# Why is the dam of water reservoir thick @ the bottom?

Dams are thicker at the bottom than they are at the top because water pressure at the bottom of a water reservoir is significantly higher. The dam must therefore be stronger to withstand this pressure; making it thicker achieves this objective.

Water pressure is higher at the bottom of a reservoir than at the top because there is a larger volume of water above being pulled downwards due to the force of gravity.

• Water pressure variance in action

If you have ever been diving in the sea, or attempting to swim to the bottom of a pool, you will understand the effects of higher water pressure at the bottom of a volume of water. As you travel further downwards, you experience the higher water pressure. You feel as though the water is pressing against you, and most likely want to get to the top of the water again as soon as possible. The dam experiences the same effect: The water pushes harder against it, so it must be stronger to withstand this force.

• What is the purpose of a dam?

Most dams are built in order to retain a reservoir of water in a certain place. The force of the water pressing against the dam is often converted to electric energy in water power stations and used as electricity. Alternatively, the water may be stored so it can later be distributed to various locations. Dams can also prevent widespread flooding to the local area.

Probably the most famous dam in the world is the Hoover Dam, located in the US between the states of Nevada and Arizona. The dam took five years to construct, and was the result of a mass labor force, of which over one hundred men lost their lives during construction. As well as providing energy and preventing floods, the Hoover Dam is now a popular tourist attraction.
thanked the writer.
That is where the water pressure is greatest. In an experiment 50 years ago, the French (it could only be the French) managed to use water deliberately vented** from the bottom of a dam through a narrow pipe to cut steel. There's a lot of pressure down there.

**(not really the right word, but I cannot think of a better one)
thanked the writer.
vikas jp commented
Coz presure increases with depth...water at base of reservoir is under high pressure P=hpg
John commented
High pressure water from a dam/spillway/sluice was also used in cliff mining for gold.or hydraulic mining in that one clint eastwood movie. Too much tv. : )