800s, the first modern hydroelectric dams and power plants were developed. As of 2022, hydropower accounts for around 16% of global electricity generation and over 45,000 large dams have been built worldwide (see https://www.britannica.com/science/hydroelectric-power).

Hydroelectric dams range greatly in size and capacity. Smaller “run-of-river” dams rely on the natural flow of a river, while larger dams store vast amounts of water in reservoirs. Mega dams over 15 meters tall that generate over 100 MW of power are considered major infrastructure projects (see https://www.azocleantech.com/article.aspx?ArticleID=737).

Major Players in Dam Construction

There are many large construction companies that specialize in building dams around the world. Some of the major players include:

Strabag SE (www.waterpowermagazine.com/contractors/indexAtoZ.html) – Based in Austria, Strabag is a global construction company involved in projects related to transportation infrastructure, civil engineering, and building construction. They have constructed major dam projects around the world including the Ilısu Dam in Turkey and the Nenskra Dam in Georgia.

Salini Impregilo (www.waterpowermagazine.com/contractors/indexAtoZ.html) – Headquartered in Italy, Salini Impregilo has built major dams, hydroelectric plants, irrigation systems, water conveyance tunnels and water intakes globally. Some of their major dam projects include the Grand Ethiopian Renaissance Dam in Ethiopia, Rogun Dam in Tajikistan, and Karuma Dam in Uganda.

China Three Gorges Corporation (www.waterpowermagazine.com/contractors/indexAtoZ.html) – A Chinese state-owned enterprise, this company built the massive Three Gorges Dam across the Yangtze River which is the world’s largest hydroelectric power station. They are involved in the development and construction of dams both within China and internationally.

Flatiron (www.flatironcorp.com/market/dams) – Based in Colorado, Flatiron has extensive experience with complex dam projects across North America. They have constructed new dams as well as repair and rehabilitation of existing dams. Some of their major projects include Hungry Horse Dam in Montana and Yellowtail Dam in Montana.

Financing and Ownership

Hydroelectric dam projects require substantial capital investment. There are several financing options depending on whether the dam will be publicly or privately owned. According to the U.S. Department of Energy, the federal government provides incentives for qualified hydroelectric facilities through programs like the Hydroelectric Production Incentives fund which allotted $125 million in payments in 2022. These production incentives help offset project costs over the first 10 years of operation (DOE, 2023).

For larger private dam projects, long-term financing is secured against future cash flows and energy sales. As noted by ESFC Company, an international hydropower engineering firm, private dams financed this way are expected to generate revenue over decades to repay investors (ESFC, 2023). Ownership models for private dams include independent power producers who sell electricity, public-private partnerships, or full ownership by electric utility companies.

Publicly-owned dams are financed through municipal bonds, funding from public utility districts, or state infrastructure budgets. Local, state and federal agencies collaborate to fund public hydroelectric projects. The National Hydropower Association recommends project developers research all available incentives and funding programs when planning project financing (NHA, 2023).

Site Selection and Feasibility

Selecting the optimal site for a hydroelectric dam requires careful consideration of many factors. Geography plays a key role, as the ideal location will have an adequate water source and terrain suited for dam construction. According to Electronics Lovers, major geographic factors include proximity to a perennial river with substantial flow and volume, and surrounding topography like narrow canyons or gorges that allow damming the river. Environmental factors must also be examined, such as minimizing disruption to sensitive ecosystems and wildlife habitats.

Existing infrastructure is another important consideration during site selection, explains LinkedIn. Locations near existing transmission lines, roads, and construction facilities greatly improve the feasibility and reduce costs of dam projects. Sites with easy access to construction equipment and material transport will streamline the building process. Proximity to communities that need the power generated is also ideal. By weighing all these geographic, environmental, and infrastructure factors, planners identify optimal sites for hydroelectric dams.

Permitting and Regulations

Hydroelectric dam projects are highly regulated due to their potential environmental impacts. In the United States, the main regulatory body is the Federal Energy Regulatory Commission (FERC). FERC issues licenses and exemptions for non-federal hydropower projects under the Federal Power Act. All hydroelectric projects must go through an extensive environmental impact assessment process and obtain various permits before beginning construction.

The environmental impact assessment examines how the project will affect the environment, including wildlife, vegetation, water quality, recreation, and more. This involves extensive studies by engineers and scientists to analyze the existing conditions and predict the impacts of the proposed project. FERC reviews these assessments to determine if the project is in the public interest before approving permits.

In addition to FERC licensing, dam builders must obtain Clean Water Act Section 404 permits from the U.S. Army Corps of Engineers for impacts to navigable waters. Other permits related to water quality, endangered species, and more may be required from state and federal agencies before construction can begin.

Throughout the permitting process, there are opportunities for public input and comment. FERC and other agencies hold public meetings to gather feedback on the potential impacts of a proposed hydroelectric dam project.

Design and Engineering

The design and engineering of hydroelectric dams is a complex process that requires expertise across multiple disciplines, especially civil engineering and architecture. Some key aspects of dam design include:

• Site analysis and geological studies – Engineers conduct extensive analysis of the proposed dam site, including surveying the terrain, studying the underlying bedrock, and assessing seismic risks. This informs foundational and structural design.
• Hydrological modeling – Engineers model the river’s flow patterns, seasonal variations, and flood risks to determine optimal dam height, reservoir size, and spillway capacity.
• Structural design – Dams require enormous reinforced concrete structures engineered to safely withstand massive hydrostatic pressure and water loads.
• Spillway design – Spillways carefully regulate water flow and prevent overtopping. Their capacity is designed to handle extreme floods.
• Turbine selection – The type of hydropower turbine is chosen based on head height and flow volume. Pelton, Francis and Kaplan turbines are common choices.
• Powerhouse design – This houses turbines and generators, as well as transformer equipment and monitoring systems. It requires innovative architectural design.
• Reservoir planning – The dam’s reservoir size and shape is strategically designed to account for sedimentation and shoreline impacts.

Experts across civil engineering specialties like structural, hydrological, and geotechnical engineering collaborate to create safe, efficient dam designs. Architectural design is also crucial for aesthetic and functional powerhouse construction.

Construction Process

The construction process for a hydroelectric dam involves extensive preparation and coordination. According to Energy Education, the first step is diverting the river’s flow away from the dam site to allow construction to proceed in a dry area. The river may be diverted into a tunnel or a temporary diversion channel. Next, the foundation of the future dam is prepared by excavating down to bedrock and removing any unsuitable soil or material. The type of material used for the dam depends on the design, but common options are concrete, earth and rockfill.

Major equipment involved in dam construction includes excavators, bulldozers, dump trucks, cranes and concrete pumps and mixers. The timeline varies substantially depending on the size of the dam but large projects can take 5-10 years to complete. Key stages include diverting the river, constructing the dam foundation, building spillway tunnels, assembling the main dam structure, and adding generators and other equipment. According to ProEst, construction may occur in sections, with the dam growing incrementally higher over time. Throughout the process, strict quality control and safety procedures are followed.

Testing and Commissioning

The testing and commissioning phase is crucial to ensure the hydroelectric dam and power plant are functioning safely and efficiently before full operations begin. This involves extensive inspections, trial runs, and obtaining final regulatory approvals.

Comprehensive inspections review every component and system, like the dam structure, spillway, penstocks, turbines, generators, and electrical equipment. Civil works such as the dam and waterways undergo visual checks, geotechnical and structural tests, and trial impoundment periods to validate their integrity. The hydromechanical equipment including valves, gates, turbine runners, and generators are individually start-up tested before synchronizing their operations. Control, monitoring, and safety systems are thoroughly evaluated to confirm they meet requirements.

Trial runs simulating normal operating conditions, emergency shutdowns, and peak flows push the equipment to ensure it performs as intended. Output, vibrations, temperatures, pressures, and noise are closely monitored. Issues discovered during the trial runs are addressed prior to final commissioning. According to the Chamera III plant commissioning, this testing period lasted about 3 months.

Extensive documentation of the testing and inspection results is compiled for the operating manual and submitted to regulatory agencies. Final commissioning requires sign-off from safety inspectors and environmental regulators that the project meets all codes and permit requirements. Common agencies involved are FERC in the U.S. and CEA in India.

Operation and Maintenance

Operating and maintaining a hydroelectric dam is critical to ensuring safe, reliable, and efficient power generation. Hydro dams have extensive systems that require periodic monitoring, maintenance, and repairs.

To operate the dam, control room operators monitor and regulate reservoir levels and water flow by opening and closing spillway gates and adjusting turbine wicket gates. They regulate power output based on electricity demands and optimize generation efficiency. Operators also monitor dam safety systems to identify any issues (Source).

Routine maintenance activities include inspecting the dam structure and equipment, lubricating components, cleaning trash racks and intakes, testing warning systems and safety equipment, and observing for signs of issues like cracks, leaks, vibrations, or erosion. Maintenance helps minimize unplanned outages and prolong the lifespan of equipment (Source).

Repairs involve fixing or replacing any damaged or worn components. Common repairs include patching concrete, repairing gates and valves, refurbishing turbines, replacing broken sensors, welding cracked penstocks, and more. Performing timely repairs prevents small problems from becoming major failures.

Environmental and Social Impacts

Hydroelectric dams can have significant environmental and social impacts, both upstream and downstream from the dam. According to the U.S. Department of Energy, “the end effect of hydropower facilities is often some degree of disruption to fish and wildlife habitats and migration patterns.”¹

Building a dam floods large areas of land upstream, displacing both human populations and wildlife. According to the Union of Concerned Scientists, over 80 million people worldwide have been displaced by dam construction.² This forces communities to relocate and fragments wildlife habitats. Downstream ecosystems are also disrupted due to changes in water flow and quality.

Dams impact fish migration patterns by blocking access to spawning grounds. They also change the quantity and timing of water flows, which can impact food supply and breeding cues. Dams reduce sediment flow, causing downstream erosion. They also impact water temperature, oxygenation, and nutrient levels.³

There are measures that can reduce environmental impacts such as installing fish ladders, maintaining minimum water flows, and preserving riverine habitats. However, fundamentally, hydroelectric dams disrupt the natural flow of the river with consequences for surrounding ecosystems and communities.