Can Hydro-Power Run Out?

Hydropower or hydroelectricity refers to the process of generating electrical power by harnessing the energy from flowing water. According to the Britannica Dictionary, hydropower is defined as “electricity produced from machines that are run by moving water.” Hydropower plants capture the energy of falling or flowing water to produce electricity. Typically, hydropower uses dams on rivers to store water in reservoirs which is then released through turbines connected to generators to generate electricity. Hydropower is considered a renewable energy source since it relies on water which is continuously replenished through the water cycle.

How Hydropower Works

Hydropower is generated by using the natural flow of water in rivers or streams. A hydropower plant utilizes the energy of flowing water by channeling it through a pipe or tunnel called a penstock towards a turbine. As the water flows over the turbine blades, it causes them to spin, converting the kinetic energy of the moving water into mechanical energy and rotating a shaft. The turbine shaft is connected to a generator which converts the mechanical energy into electricity.

Most hydropower plants use dams to raise the level of a river and create a height difference or head between the water upstream of the dam and the turbine below the dam. The greater the head and flow of water, the more electricity that can be generated. The water held behind the dam in a reservoir provides sustainable water flow through the turbines.[1]

After passing through the turbine, the water flows back into the river downstream. This process is highly efficient and recycles the water through the system repeatedly.

Global Hydropower Capacity

Global installed hydropower capacity was estimated at 1,360 GW in 2021, according to the 2022 Hydropower Status Report from the International Hydropower Association ( This represents an increase of 26 GW from the previous year. The top regions for hydropower capacity are Asia (44% of global capacity), Europe (19%), North America (19%), South America (11%), and Africa (6%). China has the highest installed capacity at over 380 GW, followed by Brazil, Canada, the United States, and Russia as the top five countries. While growth has slowed compared to previous decades, hydropower still provides 71% of all renewable electricity globally and remains the largest renewable energy source for electricity generation.

global installed hydropower capacity reached 1,360 gw in 2021

Hydropower Resources are Renewable but Finite

While hydropower is classified as a renewable energy source, the amount of power it can generate is finite and limited by nature. The “fuel” for hydropower is flowing water, which is continuously renewed through the water cycle of evaporation, condensation, and precipitation. However, the amount of precipitation and geographical factors limit the water available for hydropower generation. As water flows downstream, energy is continuously renewed but the volume of water is fixed based on weather patterns and terrain. Unlike fossil fuels which can eventually run out, water will continue flowing indefinitely. But the total energy obtainable from a hydropower system does have an upper limit based on hydrology and plant design.

The amount of energy available at any given site depends on factors like head height (the distance water falls), flow rate, and overall volume of water. While precipitation can fluctuate seasonally and annually, over the long-term the energy potential from a dam or river is largely fixed. Climate change further complicates hydropower generation as rainfall patterns shift. While hydropower resources are sustainable and renewable, the total energy output obtainable is constrained by nature and subject to variations.

Factors That Can Reduce Hydropower Output

While hydropower resources are renewable, there are several factors that can reduce output from existing hydropower facilities over time.

One major factor is drought and reduced rainfall which limits water availability. Many hydropower dams depend on adequate water levels and river flows to function optimally. Prolonged droughts like those caused by climate change can reduce water inflows significantly (source). With less water to pass through turbines, power generation is hampered.

Siltation, which is the accumulation of silt or sediment in the reservoir, also decreases storage capacity and power potential at hydropower stations over time. Silt is carried downstream by rivers and builds up behind dams, taking away from the amount of water that can be used for electricity generation.

In addition, climate change is projected to impact precipitation patterns and glacial melt rates, which will alter the water cycle and affect river flows relied upon by hydroelectric dams. More extreme floods and droughts could strain hydropower output.

Implementing mitigation strategies like dredging and watershed management can help maximize hydro resources. But ultimately, factors like drought and climate change impacts may mean existing facilities generate less power than originally designed for.

Maximizing Existing Hydropower Resources

There are ways to optimize existing hydropower dams and infrastructure to maximize energy generation capacity. Upgrading to more efficient turbine technologies is one approach. Modern turbine designs can capture more energy from the same water flow compared to older turbines. For example, a 2021 study found upgrading to new bulb turbines increased annual power generation at a Brazilian hydropower plant by over 8% (source). Turbine upgrades require capital investment, but can significantly boost output.

Optimizing dam operations is another way to maximize hydropower potential. Sophisticated algorithms can determine optimal release schedules to balance multiple objectives like energy generation, flood control, irrigation needs and environmental flows. For instance, machine learning techniques applied at China’s Three Gorges Dam improved power output by 2.72% compared to conventional rule-based operation (source). Better coordination between dams along a river network can also increase overall generation capacity.

Lastly, sustained investments in maintenance and modernization can improve efficiency and extend the operational lifetime of existing hydropower assets. With careful management and smart technology upgrades, we can extract more clean energy from existing infrastructure.

Expanding Hydropower Sustainably

While hydropower is a renewable resource, expanding hydropower capacity requires careful consideration of environmental impacts. New dam construction can disrupt river ecosystems and fisheries, inundate habitats, and alter sediment transport downstream (Ahmad, 2021). Working closely with stakeholders including local communities, environmental groups, and government agencies is key to sustainable hydropower expansion.

Environmental impact assessments should be conducted for all new hydropower projects. Mitigation strategies like fish ladders, minimum flow requirements, and sediment management can help reduce damages to river health. Selecting project sites with minimal biodiversity impacts is also important. Upgrades to existing dams can sometimes increase power output with less environmental disruption than building new dams.

Following best practices for sustainability, engaging with stakeholders throughout the process, and pursuing low-impact configurations can allow hydropower capacity to expand while protecting river ecosystems. With proper planning and partnerships, hydropower can continue growing as part of a renewables-based energy future (DOI, 2010).

Other Renewables Can Supplement Hydropower

While hydropower is a major source of renewable electricity globally, relying too heavily on hydropower alone can be risky if drought or other factors reduce output. Combining hydropower with other renewable sources like wind and solar photovoltaics (PV) can provide more resilient renewable electricity capacity.

Wind and solar PV output tends to complement hydropower seasonally. For example, wind speeds often increase during dry seasons when hydropower output is lower. And solar PV generates more electricity during sunny days when overall electricity demand is higher. According to an analysis by Li et al., a hybrid system utilizing hydropower, wind, solar PV and energy storage can provide more stable and economical renewable power than hydropower alone (Li, 2023).

Strategically integrating complementary renewable sources like wind and solar with existing hydropower improves resilience and flexibility of renewable electricity. Hybrid renewable systems can meet demand during fluctuations and outages from any one source. This integration and optimization of multiple renewables helps maximize the use of available renewable resources (Utilities One, 2023).

The Future of Hydropower

Many experts see hydropower playing an essential role in a decarbonized electricity grid due to its ability to provide reliable power and grid services. Hydropower is viewed as a critical enabling resource, supporting the integration of variable renewable resources such as wind and solar.

As stated in the Hydropower Vision Report, “Increased deployment of hydropower could enable greater grid flexibility and greater integration of variable renewables into the U.S. electric grid…” (A New Vision for United States Hydropower, 2016).

Innovations in hydropower technology can further enhance the value and flexibility of hydro resources. Some key areas being explored include:

  • Advanced turbines and control systems to improve grid integration capabilities.
  • New pumped storage configurations to increase storage capacity.
  • Upgrades at existing dams to increase efficiency and power production.

With continued technology advancement and sustainable development, hydropower is poised to meet a significant portion of renewable energy needs in a decarbonized future.


In summary, hydropower is a renewable resource but not an unlimited one. The amount of power generated depends on water flow, which can vary due to climate, droughts, population growth, and environmental concerns. While hydropower capacity has expanded globally, there are limits to suitable new sites. Existing facilities can be upgraded for greater efficiency, but most major rivers are already dammed.

Rather than expecting hydropower alone to meet all energy needs indefinitely, it can be part of a diverse renewable mix. Other sources like solar, wind, geothermal and newer technologies will likely play bigger roles. With sustainable management of watersheds and fisheries, hydropower can continue serving communities for decades to come. But it is not a limitless resource.

The key is to maximize hydropower’s capabilities through innovation while balancing environmental and social impacts. This will allow hydropower to remain a major clean energy provider in the global renewable transition. But ultimately its potential is finite, and growth will depend on emerging technologies to complement it.

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