Technology
How does a dam work?
A dam works by blocking a river to hold back a large reservoir of water, using the wall's strength to resist the immense pressure. Many dams also generate electricity by letting the stored water rush down through turbines on its way out.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how a dam works.
Step by step
- 1A thick, strong wall holds back the river, forming a reservoir behind it.
- 2Water pressure rises with depth, so dams are built much thicker at the base.
- 3Controlled gates and spillways release water and prevent dangerous overflow.
- 4In a hydroelectric dam, falling water spins turbines that drive generators.
- 5Dams also store water for drinking and irrigation and help control floods.
Frequently asked questions
- How does a dam generate electricity?
- Water released from the reservoir falls through turbines, spinning them; the turbines drive generators that produce electricity — this is hydroelectric power.
- Why are dams thicker at the bottom?
- Water pressure increases with depth, so the greatest force is near the base — the dam is built thickest there to withstand it.
- What is a spillway?
- A channel that safely releases excess water during heavy rain or floods, preventing water from overtopping and damaging the dam.