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Machinery

What is a Water Wheel?

By M.R. Anglin
Updated May 17, 2024
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Moving water has a lot of energy. Just six inches (15 centimeters) of running water can wash away a small car. A water wheel is an early, successful attempt to harness the energy of running water and put it to human use. A water wheel is a wheel with paddles or buckets attached to it. Water flows over the paddles or buckets, causing the wheel to move and allowing energy to be transferred in order to do work.

Water wheels have been in use for millennia. In fact, there is evidence that they were in use as early as 4000 BC. A Greek writer, Antipater, mentioned a water wheel in one of his works. Evidence of water wheels can be found all over the world, including in Italy, India, China and the Americas. No matter where they are found, water wheels are commonly classified in three categories: the horizontal wheel, the overshot wheel and the undershot wheel.

A horizontal wheel is thought to be the earliest form of water wheel. The wheel itself is usually placed on the floor of a mill or wherever it is being used. Rapidly running water is then allowed to wash over it, hitting the paddles and causing the wheel to turn. The turning wheel is attached by a vertical axle to the upper millstone, which turns and grinds the wheel against a stationary lower millstone. This is the least efficient form of water wheel.

The undershot water wheel is more efficient. This type of vertical wheel can be used where the landscape is flat. The force of the water pushes the paddles below the wheel, causing it to revolve. A variation of this type of wheel, though sometimes classified as its own type, is the breastshot wheel. With this type of wheel, the water hits the buckets close -- or just above --the center of the wheel.

Using about 63% of the water’s energy, the overshot wheel is the most efficient type of water wheel. A backshot wheel is one varitation of this type. This vertical wheel uses the water pouring on top of the wheel to move it. Thus, not only does the wheel move with the power of the water, but it also takes advantage of the power of gravity. Oftentimes, the water used to move these wheels will have to be dammed or diverted in some way. Even though this type of water wheel is the most efficient, its construction can also impact the environment the most.

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Discussion Comments

By pastanaga — On Jun 17, 2011

There is a massive water wheel in the local botanic gardens near where I live and my nephew absolutely adores it. I don't think it does anything in particular.

It doesn't power anything or grind anything. It just looks cool and they light it up for Christmas.

I actually wonder if they should try to hook it up to something to demonstrate the power of it. It seems a bit of a waste for it to be a fully working water wheel with no real purpose besides looks.

By parmnparsley — On Jun 17, 2011

@GlassAxe- That sounds like a neat way to generate electricity. Do you know of any companies that sell water wheel generator kits? My family owns a small hunting camp near a brook in Vermont, and we normally use a gas generator. I would be interested in knowing if I could purchase and install one of these kits on the property. It is almost impossible to haul enough fuel up for a two week stay at the camp, so we have to leave every once in a while to refuel. The camp is far north, and it is in the middle of the woods, so solar panels are out of the question.

By GlassAxe — On Jun 17, 2011

I recently went to an energy presentation about bringing power to rural and impoverished regions of the world, and one of the technologies that NGOs use is water wheel generators. One of the presenters was part of a group that brought power to rural villages in Afghanistan by installing micro-hydroelectric plants in the towns.

The plants were very small, only producing a few kilowatts, but it was enough to allow the villagers to perform tasks that were nearly impossible before. If people wanted to weld a piece of metal, refrigerate food, have lights, or use any other type of electricity, they used to need gas or diesel generators that required expensive fuel. With the new generators, they could harness the power of even the smallest stream to generate electricity. I thought it was a neat idea, and I would like to see something like this catch on i other parts of the world.

By Alchemy — On Jun 17, 2011

@ GenevaMech- Believe it or not, the water wheel is used all over the world today, and is very important in your everyday life. Water wheels generate electricity at every hydroelectric plant in the world. If I am not mistaken, seven percent of the electricity generated in the United States is done so by water wheels. There are four main types of water wheels in use today, and they can be mounted horizontally, or vertically.

The falling water created by damming a river spins a water wheel that in turn spins a shaft connected to a generator. That shaft spins a rotor inside of a stator, producing electricity. Electricity generated from water wheel turbine is one of the best types of renewable energy because it is always on, power can be ramped up quickly, and it is cheap to maintain.

The downside though is that hydroelectric power generation is the most disruptive form renewable energy when it comes to the environment. The dams change the entire river ecosystem because it does not allow nutrient rich sediment to travel downstream. Dams also block the path of migratory fish, and are a major cause of the collapse of many fresh water fisheries. Anyway, I hoped this answered your question.

By GenevaMech — On Jun 17, 2011

Do people even use waterwheels anymore? The only thing that comes to mind when I picture a waterwheel is an old textile mill in the early 19th century. It seems like electricity would be a much simpler source of power than a water wheel. Is this something that they use in developing countries?

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