The windmills at Kinderdijk, The Netherlands: a World Heritage site
Land from the sea
The people of the Netherlands have a long history of creating farmland from what Nature intended should be the floor of the sea! Land reclamation began in about 1000 AD with the building of dykes (sea walls) to prevent the sea from inundating the low-lying land of Holland and Utrecht.
Efforts to drain marshland and create new farmland began in the 14th century with the digging of canals and regulating the flow of water with a network of sluices and reservoirs. The new farmland proved to be fertile and peaty, and ideal for pasture and crop-growing.
However, the process of drainage behind the dykes caused the reclaimed land to sink below the level of the sea and therefore become subject to flooding from both the sea and the major rivers that flow through the region (notably the Rhine and its distributaries). A method was needed to lift excess water from the farmland (known as polder land) so that it could be deposited on the other side of the dykes.
Windmills as pumps
The Dutch did not invent the windmill (the Persians of the 9th century had that honour), but they must be credited for appreciating the potential of wind power to pump water in large quantities.
From the early 18th century, windmills were erected in the Netherlands to power rotary iron scoops that lifted water from the fields into reservoirs that were then emptied at low tide. Thousands of windmills were built, but they were gradually replaced by steam-powered pumps when the technology became available. However, some windmills still stand, and those at Kinderdijk are particularly impressive.
The Kinderdijk World Heritage Site
The site, which is to the east of Rotterdam, consists of a network of dykes, reservoirs and pumping station as well as windmills. The district at one time boasted 150 windmills, but only 28 remain today, of which 19 are within the area covered by the World Heritage site. They were built between 1738 and 1740 and are kept in full working order, although their function as pumps has not been needed since the 1940s. They are, however, still available in reserve should the modern diesel-generated pumps break down.
The windmills that form such as impressive sight as they stand in a row are known as “ground sailers”, because their sails come to within 30 centimetres of the ground. The towers were built from brick and wood and most are of the “bonnet” design, which means that the top sections revolve in order to catch the wind.
The Kinderdijk windmills were declared a World Heritage site in 1997.