Answer:
Step-by-step explanation:
The first documented use of watermills was in the first century BC and the technology spread quite quickly across the world.
Water mills use the flow of water to turn a large waterwheel. A shaft connected to the wheel axle is then used to transmit the power from the water through a system of gears and cogs to work machinery, such as a millstone to grind corn.
There are various designs of waterwheel, depending on the water supply available, including undershot (water hits the wheel paddles at the bottom of the wheel), breast-shot (water hits the wheel half way up) and overshot (water hits the wheel at the top).
Watermills are usually built beside streams or rivers to use them as a water supply. Very often these supplies were improved by the provision of mill races and weirs to help overcome the problems of different seasonal water levels. Many of the weirs seen on rivers today were originally built to help control water levels for watermills.