Hydro Power Generation and Aquatic Life Protection

 

Hydropower generation may seem complex but it primarily involves releasing water from the reservoir to the turbines which activates the generators that convert the mechanical energy to electrical energy.

Like other renewable sources of energy (solar, wind, and coal), hydropower generation ensures that clean and sustainable electricity is produced

Although hydropower provides clean electricity, it causes a lot of damages to the environment including harm to aquatic life. The effects of hydropower generation on aquatic life are very complicating and require evaluating the lifecycle of hydropower plants. However, new and improved hydropower technologies are being put in place to protect aquatic life and make hydropower a cleaner source of power.

READ ALSO: Autonomous Mini Hybrid Hydro Power Plant

In this article, we will examine how hydropower is generated, its effects on the environment especially on aquatic life, and how aquatic life can be protected.

 How Does Hydro Power Generation Work?

Hydropower generation began in the 20th century and it is the oldest form of energy conversion. Studies show that hydroelectric power was the most widely used form of renewable energy source in the early 21st century. In addition, the hydroelectric power supply accounted for over 18% of the world's total power generation capacity in 2019.

For hydroelectric power to be generated, water is collected at a higher elevation and made to run down through large pipes or tunnels (penstocks) to a lower elevation. The difference between the higher elevation and lower elevation is called ahead.

This water flowing through the pipes causes the turbines to rotate which in turn drives generators. The driving of the generators converts the turbines' mechanical energy into electrical energy. Transformers are connected to the generators to convert the alternating voltage to a higher voltage for long-distance transmission. A powerhouse houses the turbines and generators.

Hydroelectric power plants are usually constructed in dams that contain a large volume of water that creates a high head every time. The potential power of a volume of water is proportional to the head whereby a high-head installation needs a smaller volume of water than a low-head installation to generate an equal amount of power.

Some dams have their powerhouses built on one flank whereby a part of the dam serves as a spillway where excess enters during flooding. In a situation where the river flows in a narrow steep gorge, the powerhouse is built inside the dam.

On the other hand, the demand for electricity supply varies at different times of the day. To this effect, pumped-storage generators are now constructed to lessen the burden on generators. In times of off-peaks, the extra power available is supplied to the generator to drive the turbine so that water is pumped into the elevated reservoir. During times of peak demand, the water is freed to flow down again through the turbine so that electricity can be generated.

In coastal areas, hydropower plants are built where tides rise and fall steadily. If the tide rises, water is collected or stored in the reservoir, once the tide falls, the water in the reservoir is allowed to drive the turbines and the generators to produce electricity.

Effects of Hydro Power Generation on Aquatic Life and Other Parts of The Environment

Hydropower provides clean and cost-effective electricity for use in the home, office, industry, etc. However, the generation of hydropower causes a lot of harm to aquatic life and other parts of the environment. These damages are discussed below.

READ ALSO: Autonomous Mini Hybrid Hydro Power Plant

Damages on Aquatic Life

The building of large pumped-storage hydropower plants lead to the blocking and diversion of the natural flow of rivers. This results in the blocking of the migration routes of fishes in the river.

Many fishes including Atlantic salmon or European eel (migratory fishes) spend part of their lives and reproduce in the sea and in freshwater. While migrating upstream and downstream into utilized watercourses, they are blocked at some dams and exposed to danger as a result of the passage of the turbines from the hydropower plants. The blockage will prevent them from getting to their breeding grounds. By not getting to their breeding grounds, they cannot reproduce and this causes a reduction in the population of fishes. The reduction in the population of fishes means that there will be reduced aquatic food for humans.

In addition, some hydropower plants are constructed with fish ladders to help fishes cross dammed rivers, but the fish ladders are hardly big enough to help fishes migrate in large numbers.

The construction of dams in rivers usually reduces the flow of water and sediments to dangerous levels and this impacts downstream aquatic populations. The reduction in the flow of water and sediments (low water flow downstream and low nutrient flow) can result in the loss of habitat and healthy water for aquatic life.

Land Use

Several large hydropower plants impact the landscape of the environment especially around reservoirs created by damming rivers. Like the damages caused by downstream water flow, the construction of reservoirs to generate electricity in storage and pumped-storage hydropower systems usually lead to upstream flooding. This upstream flooding damages aquatic habitat and farmlands. On certain occasions, upstream flooding causes the human population to relocate to another geographic area.

 Greenhouse Gas Emissions from Reservoirs

The generation of electricity by turning the turbines with water does not involve the burning of fossil fuels or the emission of greenhouse gases. However, recent and emerging research shows that reservoirs created by damming rivers contribute to the emission of greenhouse gases in the atmosphere.

How does this happen? Whenever reservoirs trap organic materials including dead plants, these materials break down and release gases such as carbon (iv) oxide (CO2) and methane (CH4) into the reservoir water.

Protection of Aquatic Life in Hydro Power Generation Areas

The dangers posed by hydropower generation can be reduced so as to protect aquatic life and make hydropower systems to be environmentally friendly.

Aquatic life can be protected in hydropower areas by planning land use very well around the river basin upstream of dams. If the natural environment in a river's watershed is well-protected, erosion will be controlled very well. This will help to reduce greenhouse gas emission from the reservoirs into the atmosphere since there will be reduced decaying organic materials in the water.

On the other hand, efforts are being put in place to reduce the effect of hydropower on aquatic habitat and migrations. Here, some hydropower systems are constructed with trap-and-haul programs so that they can collect fishes, transport them over a dam, and release them.

Recently, the Department of Energy (DOE) sponsored research and development of salmon cannons that launch migrating fishes over a dam.

Above all, a long-term solution that is more feasible will be to carefully plan the construction of dams so that no disturbances will affect migration paths. Another option that will help to protect aquatic life in hydropower regions is to remove old dams so that the river flow can return back to its natural state. This will lead to the restoration of the habitat for fishes to live in and reproduce.

References

Hydroelectric Power: How it Works

Hydropower Generation and Its Related Impacts on Aquatic Life

Fish Protection at Hydroelectric Power Plants