Hydropower, the process of generating electricity from moving water, has historically been a major contributor to the global energy mix. It currently provides around 14% of the world’s electricity and remains the largest source of renewable electricity generation globally, though its share is expected to decline as solar and wind expand rapidly. While capacity growth has slowed in many developed nations, the industry is shifting away from new, large-scale dam construction toward modernization and flexibility. The future of hydropower lies in its ability to adapt its function, embrace new technologies, and address environmental pressures to become an integrated and reliable partner to modern power systems.
The Evolving Role in Modern Grids
The defining feature of hydropower in the coming decades will be its unique ability to provide grid flexibility, which is increasingly valuable as more intermittent renewable sources like solar and wind are deployed. Hydropower plants can quickly adjust their power output, referred to as ramping capability, allowing them to balance the rapid fluctuations inherent in variable generation. This instantaneous response capability is a functional advantage that few other generation sources possess.
Hydropower is also highly valuable for providing ancillary services, which are necessary functions that maintain the stability and quality of the electrical grid. These services include frequency regulation, where the plant constantly adjusts output to keep the system frequency stable, and voltage control, where it provides reactive power support. For instance, despite representing less than 10% of U.S. electricity capacity, hydropower provides approximately 40% of the resources needed for “black start” capability—the ability to restore power to the grid following a complete system-wide blackout.
The dispatchable nature of hydropower, meaning its output can be controlled on demand, makes it an ideal partner for variable renewables. When solar production drops off in the evening or wind speeds fall, hydropower can rapidly ramp up to fill the resulting energy gap, ensuring continuous and reliable power supply. This function effectively turns the water stored in reservoirs into a large-scale, long-duration energy storage system, acting as a natural battery for the power system. The capability to quickly change power outputs makes it suited to stabilizing the grid during extreme weather events or sudden system disturbances.
Technological Advancements and Innovations
A primary driver of new capacity and grid flexibility is the expansion of Pumped Storage Hydropower (PSH). PSH facilities store energy by pumping water from a lower reservoir to an upper reservoir when electricity prices are low or supply is abundant, then releasing the water to generate power when demand is high. This technology is a mature and proven form of long-duration energy storage, necessary to integrate high levels of variable renewables. China, for example, has significantly invested in PSH, reflecting global ambitions to treat these water batteries as a component of the future energy system.
Beyond new construction, a major focus is on the modernization of existing hydropower assets, known as repowering. Much of the global fleet is aging, with a significant portion expected to be over 55 years old by 2030, necessitating the replacement of major electromechanical equipment. Modernization involves upgrading turbines, generators, and control systems to increase efficiency, boost capacity, and enhance flexibility without constructing new dams. This repowering effort is forecast to account for a large percentage of total hydropower investment in regions like North America and Europe over this decade.
Another avenue for growth is the development of low-impact generation, often involving existing infrastructure. This includes adding generation capacity to existing non-powered dams (NPDs) originally built for flood control or irrigation. New technologies like variable speed pump-turbines and hybrid systems that couple PSH with battery storage are emerging to enhance performance and provide a broader range of grid services, such as faster frequency response. These innovations, including modular turbine designs, make small-scale repowering projects more feasible and cost-effective.
Climate Adaptation and Environmental Mitigation
Hydropower’s long-term viability is intrinsically linked to its ability to manage the challenges of climate change and ecological preservation. Climate change introduces significant uncertainty, primarily through changes in hydrological patterns that lead to reduced water flows from prolonged droughts or extreme flooding events. Hydropower facilities are increasingly adjusting reservoir operating policies and water release schedules to manage fluctuating inflow conditions and minimize unproductive water spills.
Infrastructure improvements are necessary to ensure resilience against climate impacts, such as reinforcing dams to safely handle higher flood levels. The industry is focused on implementing the Hydropower Sector Climate Resilience Guide to systematically identify and manage climate risks. This planning includes designing facilities with more efficient turbines that can generate more power with less water, a direct response to potential water scarcity.
To mitigate environmental impacts, innovation is focused on improving ecological flow and fish passage. This involves designing and implementing advanced fish ladders and screens to protect aquatic life during migration. Sediment management is also a concern, as the buildup of sediment behind dams reduces reservoir capacity and impacts downstream river ecosystems. Addressing these ecological and climate-related constraints is fundamental to ensuring that hydropower remains a sustainable and accepted component of the future energy landscape.