Is Hydro Energy Worth It?

Hydroelectric power, also called hydropower, is electricity generated from flowing water. It harnesses the energy of flowing rivers or waterfalls to produce electricity via a turbine and generator (International Energy Agency, https://www.iea.org/energy-system/renewables/hydroelectricity).

Humans have used hydropower for thousands of years, but it began being used to generate electricity in the late 19th century. The first hydroelectric power plant opened on the Fox River near Appleton, Wisconsin in 1882 (https://www.iea.org/energy-system/renewables/hydroelectricity).

Today, hydropower is the largest renewable energy source for electricity generation globally. As of 2022, hydropower accounted for around 16% of total global electricity production and over 70% of all renewable electricity (Our World in Data, https://ourworldindata.org/grapher/hydropower-consumption). In the United States, hydropower generates around 7% of total electricity.

Benefits of Hydropower

Hydropower is considered a very beneficial and valuable energy source for several reasons. First, hydropower is renewable and sustainable. Hydropower relies on the water cycle and is therefore an inexhaustible resource as long as there is an adequate water supply (Department of Energy, n.d.). Hydroelectric power plants are powered by flowing water, not fossil fuels, so they produce clean electricity without emitting greenhouse gases or other pollutants.

Second, hydropower has relatively low operating costs because the ‘fuel’ (flowing water) is free. The initial construction costs for hydropower facilities can be high, but once built and operational, the electricity generation costs are quite low compared to fossil fuel plants (Enel Green Power, n.d.).

Third, hydropower can provide reliable baseload power. Hydropower plants typically have the ability to start up and shut down quickly to meet peak demands. Additionally, hydropower can adjust rapidly to changes in electricity demand since the flow of water can be increased or decreased through the turbines (Department of Energy, n.d.).

Fourth, hydropower has inherent energy storage capabilities. By using pumped storage hydropower facilities, water can be pumped uphill into reservoirs when electricity demand is low to be released and generate electricity when demand is high (Enel Green Power, n.d.). This provides a way to store energy and balance electricity supply and demand.

Drawbacks of Hydropower

While hydropower provides clean and renewable energy, it also has some significant drawbacks. Some of the main issues are:

High upfront costs – Building large dams and reservoirs requires huge capital investment upfront. According to one source, the initial project costs per kWh for hydropower can be high compared to other renewable sources like wind or solar.

Impact on rivers and wildlife – Dams drastically alter the natural flow of rivers and can harm the plants, fish, birds and other wildlife that depend on the river ecosystem. Hydropower turbines can also injure or kill fish that get caught in them.

Drought sensitivity – Hydropower depends on adequate water flows. During droughts, hydropower facilities may have to shut down or operate at reduced capacity. This can lead to blackouts if hydropower is a region’s main electricity source.

Methane emissions – Organic matter like trees and plants flooded by dam reservoirs produce methane as they decompose underwater. This is a potent greenhouse gas that can undermine hydropower’s low-carbon benefits.

Small vs Large Hydropower Projects

Hydropower projects vary greatly in scale, with small hydropower defined as under 30 megawatts (MW) according to the California Energy Commission, while large hydro includes facilities above 30 MW (Types of Hydropower Plants). The scale of a hydropower project has implications for environmental impacts and costs.

Small hydropower projects are often touted as more environmentally friendly, as they involve building smaller dams and infrastructure. However, one study found that small hydropower actually created over 7 times more barriers like dams compared to large projects. This fragmentation of rivers can negatively impact migratory fish and ecosystems (The Unexpectedly Large Impacts of Small Hydropower).

In terms of costs, large hydropower facilities require massive upfront investments but can generate electricity fairly cheaply over time. Smaller facilities cost less to construct but may have higher costs per unit of electricity generated. Overall costs depend on the site conditions and project design.

Hydropower and Climate Change

Hydropower plays an important role in the transition to clean energy and reducing greenhouse gas emissions. According to the International Energy Agency, hydropower meets 16% of global electricity demand and provides over 85% of all renewable electricity globally^[1]. As a renewable energy resource, increased investment in hydropower can help displace fossil fuel electricity generation and contribute to climate change mitigation goals^[2].

However, hydropower systems are also vulnerable to the impacts of climate change. Changing patterns of precipitation, rising temperatures affecting evaporation rates, melting glaciers, and shifts in seasonal runoff all influence hydropower potential and generation^[3]. More variability and uncertainty in water availability due to climate change can create challenges for hydropower operation and planning. Extreme weather events like floods and droughts also threaten hydropower infrastructure. Adaptation measures like increased storage capacity, improved forecasting tools, and climate risk assessments may be needed to increase the climate resilience of hydropower projects.

Overall, while hydropower can aid the clean energy transition, steps must be taken to ensure hydropower systems are designed and operated sustainably, equitably and adapted to intensifying climate impacts.

^[1] https://www.iea.org/events/iea-at-cop27-the-role-of-hydropower-in-achieving-climate-resilience

^[2] https://www.hydropower.org/what-we-do/climate-change

^[3] https://www.energy.gov/eere/water/articles/effects-climate-change-federal-hydropower

Environmental Impacts

Hydroelectric power has several negative environmental impacts, largely stemming from the dams and reservoirs required to generate electricity. Dams significantly alter river ecosystems and disrupt natural water flows.

One major impact is the disruption of fish migration and spawning. Dams act as a physical barrier that blocks many fish species from reaching their traditional spawning grounds upstream [1]. This can decimate local fish populations that are unable to reproduce. Some hydro facilities have installed fish ladders to help mitigate this issue, but their effectiveness varies.

Dams also change natural sediment flows in rivers. The reservoirs act as sediment traps, depriving downstream habitats of nutrients and altering riverbanks and coastal ecosystems [2]. Over time, the lack of sediment replenishment can damage aquatic and riparian habitats.

Other notable impacts include loss of terrestrial wildlife habitat and agricultural land when valleys are flooded to create reservoirs. Overall, dams disrupt ecosystems and can threaten biodiversity in river environments.

Social & Cultural Impacts

Hydropower dam projects often require the resettlement of communities living in the area that will be flooded by the reservoir. This can cause major disruptions and hardships as people are forced to leave their homes and relocate. For example, the Three Gorges Dam in China required the resettlement of over 1.4 million people (UN, 2021).

Resettlement sometimes fails when the new settlements lack adequate housing, infrastructure, or means of livelihood. According to Cernea (2004), resettlement related to hydropower dams has impoverished many communities when their productive systems were dismantled and livelihoods were not restored. Studies suggest resettlement caused by dams disproportionately impacts indigenous communities, ethnic minorities, and vulnerable social groups.

Dams and reservoirs also often inundate locations of cultural or religious significance, such as sacred sites, graves, and archaeological ruins. This can be devastating for local cultural heritage and identity. When the Braldu Valley in Pakistan was flooded for a hydroelectric dam, hundreds of cultural sites were lost, severely impacting local Buddhist heritage (UNESCO, 2021).

Changes to river flows and landscapes caused by dams also transform livelihoods and traditional ways of life that are closely tied to the local ecosystem. For instance, downstream floodplain farming may be disrupted, while reservoir fisheries require adaptation to the new conditions (Cernea, 2004). Such impacts can undermine food security, economic stability and community resilience.

Improving Sustainability

There are several ways hydropower projects can be designed and operated to reduce environmental impacts and improve sustainability. Strategic site selection is important – locating projects on existing dams or conduits rather than free-flowing rivers avoids fragmentation and allows fish passage (1). Building fish ladders and bypass systems creates routes for fish migration past dam barriers. According to researchers at MIT, new technologies like flexible membrane barriers can allow fish passage without energy losses (2).

Mimicking natural flow patterns through environmentally optimized operating rules can maintain downstream habitat and ecosystems. Limiting hydropeaking surges and maintaining minimum flows prevents the stranding of aquatic species. Monitoring biodiversity and supporting conservation programs also enhances sustainability (1). Overall, careful planning and innovative solutions can allow hydropower to generate renewable electricity while coexisting with healthy rivers.

The Future of Hydropower

There is still major untapped potential for hydropower globally, especially in developing regions like Africa and South America. According to the International Energy Agency, only about 22% of technically feasible hydropower potential has been utilized so far (IEA). With technology improvements like advanced turbines, pumped storage, and small/low-head hydropower, even more of the world’s feasible hydropower capacity could be harnessed in the future.

However, hydropower does face increasing competition from other renewable energy sources like wind and solar. These technologies have seen dramatic cost reductions in recent years, making them highly competitive alternatives for new power generation capacity. There are also sustainability concerns around large hydropower dams that may limit growth potential. Overall though, hydropower will remain an essential renewable energy source globally, especially for providing flexible grid balancing services.

Conclusion

In summary, hydropower offers both benefits and drawbacks as an energy source. On the plus side, it provides renewable, low-emission electricity and supports grid reliability. Dams also offer flood control, water storage, and recreational opportunities. However, hydropower projects can negatively impact local ecosystems, wildlife, homes, and cultural sites. Large dams are controversial, but smaller run-of-river projects have less impact.

Looking ahead, hydropower will likely play an important but balancing role in the renewable energy mix. It offers flexibility to complement variable solar and wind power. However, continued technological and sustainability improvements will be needed to minimize hydropower’s environmental footprint. With proper planning and mitigation, hydropower can support the transition to a clean energy future while protecting our natural and cultural resources.