Utilizing renewable energy is essential to reduce reliance on highly polluting fossil fuels. Hydroelectricity is fueled by water, making it clean, affordable and non-polluting: it also offers additional benefits such as flood control, irrigation, and water supply. Furthermore, it is a domestic source of energy that allows each area to produce its own electricity without relying on international fuel sources. But does it have any detrimental effects on the environment?
How Does Hydroelectricity Work?
An impoundment facility - the most common type of hydroelectric plant – stores water in a reservoir behind a dam. Water released from the reservoir spins a turbine to activate a generator that produces electricity. The water can be released to meet electricity needs or maintain a constant reservoir level. Facilities like this also offer recreational opportunities for the wider community such as fishing, swimming, and boating.
Diversion or run-of-the-river facilities channel a portion of the river through a canal and often doesn’t require the use of a dam.
How Impoundment Facilities Affect the Environment?
Hydroelectric facilities can have huge impacts on the environment by changing the use of the land, which has knock-on effects on surrounding areas. Impoundment facilities require flooding huge areas, with the size of the generators and topography of the land dictating the scope of the reservoir. Those in flat areas also require more land than hilly areas, where deeper reservoirs can hold more water in a smaller space. Flooding destroys forests, wildlife habitats and agricultural land, even important natural areas. It can also require relocating whole communities.
Fish and other aquatic creatures veering to near to turbine blades can be injured or killed; to protect fish, adequate screening must be in place. Some dams can obstruct fish migration. In the Columbia River on the border of Oregon and Washington, salmon swim upstream to reach their spawning grounds, but installation of a series of dams have prevented their migration. To overcome this, fish ladders have been installed to help the salmon step up to their spawning ground.
Dammed reservoirs can also change the water temperature and river flow, harming native plants and animals both in the river and on land. They tend to lose water via evaporation at a higher rate than flowing rivers, and if too much water is held behind the dam, the river downstream can dry out. For this reason, operators are required to release a minimum amount at certain times of the year – if they don’t, animal and plant life is lost.
Reservoir water is more likely to be stagnant, leading to higher than normal levels of sediments and nutrients. This causes an excess of algae and aquatic weeds, which can crowd out other plant life and animals. Manual harvesting can prevent this excess, as can introducing fish to eat the plants.
Dammed water is also typically lower in dissolved oxygen and colder than river water, particularly at the bottom. Aerating turbines can introduce more oxygen into the water, and multilevel water intakes release water from different levels of the reservoir. In some reservoirs, methane forms and bubbles into the atmosphere.
However that’s not all – manufacturing the concrete and steel for the infrastructure releases emissions, most likely from burning fossil fuels. Given the typical operating lifetime of a hydroelectric plant is between 50 and 100 years, these emissions are likely to be offset by the emission-free electricity generated.
Global warming emissions produced during the installation – and dismantling – of hydroelectric power plants, and those released during use are significant. Their volume varies depending on the location of the reservoir – higher in tropical areas or temperate peatlands – and run-of-the-river plants tend to emit lower emissions than impoundment facilities.
Run-of-the-River Facilities and their Impact
Smaller run-of-the-river plants tend to have many of the same issues as impoundment plants during installation and running. They often have a lesser impact on the immediate environment, but can still affect the course of the river and river life. The amount of water the system requires from the main water course needs to be taken into consideration, as well as any changes in the river levels which may present a flood risk or cause drainage issues. There is also the issue of silt and sediment build up as a result of the processes, which could have a detrimental impact over a long period of time.
Renewable energy is never emission free; although the generation of hydroelectricity is free and clean, manufacturing and installing infrastructure releases emissions, as can general operation. Hydroelectric plants can have massive effects of the local environment, from flooding large areas, affecting the water and the fish and plants that reside there.