page_title: Drainage
section_title: Reasons for artificial drainage
hierarchical_section_title: Drainage / Reasons for artificial drainage
caption_attribution_description: English: Haarlemmermeer in the middle ages (oude Haarlemmermeer) and the 18th century. See http://www.cruquiusmuseum.nl/mapleft.jpg . Nederlands: Deze overzichtskaart van de ontwikkeling van de Haarlemmermeer komt ook voor op de website van het Cruquius Museum (http://www.cruquiusmuseum.nl/mapleft.jpg). Daar wordt deze kaart aangemerkt als "historisch", wat ook overeenkomt met de stijl van de kaart, die hem plaatst tegen het einde van de 19e eeuw. Hij is getekend naar het orgineel van Melchior Bolstra uit 1740. Русский: Озеро Харлеммермер в средние века ("старый Харлеммермер"; штриховка) и в XVIII веке (очертания берегов)
context_page_description: Drainage is the natural or artificial removal of surface and sub-surface water from a given area. Many agricultural soils need drainage to improve production or to manage water supplies.
context_section_description: Wetland soils may need drainage to be used for agriculture. In the northern USA and Europe, glaciation created numerous small lakes which gradually filled with humus to make marshes. Some of these were drained using open ditches and trenches.
  The largest project of this type in the world has been in process for centuries in the Netherlands. The area between Amsterdam, Haarlem and Leiden was, in prehistoric times swampland and small lakes. Turf cutting (Peat mining), subsidence and shoreline erosion gradually caused the formation of one large lake, the Haarlemmermeer, or lake of Haarlem. The invention of wind powered pumping engines in the 15th century permitted drainage of some of the marginal land, but the final drainage of the lake had to await the design of large, steam powered pumps and agreements between regional authorities. The elimination of the lake occurred between 1849 and 1852, creating thousands of km² of new land.
caption: Historic map of the Haarlemmermeer prior to reclamation.
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