• 19 parts
  • Checked September 2026

Parts of a Dam

A concrete dam cut through, its power plant, and the spillway from downstream.

Parts of a Dam

Name Date

Tap any part to read, rename or leave it out

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
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Write the name of each numbered part.Answer key

  1. Reservoir
  2. Crest
  3. Upstream face
  4. Downstream face
  5. Heel
  6. Toe
  7. Foundation
  8. Gallery
  9. Intake
  10. Trashrack (trash rack)
  11. Penstock
  12. Turbine
  13. Generator
  14. Powerhouse (powerplant)
  15. Tailrace
  16. Abutment
  17. Spillway
  18. Spillway gate (crest gate)
  19. Stilling basin

Drawn for this site on 2026-09-30 from plain geometry. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: the parts of a bridge

All 19 parts on the diagram

Show the list

Start here: 7 main parts 7

  1. Reservoir The body of water stored behind the dam.
  2. Crest The top surface of the dam.
  3. Penstock A pipe carrying water under pressure down to the turbine.
  4. Turbine Moving water spins its blades; its shaft turns the generator.
  5. Generator Turned by the turbine's shaft, it produces electricity.
  6. Powerhouse (powerplant) The building that houses the turbines and generators.
  7. Spillway A structure that passes flood water safely past the dam.

Cut through the dam 6

  1. Upstream face The surface of the dam in contact with the reservoir.
  2. Downstream face The sloping surface of the dam away from the reservoir.
  3. Heel Where the upstream face meets the ground.
  4. Toe Where the downstream face meets the ground.
  5. Foundation The excavated rock or soil the dam is placed on.
  6. Gallery A passage inside the dam for inspection and drainage.

Through the power plant 3

  1. Intake The opening where water enters on its way to the turbine.
  2. Trashrack (trash rack) A grate over the intake that stops floating debris.
  3. Tailrace The water just below the powerhouse, carrying the flow away.

From downstream 3

  1. Abutment The valley side each end of the dam is built against.
  2. Spillway gate (crest gate) A movable barrier that controls the flow down the spillway.
  3. Stilling basin A concrete-lined pool where the falling water loses its energy.

How this list was compiled: Read 2026-09-30; a name is kept only where two of these use it. (1) US Bureau of Reclamation, Reclamation Glossary, https://www.usbr.gov/library/glossary/ : reservoir (a body of water impounded by a dam), crest (the top surface of the dam; a roadway may be constructed across it), upstream face (the surface of the dam in contact with the reservoir), downstream face (the inclined surface of a dam away from the reservoir), heel of dam (the junction of the upstream face of a concrete gravity dam with the ground surface; for an embankment dam, the upstream toe), toe of dam (the junction of the face of a dam with the ground surface), foundation (the excavated surface upon which a dam is placed), abutment (that part of the valley wall against which the dam is constructed), gallery (a passageway within the body of a dam used for inspection, foundation grouting and drainage), spillway (a structure over or through which flow is discharged from a reservoir), crest gate or spillway gate (a gate on the crest of a spillway), stilling basin (a pool, usually lined with reinforced concrete, located below a spillway, into which the discharge dissipates energy), intake, trashrack (a structure at an intake that prevents entrance of debris), penstock (a conduit used to convey water under pressure to the turbines of a hydroelectric plant), turbine, generator, powerplant (structure that houses turbines, generators and control equipment), afterbay or tailrace (the body of water immediately downstream from a powerplant). (2) US Army Corps of Engineers, EM 1110-2-2200, Gravity Dam Design, 1995, https://archive.org/details/DTIC_ADA402909 : its glossary (abutment, foundation, gallery, heel of dam, toe of dam, intake structure, spillway, stilling basin) and its text (crest, upstream and downstream faces, spillway gates, penstock, powerhouse, trashrack, reservoir). (3) US Geological Survey, Hydroelectric Power: How it Works, https://www.usgs.gov/special-topics/water-science-school/science/hydroelectric-power-how-it-works : the dam stores water in the reservoir; near the bottom of the dam wall is the water intake; water falls through the penstock inside the dam to a turbine; the shaft from the turbine goes up into the generator; the water continues through the tailrace into the river. (4) Wikipedia, Dam: crest, upstream and downstream faces, abutments, foundation, spillway with gates, galleries, penstock, trash rack over the intake, turbine, generator, power plant. Wikipedia's note on toe and heel cites the Reclamation glossary, so those two names rest on the Bureau of Reclamation and the Corps of Engineers. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work

How it works

A dam holds a river back to make a reservoir. These are the names engineers use for a concrete gravity dam, for the power plant at its foot, and for the spillway that lets floods past.

Read the full guide

The dam itself

The crest is the top. The upstream face holds back the reservoir and the downstream face slopes away from it. The heel is where the upstream face meets the ground, and the toe is where the downstream face does. The dam sits on its foundation and ends against an abutment each side. A gallery is a passage inside, used for inspection and drainage.

Where the water goes

Water for power enters at the intake, behind a trashrack that stops debris. The penstock carries it down to a turbine, which turns a generator in the powerhouse, and it leaves by the tailrace. Flood water goes down the spillway, past its gates, into the stilling basin.

  • Upstream is the reservoir side. Downstream is the way the river flows on.
  • Heel and toe: picture the dam as a foot stepping downstream.

Questions and answers

What are the parts of a dam called?

On a concrete dam: the crest on top, the upstream and downstream faces, the heel and toe where they meet the ground, the foundation, an abutment at each end and the spillway. A dam that makes electricity adds an intake, penstock and powerhouse.

What is the top of a dam called?

The crest. It is the top surface of the dam, and a road often runs along it. The same word is used for the high point of a spillway, the level water must reach before it flows over.

What is the difference between the heel and the toe of a dam?

The heel is where the upstream face meets the ground, on the reservoir side. The toe is where the downstream face meets the ground. On an earth dam both are called toes: the upstream toe and the downstream toe.

What does a spillway do?

It lets water out of a full reservoir safely, so a flood does not pour over the top of the dam. Gates on its crest control the flow, and a stilling basin at the bottom slows the water before it rejoins the river.

What is a penstock?

A pipe or passage that carries water under pressure from the reservoir down to the turbines of a power plant. The falling water spins the turbine, and the turbine's shaft turns the generator.

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