More than 4000 hydroelectric dams have been built in the United States since the late 19th century, representing six percent of all-time additions to electric generation capacity from all sources.
Dams serve various purposes such as navigation improvement, flood control, and electricity generation. There are over 40,000 dams worldwide, with significant hydroelectric capacity. The environmental impact of these large projects, including disturbance of ecosystems and displacement of communities, must be carefully assessed and balanced with their low-cost and low-carbon benefits.
Hydropower, a pioneer in grid-scale electricity generation since the late 19th century, now provides 17% of global electricity, surpassing nuclear, wind, solar, bioenergy, and geothermal combined. While the US and Europe have well-established capacity with limited room for expansion, China, India, Africa, and South America are developing new projects to meet rising electricity demand and reduce greenhouse gas emissions.
Hydropower plants utilize different technologies to generate electricity. Impoundment facilities use a dam to create a reservoir, releasing water through turbines. Run-of-river plants channel river water to generate power while pumped storage hydropower stores energy by moving water between reservoirs of different elevations. Each technology has its advantages and impacts on the environment and infrastructure.
Pumped storage plants for hydroelectric power in the United States were primarily built between 1960 and 1990. There have been no new projects since 2012, but three new ones have been proposed, potentially adding 2.6 GW to the existing 22 GW capacity. The largest facility is the Bath County Pumped Storage Station in Virginia, with 2.9 GW.
Hydropower, the world’s largest source of renewable, low-carbon electricity, faces a significant gender gap. Women hold only a quarter of jobs globally, mainly in non-technical roles. Factors hindering women include a lack of STEM skills, limited awareness, inadequate female role models, and managerial bias. Improved family-friendly policies and female inclusion in policymaking are required for industry advancement.
Hydropower’s history traces back to 1882 when the first facility began supplying electricity in Wisconsin. Its adoption surged across North America, Europe, and beyond, with China notably driving expansion in recent decades. Hydropower now contributes 17% of global electricity, surpassing nuclear, wind, solar, bioenergy, and geothermal combined.