Ijsselmeer

The IJsselmeer is a large, shallow freshwater lake in the central Netherlands. It is the largest lake by surface area in the country, covering about 1,100 square kilometers. The lake was created in 1932 when the enclosing dike, the Afsluitdijk, closed off the Zuiderzee, a saltwater inlet of the North Sea, converting it into a freshwater lake and enabling flood protection and land reclamation in the surrounding polder lands.

Geography and subdivisions: It borders the provinces of North Holland and Flevoland. It is currently divided by the Houtribdijk, completed in 1975, into IJsselmeer to the southwest and the Markermeer to the northeast. The water level is managed for flood protection and freshwater supply, and the lake is relatively shallow, with depths typically around five meters.

Administration and ecology: The lake is managed by the national water authority Rijkswaterstaat, which oversees water levels and infrastructure, including the sluices at Den Oever and Kornwerderzand along the Afsluitdijk. The Oostvaardersplassen, a major nature reserve on the southeastern shore, arose from land reclamation in the mid-20th century and provides important habitat for migratory birds and other wildlife.

Economy and use: The IJsselmeer area supports shipping, fishing, and tourism. Towns around its shore include Enkhuizen, Hoorn, Medemblik, Lelystad, and Muiden, and the region is a popular destination for sailing and other watersports.