Hydropower - Wikiparency

# Hydropower **Hydropower** is the use of falling or fast-running [[Water|water]] to produce electricity or to drive machines. A hydropower plant converts the gravitational potential [[Energy|energy]] of water held at a height, or the kinetic energy of a moving stream, into shaft work through a wheel or turbine, and usually from shaft work into electricity. It is one of the oldest sources of industrial power, and it remains the largest renewable source of electricity: [[Hydroelectricity|hydroelectric]] stations produced about 14.3% of the world's power in 2024.[^iha2025] In the Thury Hydrodynamics spine it is where [[Hydrostatics|still water]] and [[Fluid_dynamics|moving water]] become work — the same pressure-and-flow physics, now with a turbine in the way. Minnesota's version of the story is St. Anthony Falls on the [[Mississippi_River]], where water wheels drove the sawmills and flour mills that built Minneapolis, and where, on September 5, 1882, the country's first central hydroelectric station lit Washington Avenue.[^mnopedia1882] ## Microsims — p5.js <ul class="microsim-gallery"> <li class="microsim-card" data-lib="p5js"> <iframe src="https://wikitube-3d-microsims.netlify.app/Water_wheel.html" loading="lazy" frameborder="0" sandbox="allow-scripts allow-same-origin" allow="accelerometer; gyroscope" title="Water wheel — p5js microsim"></iframe> <div class="ms-meta"><div class="ms-title"><a href="https://en.wikitube.io/wiki/Water_wheel">Water wheel</a></div><div class="ms-sub">p5js · <a href="https://wikitube-3d-microsims.netlify.app/Water_wheel.html" target="_blank" rel="noopener">open full-screen</a></div></div> </li> <li class="microsim-card" data-lib="p5js"> <iframe src="https://wikitube-3d-microsims.netlify.app/Water_turbine.html" loading="lazy" frameborder="0" sandbox="allow-scripts allow-same-origin" allow="accelerometer; gyroscope" title="Water turbine — p5js microsim"></iframe> <div class="ms-meta"><div class="ms-title"><a href="https://en.wikitube.io/wiki/Water_turbine">Water turbine</a></div><div class="ms-sub">p5js · <a href="https://wikitube-3d-microsims.netlify.app/Water_turbine.html" target="_blank" rel="noopener">open full-screen</a></div></div> </li> <li class="microsim-card" data-lib="p5js"> <iframe src="https://wikitube-3d-microsims.netlify.app/Pelton_wheel.html" loading="lazy" frameborder="0" sandbox="allow-scripts allow-same-origin" allow="accelerometer; gyroscope" title="Pelton wheel — p5js microsim"></iframe> <div class="ms-meta"><div class="ms-title"><a href="https://en.wikitube.io/wiki/Pelton_wheel">Pelton wheel</a></div><div class="ms-sub">p5js · <a href="https://wikitube-3d-microsims.netlify.app/Pelton_wheel.html" target="_blank" rel="noopener">open full-screen</a></div></div> </li> <li class="microsim-card" data-lib="p5js"> <iframe src="https://wikitube-3d-microsims.netlify.app/Francis_turbine.html" loading="lazy" frameborder="0" sandbox="allow-scripts allow-same-origin" allow="accelerometer; gyroscope" title="Francis turbine — p5js microsim"></iframe> <div class="ms-meta"><div class="ms-title"><a href="https://en.wikitube.io/wiki/Francis_turbine">Francis turbine</a></div><div class="ms-sub">p5js · <a href="https://wikitube-3d-microsims.netlify.app/Francis_turbine.html" target="_blank" rel="noopener">open full-screen</a></div></div> </li> <li class="microsim-card" data-lib="p5js"> <iframe src="https://wikitube-3d-microsims.netlify.app/Hydraulic_head.html" loading="lazy" frameborder="0" sandbox="allow-scripts allow-same-origin" allow="accelerometer; gyroscope" title="Hydraulic head — p5js microsim"></iframe> <div class="ms-meta"><div class="ms-title"><a href="https://en.wikitube.io/wiki/Hydraulic_head">Hydraulic head</a></div><div class="ms-sub">p5js · <a href="https://wikitube-3d-microsims.netlify.app/Hydraulic_head.html" target="_blank" rel="noopener">open full-screen</a></div></div> </li> <li class="microsim-card" data-lib="p5js"> <iframe src="https://wikitube-3d-microsims.netlify.app/Spillway.html" loading="lazy" frameborder="0" sandbox="allow-scripts allow-same-origin" allow="accelerometer; gyroscope" title="Spillway — p5js microsim"></iframe> <div class="ms-meta"><div class="ms-title"><a href="https://en.wikitube.io/wiki/Spillway">Spillway</a></div><div class="ms-sub">p5js · <a href="https://wikitube-3d-microsims.netlify.app/Spillway.html" target="_blank" rel="noopener">open full-screen</a></div></div> </li> </ul> - [[Water_wheel]] — switch undershot, breastshot and overshot: how much of ρgQH reaches the shaft (about 85% for overshot, at most half for flat blades). - [[Water_turbine]] — slide head and flow across a log chart and the runner changes: Kaplan, Francis, Pelton. - [[Pelton_wheel]] — tune the bucket speed; efficiency peaks when the buckets move at half the jet speed. - [[Francis_turbine]] — open the guide vanes and watch the velocity triangles; the best point is where the exit swirl vanishes. - [[Hydraulic_head]] — piezometer tubes trace the hydraulic grade line that friction bends downward. - [[Spillway]] — crest discharge climbs with H^{3/2}; the hydraulic jump holds only with enough tailwater. *Six stations built 2026-09-10 from the Portal Books; each child article carries its own player, sources and a 16:9 and 9:16 video.* ## Calculating the amount of available power The power a site can deliver depends on two quantities: how far the [[Water|water]] falls — the *head*, H — and how much of it passes per second — the volumetric flow rate, Q. Each kilogram of water that falls through a height H releases *gH* joules of potential energy, where *g* is the acceleration of [[Gravity|gravity]]; multiplying by the mass flow ρQ, where ρ is the [[Density|density]] of water (about 1,000 kg per cubic meter), and by the efficiency η of the machinery gives the plant's output: `P = η ρ g Q H` A worked example from the [[PORTAL_Energy|Energy portal]] shelf makes the scale concrete: a dam passing 2,000 cubic meters per second through a 50 m head moves two million kilograms of water every second, releasing about a gigawatt; at 90% efficiency it delivers roughly 900 MW of electricity.[^murphy-ch11] That efficiency is unusually high among power sources. [[Electric_motor|Motors]] and generators convert between rotation and electricity at better than 90%, and a well-designed turbine loses little to friction, so a hydroelectric plant keeps most of the energy it is given — unlike a [[Thermodynamics|heat engine]], which must reject most of its fuel's energy as waste heat under the [[Second_law_of_thermodynamics|second law]].[^murphy-ch11] The head is not only a height. In a pipe or channel it is the total energy per unit weight of water, and part of it can be carried as [[Velocity|velocity]] rather than elevation — the bookkeeping of [[Bernoulli's_principle|Bernoulli's principle]]. Friction in the penstock, the rise of the tailwater when the plant runs hard, and [[Turbulence|turbulent]] losses at bends and gates all subtract from the gross head, and the difference between gross and net head is where [[Hydraulic_engineering|hydraulic engineering]] earns its keep. Where pressure at a runner blade falls below the vapor pressure of the water, [[Cavitation|cavitation]] bubbles form and collapse against the metal, which is why turbine setting and draft-tube design are part of the power calculation, not an afterthought. Gravitational energy is weak per kilogram, which is why hydropower is a business of very large volumes. The energy in one AA battery equals that of about 340 kg lifted four meters; a few milliliters of gasoline would need six tonnes lifted the same height.[^murphy-ch11] Flow also varies: river discharge can change severalfold between spring melt and late-summer low water, so a plant's average output is a fraction of its rating. United States hydroelectric capacity of about 80 GW ran at an annual average of about 33 GW, a capacity factor near 40%; Hoover Dam's 2,080 MW produce about 4.2 TWh a year, a capacity factor of about 23%.[^murphy-ch11] The ceiling on hydropower is set upstream, in the [[Hydrology|water cycle]]. Evaporating a gram of water takes about 2,250 J of [[Sun|solar]] energy, but lifting that gram to cloud height stores only about 50 J of potential energy, and rain falling on land at the average elevation of about 800 m keeps about 8 J of it. Averaged over the globe this makes the theoretical hydroelectric potential about 44 TW; technically feasible development is estimated near 2 TW, and only about half of that is economic.[^murphy-ch11] World generation of 4,578 TWh in 2024[^iha2025] corresponds to an average of about 0.52 TW, so roughly half of the practical resource is already in use. ## Disadvantages and limitations A dam changes a river and its [[Ecosystem|ecosystem]] from end to end. Upstream, a reservoir drowns valley land, forests and settlements; downstream, the river receives water that has been cooled, stripped of dissolved [[Oxygen|oxygen]], or held back in pulses that follow electricity demand rather than the seasons. Reservoirs trap the sediment that would have built banks, bars and deltas, so the channel below scours while the reservoir slowly fills — a problem of [[Geomorphology|geomorphology]] as much as of engineering. Dams block the upstream migration of fish, and turbines kill a share of the fish and eels that pass through them. Where forest is flooded without clearing, especially in the tropics, decaying vegetation releases methane, and the reservoir's greenhouse emissions can rival those of a fossil plant. These effects put hydropower inside [[Environmental_engineering|environmental engineering]] and [[Ecology|ecology]], not beside them. Hydropower is also thin. Even Washington State, with the Columbia River, delivers no more than about 0.05 W of hydroelectric power per square meter of land, against roughly 200 W per square meter of [[Sun|sunlight]] at the surface.[^murphy-ch11] A dam must also be designed for the largest flood its catchment can produce, the probable maximum flood, and its spillway must pass that flood without overtopping the structure; the energy of the spilled water is then dissipated in a stilling basin through a [[Hydraulic_jump|hydraulic jump]], whose strength is set by the [[Froude_number|Froude number]] of the incoming flow. Dam failure, however rare, is the one hydropower hazard measured in lives. In the United States these trade-offs are settled in licenses. The Federal Energy Regulatory Commission licenses non-federal dams for 30 to 50 years at a time, and state agencies — in Minnesota, the Department of Natural Resources among them — review each license and relicense for minimum flows, fish passage and watershed management.[^dnr-hydro] ## Applications ### Mechanical power For most of its history hydropower meant a shaft. Water wheels ground grain, sawed timber, fulled cloth, drove bellows and trip hammers, and lifted water for irrigation. An undershot wheel is pushed by the current; an overshot wheel is filled from above and turned by the weight of the water, capturing head as well as flow. Enclosed turbines, a product of nineteenth-century [[Mechanical_engineering|mechanical engineering]], replaced open wheels because they could run faster, use higher heads and deliver more power from the same stream. A variant with no moving parts, the trompe, lets falling water entrain air and compress it in an underground chamber, delivering compressed air to machinery at a distance. St. Anthony Falls shows the mechanical era at its peak. Minneapolis became the country's leading flour producer in 1880 and held the title for about fifty years; output rose from 193,000 barrels in 1870 to 2,051,840 barrels in 1880, and the Pillsbury A Mill, completed in 1881, was briefly the largest flour mill in the world.[^nps-ch6] Every barrel was ground by water falling through the canals and tailraces of the milling district. ### Electricity Coupling a turbine to an electrical generator turned hydropower from a local power source into a regional one, because electricity could be carried by wire where a shaft could not. Today electricity is by far the largest application; the conversion, the kinds of plant, and the role of [[Electric_power_transmission|transmission]] and storage are the subject of [[Hydroelectricity]]. Hydropower is also one half of pumped-storage hydroelectricity, which uses surplus electricity to pump water uphill and recovers it later through turbines — a way of storing [[Electrical_grid|grid]] energy as head. ## Rain power Rain is hydropower before it has been collected. The same water-cycle bookkeeping that limits large dams applies to a single drop: a gram of rain reaching land at average elevation carries only about 8 J of recoverable potential energy, and much less by the time it has run off a roof.[^murphy-ch11] Devices that harvest the impact of raindrops with piezoelectric [[Transducer|transducers]] have been demonstrated at laboratory scale, and gutter-mounted microturbines have been proposed for off-grid [[Sensor|sensors]] and battery charging; both produce milliwatts to watts. The phrase *rain power* is also used, more loosely, for conventional hydropower described as the capture of rainfall. ## History ### Ancient history Water wheels were in use in the Mediterranean world and in China by the last centuries BC. The Roman architect Vitruvius described a water-powered mill in the first century BC, and Roman engineers later combined wheels with cranks to drive stone saws. In Han-dynasty China, water power drove trip hammers and the bellows of iron furnaces. In the medieval Islamic world, water mills ground grain, pressed sugar and made paper across a region from Spain to Central Asia, and [[Tide|tide]] mills used the rise and fall of the sea. Hushing — releasing a stored flood of water to strip soil from ore veins — was an early [[Mining_engineering|mining]] use of the same energy. ### 19th century The nineteenth century turned the wheel into the turbine. Benoît Fourneyron's outward-flow reaction turbine in France was followed by James B. Francis's inward-flow design, developed from systematic testing at the Lowell mills in Massachusetts, and by Lester Pelton's impulse wheel for the high heads of the Sierra Nevada; Francis and Pelton turbines remain the standard machines for medium and high heads. The same century saw hydropower anchor whole industrial towns on falls and rapids. At St. Anthony Falls, soldiers from Fort Snelling built the first mills between 1821 and 1823, and Franklin Steele opened commercial sawmilling in 1848.[^nps-ch6] The falls themselves were unstable: a cap of hard Platteville limestone lay over soft St. Peter sandstone, and the river had been undercutting the sandstone and moving the falls upstream for thousands of years. On October 5, 1869, the Eastman tunnel, dug beneath the riverbed, collapsed and opened a whirlpool that threatened to destroy the falls and the power they supplied. Congress appropriated money in 1870, and by November 1876 the United States Army Corps of Engineers had completed a concrete cutoff wall 1,850 feet long beneath the river.[^nps-ch6] ### 20th century Electrification changed the scale. Plants grew from serving a single mill to serving cities, then regions, as [[Alternating_current|alternating-current]] [[Electric_power_transmission|transmission]] let power travel hundreds of kilometers. At St. Anthony Falls, William de la Barre's engineering raised the installed turbine capacity from about 13,000 horsepower in the 1880s to 55,068 horsepower by 1908.[^nps-ch6] The large multipurpose dams of the American West followed; Hoover Dam is rated at just over 2 GW and Grand Coulee on the Columbia River at about 6.8 GW, while China's Three Gorges Dam, at 22.5 GW, is the largest hydroelectric facility in the world.[^murphy-ch11] In the second half of the century the costs of displacement, lost fisheries and drowned landscapes became part of every project's accounting, and many rich countries stopped building large dams while continuing to build small ones. ## Minnesota *This section is specific to Wikitube.* [[Minnesota]]'s hydropower is a matter of many small heads rather than one large one. The state has no mountains; its power sites are falls and rapids where rivers cross resistant rock or drop off the edge of old glacial lakes. Minnesota Power, which began in 1906 by harnessing the St. Louis River near Duluth, operates eleven hydroelectric stations with more than 120 MW of combined capacity — Blanchard, Little Falls and Grand Rapids on the [[Mississippi_River|Mississippi]], Winton on the Kawishiwi River, Pillager and Sylvan on the [[Crow_Wing_River]], a station on the Prairie River, and Fond du Lac, Knife Falls, Scanlon and Thomson on the St. Louis.[^mnpower] More hydroelectricity reaches Minnesota from the north, from Manitoba's stations on the [[Nelson_River|Nelson]] and Winnipeg rivers, which drain to Hudson Bay. A [[Voltage|500-kilovolt]] line built by Manitoba Hydro and Minnesota Power, energized in June 2020, carries 250 MW of firm power from Manitoba's hydroelectric stations into Minnesota and lets those reservoirs back up the utility's wind generation — water in a northern reservoir acting as storage for wind on the Minnesota prairie.[^mb-hydro] That arrangement reads the state's three drainage basins as a single machine: [[WT!Minnesota_Hudson_Bay_Basin|Hudson Bay]] water generating power for a [[Electrical_grid|grid]] whose rain drains to the [[WT!Minnesota_Great_Lakes_Basin|Great Lakes]] and the [[WT!Minnesota_Gulf_of_Mexico_Basin|Gulf of Mexico]]. **On the spine:** [[Hydrostatics]] · [[Fluid_dynamics]] · [[Hydroelectricity]] · [[Hydrology]] · [[Mississippi_River]] · [[WT!Thury_Hydrodynamics_Compendium]]. ## See also - [[Hydroelectricity]] - [[Hydrology]] - [[Hydraulic_engineering]] - [[River_engineering]] - [[Bernoulli's_principle]] - [[Hydraulic_jump]] - `Hydraulic_head` · `Water_wheel` · `Water_turbine` · `Pumped-storage_hydroelectricity` · `Tidal_power` — not yet on Wikitube ## Notes - The sign convention: Wikipedia writes the output as −η ṁ g Δh, with Δh the change in height from inlet to outlet (negative for falling water). Wikitube writes it with the head H = −Δh, so the power comes out positive. The physics is the same. - The 0.52 TW average is simple arithmetic on the IHA generation figure: 4,578 TWh divided by the 8,760 hours in a year. ## References [^iha2025]: International Hydropower Association (June 25, 2025). "Global hydropower generation rebounds in 2024 and pumped storage development surges — flagship 2025 World Hydropower Outlook out now." https://www.hydropower.org/news/flagship-2025-world-hydropower-outlook-out-now [^mnopedia1882]: Huber, Molly. "Hydroelectricity in Minneapolis, September 5, 1882." *MNopedia*, Minnesota Historical Society. https://www.mnhs.org/mnopedia/search/index/event/hydroelectricity-minneapolis-september-5-1882 [^murphy-ch11]: Murphy, Tom W., Jr. (2021). *Energy and Human Ambitions on a Finite Planet*, chapter 11, "Hydroelectric Energy," pp. 173–181. eScholarship, University of California. CC BY-NC 4.0. https://escholarship.org/uc/item/9js5291m [^nps-ch6]: National Park Service, Mississippi National River and Recreation Area. "River of History — Chapter 6." https://home.nps.gov/miss/learn/historyculture/river-of-hisory-chapter-6.htm [^dnr-hydro]: Minnesota Department of Natural Resources. "Hydropower." https://www.dnr.state.mn.us/waters/surfacewater_section/stream_hydro/hydropower.html [^mnpower]: Minnesota Power. "Hydro." Company page. https://www.mnpower.com/Environment/Hydro [^mb-hydro]: Manitoba Hydro (July 2020). "New transmission line makes grid more reliable and benefits Manitobans." Company release. https://www.hydro.mb.ca/articles/2020/07/new_transmission_line_makes_grid_more_reliable_and_benefits_manitobans/ ## Sources - Murphy, Tom W., Jr. (2021). *Energy and Human Ambitions on a Finite Planet*. eScholarship, University of California. — on the [[PORTAL_Energy]] book shelf (`Portal Books/PORTAL_Energy/`). - Smyth, W. D. (2019). *All Things Flow: Fluid Mechanics for the Natural Sciences*. Oregon State University. [OTL record](https://open.umn.edu/opentextbooks/textbooks/all-things-flow-fluid-mechanics-for-the-natural-sciences) — on the [[PORTAL_Thury_Hydrodynamics_Apex_Spine]] book shelf; chapter 9 covers open-channel flow, hydraulic jumps and spillways. ## External links - [International Hydropower Association](https://www.hydropower.org/) - [Water Power Technologies Office](https://www.energy.gov/eere/water/water-power-technologies-office), U.S. Department of Energy - [Hydropower](https://www.dnr.state.mn.us/waters/surfacewater_section/stream_hydro/hydropower.html), Minnesota Department of Natural Resources  **Part of the [[WT!Thury_Hydrodynamics_Compendium|Thury Hydrodynamics Compendium]]** — main article for section 15, *Hydropower*. Related sections: [[Hydrostatics]] · [[Hydroelectricity]] · [[Hydrology]] · [[Dam]].   **Microsim — three.js (Wikitube framework):** *Hydropower* <div class="wt-sim" data-src="https://wikitube-3d-microsims.netlify.app/thury/Hydropower.html" data-title="Hydropower"></div> *Built from `MICROSIM_GUIDE/specs/sims/Hydropower.json`; part of the [[WT!Thury_Hydrodynamics_Compendium|Thury Hydrodynamics Compendium]] set.*  ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Hydropower) : [Wikitube](https://en.wikitube.io/wiki/Hydropower) · pinned revision [1372471663](https://en.wikipedia.org/w/index.php?oldid=1372471663) · 2026-09-10 ## Previous hub tags Hubs: `Life_Physics`, `Systems`. Portals: [[PORTAL_Thury_Hydrodynamics_Apex_Spine]], [[PORTAL_Energy]]. --- *Thury main articles · 2026-09-10 · drafted · microsim layer pending (THY-052).*