The pressure is proportional to the height of the dam (depth of the water), as P=ρgh where ρ is the density of the water, g is the acceleration of gravity at the surface of the Earth, and h is the depth of the water. Because of this, the taller the dam, the greater the force that can be generated to turn a turbine faster and generate electricity. This also explains why the turbines are located at the base of the dam.

The width of the dam does not matter, but is often controlled by the topography of the area that makes wider dams necessary to catch all the water flow.

If more water is allowed to flow through the turbine than the river supplies from upstream, the water level will decrease and the reservoir can eventually run dry.

DID YOU KNOW?

There are a tremendous number of large dams in the world. Only a small percentage of them were built for power generation. Most dams are built for irrigation, flood control, navigation, and many other reasons. This dam on the White River near Enumclaw, Washington was built to prevent massive floods that occurred on an annual basis.