A pond is an artificially created still water, usually with inflow and outflow. In contrast to a lake, the depth is so shallow that no stable temperature stratification is formed. Ponds are considered to be a historically significant development in hydraulic engineering. It was only through the storage of drinking and process water that the expansion of settlement in urban and rural areas became possible. This importance of ponds for water storage has only gradually declined in recent times with the modern water supply from the ground water by means of deep wells and pressure pipes - this also applies to the function of a mill pond for the operation of water mills for the purpose of driving various aggregates, which has been highly significant for more than 2000 years before the spread of steam power in the 19th century. While some cities had been equipped with new water supply technologies since the middle of the 19th century, rural areas were still dependent on ponds for a long time.
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