|Surface area||700 km²|
|Max. depth||5 m|
The Markermeer is a 700 km2 (270 sq mi) lake in the central Netherlands in between North Holland, Flevoland and its larger sibling, the IJsselmeer. A shallow lake at some 3 to 5 m in depth, it is named after the small former island, now peninsula, of Marken that lies within it. The southwest side of the lake that begins where the IJ once emptied into the Zuiderzee is known as the IJmeer.
The Markermeer was not originally intended to remain a lake. It used to be part of the Zuiderzee, a saltwater inlet of the North Sea, that was dammed off by the Afsluitdijk (Closure Dike) in 1932, turning the Zuiderzee into the freshwater IJsselmeer. The following years saw the reclamation of extensive tracts of land as large polders in a massive project known as the Zuiderzee Works (this article has a map of the area). One of these, the Markerwaard, was to occupy the area of the current Markermeer. Part of the construction of this last polder was building the Houtribdijk, also called Markerwaarddijk, finished in 1976, which hydrologically splits the IJsselmeer in two, the southern section being the Markermeer.
Because of changing priorities and doubts about the financial feasibility, the Markerwaard was indefinitely postponed in the 1980s and the Markermeer has since begun to become a valuable ecological and recreational asset of its own.
The Markermeer is used as a freshwater reservoir and a buffer against floodwaters and droughts. In 2003 the Netherlands was hit by drought, and several minor dikes were endangered. Water from the Markermeer was used to keep the area surrounding Amsterdam wet, thereby keeping the dikes safe.