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The History Of Hydro

Hydropower tells a complicated tale of energy history

March 2023

The Hoover Dam in Nevada generates about 4 billion kilowatt-hours of hydropower annually. That power is used by 1.3 billion people in Nevada, Arizona and California.

by Paul Wesslund, Contributing Columnist

Electricity generated from hydropower tells an interesting story about today’s energy trends that’s deeper than just water flowing over the dam.

It’s a story about a renewable resource that once generated nearly a third of the nation’s electricity; a share that has declined dramatically over the decades with the rise of nuclear power, natural gas and even wind and solar.

More recently, it’s told a story about how weather and climate can affect energy supplies, as the extended drought —especially in the western United States—has reduced the amount of water available to generate power.

It’s also a story about diversity in fuel sources. Although hydropower is less a part of our energy picture than it was back then, it’s still a useful part of today’s energy mix. And in certain areas of the country, it’s one of the most important parts of a strong regional economy.


Hydropower works by converting falling water into energy. That could come in the form of a water wheel turned by a flowing river at an old New England grain mill, or from a giant dam built on a river both for flood control, as well as to channel the water through a large turbine that generates electricity.

Hydropower generates about 6% of the nation’s electricity. That’s not much compared to fuels like natural gas at 38%, but those averages hide its local importance. All but two states receive at least some of their electricity from hydropower. In the 1930s, dams went up across the Tennessee River valley and in the western states. Today, Washington State receives two-thirds of its electricity from hydropower.

While flowing water might seem to be an endless energy source, hydropower has a complicated relationship with the environment.

Some question hydro’s claims as a provider of clean energy since the larger projects involve building a huge dam that floods a river valley to create a reservoir. But the Environmental Protection Agency classifies hydro as a renewable resource, and U.S. Department of Energy (DOE) figures list hydroelectricity as the source of 31% of the nation’s renewable electricity.

Recent weather patterns also seem to be redefining what renewable energy means.Hydroelectric generation fell 9% during 2021 because of drought conditions.


Still, hydro has a lot going for it. It’s one of the cheapest forms of energy, especially after the initial investment costs. Its normal operations don’t produce greenhouse gases. And utility grid operators like its flexibility as a source of electricity that can be turned on and off relatively easily, especially compared with fuels like coal, nuclear, solar and wind.

Those assets have raised interest in adding new hydro projects. Some $8 billion has been invested over the past 15 years to add enough capacity to power one million homes. While many hydro dams have been around a long time and are ready to be retired, new projects are planned, including modernizing older hydro facilities. The DOE reports proposed projects that could generate enough electricity to power yet another one million homes.

In addition to upgrading existing sites, DOE reports at least 200 “non-powered dams” could have generators added. Out of about 90,000 dams in the U.S., only about 2,200 generate electric power.

Those efforts will be getting a boost from the federal infrastructure law passed in 2021. That measure includes more than $2 billion in hydropower incentives for river restoration and dam rehabilitation.

Hydropower doesn’t always get the attention of flashier advancements like wind and solar technologies. But it’s been around for 2,000 years, when the Greeks used it to turn wheels that ground wheat into flour.

Only the future will tell how much of a role hydro will play, but its time-tested techniques and green energy benefits promise it will still be providing some level of power 2,000 years from now.

Paul Wesslund writes on consumer and cooperative affairs for the National Rural Electric Cooperative Association.